HIGH RATE RESIN INFUSION HORIZONTAL STABILIZER

STIFFENED SKIN TECHNOLOGY

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/091,782, filed on October 14, 2020, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] The present disclosure generally relates to methods for forming composite structures, and more particularly, to high rate resin infusion horizontal stabilizer stiffened skin technology.

BACKGROUND

[0003] Composite materials and structures, including resin-infused carbon-fiber laminates, are commonly used in applications requiring high strength and light weight. For example, in the aerospace industry, composite structures are used in increasing quantities to form stiffened skin structures, horizontal stabilizers, wings, and other components of aircraft.

However, conventional methods and systems for forming composite structures are often time- and labor-intensive, especially for composite structures combining complementary pieces, such as horizontal stabilizer or wing skins and stringers into a single composite structure. Further, using current aerospace composite-fabrication materials and methods to produce composite structures at high rates would require multiple sets of tooling and processing equipment along with the factory-floor space required to accommodate said equipment. Thus, fabricating high-quality composite structures with aerospace-grade materials to meet performance characteristics at high rates using current production methods would be difficult and expensive, limiting the rate of production at an affordable cost.

[0004] Accordingly, there is a need for systems and methods for forming composite structures that offer improvements in a rate of production, particularly for composite structures of larger size and complexity, as typically associated with the aerospace industry.

BRIEF SUMMARY

[0005] This summary is intended merely to introduce a simplified summary of some aspects of one or more implementations of the present disclosure. This summary is not an extensive overview, nor is it intended to identify key or critical elements of the present teachings, nor to delineate the scope of the disclosure. Rather, its purpose is merely to present one or more concepts in simplified form as a prelude to the detailed description below.

[0006] The foregoing and/or other aspects and utilities exemplified in the present disclosure may be achieved by providing a method for forming a composite part, including placing two or more preforms in a constant-temperature mold; infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin-infused preform; and curing the combined resin-infused preform to form a cured composite part, wherein the constanttemperature mold maintains a constant curing temperature during infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin-infused preform and curing the combined resin-infused preform to form a cured composite part, and wherein the resin has a period of latency and the resin is configured to cure within a predetermined curing time at the constant curing temperature.

[0007] The method can further include ply-cutting raw material into flat patterns; and forming the flat patterns into two or more preforms, wherein the two or more preforms includes at least two complementary preforms, and wherein the constant-temperature mold accommodates the two or more preforms in a predetermined configuration relative to each other.

[0008] The two or more preforms can include at least one skin panel preform and at least one stringer preform.

[0009] The method can further include removing the cured composite part from the constanttemperature mold; and post-processing the cured composite part, wherein post-processing the cured composite part can include further curing the cured composite part at a temperature higher than the constant curing temperature.

[0010] Infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin-infused preform can include a predetermined infusion time, and wherein the resin has a period of latency corresponding to the predetermined infusion time. [0011] The resin can be maintained at the constant curing temperature for the predetermined infusion time, and wherein the resin maintains a viscosity of about 50 cP or less for the predetermined infusion time.

[0012] The constant curing temperature can be from about 100°C to about 200°C, wherein the predetermined curing time is from about 5 minutes to about 180 minutes, and wherein the resin has a period of latency from about 5 minutes to about 1 hour. [0013] The constant-temperature mold can include a lower mold die and an upper mold die, wherein placing two or more preforms in a constant-temperature mold comprises placing the two or more preforms in the lower mold die, and wherein the lower mold die maintains the two or more preforms at the constant curing temperature.

[0014] The lower mold die is configured to accommodate the at least two complementary preforms in a predetermined configuration relative to each other.

[0015] Infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin-infused preform can include placing the upper mold die over the lower mold die to create a sealed cavity, the sealed cavity defining a gap, the gap corresponding to a cavity volume equivalent to an amount of resin sufficient to infuse the two or more preforms; injecting the resin into the gap of the sealed cavity to infuse the two or more preforms for the predetermined infusion time; and lowering the upper mold die to close the gap and to apply a curing pressure to the combined resin-infused preform for the predetermined curing time, wherein the resin is injected into the sealed cavity at a pressure from about 5 psig to about 40 psig, wherein the constant-temperature mold maintains the resin at the curing temperature, and wherein the upper mold die applies a curing pressure of from about 5 psig to about 150 psig.

[0016] The foregoing and/or other aspects and utilities exemplified in the present disclosure may also be achieved by providing an integrated system for forming a composite part including a ply-cutting station to cut raw material into flat patterns; a picking-and-placing station to receive the flat patterns from the ply-cutting station and to form two or more preforms; a preform-transfer station to receive the two or more preforms from the picking- and-placing station and to place the two or more preforms into a constant-temperature lower mold die; an infusing-and-curing station to receive the constant-temperature lower mold die, to infuse the two or more preforms with a resin to form a combined resin-infused preform, and to cure the combined resin-infused preform to form a cured composite part; and a cured- part transfer station to receive the cured composite part from the infusing-and-curing station and to remove the cured composite part from the constant-temperature lower mold die, wherein the two or more preforms include at least two complementary preforms, wherein the constant-temperature lower mold die accommodates the two or more preforms in a predetermined configuration relative to each other, wherein the constant-temperature lower mold die maintains the two or more preforms at a constant curing temperature, and wherein the resin has a period of latency and the resin is configured to cure within a predetermined curing time at the constant curing temperature. [0017] The system can further include a post-curing station to receive the cured composite part from the cured-part transfer station and to further process the cured composite part. [0018] The ply-cutting station can include a ply-cutting table, a raw-material dispenser to supply raw material to the ply-cutting table; and a cutter to cut the raw material on the ply- cutting table into flat patterns, wherein the raw material comprises from 1 to 8 plies of a fibrous material with a per-ply areal weight from about 50 gsm to about 400 gsm.

[0019] The ply-cutting table can include a staging area; and a material conveyor configured to simultaneously advance raw material from the material dispenser onto the ply-cutting table and the flat patterns to the staging area.

[0020] The picking-and-placing station can include a pick-and-place end effector to pick the flat patterns from the ply-cutting table; and an assembly jig to receive the flat patterns picked by the pick-and-place end effector, wherein the pick-and-place end effector locates and secures the flat patterns on the assembly jig. In some implementations, the picking-and- placing station applies a pressure to the flat patterns on the assembly jig to form a preform. In other implementations, the picking-and-placing station places the flat patterns on the assembly jig to form a preform.

[0021] The picking-and-placing station can include consolidating the preform prior to transferring the preform to the preform-transfer station as described below. The picking-and- placing station can be configured to form at least one of the at least two complementary preforms.

[0022] The preform-transfer station can include a lifting structure to place two or more preforms in the constant-temperature lower mold die, wherein the constant-temperature lower mold die is at the curing temperature when the two or more preforms are placed in the constant-temperature lower mold die.

[0023] The infusing-and-curing station can include a constant-temperature upper mold die; a constant-temperature lower mold die; and a resin-infusion system, wherein the constanttemperature upper mold die is configured to press against the constant-temperature lower mold die, wherein, in a first position, the constant-temperature upper mold die defines a sealed gap having a volume equivalent to an amount of resin sufficient to infuse the two or more preforms, and wherein in a second position, the constant-temperature upper mold die defines a cavity corresponding to final dimensions of the cured composite part. The infusing- and-curing station can further include a press to move at least one of the constant-temperature upper mold die and the constant-temperature lower mold die against each other. [0024] The constant-temperature mold can include one or more cavities and one or more channels configured to hold the two or more preforms in a position relative to each other. For example, the constant-temperature mold can include one or more cavities configured to hold one type of complementary preform and one or more channels configured to hold another type of complementary preform in a position relative to each other.

[0025] The resin-infusion system can inject the resin into the sealed gap for the predetermined infusion time to form a combined resin-infused preform, and wherein the constant-temperature upper mold die applies a curing pressure to the combined resin-infused preform to form a cured composite part.

[0026] Further areas of applicability will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in, and constitute a part of this specification, illustrate implementations of the present teachings and, together with the description, serve to explain the principles of the disclosure. In the figures:

[0028] FIG. 1 illustrates a method for forming a composite part according to implementations of the present disclosure;

[0029] FIG. 2 illustrates an integrated system for forming a composite part according to implementations of the present disclosure;

[0030] FIGS. 3-4 and 5A-5B illustrate a ply-cutting station 100 according to implementations of the present disclosure;

[0031] FIGS. 6-13 illustrate a picking-and-placing station according to implementations of the present disclosure;

[0032] FIGS. 14-15, 16A-16D, and 17A-17E illustrate a preform-transfer station according to implementations of the present disclosure;

[0033] FIGS. 18-20 and 21A-21F illustrate an infusion-and-curing station according to implementations of the present disclosure;

[0034] FIGS. 22 and 23A-23F illustrate a cured-part transfer station according to implementations of the present disclosure;

[0035] FIGS. 24-25 illustrate a post-curing station according to implementations of the present disclosure; [0036] FIG. 26 illustrates a shuttling system according to implementations of the present disclosure;

[0037] FIG. 27 illustrates a flow diagram of aircraft production and service methodology; and

[0038] FIG. 28 illustrates a block diagram of an aircraft.

[0039] It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding of the present teachings rather than to maintain strict structural accuracy, detail, and scale.

DETAILED DESCRIPTION

[0040] Reference will now be made in detail to exemplary implementations of the present teachings, examples of which are illustrated in the accompanying drawings. Generally, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0041] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. Phrases, such as, “in an implementation,” “in certain implementations,” and “in some implementations” as used herein do not necessarily refer to the same implementation(s), though they may. Furthermore, the phrases “in another implementation” and “in some other implementations” as used herein do not necessarily refer to a different implementation, although they may. As described below, various implementations can be readily combined, without departing from the scope or spirit of the present disclosure.

[0042] As used herein, the term “or” is an inclusive operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described unless the context clearly dictates otherwise. In the specification, the recitation of “at least one of A, B, and C,” includes implementations containing A, B, or C, multiple examples of A, B, or C, or combinations of A/B, A/C, B/C, A/B/B/ B/B/C, A/B/C, etc. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on.” Similarly, implementations of the present disclosure may suitably comprise, consist of, or consist essentially of, the elements A, B, C, etc.

[0043] It will also be understood that, although the terms first, second, etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first object, component, or step could be termed a second object, component, or step, and, similarly, a second object, component, or step could be termed a first object, component, or step, without departing from the scope of the invention. The first object, component, or step, and the second object, component, or step, are both, objects, component, or steps, respectively, but they are not to be considered the same object, component, or step. It will be further understood that the terms “includes,” “including,” “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. Further, as used herein, the term “if” can be construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context.

[0044] All physical properties that are defined hereinafter are measured at 20° to 25° Celsius unless otherwise specified.

[0045] When referring to any numerical range of values herein, such ranges are understood to include each and every number and/or fraction between the stated range minimum and maximum, as well as the endpoints. For example, a range of 0.5% to 6% would expressly include all intermediate values of, for example, 0.6%, 0.7%, and 0.9%, all the way up to and including 5.95%, 5.97%, and 5.99%, among many others. The same applies to each other numerical property and/or elemental range set forth herein, unless the context clearly dictates otherwise.

[0046] Additionally, all numerical values are “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. It should be appreciated that all numerical values and ranges disclosed herein are approximate values and ranges. The terms “about” or “substantial” and “substantially” or “approximately,” with reference to amounts or measurement values, are meant that the recited characteristic, parameter, or values need not be achieved exactly. Rather, deviations or variations, including, for example, tolerances, measurement error, measurement accuracy limitations, and other factors known to those skilled in the art, may occur in amounts that do not preclude the effect that the characteristic was intended to provide. As used herein, “about” is to mean within +/- 10 % of a stated target value, maximum, or minimum value

[0047] Unless otherwise specified, all percentages and amounts expressed herein and elsewhere in the specification should be understood to refer to percentages by weight. The percentages and amounts given are based on the active weight of the material. For example, for an active ingredient provided as a solution, the amounts given are based on the amount of the active ingredient without the amount of solvent or may be determined by weight loss after evaporation of the solvent.

[0048] With regard to procedures, methods, techniques, and workflows that are in accordance with some implementations, some operations in the procedures, methods, techniques, and workflows disclosed herein can be combined and/or the order of some operations can be changed.

[0049] As used herein, the term “constant-temperature” refers to a temperature value having a variance of less than ±5°C of the desired value. For example, a constant-temperature of 100°C would refer to a temperature maintained between 95°C and 105°C. Similarly, a constant-temperature mold refers to a mold configured to maintain a temperature at ±5°C of a desired value, and a constant curing temperature refers to a desired curing temperature at a variance of less than ±5°C.

[0050] FIG. 1 illustrates a method for forming a composite part according to implementations of the present disclosure. As illustrated in FIG. 1, a method 800 for forming a composite part includes placing two or more preforms in a constant-temperature mold in operation 830, infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin-infused preform in operation 840, and curing the combined resin-infused preform to form a cured composite part in operation 850. The two or more preforms include at least two complementary preforms, and the combined resin-infused preform can include two or more complementary preforms. The constant-temperature mold maintains a constant curing temperature during the operations of infusing the two or more preforms in the constant-temperature mold with a resin and curing the combined resin-infused preform. The resin has a period of latency, and the resin is configured to cure within a predetermined curing time at the constant curing temperature.

[0051] As used herein, the terms “complementary preforms” refers to different types of preforms configured to function together in a co-cured or combined composite structure. For example, complementary preforms may include horizontal or vertical stabilizer skins, wing skins, and skin panels providing an overall shape and outer bending and shear strength to an overall composite structure, and stringers or stiffening members to provide adding additional stiffness to the overall composite structure. In some implementations, stabilizer skins, wing skins, and skin panels are one type of complementary preform and stringers or stiffening members are another type of complementary preform. [0052] The constant-temperature mold can be configured to accommodate two or more complementary preforms in a predetermined configuration relative to each other, such as, as the complementary preforms are ultimately located in the co-cured composite part. The constant-temperature mold can include one or more cavities and/or one or more channels configured to hold one type of complementary preform in a relative position to another type of complementary preform. For example, the constant-temperature mold can include one or more cavities configured to hold one type of complementary preform and one or more channels configured to hold another type of complementary preform in a position relative to each other.

[0053] As used herein, the term “cured” refers to a sufficient degree of stiffness and strength in the composite part, such that the composite part can be safely removed from the mold tool. For example, a cured composite part can refer to a composite part sufficiently cured to maintain its shape without any distortion or damage after removal from the mold tool. After removal from the mold tool, additional curing, or post-curing, may be performed to further develop additional stiffness and strength within composite part to meet desired targets. The degree of cure can be a measure of crosslinking of the resin matrix that is typically calculated and/or tested by well-known means.

[0054] The method 800 can further include ply-cutting raw material into flat patterns in operation 810 and forming the flat patterns into two or more preforms in operation 820. For example, the flat patterns can be placed onto the assembly jig in operation 820 to form the two or more preforms. Ply-cutting raw material into flat patterns can include consolidating the plies to eliminate dry material bulk. Stringer preforms can be created in operation 820 by combining plies and forming a basic stringer shape. The stringer preform can then be formed into a desired lofted shape and consolidated to eliminate the dry material bulk. The two or more preforms can be complementary. For example, the two or more preforms can include one horizontal or vertical stabilizer skin or wing skin preform and at least one stringer or stiffener preform.

[0055] The method 800 can further include removing the cured composite part from the constant-temperature mold in operation 860 and transferring the cured composite part to a post-cure fixture in operation 870. The method 800 can further include post-processing the cured composite part in operation 880. One example of post-processing includes additional curing of the cured composite part at a temperature higher than the constant curing temperature. For example, for resins that cure at about 130°C, post-processing the cured composite part can include further curing the cured composite part at a post-processing temperature from about 150°C to about 200°C for from about 30 minutes to about 120 minutes to attain a full cure of the composite part. In some implementations, the postprocessing temperature is from about 170°C to about 190°C. In other implementations, the post-processing temperature is from about 10°C to about 50°C higher than the constant curing temperature.

[0056] Infusing the at least two preforms in the constant-temperature mold with a resin to form a combined resin-infused preform in operation 840 can include a predetermined infusion time, and the resin can have a period of latency corresponding to the predetermined infusion time. The predetermined infusion time can be selected according to the resin used to allow enough time for the resin to fully wet-out the two or more preforms before the resin begins to cure. The predetermined infusion time can be about 1 hour or less, about 45 minutes or less, about 30 minutes or less, about 25 minutes or less, about 20 minutes or less, about 15 minutes or less, about 10 minutes or less, or about 5 minutes or less. For example, the infusion time can be from about 5 minutes to about 1 hour, or the infusion time can be about 30 minutes or less.

[0057] The resin can be an epoxy resin. The resin can have a period of latency. For example, the resin can include a pre-mixed and degassed epoxy resin having period of latency. In other implementations, the resin can include epoxies, cyanate esters, benzoxazines, bismaleimides, polyimides, crosslinkable thermoplastics, and in situ polymerizable thermoplastics, or combination thereof. For example, the resin can include, without limitation, epoxy/cyanate esters and epoxy /benzoxazines.

[0058] As used herein, the “period of latency” of a resin refers to the time before unacceptable increases in resin viscosity are reached after mixing the components of the resin. For example, an epoxy resin can be formed by mixing an epoxy component with a hardener, such as an amine. Once mixed, the epoxy resin will crosslink, increasing its viscosity. The resin can have a period of latency from about 5 minutes to about 1 hour. For example, the resin can have a period of latency of about 30 minutes or less.

[0059] The infusing of resin occurs over time, such time is sometimes referred to herein as a period of latency. The period of latency is the time needed to fully wet-out the preform within the constant-temperature mold. The resulting structure is sometimes referred to herein as a resin-infused preform in operation 840 for the predetermined infusion time. For example, the resin can maintain a viscosity of about 100 cP or less for the predetermined infusion time, a viscosity of about 50 cP or less for the predetermined infusion time, a viscosity of about 25 cP or less for the predetermined infusion time, or a viscosity of about 20 cP or less for the predetermined infusion time. In some implementations, the resin is infused into the two or more preforms at the constant curing temperature. The constant-temperature mold maintains the resin at the constant curing temperature for the predetermined infusion time.

[0060] A cured composite part is formed in operation 850 by curing the combined resin- infused preform at the constant curing temperature for the predetermined curing time.

[0061] The constant curing temperature must be set according to the resin. For example, some aerospace epoxy resins cure initially at 130°C, but fully cure at a temperature of about 170-190°C. Accordingly, the constant curing temperature can be set at a temperature from about 100°C to about 200°C. For example, the constant curing temperature can be a temperature from about 170°C to about 190°C. In some implementations, the constant curing temperature can be a temperature of about 130°C. In other implementations, the constant curing temperature can be a temperature from about 70°C to about 190°C. For example, the constant curing temperature can be a temperature from about 90°C to about 170°C or from about 100°C to about 150°C.

[0062] The predetermined curing time can be set to maximize a production rate of the method 800. For example, the predetermined curing time can be set to cure the combined resin-infused preform to a point where it can be removed from the constant-temperature mold without damaging the cured composite structure for further curing outside the constanttemperature mold. The predetermined curing time can be set to cure the combined resin- infused preform to a point where the two or more preforms do not separate, or become one, integral part, when removed from the constant-temperature mold. In other implementations, the predetermined curing time can be set to fully cure the two or more preforms in the constant-temperature mold. The predetermined curing time can be from about 5 minutes to about 180 minutes. For example, the predetermined curing time can be from about 60 minutes to about 180 minutes, from about 90 minutes to about 150 minutes, or from about 110 minutes to about 130 minutes.

[0063] Ply-cutting raw material into flat patterns can include advancing raw material from a material dispenser onto a ply-cutting table, and cutting the raw material into predetermined shapes to form the flat patterns.

[0064] The raw material can include from 1 to 8 plies of a fibrous material with a per-ply areal weight from about 50 gsm to about 400 gsm. For example, the raw material can have a per-ply areal weight from about 100 gsm to about 200 gsm. [0065] The raw material can have a carbon-fiber content up to 70 weight percent. The raw material can include carbon fiber with a knit thread, carbon fiber with a knit thread and a thermoplastic veil, or carbon fiber with a veil. For example, for the knit-thread-only material, the knit thread can be about 1-2 weight percent of the total weight of the raw material. For the carbon fiber with a knit thread and a thermoplastic veil, the combination is about 4-10 weight percent of total areal weight, and for the carbon fiber with a veil it is around 3 weight percent.

[0066] The raw material can include carbon-fiber-based fabrics, such as non-crimp fabrics (NCFs). One example is a dry multiaxial non-crimped fabric (MA-NCF).

[0067] Placing the flat patterns into two or more preforms can include picking and placing the flat patterns on an assembly jig to create the two or more preforms. Placing the flat patterns can also include inspecting the newly placed material for defects. Any defects found on the preforms can be fixed in situ or, if in situ correction is not desired, a defective preform can be move to an inspection station.

[0068] In some implementations, the two or more preforms include a stringer preform. Accordingly, forming the flat patterns into two or more preforms can include cutting, shaping, the raw material to form a stringer preform. However, the present disclosure is not limited thereto, and forming the flat patterns into two or more preforms can include other methods known in the art for creating stringer preforms, such as forming a stringer preform to a desired loft using an inner mold line and/or a stringer loft former.

[0069] The constant-temperature mold can include a lower mold die and an upper mold die, and placing two or more preforms in a constant-temperature mold can include placing the two or more preforms in the lower mold die. The lower mold die maintains the two or more preforms at the constant curing temperature and applying a pressure to the two or more preforms. The constant-temperature mold can be insulated to prevent heat loss.

[0070] In one implementation, the lower mold die is configured to accommodate the at least two complementary preforms in a predetermined configuration relative to each other, such as, where at least two complementary preforms are ultimately located in the cured composite part. For example, the lower mold die can include one or more cavities configured to hold one type of complementary preform and one or more channels configured to hold another type of complementary preform in a relative position to each other. As illustrated in FIGS. 16A-16D and 17A-17E, a constant-temperature lower mold die 420 can be configured to hold the two or more preforms 40 in specific positions with respect to each other, such as holding stringer preforms 43 at specific distances and positions with respect to a horizontal or vertical stabilizers or wing skin preform 42.

[0071] The constant-temperature mold can substantially correspond to desired final dimensions of the composite part, such that no shims, no flow media, no peel plies, no chromate tape, no separator plies, and no vacuum bagging are required to form the cured composite part to the desired final dimensions. In other implementations, the preform can be coated with a mold release to reduce the need for peel plies, vacuum bagging, etc.

[0072] Infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin-infused preform can include placing the upper mold die over the lower mold die to create a sealed cavity, the sealed cavity defining a gap, the gap corresponding to a cavity volume substantially equivalent to an amount of resin sufficient to infuse the two or more preforms; injecting the resin into the gap of the sealed cavity to infuse the two or more preforms ; and lowering the upper mold die applying pressure to close the gap and infuse the two or more preforms for the predetermined infusion time as the upper mold die is lowered; and applying a curing pressure to the combined resin-infused preform for the predetermined curing time. The resin can be injected into the sealed cavity at a pressure from about 5 psig to about 40 psig. The constant-temperature mold can maintain the resin at the curing temperature. The upper mold die can apply a pressure of from about 5 psig to about 150 psig. The sealed cavity can be evacuated before injecting the resin into the sealed cavity.

[0073] As described above, the cured composite part can be removed from the constanttemperature mold for post-processing. As mentioned above, the cured composite part can be further cured at a temperature higher than the constant curing temperature. For example, the cured composite part can be further cured at a temperature from about 20°C to about 70°C higher than the curing temperature for about 30 minutes to about 120 minutes. In some implementations, an autoclave is not required to fully cured or post-process the cured composite part.

[0074] FIGS. 2-26 illustrate an integrated system for forming a composite part according to implementations of the present disclosure. FIGS. 2-26 illustrate a system that, for instance, could be used to implement the method 800 for forming a composite part as described above and illustrated in FIG. 1. As such, the discussion below will reference various operations and components as described above.

[0075] As illustrated in FIGS. 2-26, an integrated system 10 for forming a composite part includes a ply-cutting station 100 to cut raw material 20 into flat patterns 30; a picking-and- placing station 200 to receive the flat patterns 30 from the ply-cutting station 100 and to form two or more preforms 40; a preform-transfer station 300 to receive the two or more preforms 40 from the picking-and-placing station 200 and to place the two or more preforms 40 into a constant-temperature lower mold die 420; an infusing-and-curing station 400 to receive the constant-temperature lower mold die 420, to infuse the two or more preforms 40 with a resin 45 to form a combined resin-infused preform 41, and to cure the combined resin-infused preform 41 to form a cured composite part 50; and a cured-part transfer station 500 to receive the cured composite part 50 from the infusing-and-curing station 400 and to remove the cured composite part 50 from the constant-temperature lower mold die 420.

[0076] The two or more preforms 40 can include at least two complementary preforms, and the constant-temperature lower mold die 420 can accommodate the at least two complementary preforms 40 in a predetermined configuration relative to each other. For example, the two or more preforms 40 can include stiffening member or stringer preforms 43 and horizontal or vertical stabilizers or wing skin preforms 42. The constant-temperature lower mold die 420 can include one or more cavities configured to hold one type of complementary preform 42 and one or more channels configured to hold another type of complementary preform 43 in a predetermined configuration relative to each other.

[0077] The constant-temperature lower mold die 420 maintains the two or more preforms 40 at a constant curing temperature. The constant-temperature lower mold die 420 can be insulated to minimize heat loss. The resin 45 has a period of latency and the resin 45 may be configured to cure within a predetermined curing time at the constant curing temperature. [0078] The system 10 can further include a post-curing station 600 to receive the cured composite part 50 from the cured-part transfer station 500 and to further process the cured composite part 50.

[0079] FIGS. 3-4 and 5A-5B illustrate a ply-cutting station 100 according to implementations of the present disclosure. As illustrated in FIGS. 3-4 and 5A-5B, a ply-cutting station 100 can include a raw-material dispenser 101, a ply-cutting table 103, and a cutter 104.

[0080] The raw-material dispenser 101 can supply raw material 20 to the ply-cutting table 103. For example, the raw-material dispenser 101 can include one or more rolls of raw material 102 configured to automatically advance raw material 20 from the raw-material dispenser 101 to the ply-cutting table 103, so that the new rolls of raw material 102 can be continuously loaded on the raw-material dispenser 101 as the raw material 20 is being consumed. Advancing the raw material 20 from the raw-material dispenser 101 to the ply- cutting table 103 can include pulling the raw material from the rolls of raw material 102 onto flat sheets of raw material 20 on the ply-cutting table 103 via an automated material spreader (not illustrated).

[0081] As described above, the raw material 20 can include non-crimp carbon-fiber-based fabrics, such as dry multiaxial non-crimped fabric (MA-NCF). The raw material 20 can include from 1 to 8 plies of a fibrous material with a per-ply areal weight from about 50 gsm to about 400 gsm. In some implementations, the angles of the plies of fibrous material can be rotated. For example, the angles of the plies can be about -60 degrees, about -45 degrees, about -30 degrees, about 0 degrees, about +30 degrees, about +45 degrees, about +60 degrees, about 90 degrees, or any combination thereof, with respect to each other. MA-NCF can have plies of varying orientations knitted together by knit thread. Accordingly, in one implementation, the raw-material dispenser 101 supplies dry MA-NCF comprising about 4 plies of oriented fibrous material to the ply-cutting table 103. While not wanting to be limited by theory, using more plies within the raw material 20 reduces the number of flat patterns 30 required, saving cycle time, and increasing an overall rate of production.

[0082] Cutting the raw material 20 into flat patterns 30 can include cutting flat sheets of raw material 20 into the flat patterns 30 using a cutter 104. The cutter 104 can include a blade, an ultrasonic cutter, a laser, or other means known in the art for cutting non-crimp carbon fiberbased fabrics, such as dry multiaxial non-crimped fabric (MA-NCF). Two or more flat patterns 30 can be cut from the same piece of raw material 20. Each flat pattern 30 can be rotated to minimize wasted raw material 20. For example, the flat patterns can be rotated 180 degrees from each other, or can be cut in complementary pairs. While not wanting to be limited by theory, using complementary flat patterns allows higher usage of raw material 20 and decrease buy-to-fly ratio.

[0083] For smaller flat patterns 30, a plurality of flat patterns 30 can be cut. For example, a plurality of flat patterns 30 can be cut optimally arranged together for improved material utilization. Flat patterns 30 are best fit into the raw material 20 while considering the material placement sequence to create preforms 40. For methods with smaller flat patterns 30, flat patterns 30 can be stacked into a holding carriage or drawer (not illustrated), until needed or on a staging area 105 of the ply-cutting table 103.

[0084] The ply-cutting table 103 may include a staging area 105. The staging area 105 may be configured to receive the flat patterns 30 cut on the ply-cutting table 103. The staging area 105 can allow for sorting and parallel processing of multiple flat patterns 30.

[0085] The ply-cutting station 100 can include one or more raw-material dispensers 101, ply- cutting tables 103, staging areas 105, and cutters 104. For example, in some implementations, there can be one staging area 105 serving each ply-cutting table 103. In one implementation, for spar forming for example, as illustrated in FIG. 5A, there is one staging area 105 for each ply-cutting table 103a, 103b, and 103c. The flat patterns 30 are advanced from the ply-cutting tables 103 to the staging areas 105 simultaneously as raw material 20 is advanced from the raw-material dispenser 101 onto the ply-cutting tables 103. Each ply-cutting table 103a, 103b, and 103c can have its own raw-material dispenser 101 where rolls of raw material 102 can be laid on to each ply-cutting table 103a, 103b, and 103c simultaneously.

[0086] FIG. 5B illustrates another implementation of a ply cutting station 100. For example, FIG. 5B illustrates a stabilizer forming station. As illustrated in FIG. 5B, a ply cutting station 100 can include one or more raw-material dispensers 101, ply-cutting tables 103a and 103b, staging areas 105, and cutters 104. As illustrated in FIG. 5B, the flat patterns 30 are advanced from the ply-cutting tables 103 to the staging areas 105 simultaneously as raw material 20 is advanced from the raw-material dispenser 101 onto the ply-cutting tables 103. Each ply-cutting table 103a and 103b can have its own raw-material dispenser 101 where rolls of raw material 102 can be laid on to each ply-cutting table 103a and 103b simultaneously.

[0087] As illustrated in FIG. 4, the ply-cutting station 100 can also include a material conveyor 106. For example, the ply-cutting table 103 can include a material conveyor 106. The material conveyor 106 can advance the flat patterns 30 from the ply-cutting table 103 to a staging area 105. The material conveyor 106 can simultaneously advance raw material 20 from the raw-material dispenser 101 onto the ply-cutting table 103 as it advances the flat patterns 30 from the ply-cutting table 103 to the staging area 105. The same material conveyor 106 can be used to advance both the flat patterns 30 and the raw material 20, albeit in different locations on the material conveyor 106.

[0088] Accordingly, in one implementation, the ply-cutting station 100 includes a ply-cutting table 103, a raw-material dispenser 101 to supply raw material 20 to the ply-cutting table 103, and a cutter 104 to cut the raw material 20 on the ply-cutting table 103 into flat patterns 30, wherein the raw material 20 includes from 1 to 8 plies of a fibrous material with a per-ply areal weight from about 50 gsm to about 400 gsm. The ply-cutting table 103 can include a staging area 105 and a material conveyor 106 configured to simultaneously advance raw material 20 from the raw-material dispenser 101 onto the ply-cutting table 103 and the flat patterns 30 to the staging area 105. [0089] FIGS. 6-13 illustrate a picking-and-placing station according to implementations of the present disclosure. The integrated system 10 can include two or more picking-and- placing stations 200. As illustrated in FIGS. 6-13, a picking-and-placing station 200 can include a pick-and-place end effector 210 and an assembly jig 230. The pick-and-place end effector 210 can pick flat patterns 30 from the ply-cutting table 103 and form the flat patterns 30 around the assembly jig 230 to create a preform 40. Each preform 40 can be formed of one or more flat patterns 30 placed on the assembly jig 230. Alternatively, a stack of flat patterns 30 may be placed on the assembly jig 230.

[0090] The picking-and-placing station 200 can include a plurality of pick-and-place end effectors 210 and a plurality of assembly jigs 230. For example, as illustrated in FIGS. 5-8, the picking-and-placing station 200 can include full-length pick-and-place end effectors 215 for picking, forming or placing large flat patterns 30 and preforms 40 and smaller pick-and- place end effectors 216 for picking or placing small flat patterns 30 and preforms 40. As illustrated in FIGS. 5-8, the plurality of pick-and-place end effectors 210 can include a full- length pick-and-place end effector 215 and one or more smaller pick-and-place end effectors 216. The full-length pick-and-place end effector 215 can be mounted on a gantry 220 configured to raise and lower the full-length pick-and-place end effector 215 over the ply- cutting table 103 and the assembly jig 230. The smaller pick-and-place end effectors 216 can be mounted on a movable pick-and-place robot 221 configured to raise and lower the full- length pick-and-place end effector 215 over the ply-cutting table 103 and the assembly jig 230. The pick-and-place robot 221 can use a wheel-based system or a rail-based system to move between the ply-cutting table 103 and the assembly jig 230.

[0091] The pick-and-place end effectors 210 can include 3D shaping of the raw material. For example, as illustrated in FIG. 9, the pick-and-place end effectors 210 can include a plurality of actuated grippers 213 extending downward from a bottom surface 212 of the pick-and- place end effectors 210. The actuated grippers 213 can include a plurality of vacuum heads configured to pick up and transfer the flat patterns 30 by applying a negative pressure differential. The actuated grippers 213 can also include a plurality of needle grippers with barbs configured to puncture the flat patterns 30 and then hold them for pick-up and transfer. In some implementations, the actuated grippers 213 include both a plurality of vacuum heads and a plurality of needle grippers.

[0092] As illustrated in FIGS. 9-13, a pick-and-place end effector 210 can pick up flat patterns 30 from the ply-cutting table 103 and then lower the flat patterns 30 on an assembly jig 230, where the geometry of the pick-and-place end effector 210 and/or the assembly jig 230 deforms the flat patterns 30 to a desired topology to form a particular preform 40. For example, as illustrated in FIGS. 9-10, the pick-and-place end effector 210 can be lowered over the ply-cutting table 103 to be in close proximity with a flat pattern 30. The pick-and- place end effector 210 can then pick up the flat pattern 30 via the actuated grippers 213 and raise to remove the flat pattern 30 from the ply-cutting table 103 as illustrated in FIG. 10. The pick-and-place end effector 210 can then shape the flat pattern 30 into the lofted shape and move over to the assembly jig 230, for example via the gantry 220, and lowered to place the shaped flat pattern 30 on the assembly jig 230 as illustrated in FIGS. 11-12. The pick- and-place end effector 210 can repeat this process to place a plurality of flat patterns 30 on the assembly jig 230. Alternatively, the pick-and-place end effector 210 can pick a stack of pre-combined flat patterns 30 and place the stack of flat patterns 30 on the assembly jig 230. [0093] While FIGS. 9-13 illustrate forming a flat preform 40 on an assembly jig 230, the present disclosure is not limited thereto. In other implementations, forming the flat patterns 30 around the assembly jig 230 to create a preform 40 can include other methods known in the art for creating preforms. For example, a stringer preform can be formed to a desired loft using an inner mold line and/or a stringer loft former.

[0094] The assembly jig 230 can include constraints, such as aligning pins, to prevent movement of the assembly jig 230. The assembly jig 230 can also include metrology indicators, such as position indicators, alignment pins, guides, or the like, to ensure accurate positioning of the flat patterns 30 on the assembly jig 230.

[0095] As illustrated in FIGS. 11-12, the actuated grippers 213 can maintain a hold of the flat patterns 30 to secure the flat pattern 30 to the assembly jig 230.

[0096] As illustrated in FIG. 11, in one implementation, the actuated grippers 213 can impart a preferred shape to the flat pattern 30 before placing the flat pattern 30 on the assembly jig 230.

[0097] As illustrated in FIG. 12, the pick-and-place end effector 210 can apply a pressure to the flat patterns 30 once placed on the assembly jig 230 to create a preform 40.

[0098] As illustrated in FIG. 13, after forming or placing the flat pattern 30 on the assembly jig 230, the pick-and-place end effector 210 can be removed leaving a formed preform 40 on the assembly jig 230.

[0099] In some implementations, after the pick-and-place end effector 210 is removed, the newly formed preform 40 can be inspected for defects. For example, as illustrated in FIGS. 7-8, the picking-and-placing station 200 can include a tracked inspection robot 240. The inspection robot 240 can use automated visual-detection algorithms to detect defects in the newly formed preform 40. When a defect is found and classified as something that can be autonomously fixed, the pick-and-place robot 221 can attempt to fix the defect. In other implementations, if the defect requires human intervention, the pick-and-place robot 221 can remove the defective preform 40 to an inspection station (not illustrated). In situ inspection of each formed preform 40 enables non-conformances to be detected and corrected during fabrication of the composite part instead of retroactively fixing or accepting a defect in the finished part or rejecting that finished part.

[00100] Accordingly, the picking-and-placing station 200 can include a pick-and-place end effector 210 to pick the flat patterns 30 from the ply-cutting table 103, and an assembly jig 230 to receive the flat patterns 30 picked by the pick-and-place end effector 210, wherein pick-and-place end effector 210 applies a pressure to secure the flat patterns 30 and/or form at least one of the at least two complementary preforms 40.

[00101] FIGS. 14-15, 16A-16D, and 17A-17E illustrate a preform-transfer station according to implementations of the present disclosure. As illustrated in FIG. 14, a preformtransfer station 300 can include a lifting structure 301 to remove the two or more preforms 40 from their respective assembly jigs 230 and to place the two or more preforms 40 in the constant-temperature lower mold die 420. As described above, the constant-temperature lower mold die 420 is at the curing temperature when the two or more preforms 40 are placed in the constant-temperature lower mold die 420.

[00102] As illustrated in FIGS. 16A-16D, the assembly jig 230 can be implemented as a stringer or stiffener assembly jig 230 configured to hold one type of complementary preform 40, such as a stringer preform 43. As illustrated in FIGS. 17A-17-E, the assembly jig 230 can be implemented as a skin assembly jig 230 configured to hold another type of complementary preform 40, such as a stabilizer skin preform 42. The assembly jig 230 can shuttle from the picking-and-placing station 200 to the preform-transfer station 300. The assembly jig 230 can be disposed on a conveyor 302, and the conveyor 302 can be configured to shuttle from the picking-and-placing station 200 to the preform-transfer station 300 to place the assembly jig 230 under the lifting structure 301. The metrology indicators of the assembly jig 230 can be used to ensure accurate positioning of the assembly jig 230 at each location.

[00103] Similarly, the constant-temperature lower mold die 420 can also be configured to shuttle from the infusing-and-curing station 400 to the preform-transfer station 300. For example, as illustrated in FIGS. 15, 16A-16D, 17A-17E, and 26, the constant-temperature lower mold die 420 can be disposed on a conveyor 302, and the conveyor 302 can be configured to shuttle the constant-temperature lower mold die 420 between the infusing-and- curing station 400 and the preform-transfer station 300 to place the constant-temperature lower mold die 420 under the lifting structure 301. In addition, the conveyor 302 can also be configured to shuttle the constant-temperature lower mold die 420 between the infusing-and- curing station 400 and the cured-part transfer station 500. The constant-temperature lower mold die 420 can include metrology indicators, such as position indicators, alignment pins, guides, or the like, to ensure accurate positioning of the constant-temperature lower mold die 420 at each location.

[00104] The constant-temperature lower mold die 420 can be configured for clearance. For example, as illustrated in FIGS. 19, 23A-23F, and 26, the constant-temperature lower mold die 420 can have a height “h” configured to allow the constant-temperature lower mold die 420 to shuttle under the lifting structure 301 of the preform-transfer station 300 and the constant-temperature upper mold die 410 of the infusion-and-curing station 400.

[00105] FIG. 26 illustrates a shuttling system according to implementations of the present disclosure. As illustrated in FIG. 26, the constant-temperature lower mold die 420 can be configured for clearance and movement between the preform-transfer station 300, the infusion-and-curing station 400, and the cured-part transfer station 500. As illustrated in FIG. 26, the constant-temperature lower mold die 420 can be disposed on a conveyor 302 configured to shuttle the constant-temperature lower mold die 420 between the preformtransfer station 300, the infusing-and-curing station 400, and the cured-part transfer station 500. The constant-temperature lower mold die 420 can have a height “h” configured to allow the constant-temperature lower mold die 420 to shuttle under the lifting structure 301 of the preform-transfer station 300, the constant-temperature upper mold die 410 of the infusion- and-curing station 400, and the handling jig 510 of the cured-part transfer station 500.

[00106] A preform-transfer station 300 can be served by two or more picking-and- placing stations 200. For example, as illustrated in FIG. 15, a first picking-and-placing station 201 and a second picking-and-placing stations 202 can deliver two or more preforms 40 placed on their respective assembly jigs 230. As illustrated in FIG. 15, the first picking- and-placing station 201 can be configured to create horizontal stabilizer skin preforms 42 and the second picking-and-placing station 202 can be configured to create stringer preforms 43. Material conveyors 106 can shuttle assembly jigs 230 from the first and second picking-and- placing stations 200, respectively, to the preform-transfer station 300.

[00107] As illustrated in FIGS. 16A-16D and 17A-17E, the lifting structure 301 is configured to lift the two or more preforms 40 from their respective assembly jigs 230 and lower the two or more preforms 40 into the constant-temperature lower mold die 420. For example, the lifting structure 301 can include a plurality of attachment points 311. The lifting structure 301 can lower the plurality of attachment points 311 to an assembly jig 230, such that, when attached, the plurality of attachment points 311 can lift the two or more preforms 40. The lifting structure 301 can lower a preform 40 into close proximity to the constant-temperature lower mold die 420, such that, when the preform 40 is released, the preform 40 is placed at a desired position within the constant-temperature lower mold die 420. For example, the lifting structure 301 can place stringer preforms 43 in the one or more channels 422 and a stabilizer skin preform 42 in a cavity 421 such that the stringer preforms 43 are in the exact position relative to the stabilizer skin preform 42 within the constanttemperature lower mold die 420.

[00108] The constant-temperature lower mold die 420 is configured to accommodate the two or more preforms 40 in a predetermined configuration relative to each. For example, the constant-temperature lower mold die 420 can include one or more cavities 421 and one or more channels 422 configured to define the final position of the two or more preforms 40 in the cured composite part 50. As illustrated in FIGS. 16A-16D and 17A-17E, the constanttemperature lower mold die 420 can include a cavity 421 configured to accommodate a horizontal stabilizer skin preform 42 and/or one or more channels 422 configured to accommodate one or more stringer preforms 43 in a relative position to the horizontal stabilizer skin preform 42. For example, as illustrated in FIG. 16A, a lifting structure 301 can lower a plurality of attachment points 311 to attach to one or more stringer preforms 43 on an assembly jig 230. As illustrated in FIG. 16B, the lifting structure 301 can then raise the plurality of attachment points 311 to remove the one or more stringer preforms 43 from the assembly jig 230. As illustrated in FIG. 16C, the lifting structure 301 can then be positioned over the constant-temperature lower mold die 420 and the plurality of attachment points 311 can be lowered to place the one or more stringer preforms 43 within the constant-temperature lower mold die 420. For example, within the one or more channels 422. As illustrated in FIG. 16D, the lifting structure 301 can then raise the plurality of attachment points 311 to leave the one or more stringer preforms 43 placed within the one or more channels 422 of the constant-temperature lower mold die 420. The lifting structure 301 can then be position over another assembly jig 230 to pick up a complementary preform 40. For example, as illustrated in FIG. 17A, the lifting structure 301 can be positioned over an assembly jig 230 holding a horizontal stabilizer skin preform 42. The lifting structure 301 can lower the plurality of attachment points 311 to attach to the horizontal stabilizer skin preform 42. As illustrated in FIG. 17B, the lifting structure 301 can then raise the plurality of attachment points 311 to remove the horizontal stabilizer skin preform 42 from the assembly jig 230. As illustrated in FIG. 17C, the lifting structure 301 can then be positioned over the constant-temperature lower mold die 420 and the plurality of attachment points 311 can be lowered to place the horizontal stabilizer skin preform 42 within the constant-temperature lower mold die 420. For example, placing the horizontal stabilizer skin preform 42 within the cavity 421. As illustrated in FIG. 17D, the lifting structure 301 can then raise the plurality of attachment points 311 to leave the one or more stringer preforms 43 placed in the exact position within the one or more channels 422 relative to the horizontal stabilizer skin preform 42 with the cavity 421 of the constant-temperature lower mold die 420.

[00109] Accordingly, as illustrated in FIG. 17E, the preform-transfer station 300 can include a lifting structure 301 to place two or more preforms 40 in the constant-temperature lower mold die 420, wherein the constant-temperature lower mold die 420 is at the curing temperature when the two or more preforms 40 are placed in the constant-temperature lower mold die 420. For example, the constant-temperature mold can include one or more cavities 421 and channels 422 configured to hold one or more stringer preforms 43 in a relative position to the horizontal stabilizer skin preform 42.

[00110] The integrated system 10 can further include one or more conveyors 302, wherein the one or more conveyors 302 shuttle the respective assembly jigs 230 from the picking-and-placing stations 200 to the preform-transfer station 300 and shuttle the constanttemperature lower mold die 420 from the preform-transfer station 300 to the infusing-and- curing station 400.

[00111] FIGS. 18-20 and 21A-21F illustrate an infusion-and-curing station according to implementations of the present disclosure. As illustrated in FIGS. 18-20 and 21A-21F, an infusion-and-curing station 400 can include a press 450, a constant-temperature upper mold die 410, the constant-temperature lower mold die 420, and a resin-infusion system 430. [00112] As described above, the constant-temperature lower mold die 420 can be configured to shuttle between the infusing-and-curing station 400 and the preform-transfer station 300 and/or between the infusing-and-curing station 400 and the cured-part transfer station 500. The constant-temperature lower mold die 420 can be maintained at a constant curing temperature and not allowed to cool to ambient temperate. As described above, the constant curing temperature can be a temperature from about 100°C to about 200°C. The constant-temperature lower mold die 420 can maintain the two or more preforms 40 at the curing temperature. [00113] The constant-temperature lower mold die 420 can be maintained at the constant curing temperature by electrical or resistive heating, inductive heating, liquid heating, steam heating, or the like. In some implementations, a mass and heat capacity of the constant-temperature lower mold die 420 are configured to prevent large temperature fluctuations due to an external environment or any exothermic or endothermic reactions. For example, the constant-temperature lower mold die 420 can comprise materials, such as steel, aluminum, Invar, and the like, selected for their high heat capacity. Similarly, a large mass can help maintain a constant temperature by acting as a heat sink to control exothermic reactions as well maintaining temperature during ambient losses.

[00114] As illustrated in FIGS. 19-20 and 21 A-21F, after the two or more preforms 40 are placed in the constant-temperature lower mold die 420, a conveyor 302 can shuttle the constant-temperature lower mold die 420 from the preform-transfer station 300 to the infusion-and-curing station 400. The constant-temperature lower mold die 420 can be placed below the constant-temperature upper mold die 410. The constant-temperature lower mold die 420 can be constrained to a determined position below the constant-temperature upper mold die 410 using metrology indicators.

[00115] The constant-temperature upper mold die 410 can be placed within the press 450, and the press 450 can be configured to lower the constant-temperature upper mold die 410 against the constant-temperature lower mold die 420. When pressed together, the constant-temperature upper mold die 410 and the constant-temperature lower mold die 420 can define a cavity corresponding to an external envelop of the final cured composite part 50. In some implementations, when pressed together, the constant-temperature upper mold die 410 and the constant-temperature lower mold die 420 can define a sealed gap 440 to infuse the two or more preforms 40 with resin 45 and to cure a combined resin-infused preform 41 to form a cured composite part 50.

[00116] The constant-temperature upper mold die 410 can be maintained at a constant curing temperature and not allowed to cool to ambient temperate. The constant-temperature upper mold die 410 can also be insulated to minimize heat loss. As described above, the constant curing temperature can be a temperature from about 100°C to about 200°C. The constant-temperature upper mold die 410, together with the constant-temperature lower mold die 420, can maintain the two or more preforms 40, the combined resin-infused preform 41, and/or the resin 45 at the curing temperature when pressed together. The constanttemperature upper mold die 410 can be maintained at the constant curing temperature by electrical or resistive heating, inductive heating, liquid heating, steam heating, or the like. In some implementations, a mass and heat capacity of the constant-temperature upper mold die 410 are configured to prevent large temperature fluctuations due to an external environment or any exothermic or endothermic reactions. For example, the constant-temperature upper mold die 410 can comprise materials, such as metal, selected for their high heat capacity. [00117] The press 450 can lower the constant-temperature upper mold die 410 to two or more positions against the constant-temperature lower mold die 420. For example, as illustrated in FIG. 21C, in a first position 441, the constant- temperature upper and lower mold dies 410-420 can define a sealed gap 440. The sealed gap 440 can create a volume equivalent to an amount of resin 45 sufficient to infuse the two or more preforms 40. For example, as illustrated in FIGS. 21 A, the constant-temperature lower mold die 420 can include seals 425 to seal the constant-temperature upper and lower mold dies 410-420 when pressed together in the first position 441 to form the sealed gap 440. The seals 425 can include known sealing structures, such as gaskets, O-rings, and the like. The seals 425 can also seal the constanttemperature upper and lower mold dies 410-420 at other positions, for example in the second position 442 and the third position 443 as described below.

[00118] As illustrated in FIG. 21D, the resin-infusion system 430 can inject a resin 45 into the sealed gap 440. The resin-infusion system 430 can be configured to mix the components of the resin 45. For example, the resin 45 can include a resin component and a hardener component which are mixed at the resin-infusion system 430 before being injected into the sealed gap 440. The resin-infusion system 430 can include self-cleaning mixing heads. While not wanting to be limited by theory, mixing the resin near the sealed gap 440 reduces the amount of cleanup of the system after curing of the two or more preforms 40. For example, by minimizing an amount of catalyzed resin in any resin transfer lines.

[00119] The resin-infusion system 430 can also be configured to degas the components of the resin 45. For example, the resin-infusion system 430 can remove moisture and air from the resin 45 before being injected into the sealed gap 440. The resin-infusion system 430 can also be configured to pre-heat the components of the resin 45. For example, the resin-infusion system 430 can be configured to raise a temperature of the resin 45 close to the constant curing temperature before being injected into the sealed gap 440 or the resininfusion system 430 can inject the resin 45 at the constant curing temperature.

[00120] In some implementation, the infusion-and-curing station 400 can further include a vacuum system 460. The vacuum system 460 can be configured to evacuate the sealed gap 440. For example, the vacuum system 460 can create a vacuum within the sealed gap 440 before the resin-infusion system 430 injects a resin 45 into the sealed gap 440. In addition, an integrity of the vacuum within the sealed gap 440 can be checked to verify the integrity of the sealed gap 440 before the resin-infusion system 430 injects a resin 45 into the sealed gap 440. Accordingly, injecting the resin into the gap of the sealed cavity to infuse the two or more preforms for the predetermined infusion time in method 800 can include evacuating the sealed cavity and checking an integrity of a vacuum within the sealed cavity before injecting the resin into the gap of the sealed cavity.

[00121] The resin-infusion system 430 can inject the resin 45 into the sealed gap 440 for a predetermined infusion time. For example, the predetermined infusion time can be about 1 hour or less, about 45 minutes or less, about 30 minutes or less, about 25 minutes or less, about 20 minutes or less, about 15 minutes or less, about 10 minutes or less, or about 5 minutes or less. The infusion time can also be from about 5 minutes to about 1 hour, or the infusion time can be about 30 minutes or less. In some implementations, the resin 45 is injected into the sealed gap 440 for less than the predetermined infusion time. For example, the predetermined infusion time can be about 1 hour or less, and the resin-infusion system 430 can inject the resin 45 into the sealed gap 440 for about 10 minutes or less. The predetermined infusion time and/or the time the resin 45 is injected into the sealed gap 440 can be selected according to the constant curing temperature selected, the temperature of the constant-temperature upper and lower mold dies 410-420, the viscosity of the resin 45, and/or a permeability of the two or more preforms 40.

[00122] The resin-infusion system 430 can inject the resin 45 into the sealed gap 440 at a pressure from about 5 psig to about 40 psig. For example, the resin-infusion system 430 can inject the resin 45 into the sealed gap 440 at a pressure from about 5 psig to about 15 psig, from about 20 psig to about 25 psig, or from about 30 psig to about 35 psig. In one implementation, the resin-infusion system 430 can inject the resin 45 into the sealed gap 440 at a pressure of about 25 psig.

[00123] In some implementations, a vacuum can be used to inject the resin 45 at a predetermined pressure. For example, the vacuum system 460 can be used to create a partial vacuum within the sealed gap 440 while the resin-infusion system 430 injects the resin 45 at atmospheric pressure to create an effective injection pressure for the resin 45 of from about 5 psig to about 15 psig. An effective injection pressure of about 15 psig can be realized by creating a full or partial vacuum within the sealed gap 440 and injecting the resin 45 at a pressure above atmospheric pressure.

[00124] As described above, the resin 45 must have a period of latency. The period of latency allows time for the resin 45 to fully infuse the two or more preforms 40 before a viscosity of the resin 45 begins to rise rapidly, as the components of the resin 45 crosslink. For example, the resin 45 can maintain a viscosity of about 100 cP or less for the predetermined infusion time, a viscosity of about 50 cP or less for the predetermined infusion time, a viscosity of about 25 cP or less for the predetermined infusion time, or a viscosity of about 20 cP or less for the predetermined infusion time.

[00125] As illustrated in FIG. 2 IE, in a second position 442, the constant-temperature upper and lower mold dies 410-420 can define a cavity corresponding to final dimensions of the cured composite part 50. Lowering the constant-temperature upper mold die 410 to the second position 442 also helps infuse the resin 45 in the sealed gap 440 into the two or more preforms 40 to create a combined resin-infused preform 41. For example, the lowering of the constant-temperature upper mold die 410 helps the resin 45 flow through an entire thickness of the two or more preforms 40 to fully infuse the two or more preforms 40 with resin 45.

[00126] The infusion-and-curing station 400 can remove contaminants, such as air and moisture, from the two or more preforms 40 before infusing the two or more preforms 40 with the resin 45. For example, as illustrated in FIG. 21B, the press 450 can lower the constant-temperature upper mold die 410 to a third position 443 before infusing the two or more preforms 40 with the resin 45. The third position 443 can be lower than the second position 442. For example, the third position 443 can place the constant-temperature upper mold die 410 in direct contact with the at least one of the two or more preforms 40 on the constant-temperature lower mold die 420, defining a cavity smaller than the final dimensions of the cured composite part 50. As illustrated in FIG. 2 IB, the vacuum system 460 can apply a vacuum to the two or more preforms 40 while the two or more preforms 40 are maintained at the curing temperature by the constant-temperature upper and lower mold dies 410 and 420 at the third position 443. The vacuum system 460 can apply a vacuum for a period of about 10 minutes to about 1 hour, while the two or more preforms 40 are maintained at the curing temperature, to evacuate from the two or more preforms 40 contaminants, such as air and moisture, that may affect the material quality of the cured composite part 50.

[00127] After the two or more preforms 40 have been infused with resin 45 to create a combined resin-infused preform 41, the infusion-and-curing station 400 cures the resin- infused preform 41 to create a cured composite part 50. For example, the constanttemperature upper mold die 410 can apply a curing pressure to the combined resin-infused preform 41 while the constant-temperature upper and lower mold dies 410 and 420 maintain the resin-infused preform 41 at the curing temperature. The combined resin-infused preform 41 can include two or more complementary preforms 40. The constant-temperature upper mold die 410 can apply the curing pressure for a period of between about 15 minutes to about 3 hours. For example, the constant-temperature upper mold die 410 can apply a curing pressure for about 15 minutes or less, for about 30 minutes or less, for about 45 minutes or less, for about 60 minutes or less, for about 1 hour or less, for about 2 hours or less, or for about 3 hours or less. In one implementation, the constant-temperature upper mold die 410 applies the curing pressure for about 90 minutes. The constant-temperature upper mold die 410 can apply a curing pressure from about 5 psig to about 150 psig. The constanttemperature upper mold die 410 can apply the curing pressure at the second position 442. [00128] After the combined resin-infused preform 41 has been cured to create the cured composite part 50, the cured composite part 50 can be released from at least one of the constant-temperature upper mold die 410 and the constant-temperature lower mold die 420. For example, as illustrated in FIG. 2 IF, at least one of the constant-temperature upper mold die 410 and the constant-temperature lower mold die 420 can include extractors 470 configured to release the cured composite part 50 from the constant-temperature upper mold die 410 and/or the constant-temperature lower mold die 420. The extractors 470 can include pins that when retracted are flush with the cavity surface of the constant-temperature upper mold die 410 and/or the constant-temperature lower mold die 420 and when activated extend from the mold die to release the cured composite part 50.

[00129] The infusion-and-curing station 400 illustrated in FIGS. 18-20 and 21A-21F has been described with respect to a constant-temperature mold 401 including a constanttemperature upper mold die 410 and a constant-temperature lower mold die 420. The constant-temperature mold 401 can be insulated to reduce an amount of heat loss. However, the invention of the present disclosure is not limited thereto, and other configurations for a constant-temperature mold 401 can be used that are configured to maintain the two or more preforms 40, the combined resin-infused preform 41, and/or the resin 45 at the curing temperature. However, while not wanting to be limited by theory, by using double-sided- matched-metal die tooling, such as the constant-temperature upper and lower mold dies 410- 420, dimensional control can be maintained from part-to-part, reducing, and possibly, eliminating the need for shims during the assembly of the constant-temperature mold 401. In some implementations, the constant-temperature upper and lower mold dies 410-420 do not use at least one of shims, flow media, peel plies, chromate tape, separator plies, or vacuum bagging to form the cured composite part 50. In addition, since the mold dies are kept at a constant curing temperature, lower-cost materials, such as steel, can be used and expensive low-thermal-expansion materials, such as Invar, can be avoided. Another advantage of the constant-temperature upper and lower mold dies 410-420 is the lack of thermal growth or shrinkage of the tooling during processing, allowing better dimensional control of the composite part. In addition, temperature ramps can be minimized and nearly or completely eliminated throughout the entire duration of loading the two or more preforms 40, creating the combined resin-infused preform 41, and curing the combined resin-infused preform 41 to create the cured composite part 50 because the constant-temperature upper and lower mold dies 410-420 are kept at a constant curing temperature. In addition, the constant-temperature upper and lower mold dies 410-420 eliminates the need for autoclaves to apply pressure to the combined resin-infused preform 41 for curing as well as consumables related to autoclaves, such as liquid nitrogen. Maintaining the constant-temperature upper and lower mold dies 410-420 at the constant curing temperature also consumes less energy versus heating and cooling a large autoclave each cycle.

[00130] Accordingly, the infusing-and-curing station 400 can include a constanttemperature upper mold die 410, a constant-temperature lower mold die 420, and a resininfusion system 430. The constant-temperature upper mold die 410 can be configured to press against the constant-temperature lower mold die 420. In a first position 441, the constant-temperature upper mold die 410 defines a sealed gap 440 having a volume equivalent to an amount of resin 45 sufficient to infuse the two or more preforms 40. In a second position 442, the constant-temperature upper mold die 410 defines a cavity corresponding to final dimensions of the cured composite part 50. The constant-temperature mold can include one or more cavities 421 and one or more channels 422 configured to hold the two or more preforms 40 in a position relative to each other. The resin-infusion system 430 can inject the resin 45 into the sealed gap 440 for the predetermined infusion time to form a combined resin-infused preform 41. The two or more preforms 40 can be complementary, and the combined resin-infused preform 41 can include two or more complementary preforms 40. The constant-temperature upper mold die 410 can apply a curing pressure to the combined resin-infused preform 41 to form a cured composite part 50. The constant-temperature upper mold die 410 and the constant-temperature lower mold die 420 can be at the curing temperature when the constant-temperature upper mold die 410 is in the first position 441 and the second position 442. The resin-infusion system 430 can inject the resin 45 into the sealed gap 440 at a pressure from about 5 psig to about 40 psig, and the constant-temperature upper mold die 410 can apply a curing pressure from about 5 psig to about 150 psig. The infusing-and-curing station 400 can further include a vacuum system 460, wherein the vacuum system 460 is configured to evacuate the sealed gap 440 before the resin-infusion system 430 injects the resin 45 into the sealed gap 440.

[00131] FIGS. 22 and 23A-23F illustrate a cured-part transfer station according to implementations of the present disclosure. As illustrated in FIGS. 22 and 23A-23F, a cured- part transfer station 500 can include a handling jig 510 and a post-cure fixture 550. The handling jig 510 can be configured to remove the cured composite part 50 from the constanttemperature lower mold die 420. The post-cure fixture 550 can be configured to receive the cured composite part 50 from the handling jig 510.

[00132] As described above, the constant-temperature lower mold die 420 can be configured to shuttle between the infusing-and-curing station 400 and the cured-part transfer station 500. Accordingly, the constant-temperature lower mold die 420 can have a height “h” configured to allow the constant-temperature lower mold die 420 to shuttle under the handling jig 510 of the cured-part transfer station 500.

[00133] As illustrated in FIGS. 22 and 23A-23F, the handling jig 510 can be mounted on a transport system, such as an overhead lifting fixture 520, configured to move the handling jig 510 from a position above the constant-temperature lower mold die 420 to a position above the post-cure fixture 550.

[00134] As illustrated in FIGS. 23A-23C, the overhead lifting fixture 520 can lower the handling jig 510 to contact the cured composite part 50 in the constant-temperature lower mold die 420. The handling jig 510 can be configured to attach to the cured composite part 50 and the overhead lifting fixture 520 can lift the handling jig 510 to remove the cured composite part 50 from the constant-temperature lower mold die 420. For example, the handling jig 510 can include a vacuum system 560 (not illustrated), and the vacuum system 560 can apply a vacuum to a surface of the cured composite part 50 to attach to the cured composite part 50.

[00135] As illustrated in FIGS. 23D-23F, the overhead lifting fixture 520 can then move the handling jig 510 to a position above the post-cure fixture 550, and then lower the handling jig 510 to release the cured composite part 50 on the post-cure fixture 550. For example, the handling jig 510 can release the cured composite part 50 by positioning it in close proximity to the post-cure fixture 550 and releasing a vacuum created by the vacuum system 560.

[00136] In some implementations, after the cured composite part 50 is removed from the constant-temperature lower mold die 420, the constant-temperature lower mold die 420 can be inspected and cleaned as needed and shuttled back to the infusing-and-curing station 400 to receive the next set of two or more preforms 40.

[00137] The post-cure fixture 550 can be a freestanding post-cure fixture. That is, the cured composite part 50 can be sufficiently cured to maintain a freestanding shape once placed on the post-cure fixture without use of additional structural supports.

[00138] The post-cure fixture 550 can be configured to move between the cured-part transfer station 500 and the post-curing station 600. For example, as illustrated in FIGS. 23D-23F, the post-cure fixture 550 can be mounted on rails or wheels 555 configured to move the post-cure fixture 550 between the cured-part transfer station 500 and the postcuring station 600.

[00139] In some implementations, the cured composite part 50 is a finished and completed part. However, in other implementations, the cured composite part 50 can undergo post-processing. For example, as described below, the cured composite part 50 can undergo further curing at a post-processing temperature higher than the curing temperature. [00140] In other implementations, the cured composite part 50 can undergo further inspection and post-processing. Further inspection and post-processing can include flipping the cured composite part 50, machining panels into the cured composite part 50, rotating the cured composite part 50 to a vertical position, washing the cured composite part 50, non- destructively inspecting the cured composite part 50, drying the cured composite part 50, preparing outer surfaces of the cured composite part 50 for painting, and painting the cured composite part 50.

[00141] FIGS. 24-25 illustrate a post-curing station according to implementations of the present disclosure. As illustrated in FIGS. 24-25, a post-curing station 600 can include an oven 610. The post-curing station 600 can be configured to receive the cured composite part 50 from the cured-part transfer station 500 and to further process the cured composite part 50. For example, as described above, the post-cure fixture 550 can be configured to move the cured composite part 50 to the post-curing station 600. As illustrated in FIG. 24, the postcure fixture 550 can be placed within the oven 610 to further process the cured composite part 50. For example, the oven 610 can further cure the cured composite part 50 at a postprocessing temperature. The post-processing temperature can be higher than the constant curing temperature. For example, the post-processing temperature can be from about 20°C to about 50°C higher than the constant curing temperature. The oven 610 can heat the cured composite part 50 at a post-processing temperature from about 10°C to about 200°C. For example, the oven 610 can heat the cured composite part 50 at a post-processing temperature of about 110°C, of about 115°C, of about 116°C, of about 130°C, of about 150°C, of about 165°C, of about 180°C, of about 182°C, of about 185°C, of about 190°C, or of about 200°C. In some implementations, the oven 610 heats the cured composite part 50 at a postprocessing temperature from about 116°C to about 182°C or of about 180°C.

[00142] The oven 610 can heat the cured composite part 50 at the post-processing temperature for a predetermined amount of time. For example, the oven 610 can heat the cured composite part 50 at the post-processing temperature for about 30 minutes to about 120 minutes, excluding any pre-heating and cooling periods.

[00143] As illustrated in FIG. 24, after post-processing, the cured composite part 50 can be removed from the oven 610 as a fully completed composite part 690. That is, the fully completed composite part 690 can have a higher stiffness and strength than the cured composite part 50.

[00144] As illustrated in FIGS. 24-25, in some implementations, the oven 610 can be implemented as a pulse oven 610. The pulse oven 610 can include one or more stages, and the pulse oven can heat the cured composite part 50 by moving it through the stages at predetermined times, a pulse. For example, the post-cure fixture 550 holding the cured composite part 50 can move through a floor of the pulse oven 610 via a conveyor 615 configured to move at a predetermined interval between the stages. The conveyor 615 can be configured to accommodate a plurality of post-cure fixtures 550 holding cured composite parts 50 moving simultaneously through the pulse oven 610.

[00145] The pulse oven 610 can have between 1 and 12 stages. For example, the pulse oven 610 can have 1 stage, 2 stages, 3 stages, 4 stages, 5 stages, 6 stages, 7 stages, 8 stages, 9 stages, 10 stages, 11 stages, or 12 stages. While not wanting to be limited by theory, the number of stages used will depend on the time and temperature ramp limitations required to prevent distortion of the cured composite part 50 during post-processing. Additional stages can be added to the pulse oven 610 to increase a parallel loading capacity of the post-curing station 600 to preclude cured composite parts 50 from cooling-off while waiting to enter the pulse oven 610 between pulses.

[00146] The time in which the cured composite part 50 is moved through each stage can depend on how many stages are present and the overall post-processing heating time required to prevent distortion of the cured composite part 50. For example, the pulse time for each stage can be from about 10 minutes to about 60 minutes, such as up to about 20 minutes, up to about 25 minutes, up to about 30 minutes, up to about 35 minutes, up to about 40 minutes, up to about 45 minutes, up to about 50 minutes, up to about 55 minutes, or up to about 60 minutes.

[00147] The pulse oven 610 can include preheating, heating, and cooling stages. The temperature difference between the stages can be limited. For example, a temperature difference between stages of the pulse oven can be from about 0°C to about ±60°C. The temperature difference between stages of the pulse oven can be about 0°C, about ±5°C, about ±14°C, about ±17°C, or about ±22°C. For example, heating the cured composite part 50 in the pulse oven 610 at a post-processing temperature to create a fully completed composite part 690 can include heating the cured composite part 50 in an 8-stage pulse oven 610, wherein the stages pulse about every 30 minutes. The pulse oven 610 can include two preheating stages at about 149°C and about 166°C, respectively, three heating stages at about 182°C, and three cool-down stages at about 154°C, about 132°C, and about 116°C, respectively.

[00148] The pulse oven 610 can heat the cured composite part 50 for a total time of between about 30 minutes and 120 minutes. For example, the pulse oven 610 can heat the cured composite part 50 for about 30 minutes, for about 45 minutes, for about 60 minutes, for about 75 minutes, for about 90 minutes, for about 100 minutes, or for about 120 minutes. The total heating time will depend on the pulse oven 610 stage temperatures. In some implementations, the pulse oven heats the cured composite part 50 at the post-processing temperature for about 90 minutes.

[00149] FIG. 25 illustrates a flow through a pulse oven 610 according to an implementation of the present disclosure. As illustrated in FIG. 25, four lines, right and left, of cured composite parts 50 can feed a pulse oven 610. Each cured composite parts 50 can be mounted on a different post-cure fixture 550 fed into the pulse oven 610. As illustrated in FIG. 25, a right forward cured composite part 631 and its associated post-cure fixture 632, a right aft, cured composite part 633 and its associated post-cure fixture 634, a left forward, cured composite part 635 and its associated post-cure fixture 636, and a left aft cured composite part 637 and its associated post-cure fixture 638 all go into the pulse oven 610 through entrance 611, and then enter the separate stages of the pulse oven 610 to be heated. The cured composite parts and their respective post-cure fixtures then exit the pulse oven 610 through exit 612. The now fully cured and completed parts are then removed from their respective post-cure fixtures, and the post-cure fixtures are returned to the cured-part transfer station 500 to pick up the next cured composite parts 50. [00150] Implementations of the present disclosure may find use in a variety of potential applications, particularly in the transportation industry, including for example, aerospace, marine, rail, automotive applications, and other application where resin-infused composite structures are desired. However, the present disclosure is not limited thereto, and implementations of the present disclosure may be used in applications outside the transportation industry. Thus, referring now to FIGS. 27 and 28, implementations of the disclosure may be used in the context of an aircraft manufacturing and service method 1000 as shown in FIG. 27 and an aircraft 2000 as shown in FIG. 28. While FIG. 28 is described in terms of an aircraft 2000, the present disclosure is not limited thereto, and the service method 1000 can be applied to other structures. During pre-production, exemplary method 1000 may include specification and design 1102 of the aircraft 2000 and material procurement 1104. During production, component and subassembly manufacturing 1106 and system integration 1108 of the aircraft 2000 takes place. Thereafter, the aircraft 2000 may go through certification and delivery 1110 in order to be placed in service 1112. While in service by a customer, the aircraft 2000 is scheduled for routine maintenance and service 1114, which may also include modification, reconfiguration, refurbishment, and so on.

[00151] Each of the processes of method 1000 may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on.

[00152] As shown in FIG. 28, the aircraft 2000 produced by exemplary method 1000 may include an airframe 2115 with a plurality of systems 2118 and an interior 2120. Examples of systems 2118 include one or more of a propulsion system 2122, an electrical system 2124, a hydraulic system 2126, and an environmental system 2128. Any number of other systems may be included. Although an aerospace example is shown, the principles of the disclosure may be applied to other industries, such as the marine and automotive industries.

[00153] Systems and methods exemplified herein may be employed during any one or more of the stages of the aircraft manufacturing and service method 1000. For example, components or subassemblies corresponding to component and subassembly manufacturing 1106 may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft 2000 is in service. Also, one or more apparatus examples, method examples, or a combination thereof may be utilized during the component and subassembly manufacturing 1106 and system integration 1108, for example, by substantially expediting assembly of or reducing the cost of an aircraft 2000. Similarly, one or more of apparatus examples, method examples, or a combination thereof may be utilized while the aircraft 2000 is in service, for example and without limitation, to maintenance and service 1114.

[00154] While FIGS. 27 and 28 describe the disclosure with respect to aircraft and aircraft manufacturing and servicing, the present disclosure is not limited thereto. The systems and methods of the present disclosure may also be used for spacecraft, satellites, rotorcraft, submarines, surface ships, automobiles, autonomous vehicles, tanks, trucks, power plants, railway cars, and any other suitable type of objects.

[00155] This disclosure provides examples according to the following clauses.

[00156] Clause 1: A method for forming a composite part, comprising: placing two or more preforms in a constant-temperature mold; infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin-infused preform; and curing the combined resin-infused preform to form a cured composite part, wherein the constanttemperature mold maintains a constant curing temperature during infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin-infused preform and curing the combined resin-infused preform to form a cured composite part, and wherein the resin has a period of latency and the resin is configured to cure within a predetermined curing time at the constant curing temperature.

[00157] Clause 2: The method of clause 1, further comprising: ply-cutting raw material into flat patterns; and forming the flat patterns into two or more preforms, wherein the two or more preforms comprise at least two complementary preforms, and wherein the constanttemperature mold accommodates the two or more preforms in a predetermined configuration relative to each other.

[00158] Clause 3: The method of any of clauses 1-2, wherein the two or more preforms comprises at least one skin panel preform and at least one stringer preform.

[00159] Clause 3: The method of any of clauses 1-3, further comprising: removing the cured composite part from the constant-temperature mold; and post-processing the cured composite part, wherein post-processing the cured composite part comprises further curing the cured composite part at a temperature higher than the constant curing temperature.

[00160] Clause 5: The method of any of clauses 1-4, wherein infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin-infused preform comprises infusing the two or more preforms with the resin for a predetermined infusion time, and wherein the resin has a period of latency corresponding to the predetermined infusion time.

[00161] Clause 6: The method of any of clauses 1-5, wherein the resin is maintained at the constant curing temperature for the predetermined infusion time, and wherein the resin maintains a viscosity of about 50 cP or less for the predetermined infusion time.

[00162] Clause 7: The method of any of clauses 1-6, wherein the constant curing temperature is from about 100°C to about 200°C, wherein the predetermined curing time is from about 5 minutes to about 180 minutes, and wherein the resin has a period of latency from about 5 minutes to about 1 hour.

[00163] Clause 8: The method of any of clauses 1-7, wherein the constant-temperature mold comprises a lower mold die and an upper mold die, wherein placing two or more preforms in a constant-temperature mold comprises placing the two or more preforms in the lower mold die, and wherein the lower mold die maintains the two or more preforms at the constant curing temperature.

[00164] Clause 9: The method of any of clauses 1-8, wherein the lower mold die is configured to accommodate the at least two complementary preforms in a predetermined configuration relative to each other.

[00165] Clause 10: The method of any of clauses 1-9, wherein infusing the two or more preforms in the constant-temperature mold with a resin to form a combined resin- infused preform comprises: placing the upper mold die over the lower mold die to create a sealed cavity, the sealed cavity defining a gap, the gap corresponding to a cavity volume equivalent to an amount of resin sufficient to infuse the two or more preforms; injecting the resin into the gap of the sealed cavity to infuse the two or more preforms for the predetermined infusion time; and lowering the upper mold die to close the gap and to apply a curing pressure to the combined resin-infused preform for the predetermined curing time, wherein the resin is injected into the sealed cavity at a pressure from about 5 psig to about 40 psig, wherein the constant-temperature mold maintains the resin at the curing temperature, and wherein the upper mold die applies a curing pressure of from about 5 psig to about 150 psig.

[00166] Clause 11 : An integrated system for forming a composite part comprising: a ply-cutting station to cut raw material into flat patterns; a picking-and-placing station to receive the flat patterns from the ply-cutting station and to form two or more preforms; a preform-transfer station to receive the two or more preforms from the picking-and-placing station and to place the two or more preforms into a constant-temperature lower mold die; an infusing-and-curing station to receive the constant-temperature lower mold die, to infuse the two or more preforms with a resin to form a combined resin-infused preform, and to cure the combined resin-infused preform to form a cured composite part; and a cured-part transfer station to receive the cured composite part from the infusing-and-curing station and to remove the cured composite part from the constant-temperature lower mold die, wherein the two or more preforms include at least two complementary preforms, wherein the constanttemperature lower mold die accommodates the two or more preforms in a predetermined configuration relative to each other, wherein the constant-temperature lower mold die maintains the two or more preforms at a constant curing temperature, and wherein the resin has a period of latency and the resin is configured to cure within a predetermined curing time at the constant curing temperature.

[00167] Clause 12: The system of clause 11, further comprising: a post-curing station to receive the cured composite part from the cured-part transfer station and to further process the cured composite part.

[00168] Clause 13: The system of any of clauses 11-12, wherein the ply-cutting station comprises: a ply-cutting table; a raw-material dispenser to supply raw material to the ply-cutting table; and a cutter to cut the raw material on the ply-cutting table into flat patterns, wherein the raw material comprises from 1 to 8 plies of a fibrous material with a per-ply areal weight from about 50 gsm to about 400 gsm.

[00169] Clause 14: The system of any of clauses 11-13, wherein the ply-cutting table comprises: a staging area; and a material conveyor configured to simultaneously advance raw material from the material dispenser onto the ply-cutting table and the flat patterns to the staging area.

[00170] Clause 15: The system of any of clauses 11-14, wherein the picking-and- placing station comprises: a pick-and-place end effector to pick the flat patterns from the ply- cutting table; and an assembly jig to receive the flat patterns picked by the pick-and-place end effector, wherein pick-and-place end effector applies a pressure to the flat patterns on the assembly jig to form a preform.

[00171] Clause 16: The system of any of clauses 11-15, wherein the picking-and- placing station is configured to form at least one of the at least two complementary preforms. [00172] Clause 17: The system of any of clauses 11-16, wherein the preform-transfer station comprises: a lifting structure to place two or more preforms in the constanttemperature lower mold die, wherein the constant-temperature lower mold die is at the curing temperature when the two or more preforms are placed in the constant-temperature lower mold die.

[00173] Clause 18: The system of any of clauses 11-17, wherein the infusing-and- curing station comprises: a constant-temperature upper mold die; a constant-temperature lower mold die; and a resin-infusion system, wherein the constant-temperature upper mold die is configured to press against the constant-temperature lower mold die, wherein, in a first position, the constant-temperature upper mold die defines a sealed gap having a volume equivalent to an amount of resin sufficient to infuse the two or more preforms, and wherein in a second position, the constant-temperature upper mold die defines a cavity corresponding to final dimensions of the cured composite part.

[00174] Clause 19: The system of any of clauses 11-18, wherein the constanttemperature mold comprises one or more cavities and one or more channels configured to hold the two or more preforms in a position relative to each other.

[00175] Clause 20: The system of any of clauses 11-18, wherein the constanttemperature mold comprises one or more cavities configured to hold one type of complementary preform and one or more channels configured to hold another type of complementary preform in a position relative to each other.

[00176] Clause 21 : The system of any of clauses 11-20, wherein the resin-infusion system injects the resin into the sealed gap for the predetermined infusion time to form a combined resin-infused preform, and wherein the constant-temperature upper mold die applies a curing pressure to the combined resin-infused preform to form a cured composite part.

[00177] The present disclosure has been described with reference to exemplary implementations. Although a few implementations have been shown and described, it will be appreciated by those skilled in the art that changes can be made in these implementations without departing from the principles and spirit of preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.