Hybridization of Natural-Fiber Reinforcement for Composites and Fabrics Made of the Same

The present patent application claims priority from the French patent application filed on 23 July 2021 and assigned application no. FR2107994, the contents of which is hereby incorporated by reference.

Technical field

[0001] The present disclosure relates generally to the field of fiber or fabric reinforced composites, and in particular to a roving, a tow, or a fabric for a use in a fiber-reinforced composite, and to the resulting compositions.

Background

[0002] Each year millions of kilograms of carbon fiber, fiberglass, flax fiber, basalt fiber, and other fibers with advantageous tensile, compressive and/or flexural strengths are produced for use as reinforcement materials in Fiber- Reinforced Composites, or FRCs (which may also be synonymously referred to as Fiber-Reinforced Plastics, or FRPs). These reinforcement fibers are combined with Thermoset or Thermoform plastic resins (collectively referred to as the Matrix) to create structural materials with superior properties to the separate components.

[0003] A problem is that the ecological impact of producing synthetic fibers is very high, but there are technical problems in replacing synthetic fibers by natural fibers while maintaining relatively high performance of the resulting FRC in terms of tensile, compressive and/or flexural strength.

Summary of Invention

[0004] There is a need in the art for an improved reinforcement fiber construction and reinforcement fabric composition providing effective hybridization of fiber materials, particularly with relation to natural-fiber reinforcements .

[0005] Embodiments of the present disclosure aim to at least partially address some or all of the needs in the prior art.

[0006] According to one aspect, there is provided a roving or tow for a fiber-reinforced composite comprising: one or more natural reinforcement fibers of a first type of material; and one or more further reinforcement fibers of a second type of material different from the first type, wherein the natural and further reinforcement fibers are orientated lengthwise without twist, or with minimal achievable twist, in a single roving or tow configured to reinforce a matrix of the fiber- reinforced composite.

[0007] According to one embodiment, the natural and further reinforcement fibers are held coherent with each other by a sizing agent.

[0008] According to one embodiment, the natural and further reinforcement fibers are held coherent with each other by an external mechanical element, such as a coil, helix, tubular braid or sleeve.

[0009] According to one embodiment, the natural and further reinforcement fibers are distributed throughout the roving or tow.

[0010] According to one embodiment, the roving or tow has a weight of not less than lOOg per linear kilometer and not more than 2000g per linear kilometer.

[0011] According to one embodiment, fiber content of the roving or tow for the purpose of providing the reinforcement to the composite in the form of the one or more natural reinforcement fibers is a mineral, vegetal-based, plant-based, bio-based or animal-based fiber, and wherein the weight percentage of natural fiber in such assembled fiber for the purpose of providing the reinforcement to the composite in the roving or tow is of at least 50%.

[0012] According to one embodiment, the one or more further reinforcement fibers are natural fibers of a different type of material to the first type, the natural reinforcement fibers of the first type for example having a first length, and the natural reinforcement fibers of the second type for example having a second length different to the first length by at least 10 percent, and preferably by at least 30 percent.

[0013] According to one embodiment, the one or more natural reinforcement fibers or the one or more further reinforcement fibers are extracted cellulose fiber.

[0014] According to one embodiment, all fibers of the roving or tow are natural reinforcement fibers.

[0015] According to one embodiment, the roving or tow further comprises one or more fibers which are formed of a thermoplastic material capable of being melted during a composite curing cycle to form the matrix of the composite.

[0016] According to one embodiment, the roving or tow further comprises one or more reinforcement fibers of a third type of material different to the first and second types of material and, for example, one or more reinforcement fibers of one or more further types of materials different to the first, second and third types of material.

[0017] According to a further aspect, there is provided a reinforcement tape for a fiber reinforced composite comprising at least one tow as defined in any of the above embodiments .

[0018] According to a further aspect, there is provided a braided reinforcement for a fiber reinforced composite comprising at least one tow as defined in any of the above embodiments . [0019] According to yet a further aspect, there is provided a fabric reinforcement for a fiber reinforced composite comprising at least one tow as defined in any of the above embodiments that is stitched, woven, or bonded into form.

[0020] According to yet a further aspect, there is provided a fiber-reinforced composite comprising a reinforcement element comprising a plurality of the roving or tow as defined in any of the above embodiments and/or the reinforcement tape and/or the braided reinforcement and/or the fabric reinforcement, situated within the matrix.

[0021] According to a further aspect, there is provided a method of forming a roving or tow for a fiber-reinforced composite comprising: orientating lengthwise one or more natural reinforcement fibers of a first type of material; orientating lengthwise one or more further reinforcement fibers of a second type of material different from the first type; and combining, without twist, or with minimal achievable twist, the natural and further reinforcement fibers into a single roving or tow configured to reinforce a matrix of the fiber-reinforced composite.

[0022] According to one embodiment, combining the natural and further reinforcement fibers comprises applying a sizing agent to hold the natural and further reinforcement fibers coherent with each other.

[0023] According to one embodiment, combining the natural and further reinforcement fibers comprises wrapping an external mechanical element, such as a coil, helix, tubular braid or sleeve, around the natural and further reinforcement fibers.

[0024] According to one embodiment, orientating lengthwise the one or more natural reinforcement fibers comprises orienting lengthwise the natural reinforcement fibers without twist, or with minimal achievable twist to form a first continuous fiber ribbon; orientating lengthwise the one or more further reinforcement fibers comprises orienting lengthwise the natural reinforcement fibers without twist, or with minimal achievable twist to form a second continuous fiber ribbon; and combining the natural and further reinforcement fibers into a single roving or tow comprises combining and drawing the fibers of the first and second ribbons such that the natural and further reinforcement fibers are distributed throughout the roving or tow.

[0025] According to another aspect, there is provided a method of forming a fiber-reinforced composite comprising: forming at least one roving or tow according to the method of any of the above embodiments; and reinforcing the matrix of the fiber-reinforced composite by incorporating the at least one roving or tow into the matrix.

[0026] According to yet a further aspect, there is provided a roving or tow for a fiber-reinforced composite comprising: at least one natural fiber of a first type; and at least one further fiber of a second type, wherein the natural and further fibers are for example combed or hackled together in a single roving or tow.

[0027] According to one embodiment, the natural and further fibers of any previous embodiment are oriented lengthwise, for example without twist, or with minimal achievable twist to the fibers in the roving or tow to form a continuous fiber ribbon. According to one embodiment, the natural and further fibers of any previous embodiment are distributed throughout the roving or tow, the roving or tow having a weight of not less than lOOg per linear kilometer and not more than 2000g per linear kilometer.According to one embodiment, the natural fiber of any previous embodiment is a mineral, vegetal-based or animal-based fiber, and wherein the weight percentage of natural fiber in the roving or tow is of at least 50%. According to one embodiment, the further fiber is a synthetic fiber. According to one embodiment, the further fiber is a natural fiber of a different type to the first type.According to one embodiment, the natural fiber is an extracted cellulose fiber. According to one embodiment, the roving or tow of consists of only fibers of the first and second type, and unavoidable impurities. According to one embodiment, the roving or tow consists only of fibers of the first and second type, and of fibers which are formed of a thermoplastic material which is melted during the composite curing cycle to form the matrix of the composite.According to one embodiment, the roving or tow consists of more than two fiber types. According to further aspects, there is provided a reinforcement tape, a braided reinforcement, or a fabric reinforcement which is stitched, woven, or bonded into form, consisting of at least one roving as defined by any previous embodiment. According to a further aspect, there is provided a fiber-reinforced composite comprising a reinforcement element comprising a plurality of the roving or tow, reinforcement tape, or reinforcement fabric as defined by any above embodiment situated within a thermoset or thermoform matrix. According to yet a further aspect there is provided a sliding board having a structural ply formed of the fiber- reinforced composite or a hand-held pole comprising a shaft formed of the fiber-reinforced composite.

[0028] According to yet a further aspect, there is provided a method of forming a roving or tow for a fiber-reinforced composite comprising: combing or hackling together at least one natural fiber of a first type; and at least one further fiber of a second type to form a single roving or tow.

Brief description of drawings

[0029] The foregoing features and advantages, as well as others, will be described in detail in the following description of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings, in which:

[0030] Figure 1 illustrates a continuous filament and a roving formed of continuous filaments;

[0031] Figure 2 illustrates a finite-length filament and a roving formed of finite-length filaments;

[0032] Figure 3 illustrates a natural finite-length filament; a further finite-length filament; a ribbon formed of natural finite-length filaments; a ribbon formed of further finite- length filaments; and a roving or tow formed of natural and further finite-length filaments, according to an embodiment of the present disclosure;

[0033] Figure 4A illustrates a natural finite-length filament having a first length; a further finite-length filament having a second length; a ribbon formed of the natural finite-length filaments; a ribbon formed of further finite-length filaments; and a roving or tow formed of the natural and further filaments according to an embodiment of the present disclosure;

[0034] Figure 4B is a flow diagram illustrating steps in a method of fabricating a roving or tow according to an embodiment of the present disclosure;

[0035] Figure 5 illustrates a unidirectional reinforcement fabric comprised of at least one fiber-reinforcement tow according to Figure 3 or 4A;

[0036] Figure 6 illustrates a unidirectional stitched fabric comprised of fiber-reinforcement tows utilizing at least one tow according to Figure 3 or 4A;

[0037] Figure 7 illustrates a multi-axial stitched fabric comprised of fiber-reinforcement tows utilizing at least one tow according to Figure 3 or 4A; [0038] Figure 8 illustrates a multi-axial woven fabric comprised of fiber-reinforcement tows utilizing at least one tow according to Figure 3 or 4A;

[0039] Figure 9 illustrates a tubular braid comprised of fiber-reinforcement tows utilizing at least one tow according to Figure 3 or 4A;

[0040] Figure 10 illustrates a unidirectional fabric comprising alternating tows of reinforcement fiber situated astride tows according to Figure 3 or 4A;

[0041] Figure 11 illustrates a biaxial fabric comprising alternating tows of reinforcement fiber situated astride tows according to Figure 3 or 4A;

[0042] Figure 12 illustrates a 2x1 twill fabric comprising alternating tows of reinforcement fiber situated astride tows according to Figure 3 or 4A; and

[0043] Figure 13 illustrates a plain weave fabric comprising alternating tows of reinforcement fiber situated astride tows according to Figure 3 or 4A.

Description of embodiments

[0044] Like features have been designated by like references in the various figures. In particular, the structural and/or functional features that are common among the various embodiments may have the same references and may dispose identical structural, dimensional and material properties.

[0045] In the following disclosure, unless indicated otherwise, when reference is made to absolute positional qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or to relative positional qualifiers, such as the terms "above", "below", "higher", "lower", etc., or to qualifiers of orientation, such as "horizontal", "vertical", etc., reference is made to the orientation shown in the figures. [0046] Unless specified otherwise, the expressions "around", "approximately", "substantially" and "in the order of" signify within 10 %, and preferably within 5 %.

[0047] It is often desired in the fabrication of composite structures where specific characteristics are required to use hybridized reinforcement in fabric layups. Those skilled in the art will be familiar with alternating plies of fabrics using different fibers and/or different constructions in order to tailor the performance of the resulting composite. It is also common to construct a fabric where the tows - which are bundles of fibers which are substantially aligned along the lengthwise axis of the roving - are alternated in at least one axis of the fabric to create a hybridized fabric. While the words "roving" and "tow" are generally understood to be synonymous, for purposes of clarity, we use "roving" in this disclosure to refer to the stand-alone bundle of fibers, and "tow" to refer to a roving that is woven or stitched together to form a fabric.

[0048] Examples of hybridized fabrics may include a 0/90 woven fabric where every second tow in both axes changes from flax fiber to basalt fiber; a biaxial +45/-45 non-crimp fabric where 5 fiberglass tows are arranged side by side with a carbon fiber tow placed before the 6-tow pattern is repeated, in both axes; or a triaxial 0/+60/-60 where the 0° axis is comprised of carbon fiber tows, and each of the +60/-60 axes are comprised of tows of aramid fibers.

[0049] The above described hybridized constructions can improve the overall performance of the final composite part in terms which may include ultimate strength, flexural stiffness, vibration damping, impact strength, or cost (among others). Notably, there can also be negative impacts on the overall performance of the composite structure due to hybridization which can be accentuated depending on the amount of difference between the mechanical characteristics of one hybridizing fiber to another. For example, if pineapple leaf fiber (PLF) tows are alternated with carbon tows in a fabric, the PLF may contribute positively to the overall vibration characteristics of the resulting part; however, the fact that the PLF fibers have both a lower elongation at failure and a lower tensile strength means that they will tend to fail under strain before the carbon fibers and are less able to contribute to the ultimate strength of the formed composite. Similarly, if e-glass fiber and HM carbon fiber tows are alternated in a fabric the significant difference in tensile stiffness means that the HM carbon tows will be bearing the majority of the load and a stress riser is likely to occur on a small scale at the point where the tows alternate, which can cause microfractures in the matrix and decrease the fatigue life of the composite.

[0050] Additionally, the ecological impact of producing 1kg of carbon fiber includes production of 30kg of greenhouse gasses and the manufacture of 1kg of e-glass generates approximately 2.8kg of greenhouse gasses. Conversely, if the carbon sequestration during cultivation is taken into account, most vegetal fiber reinforcements can be carbon-negative from cradle to gate. As the world struggles to bring into line the demands for reaching the targets for climate impact mitigation required in the Paris Climate Treaty, EU and UN climate targets, and by other national and international authorities, the demand to create viable solutions for sustainable manufacturing of performance composites increases correspondingly .

[0051] Industries which rely heavily on the use of composites for manufacturing range from automotive and aerospace to sporting equipment and housewares. Such varied industries correspondingly require varied performance characteristics as well as significant volumes of their chosen composite reinforcement fibers. In this light, additional considerations for hybridization come to the fore.Among these is scale: of the many fibers which show promise for use in natural fiber reinforcement only a small percentage are cultivated on a scale large enough to be viable for industrial use.

[0052] A second factor which is associated with scale is fiber variability, because natural fibers - and vegetal fibers more specifically - can vary greatly in mechanical characteristics based upon where they are cultivated and how the fibers are processed. Achieving a consistent roving quality requires that the variability inherent to vegetal fiber cultivation be controlled well enough that predictable performance can be delivered with natural fiber, which is a task of ever-increasing difficulty in a time of climate change

[0053] Thirdly, with the great variety of mechanical characteristics which result across the range of viable mineral and vegetal natural fibers, it is increasingly possible to tailor the performance of composite reinforcement extremely precisely; however, it is also this range of characteristics which can magnify the issues described above.

[0054] While there is significant interest in hybridization of natural fiber composites with both natural and synthetic fibers, all published research which the inventor has been able to find has focused on hybridization which is based on single-fiber type tows. The gross majority of research involves creating hybrid composites based on alternating plies of vegetal-fiber-based fabric with plies of synthetic- fiber-based fabric (typically e-glass). Significantly fewer projects have looked at the performance of fabrics where tows are alternated between natural fiber and synthetic fiber within a single fabric. [0055] In composites, the roving exists as the "smallest divisible unit" within which the reinforcement composition is uniform.

[0056] Figure 1 illustrates an example of a continuous filament 101 and of a roving 100 formed of continuous filaments 101. For example, Figure 1 illustrates an example of popular synthetic reinforcement fibers such as glass and carbon fibers, which are drawn as continuous filaments 101 and combined into rovings 100 when fibers are laid parallel and proximate to one another and lightly bonded together with a sizing agent 102.

[0057] Figure 2 illustrates an example of a finite-length filament 201 and a roving 200 formed of finite-length filaments 201. For example, Figure 2 illustrate an example of natural fibers 201 for reinforcement that often have finite lengths, and the rovings 200 are produced in a manner similar to how yarn is prepared for use from natural fibers, but without "twist" - the difference being that rovings instead rely on the surface structure of the fibers 'locking' in place, at interfaces 202, with other adjacent fibers - either with or without the use of chemical processing or bonding agents - as the continuous ribbon of fibers is pulled thinner/lighter by a series of combs and cylinders or drums in the processing.

[0058] Figure 3 illustrates a natural finite-length filament 301, a further finite-length filament 311, a ribbon 340 formed of natural finite-length filaments; a ribbon 341 formed of further finite-length filaments; and a roving or tow 300 formed of natural and further finite-length filaments 301, 311, according to an embodiment of the present disclosure.

[0059] In particular, the roving 300 is for example comprised of at least one natural reinforcement fiber 301, for example in the form of a filament, of one type of material and at least one further reinforcement fiber 311, also for example in the form of a filament, of a second type of material. The fibers of each type are oriented lengthwise and without twist, or with minimal achievable twist, into the continuous fiber ribbons 340 and 341. The at least two fiber ribbons 340, 341 are then for example laid coincident to each other and combined, for example by a process of combing and/or drawing, and/or by application of a sizing agent and/or by the addition of an external mechanical element, into a single roving, where the at least two fiber types are distributed throughout the resulting roving. For example, the resulting roving has a weight of not less than 60g per linear kilometer, and preferably not less than lOOg per linear kilometer. Additionally or alternatively, the resulting roving for example has a weight of not more than 3000g per linear kilometer, and preferably not more than 2000g per linear kilometer, and more preferably not more than 1800g per linear kilometer. This hybridized natural fiber roving or tow 300 is for example used in total or in part to form the reinforcement element or a tow of a FRC.

[0060] A "natural reinforcement fiber" is any mineral or vegetal-based or plant-based or animal-based or bio-based fiber. The natural fiber is for example in the form of a filament having a prepared length that is for example greater than 40mm, and preferably greater than 60mm, and more preferably greater than 120mm and for example less than 1200mm, and which has mechanical properties desirable for reinforcement of FRCs. Examples include basalt fibers and boron fibers (both mineral fibers); flax, hemp, ramie, bamboo, pineapple leaf, sisal, kenaf, banana leaf, and coir fibers (all vegetal fibers); extracted cellulose (plant-derived fiber) and silk, animal hair, and serosa fibers (all animal- based fibers). For purposes of this disclosure, mineral, vegetal, and animal are considered natural fiber "classes"; basalt, boron, flax, ramie, bamboo, silk, etc. are considered fiber "types".

[0061] The further reinforcement fiber 311 is also for example in the form of a filament having a prepared length that is for example greater than 60mm, a preferably greater than 150mm, and for example less than 1200mm. In some embodiments, the further fiber is a natural fiber as defined above.

[0062] A "continuous fiber ribbon" (also known as a fiber 'top' or 'sliver') is a loose, soft, untwisted ropelike strand of coincident fibers having a roughly uniform thickness and consistent fiber orientation along the length of the ribbon. It is for example produced by the carding process, which separates raw fibres to prepare them for roving production.

[0063] The rovings may then be utilized in a process such as filament winding or incorporated as unidirectional reinforcement tape in a matrix, or may be incorporated as tows into a braided, woven, or stitched fabric in a multiaxial or unidirectional construction.

[0064] The further fibers 301 of the roving may be any synthesized fibers, such as carbon, glass, aramid, etc., or any natural fibers, such as extracted cellulose, ramie, flax, basalt, etc.), or any other reinforcement that is or may become commonly used in the composites industry. In some embodiments, at least 50.1 percent of the reinforcement fiber comprising the roving is a natural fiber.

[0065] In the example of Figure 3, the filaments 301 and 311 used to form the roving 300 are finite-length filaments having substantially the same lengths as each other. In alternative embodiments, the filaments used to form the roving could be configured to have different lengths, as will now be described with reference to Figure 4A. [0066] Figure 4A illustrates a finite-length filament 401 of natural fiber of a first length, a further finite-length filament 411 of a second length different to the first length, a continuous ribbon 440 formed of the filaments 401; a continuous ribbon 441 formed of the filaments 411; and a roving or tow 400 formed of the continuous ribbons 440, 441, according to an embodiment of the present disclosure.

[0067] Fibers 401, 411, which are combined to produce the roving 400 shall each have, for example, a finite length which is not less than 60mm and not longer than 1200mm. In order to tailor the performance of the roving, the different types of fiber 401 and 411 may have different general lengths such that the natural fiber filaments 401 may have a length which is between 300mm and 400mm, while the further fiber filaments 411 of the second type may have a length which is between 100 and 200mm, for example. More generally, the natural fibers 401 of the first type of material for example have a first length in the range 40mm to 1200mm, and the further fibers of the second type of material for example have a second length different to the first length by at least 10 percent, and preferably by at least 30 percent.

[0068] The rovings and/or tows, and/or a fabric made from the tows, may be combined with any applicable matrix, such as a thermoset or thermoform plastic resin system, to form an FRC.

[0069] The rovings or tows 300, 400 are for example each formed by a pair of ribbons 440, 441, each ribbon for example comprising, in cross section, at least two or more fiber filaments. The rovings may be created having more than two fiber types, in other words fibers of more than two different materials .

[0070] Tows may be incorporated into a fabric in such a way that at least one tow in at least one axis utilizes the "hybridized natural-fiber roving" construction. [0071] Hybridized natural-fiber rovings may be incorporated into a stitched, woven or braided fabric exclusive of other fiber tows, or a tow may be created using Hybridized natural- fiber roving and incorporated into a fabric with non- hybridized reinforcement tows.

[0072] Rovings, tows and fabrics created from the Hybridized natural-fiber rovings may have resins, resin-based filaments, such as Poly-lactic-acid, polyolefin, or Polyamide, or other additional chemistry added to tailor the performance of the resulting FRC.

[0073] The benefits of the rovings or tows of Figures 3 and 4A are multifold:

[0074] 1) When natural fibers with relatively similar mechanical characteristics such as hemp, flax, ramie, nettle, alpha, pineapple leaf and/or extracted cellulose are used in a single roving, it is much more possible to repeat the mechanical characteristics of the roving, harvest after harvest, with less likelihood of batch variance because a larger fiber sample size is available to draw from. Because the characteristics of each fiber type vary slightly, this provides a greater ability to blend the fibers to achieve a specified set of mechanical values; and because the processing of the extracted cellulose provides a vegetal-based fiber which is able to mimic the repeatability of synthetic fibers. As an example, providing a tow or roving using filaments 301 or 401 made of extracted cellulose, and filaments 311 or 411 made of flax fibers or pineapple leaf, has been found to work particularly well. Indeed, both of these examples use the mechanical consistency of the man-made cellulosic fiber to reduce the variability of the plant fiber. The present inventor has performed tests which have shown that these examples of hybrids reduce the variability by upwards of 60% with respect to the variability exhibited based on a single plant-based fiber alone.

[0075] 2) Rather than use exclusively extracted cellulose in rovings, which would increase the ecological impact of the fiber reinforcement, combining the prepared vegetal fibers (i.e. flax, ramie, hemp, pineapple leaf, etc.) with extracted cellulose reduces the overall greenhouse gas production, and increases the biodegradability of the resulting rovings.

[0076] 3) Research into the flexural strength and tensile strength of certain combinations of natural fibers show an improvement of approximately 5 to 10% and in some cases more than 20% when fibers are arranged in a unidirectional orientation and molded in an epoxy matrix when comparing the performance of alternating separate rovings constructed of two vegetal fibers and the performance of the same mass of fibers combed into hybridized rovings. The increase in homogeneity of the fibers within the matrix allows a more- efficient resistance to loads among the different fibers and a decrease in microfractures within the matrix where the mechanical characteristics of the alternating rovings caused stress risers.

[0077] 4) The extreme rigidity of high-modulus carbon fibers has allowed wall thickness for composites parts to become exceptionally thin. The density of carbon fiber is typically 1.8-2.0. While much less rigid than HM carbon fiber, and requiring a thicker wall in order to obtain the same rigidity, glass fiber has a density of 2.7-3.0 making it much less efficient at producing stiffness. Conversely, natural fibers range in functional density between 0.9 and 1.8 and have the ability to be made into composites with greater wall thickness than carbon at a corresponding fiber mass. Because the wall thickness of a composite structure influences the stiffness of the structure as a cubic function [ Flexural Rigidity = (Young's Modulus * thickness cubed) / 12 * (1 - Poisson's

Ratio) ], the ability to increase the dimension of a wall with minimal additional weight by incorporating lower density fiber into the wall can be extremely beneficial in overcoming the difference in mechanical properties between carbon and vegetal fibers.

[0078] 5) By hybridizing rovings with component fibers of different types and different lengths, it is possible to optimize the performance of the roving for an application. If, for example, high elongation and high flexural stiffness are required, then using a first fiber with a high elongation (such as extracted cellulose) in a longer fiber length, for example in the range 150mm to 1200mm, and hybridizing that with a second fiber with higher flexural stiffness (such as basalt) in a shorter fiber length for example in the range 40mm to 150mm, would yield a resulting composite where the tensile elongation of the extracted cellulose is not excessively restricted by the tensile stiffness of the basalt fiber, but the flexural stiffness of the basalt fiber is able to effectively augment the flexural stiffness of the extracted cellulose fiber. With continuous fiber rovings of a single fiber type, these characteristics would be difficult to achieve, making the hybridized roving beneficial in a range of applications where seemingly antagonistic or mutually- opposing performance characteristics are desired. As a further example, there are also situations where it may be desirable to have the same fiber length in order to achieve a superior result. One such example is the use of flax fiber with sisal fiber, to increase the flexural stiffness of the composite. Flax has a greater tensile strength and a moderate flexural stiffness. With the addition of Sisal fiber, which has more flexural strength than flax, the flexural stiffness of the hybrid almost doubles the performance of Flax on its own and more than doubles the flexural stiffness of sisal on its own, while maintaining a greater flexural strength than pure flax. There is a drop in the tensile strength of the composite from the pure flax sample, but this hybrid material would be suitable for applications without high tensile- loading.

[0079] Figure 4B is a flow diagram illustrating steps in a method of fabricating a roving or tow, such as the tow or roving 300 of Figure 3 or 400 of Figure 4A, according to an embodiment of the present disclosure.

[0080] In a step 450 (ORIENT ONE OR MORE NATURAL FIBERS OF A FIRST TYPE OF MATERIAL LENGTHWISE TO FORM A FIRST RIBBON), one or more natural fibers of a first type of material are for example orientated lengthwise to form a first continuous ribbon. For example, the natural fibers are orientated lengthwise without twist, or with minimal achievable twist.

[0081] In a step 451 (ORIENT ONE OR MORE FURTHER FIBERS OF A SECOND TYPE OF MATERIAL LENGTHWISE TO FORM A SECOND RIBBON), one or more further fibers of a second type of material, which is preferably another natural fiber, are for example orientated lengthwise to form a second continuous ribbon. For example, the further fibers are orientated lengthwise without twist, or with minimal achievable twist.

[0082] In a step 452 (LAY FIRST AND SECOND RIBBONS COINCIDENT WITH EACH OTHER AND COMBINE WITHOUT TWIST TO FORM SINGLE ROVING OR TOW), the fibers of the first and second type are for example combined without twist, or with minimal achievable twist, to form a single roving or tow. This is for example achieved by laying the first and second ribbons coincident with each other, and then combining the ribbons using one or more of:

- combing and drawing the fibers of the first and second ribbons together to form the single roving or tow; and/or - applying a sizing agent to hold the natural and further fibers coherent with each other; and/or

- wrapping an external mechanical element, such as a coil, helix, tubular braid or sleeve, around the natural and further fibers.

[0083] For example, the sizing agent is one or a combination of: a plant pectin or lignin or starch dissolved into water; modified cellulose in an alcohol solution or other solvent; or a synthetic sizing agent which has been chemically synthesized.

[0084] For example, the external mechanical element is applied by a machine which winds either a spiral or a helix (a helix being a spiral in both s and z directions) of thread around the roving as it is taken up on a bobbin after the fibers are parallelized and pulled into tension. A tubular braid can for example be applied in a similar manner to the application of the helix, but involves more strands of thread capturing the parallelized reinforcement fibers. In some embodiments, the thread is made of a natural fiber such as cotton, flax, or extracted cellulose fiber; or the thread can be made up of a thermoplastic material which is able to melt into the matrix in an instance where the roving is produced for use in a thermoplastic composite application such as polylactic acid (PLA), polypropylene (PP), polyamide (PA). The sleeve is for example made of a thermoplastic material, which can for example "heat-shrink", and the sleeve may act as a pre-preg solution to introduce the parallelized fiber to a polymer matrix in a way that improves the ability of the fiber to be woven or stitched into fabrics. The heat-shrink thermoplastic film, made from PP (Polypropylene), PA

(Polyamide), PLA (Polylactic Acid) , PHA

(Polyhydroxyalkanoate) or other desirable polymers, is for example able to compress around the fibers once the roving is positioned inside the tube, and then compressed around the fibers with heat. In a thermoplastic curing process for the composite, the thermoplastic is for example taken above its melt-flow temperature and then cooled once it had been distributed among the fibers to form a matrix.

[0085] As represented by a step 453 (COMBINE ROVING WITH PLASTIC TO REINFORCE MATRIX OF FRC), the roving resulting from the method steps 450 to 452 is for example used as part of a layup for an FRC, the layup corresponding to an assembly of components for forming the FRC prior to curing. In particular, one or more of the rovings are for example combined with any thermoset or thermoform resin system to form an FRC, or they can be used as a tow that is woven or assembled to form a fabric that can then be combined with any thermoset or thermoform resin system to form an FRC. In some embodiments, the rovings, tows, or fabrics created from the tows, have resins, resin-based filaments, such as PLA or PA, or other additional chemistry or structural agents, e.g.metal filaments or other reinforcements, added in order to tailor the performance of the resulting composite.

[0086] Examples of fabrics comprising rovings or tows as described in relation with Figures 3 and 4A are shown in Figures 5 to 13, these fabrics for example being similar to those described in PCT publication W02020/222045, but with tow or roving of that application replaced by the tow or roving as described herein. The contents of this PCT application as published is hereby incorporated by reference to the extent permitted by the law.

[0087] Figure 5 illustrates a unidirectional reinforcement fabric 500 comprising tows, at least one of which corresponds to the tow 300 of Figure 3 or 400 of Figure 4A and according to an example embodiment of the present disclosure. The example of Figure 5 is a non-stitched fabric. In one embodiment, to form such a fabric, the tows are pre impregnated with an epoxy resin and are arranged astride each other and upon a backing paper or support. A removeable film is for example used to cover the surface opposite the backing paper and is removed when the fabric is used to create an FRC. Once the exposed fabric face has been adhered to either a mold or another layer of composite reinforcement fabric, the backing paper is removed.

[0088] While in the example of Figure 5 the tows are aligned in a single axis, it would also be possible to form a fabric using a similar technique, but in which a non-woven matt is formed in which the tows 300 or 400 are tangled together.

[0089] Furthermore, the above method for forming the fabric 500 could be adapted to form a multi-axial fabric. For example, the pre-pregged ply is layed upon a second, and possibly a third pre-pregged plies formed in a similar manner to the first ply, where the pre-pregged plies of each layer have their tows arranged in different orientations. The sandwich of plies is then for example covered with the protective film and the fabric ply is cut and layed-up as an integral piece/layer .

[0090] The techniques described above for forming the fabric 500, which for example has a width of at least 100 mm, could also be used to form a tape having a lower width of less than 100 mm.

[0091] Figure 6 illustrates a unidirectional (UD) stitched fabric 600 with tows, at least one of which corresponds to the tow 300 of Figure 3 or 400 of Figure 4A, according to an example embodiment of the present disclosure. In this example, the tows 300, 400, and optional further tows, are for example arranged in strips 602 shown running vertically in Figure 6, and a further thread 604 is woven across the strips 602 at regular intervals in order to join the strips 602 together. In the case of 0° UD fabrics, the strips 602 run along the length of the fabric, and the stitching is for example performed in the horizontal direction. In the case of 90° UD fabrics, the strips 602 run perpendicular to the length of the fabric, and the stitching is for example performed in the vertical direction. The further thread of the stitching is for example typically of polyester, although nylon, ramie, flax, or other materials may alternatively be used as desired. The fabric is unidirectional, as it is the tows that provide the strength along their axes and the "stitching" is used only to hold the position of the fibers until they are encapsulated in the matrix during the molding process of an FRC.

[0092] Figure 7 illustrates a multi-axial stitched fabric composed of tows 702, at least one of which corresponds to the tow 300 of Figure 3 or 400 of Figure 4A, according to an example embodiment of the present disclosure. In this fabric, a machine is for example used to orient fibers at a specific angle, typically at 0°, 90°, +45°, and/or -45° (it is also possible to orient fibers in +/- 60° angles on some machines). Fiber at a given angle is placed on a single layer, and the layers are situated one above the other and then the layers are stitched together in a 0° and/or 90° orientation to give structure to the fabric. Fabrics may be bi-axial (typically +45/-45), triaxial (0/+45/-45, 0/+60/-60 or 90/+45/-45), or quadriaxial (0/90/+45/-45). The stitching 704 is for example typically of polyester, although nylon, ramie, flax, or other materials may alternatively be used as desired.

[0093] Figure 8 illustrates a multi-axial woven fabric comprising tows, at least one of which corresponds to the tow 300 of Figure 3 or 400 of Figure 4A, according to an example embodiment of the present disclosure. The example of Figure 8 comprises tows 802 in the vertical direction, and tows 804 in the horizontal direction, the tows 802, 804 for example having substantially the same widths as each other.

[0094] Figure 9 illustrates a tubular braid 900 comprised of reinforcement tows according to an example embodiment of the present disclosure. For example, such a braid 900 comprises tows 902, at least one of which corresponds to the tow 300 of Figure 3 or 400 of Figure 4A.

[0095] Fabrics for a fiber-reinforced composite may be created in which at least one tow of the fabric corresponds to the tow 300 of Figure 3 or 400 of Figure 4A, as will now be described in more detail with reference to Figures 10 to 13.

[0096] Figure 10 illustrates a unidirectional fabric 1000 comprising at least one tow 1002 corresponding to the tow 300 or 400, and other rovings 1004 formed of other materials, such as natural or synthetic tows. Examples of natural tows include tows formed of fiber such as vegetal fibers of bamboo, flax, ramie, hemp, sisal, jute, banana, pineapple leaf, coir, abaca, rice, corn and nanocellulose, such as mineral fibers of basalt, asbestos, and ceramic fibers, and such as animal- derived fibers of goat hair, horse hair, lamb wool, and silk, while examples of synthetic tows include tows formed of carbon, glass, boron or aramid. In some embodiments, the natural fibers are organic fibers, or vegetable-derived fibers. This fabric can also incorporate, as described above, the same metal filaments, plastic or resin filaments, or other materials, which are or may become common to the production of FRCs.

[0097] The tows 1004 for example have dimensions substantially the same as those of the tows 1002 to create a uniform fabric, or their dimensions could be different to create a non-uniform fabric. Each of the tows 1004 is for example formed of bundles of two or more, and generally hundreds or thousands, of natural or synthetic fibers.

[0098] In the example of Figure 10, the fabric 1000 comprises a parallel arrangement of tows providing a unidirectional fabric, and there is a tow 1002 between every group of four adjacent tows 1004. This ratio could however be changed, the number r of tows 1004 in each group separated by a tow 1002 for example being between 1 and 100. The tows 1002 and 1004 are for example joined together to form a fabric in a similar manner to the techniques described above for fabrics 500 and 600 of Figures 5 and 6.

[0099] While in the example of Figure 10 the tows are aligned in a single axis, it would also be possible to form a fabric using a similar technique to the one described above in relation with Figure 5, but in which a non-woven matt is formed in which the tows 1002 and 1004 are all just tangled together without a precise orientation.

[0100] Figure 11 illustrates a biaxial fabric 1100 comprising tows arranged in two directions, which in the example of Figure 11 are perpendicular directions, at least one tow for example being the tow 300 of Figure 3 or 400 of Figure 4A. For example, the fabric 1100 comprises two layers 1102, 1104 of unidirectional fabric, each of which for example corresponds to the fabric 1000 of Figure 10. The layer 1102 for example lays on the layer 1104, the two layers for example being attached together in a similar manner to the fabric 700 of Figure 7 described above. Similarly, as described in relation with Figure 7, the multi-axial stitched fabric may be created with any similar arrangement of axes.

[0101] Figure 12 illustrates a 2x1 twill fabric 1200 comprising tows corresponding to the tow 300 of Figure 3 or 400 of Figure 4A, according to an example embodiment of the present disclosure. For example, like the fabric of Figure 11, the fabric 1200 of Figure 12 comprises tows arranged in perpendicular directions, there being a tow 1002 between every group of r tows 1004 in each of the directions. However, in the example of Figure 12, the tows are woven in a 2x1 twill pattern. The step of the twill pattern may vary according to the use of the fabric and may include, among others, patterns with a 2x1, 2x2, 2x3, 2x4, 3x1, 3x3, 3x4, etc. step. The distribution of tows 1002 may vary in the different axes.

[0102] Figure 13 illustrates a plain weave fabric 1300 comprising tows corresponding to the tow 300 of Figure 3 or 400 of Figure 4A, according to an example embodiment of the present disclosure. The example of Figure 13 is similar to the example of Figure 12, except that the tows are woven in a plain weave pattern.

[0103] The fabrics and compositions described herein have many applications. For example, the fiber-reinforced composite as described herein could be used in a variety of applications in which sound, vibrational and/or rebound damping is beneficial, including for construction, bicycle frames, winter sports equipment, stereophonic equipment, aerospace components, etc.

[0104] Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these embodiments can be combined and other variants will readily occur to those skilled in the art. For example, while Figures 3 and 4A illustrate examples in which the rovings or tows are formed of reinforcement fibers of two types of material, it will be apparent to those skilled in the art that, in alternative embodiments, the rovings or tows could additionally be formed of natural reinforcement fibers of one or more further types of material different to the first and second types, allowing for example to further enhance the mechanical performance of the roving or tow, and/or to further harmonize the mechanical properties. For example, in some embodiments there could be reinforcement fibers having in total up to six or more different types of materials in the tow or roving.

[0105] Finally, the practical implementation of the embodiments and variants described herein is within the capabilities of those skilled in the art based on the functional description provided hereinabove.