RADOME FABRICATION USING CYCLIC OLEFIN RESIN IN LIQUID MOLDING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application no. 62/459812, filed February 16, 2017, which is hereby incorporated herein by reference in its entirety.

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

[0002] This disclosure relates to using cyclic olefin resins in resin transfer molding applications. More particularly, this disclosure relates to using low viscosity cyclic olefin resins in resin transfer molding for article fabrication, such as radome fabrication.

Technical Background

[0003] A radome is a structure that encloses and protects an electronic device. A radome can be used in a variety of applications including communications (e.g., weather, satellite communications based on Ku band or Ka band, etc.), radar, and electronic warefare applications, among others. The structure of a radome can protect the underlying electronic device from damage from external factors such as wind, people, temperature, rain, snow, etc.

[0004] A traditional process for forming a radome is the hand lay-up process. In the hand lay-up process, substrates (e.g., fiber substrates) are laid into a mold and a resin is manually applied to the substrates using brushes, rollers, or various other means. Afterwards, the substrates with the resin are cured to form the finished article (i.e., a composite substrate). However, the hand lay-up process requires high amounts of labor and risk of chemical exposure to the workers hand laying the substrates and applying the resin to the substrates. In addition, the hand lay-up process usually results in excess of 100% fabric weight by resin, thereby unnecessarily wasting resin. Furthermore, resin by itself is relatively brittle;

therefore, any excess can actually weaken the finished article.

[0005] An improvement on the traditional hand lay-up process is to use a vacuum bag to suck excess resin out of the substrate. As such, vacuum bagging can improve the fiber-to- resin ratio and can result in a stronger and lighter product. However, there is still a hand lay- up involved in vacuum bagging. Accordingly, there is still a high amount of labor involved as well as risk of chemical exposure to workers. SUMMARY OF THE DISCLOSURE

[0006] Applicants have discovered an improved method of forming a radome.

Specifically, Applicants have unexpectedly discovered that using a vacuum assisted resin transfer method (VARTM) in combination with a low viscosity cyclic olefin resin can produce a radome with low dielectric constant, low loss tangent, low moisture absorption, light weight, and high mechanical properties such as tensile strength. In addition, a sandwich radome produced by the processes disclosed herein can have high interfacial adhesion strength.

[0007] VARTM is a method that uses vacuum pressure to drive resin into a dry substrate placed in a mold. Unlike traditional hand lay-up and vacuum bagging processes, the vacuum is drawn while the substrates are still dry. Thus, any excess resin that is introduced via the resin inlet can eventually be sucked out by the vacuum. As such, the minimum amount of resin can be introduced to the substrate, thereby providing a better fiber- to-resin ratio than even vacuum bagging. This better fiber-to-resin ratio in combination with the specific resin can lower the weight and increase the strength of the final cured article (e.g., radome). In some embodiments, the fiber-to-resin ratio can be about 70:30, about 65:35, about 60:40, about 55:45, or about 50:50. The fiber in the fiber-to-resin ratio can refer to the substrate that is impregnated with the resin. Applicants have discovered that the combination of cyclic olefin resins described herein and VARTM can produce cured articles with a lower dielectric constant, lower loss tangent, lower moisture absorption, lighter weight, and higher mechanical properties such as tensile strength than those cured articles previously produced by traditional hand lay-up processes and vacuum bagging.

[0008] In addition, unlike traditional hand lay-up processes which have a wide variety of resin content due to human inconsistency, VARTM has a very consistent resin usage. This can result in less wasted resin and therefore additional cost savings. Lastly, VARTM is a much safer and less time consuming process than traditional hand lay-up and vacuum bagging processes. In VARTM, workers are no longer required to saturate a substrate by hand with a brush or roller, thereby inhaling the various resin fumes, Accordingly,

Applicants improved method of forming a radome can deliver better controlled radomes in terms of reproducibility and efficiency as well as the benefits described above.

[0009] Reference to "about" a value or parameter herein includes (and describes) variations that are directed to that value or parameter per se. For example, a description referring to "about X" includes a description of "X". In addition, reference to phrases "less than", "greater than", "at most", "at least", "less than or equal to", "greater than or equal to", or other similar phrases followed by a string of values or parameters is meant to apply the phrase to each value or parameter in the string of values or parameters. For example, a statement that the temperature can be less than 100°C, 50°C, or 25°C is meant to mean that the temperature can be less than 100°C, less than 50°C, or less than 25°C.

[0010] The word "substantially" does not exclude "completely." For example, a composition which is "substantially free" from Y may be completely free from Y. The term "substantially free" permits trace or naturally occurring impurities. It should be noted that, during fabrication, or during operation (particularly over long periods of time), small amounts of materials present in one layer may diffuse, migrate, or otherwise move into other layers. Accordingly, use of the terms "substantial absence of and "substantially free of is not to be construed as absolutely excluding minor amounts of the materials referenced. Where necessary, the word "substantially" may be omitted from the definition of the invention.

[0011] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is also to be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It is further to be understood that the terms "includes, "including," "comprises," and/or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, components, and/or units but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, units, and/or groups thereof.

[0012] Additional advantages will be readily apparent to those skilled in the art from the following detailed description. The examples and descriptions herein are to be regarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Exemplary embodiments are described with reference to the accompanying figures, in which:

[0014] Figure 1 illustrates a cross-section of an embodiment of VARTM for a flat mold.

[001S] Figure 2 is an illustration of a radome comprising an antenna. [0016] Figure 3 illustrates the results of a water absorption test of two samples of the Example section.

[0017] It will be recognized by persons of ordinary skill in the art, given the benefit of this disclosure, that certain dimensions or features in the figures may have been enlarged, distorted, or shown in an otherwise unconventional or non-proportional manner to provide a more user friendly version of the figures. Reference to front, back, top, and bottom are provided for exemplary purposes and are not limiting.

DETAILED DESCRIPTION

[0018] Applicants have discovered an improved method of forming a radome.

Specifically, Applicants have unexpectedly discovered that using VARTM in combination with a low viscosity cyclic olefin resin can produce a radome with low dielectric constant, low loss tangent, low moisture absorption, light weight, and high mechanical properties such as tensile strength. Furthermore, a sandwich radome produced by the processes disclosed herein can have high adhesion strength. In addition, Applicants' improved method of forming a radome can deliver better controlled radomes in terms of reproducibility and efficiency.

[0019] The radomes described herein can include a substrate impregnated with a resin, wherein the resin is added to or otherwise present in or on the substrate. The substrate can be impregnated using VARTM. Figure 1 illustrates a cross-section of an embodiment of VARTM for a flat mold. Although a flat mold may not be an ideal shape for a radome, the flat mold is used herein in order to simplify the explanation of the process. However, mold 101 can come in a variety of shapes including a radome shape. The mold can be made from a metal, such as aluminum or steel, or other materials such as fiberglass or epoxy.

Release Agent (or Film) Placed into Mold

[0020] A release agent can be placed on the mold prior to adding the substrate. A release agent can be a chemical used to prevent other materials (e.g., substrates) from bonding or sticking to the mold surface. Accordingly, the mold release agent can facilitate the separation of the molded substrate from the mold after the VARTM and curing process. Without such a release agent, the substrate can be fused to the mold, thereby creating loss of product. Examples of release agent can include polytetrafluoroethylene ("PTFE") or a mold release spray containing a slip agent such as Chemlease R&B EZ from Chemtrend. In some embodiments, the release agent can be a release film. For example, release film 102 is placed on mold 101 in Figure 1. The release film can be a polytetrafluoroethylene (PTFE) film. Substrate (and Core) Placed into Mold

[0021] Next, the substrate to be impregnated by the resin can be added to the mold. In some embodiments, the substrate can be placed on the release agent. The substrate can be a dry substrate, meaning that the substrate can be substantially free from resin prior to being added to the mold or was not previously impregnated with resin prior to being placed in the mold. As shown in Figure 1, substrate 103 is placed on release agent 102. The substrate can be produced by disposing a plurality of individual plies or layers on each other, next to each other, and/or overlapping each other. In addition, the plies or layers can be coupled together and/or molded or formed into a desired shape. In some embodiments, the substrate comprises at least two plies or layers, at least three plies or layers, at least four plies or layers, at least five plies or layers, at least six plies or layers, at least seven plies or layers, at least eight plies or layers, at least nine plies or layers, at least ten plies or layers, at least eleven plies or layers, at least twelve plies or layers, at least thirteen plies or layers, at least fourteen plies or layers, or at least fifteen plies or layers. In some embodiments, the substrate comprises one ply or layer, two plies or layers, three plies or layers, four plies or layers, five plies or layers, six plies or layers, seven plies or layers, eight plies or layers, nine plies or layers, ten plies or layers, eleven plies or layers, twelve plies or layers, thirteen plies or layers, fourteen plies or layers, or fifteen plies or layers. In a situation where woven fabric is used, one ply can refer to one woven fabric layer. One or more of these plies or layers (or the entire substrate itself) can be produced using 3-D weaving or knitting technology. For example, a 3-D weaving or knitting technology can weave a one-piece substrate that can be used as a monolithic substrate. Accordingly, the substrate can be preformed using 3-D weaving or knitting technology which can allow the substrate to be a specific shape for the mold. In addition, this one-piece substrate can eliminate seams that occur when using various substrate layers or plies. By eliminating the seams, the strength of the finished, cured article can have a higher tier strength. For example, the 3-D weaving or knitting technology can create a dome-shaped substrate for a radome.

[0022] In some embodiments, the thickness of the plies or layers can be about 1-20 mil, about 5-15 mil, about 5-10 mil, about 7-9 mil, about 8-9 mil, or about 8.6 mil. The thickness of the substrate can depend on the radome design and how many plies or layers are used.

[0023] In addition, the VARTM system can include more than one substrate. For example, a sandwich fabrication method can be molded wherein there is a core layer between various substrates in the mold. In some embodiments, the same amount of plies or layers of a substrate can be below the core layer as the amount of plies or layers of the substrate on top of the core layer. For example, three plies or layers of a first substrate can be placed into the mold, a core layer (e.g., a 0.25 inch foam core) can be placed on the initial three plies or layers of the first substrate, and an additional three plies or layers of a second substrate can be placed on the core layer such that the first substrate and second substrate sandwich the core layer. In some embodiments, a different amount of plies or layers of a substrate can be below the core layer than the amount of plies or layers of the substrate on top of the core layer. In some embodiments, the substrate below the core layer can be the same as the substrate on top of the core layer. In other embodiments, the substrate below the core layer can be different from the substrate on top of the core layer. The core layer can increase the overall thickness of the finished, cured article without imparting too much additional weight. Alternatively, the core layer may be present on an inner surface of an article, e.g., near an antenna or other electronic device, to increase the overall thickness of the articles.

[0024] In some embodiments, the core layer can be a honeycomb core, a foam core, a metal core, a polymer core, or a hollow core. In some embodiments, the core layer is a closed-cell core layer. In some embodiments, the foam core can be a high temperature foam core such that it can withstand the curing process. For example, in some embodiments the post cure temperature can be between 150°C and 180°C, so the high temperature foam core has high temperature resistance and retention of mechanical strength at these high temperatures. In some embodiments, the foam core is a high strength foam so that it can withstand the pressure of the vacuum infusion process. The closed-cell foam can resist infusion of the resin and various other liquids used during article formation. In addition, the closed-cell foam can provide more surface area for contacting the substrates (in contrast to a honeycomb core) during the formation of the article, thereby reducing the potential for void formation between the core layer and the substrates. In other embodiments, the core layer can include grooves, perforations, and/or scores in the core material which can help resin traverse the substrate while simultaneously adding strength and rigidity. In some embodiments, the foam core can be a polyetherimide (PEI) foam core or a polyphenylsulfone (PPSU) foam core. In some embodiments, the foam core can be a PPSU foam core manufactured by Solvay. The core should be chemically compatible with the resin used in the VARTM process. For example, Applicants have discovered that a PPSU foam core can be chemically compatible with the resins disclosed herein. In some embodiments, the core layer is placed in the mold as a single structure. Alternatively, the core can be placed in the mold as a plurality of foam structures. In some embodiments, the plurality of foam structures can be joined together by adhesive or by a thermomelting process to form a single foam core. In some embodiments, the core layer is shaped in the general form of the final article before the process of combining the core layer with the substrates. The foam core can be about 0.1- 5 inch thick, about 0.2-2 inch thick, or about 0.25-1 inch thick. In some embodiments, the foam core can be about 0.25 inch thick.

[0025] In some embodiments, the core layer can have a density of about 2-4 lb/ft ³ , about 2.5-3.5 lb/ft ³ , about 2.75-3.5 lb/ft ³ , about 2.9-3.3 lb/ft ³ , about 3-3.2 lb/ft ³ , or about 3.1 lb/ft ³ . In some embodiments, the tensile strength of the foam can depend on the density. For example, the following Foam Table can include the density and tensile strength of certain individual foams that are commonly used in aerospace and auto industries.

FOAM TABLE

[0026] Although multiple plies or layers can be used to form a substrate, the composition or material of the individual plies or layers in the substrate can be different. For example, a substrate that comprises three plies or layers may have two plies or layers with the same composition or material and the third ply or layer may have a different composition or material. Tn addition, the thickness of the plies or layers in a single substrate may be different.

[0027] In some embodiments, the substrate is generally transparent to radio waves or microwaves (or another desired radiation frequency) when present in the cured article. For example, the substrate may pass radio signals or microwave signals sent from a transmitter within the structure formed by the substrate. In addition, the substrate may permit a receiver within the structure formed by the substrate to receive radio signals or microwave signals reflected from an object or sent from a transmitter of another device or system. The cured articles are generally thin walled but structurally robust to withstand the various forces encountered by articles.

[0028] In some embodiments, the substrates of the articles described herein may be porous substrates that can be impregnated with a resin produced as described herein. The substrates and plies or layers may be, or may comprise, a woven fabric, a non-woven fabric, a ceramic, a plastic, a glass, a polymer, or may take other forms. In some embodiments, the ply(s) or layer(s) may comprise fiberglass, nylon, polyester, a polyethersulfone, an aramid (such as KEVLAR® or NOMEX® available from Dupont), a polyethylene, a polypropylene, a polyolefin, a polyimide, a polyamide, a polyamide-imide, a polyphenylene sulfide, carbon, carbon black, graphite, diamond, a polybenzimidazole (PBI), a polybenzoxazole (PBO), a halocarbon, or other suitable materials. In some embodiments, the plie(s) or layer(s) may comprise one or more forms of glass. For example, the plie(s) or layer(s) may be produced from E-glass (alumino-borosilicate glass with less than about 1 weight percent alkali oxides), A-glass (alkali-lime glass with substantially no boron oxide), E-CR-glass (alumino-lime silicate with less than 1 % by weight alkali oxides), C-glass (alkali-lime glass with high boron oxide content), D-glass (borosilicate glass with a low dielectric constant), L-glass (ultra-low dispersion glass commonly used in optics), R-glass (aluminosilicate glass without any substantial amounts of MgO and CaO), and S-glass (aluminosilicate glass without CaO but with high MgO content). In some embodiments, the plie(s) or layer(s) can include 7781 Glass or 4581 Quartz.

[0029] In some embodiments, the plie(s) or layer(s) may be fiber- free or may be fiber-reinforced to provide additional strength. Where fibers are present, the fibers may be thermoplastic fibers, thermoset fibers, glass fibers, ceramic fibers, metal fibers, or other suitable types of fibers. For example, one or more glass fibers selected from E-glass fibers, A-glass fibers, E-CR-glass fibers, C-glass fibers, D-glass fibers, R-glass fibers, and S-glass fibers can be used in the substrate. The substrate may include a first material, e.g., a fabric, and a second different material, e.g., glass fibers, if desired. The different materials may be present as separate plies or layers of a multi-ply or multi-layer substrate or may be present in regions or zones of the same ply. In some embodiments, the fibers may be added directly to the resins described herein, e.g., a resin of formulae (I)-(III), prior to addition of the resin to the substrate. In some embodiments, two or more different types of fibers are present in the substrate or the final article.

[0030] In some embodiments, the substrates described herein and/or the resins described herein may comprise one or more additives. For example, the substrate or plie(s) or layer(s) can include crystals, quartz, glass particles, stabilizing agents, flame retardants (halogenated flame retardants, phosphorated flame retardants, etc.), smoke suppressants, or other materials to impart one or more desired physical properties to the cured article comprising the substrate. In some embodiments, one or more hardeners or curing agents may be included in the substrate or resin or both to increase (or decrease) the rate of curing to form the final article. When cured, the substrates can form a hard article that is inflexible. Such hard structures can be desirably suitable for protecting underlying electronic devices from damage from weather or unwanted physical contact. In some embodiments, the cured articles can be flexible, at least to some degree, after curing or may include flexible sections after curing. The flexible articles can be bent to at least some degree into a desired shape and may be held in the desired shape using suitable fasteners, e.g., bolts, screws, adhesives, rivets, or other suitable fasteners.

[0031] When working with molds of complex shapes, such as that of a radome, dry plies or layers may not readily sit flat or flush against the mold or may need to be held together before resin is injected by vacuum. Accordingly, adhesives can be used to remedy this problem. For example, 3M's Super 77™ Spray Adhesive can be used to provide enough adhesion to hold the plies or layers in place. When used moderately, these adhesives should not interfere with the resin infusion or curing process. In some embodiments, additional structural support elements, such as stitches, can integrally connect the plies or layers of the substrate.

Peel Ply Placed into Mold

[0032] After the substrate is added to the mold, a peel ply layer can be added. Figure 1 shows peel ply layer 104 on top of substrate 103. In some embodiments, there can be a release agent added below and/or above the peel ply layer. In some embodiments, the peel ply layer can leave a uniform texture on the surface of the substrate. In other embodiments, the peel ply layer can leave behind a rougher surface on the substrate. This rougher surface can improve mechanical bonding between the finished article and other materials. In some embodiments, the peel ply can include Teflon-coated glass release ply such as Bron Aerotech or nylon based peel ply such as Release Ply B or Econostitch from Airtech. In some embodiments, the peel ply can be incorporated into the final article. In other embodiments, the peel ply can be removed after curing so that it is not incorporated into the final article. In some embodiments, multiple peel ply layers can be added. In some embodiments, the peel ply can be added on both sides of the substrate so that the peel ply layers sandwich the substrate. In other embodiments, the peel ply can be applied as a single layer between plies or layers of the substrate.

Flow Media Placed into Mold

[0033] Flow media can also be applied to the substrate. Flow media can aid the flow of resin during resin impregnation. Many substrates can have a great deal of resistance to resin flow. Accordingly, flow media can reduce the resistance for the resin to flow into the substrates. In some embodiments, flow media can be a polypropylene flow media such as Greenflow 75 from Airtech. In some embodiments, the flow media layer can be on top of the peel ply layer. For example, Figure 1 depicts flow media layer 105 on top of peel ply layer 104. In some embodiments, multiple flow media layers can be used. In some embodiments, the flow media can be laid as a single layer between the plies or layers of the substrate. In some embodiments, the flow media can be incorporated into the final article. In other embodiments, the flow media can be removed after curing so that it is not incorporated into the final article.

Resin Inlet and Vacuum Outlet Ports Placed into Mold

[0034] In order for resin to flow in the VARTM process, resin inlet ports and vacuum outlet ports need to be added to the mold assembly. For example, Figure 1 illustrates resin inlet port 106 and vacuum outlet port 107. In some embodiments, there can be more than one resin inlet port and/or more than one vacuum outlet port. These ports can be installed before closing the vacuum bag.

[0035] In some embodiments, the substrate may comprise one or more additional layers or materials disposed on them or between the individual plies or layers of the substrates. For example, the substrate may comprise a protective covering disposed on a surface of a first ply or layer of the substrate. The first ply or layer can be coupled to another ply or layer of the substrate. The protective covering may take the form of a film, a coating, a layer, a laminate, or other suitable coverings that can act to protect the layers underneath the covering. In some embodiments, the covering may be designed to filter out wavelengths outside of a certain f equency while permitting desirable wavelengths to pass through the structure to an underlying antenna or electronic device. For example, the covering may be configured as a low pass filter, a high pass filter, or both to provide a transmission window permitting frequencies within the window to be transmitted through the substrate. In addition, if desired, a covering may be disposed on the plies or layers such that the coverings sandwich plies or layers within the substrate. In some instances, a covering may be selected for aesthetic purposes, e.g., may be camouflaged or selectively colored, but does not have any protective or functional properties. In some embodiments, the covering may comprise a different material than that which is present in the substrates. For example, the covering may comprise ultra-high molecular weight polyethylene (UHMWPE) or fiber-reinforced UHMWPE. In other instances, the covering may comprise polyetheretherketone (PEEK) or fiber-reinforced PEEK.

Make Vacuum Bag with Sealant

[0036] After the various materials and layers are in place, the vacuum bag can be added. In some embodiments, the vacuum bag can enclose the substrate(s) in the mold assembly. In some embodiments, the vacuum bag can bag the mold and substrate together as one complete piece. In other embodiments, the vacuum bag can be attached to a flange or surface of the mold. As shown in Figure 1, vacuum bag 108 is attached to mold 101 by sealant tape 109. The vacuum bag can be the outermost layer of the bagging setup that creates the airtight seal. Adhesives such as sealant tape can be used to create the airtight seal to close the vacuum bag either to itself or to the mold. The vacuum bag can stretch over the materials in the mold and into any open voids of the mold. The vacuum bag can be coated with a release agent (as previously described) on the side of the bag facing the substrate. A release agent (or film) may be added to the substrate or layered on the topmost layer on the substrate before covering it with the vacuum bag. The release agent can be added so that the finished article can be pulled away from the vacuum bag once the cure is complete.

Impregnate Substrates with Cyclic Olefin Resin

[0037] Once the vacuum bag is secured to the mold assembly, the tubing for the resin and vacuum lines can be attached. A vacuum pump can be used to create the vacuum used to pull the resin into the substrate. The vacuum pump can be turned on as a valve controlling the resin flow remains closed, thereby evacuating air between the vacuum bag and the various materials in the mold. ·

[0038] A liquid resin can be prepared and stored in a resin reservoir, which can include mixing the components of a 2-part resin (if applicable). Once the resin valve to the mold is opened, the resin can be directed from the resin reservoir through the resin port and into the space defined by the vacuum bag and layers that make up the article to be formed. The resin can be vacuum infused through the substrate(s) such that they are impregnated with resin. In some embodiments, minimal or no voids or dry spots exist in and/or on the substrate(s) after resin impregnation. After the substrate(s) are impregnated, resin may exit the mold through the vacuum outlet and be collected in a resin trap. A resin trap can be a container placed within the vacuum tubing circuit between the mold and the vacuum pump which can catch any excess resin before it reaches the vacuum pump.

[0039] The resins described herein can be considered thermoset or thermosetting resins so the cured article can withstand environmental conditions commonly encountered by radomes, though in certain instances one or more thermoplastic materials may be present in certain areas, layers or parts of the articles. In some embodiments, the resin can be those disclosed in US Publication No. 2015/004423, which is hereby incorporated by reference in its entirety. In some embodiments, the resins disclosed herein can have a low viscosity. For example, the resins disclosed herein can have a viscosity of about 1-2000 cps, about 5-1500 cps, about 10-1250 cps, or about 15-1000 cps. In addition, this low viscosity resin can reduce void content and thickness variation in the finished, cured article. A high viscosity resin can create voids and thickness variation in the cured article.

[0040] In some embodiments, the resins disclosed herein can have a density of less than about 5 g/cm ³ , about 4 g/cm ³ , about 3 g/cm ³ , about 2 g/cm ³ , or about 1.5 g/cm ³ . In some embodiments, the resins disclosed herein can have a density of about 0.9-1.1 g/cm ³ . In some embodiments, the resin can have a density of about 1.03 g/cm ³ . This low density resin can provide light weight advantages to the final cured articles.

[0041] In some embodiments, the resins described herein may be produced from any monomer which is effective to polymerize by way of ring opening metathesis polymerization (ROMP). For example, suitable materials can include one or more cyclically strained monomers comprising one or more areas of unsaturation. The monomer may include one or more strained rings or cyclic structures to favor the ROMP pathway over other potential pathways. For example, cyclically constrained alkenes comprising one, two, three or more sites of unsaturation may be used. Relief of ring strain in the cyclically strained alkene monomers by way of ROMP can relieve the ring strain and result in polymerization of the reactants. In certain embodiments described herein, the resin may be produced using monomeric reactants that comprise bicyclic and tricyclic compounds that comprise ring strain. Illustrative general compounds and specific compounds are described in more detail below.

[0042] In some embodiments, to facilitate ROMP, one or more catalysts may be present. The exact nature of the catalyst selected may depend on the particular reactants used. For example, substituted cyclically strained compounds may have groups that can poison the catalyst and terminate the polymerization. Illustrative catalysts include, but are not limited to, transition metal chlorides/alcohol mixtures (e.g., RuCb/alcohol), Grubb's catalysts (transitions metal carbene complexes such as

(H2lMes)(PCy3)(Cl)2Ru=CHPh and osmium), Schrock catalysts (tungsten and molybdenum) and other metal catalysts.

[0043] In some embodiments, the reactants used to produce the resin may comprise norbornene or a norbornene derivative. For example, the reactant may comprise a compound of

where R ¹ , R ² , R ³ and R ⁴ may each independently be hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbon atoms. In some embodiments, each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 6 carbon atoms. In other embodiments, each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen or a hydrocarbon group comprising 1 to 4 carbon atoms. In additional embodiments, each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen or a hydrocarbon group comprising 1 to 3 carbon atoms (saturated or unsaturated). In some embodiments, each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen or a hydrocarbon group (saturated or unsaturated) comprising 1 or 2 carbon atoms. In further embodiments, each of R ¹ , R ² , R ³ and R ⁴ is independently hydrogen and a methyl group. In some embodiments, each of R ¹ , R ² , R ³ and R ⁴ is hydrogen. In some embodiments, R ² and R ³ may together form a cyclic structure as shown in Formula (II)

where R ¹ and R ⁴ may be any of those groups listed above in connection with Formula (I) and R ⁵ may be -CH2, oxygen, a secondary amine or a tertiary amine.

[0044] In some embodiments, R ¹ , R ² , R ³ and R ⁴ of formula (I) and R ¹ and R ⁴ of formula (II) may each independently be -(CH2)nCOOR ⁶ , -(CH2)nOCOR ⁶ , -(CH ₂ )nOR ⁶ , where R ⁶ is hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms or 1 to 2 carbon atoms and n is 0, 1 , 2, 3 or more. In other embodiments, R ¹ , R ² , R ³ and R ⁴ of formula (I) and R ¹ and R ⁴ of formula (II) may each independently be hydrogen or - (CH2)nCN and n is 0, 1 , 2, 3 or more. In some embodiments, each of R ¹ , R ² , R ³ and R ⁴ of formula (I) and R ¹ and R ⁴ of formula (II) may be hydrogen or -(CH ₂ )nCONR ⁷ R ⁸ , where R ⁷ and R ⁸ are independently hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms and n is 0, 1 , 2, 3 or more. In other embodiments, each of R ¹ , R ² , R ³ and R ⁴ of formula (I) and R ¹ and R ⁴ of formula (II) may independently be hydrogen, - (CH ₂ )nCOOR ⁹ , -(CH2)nCOCOR ⁹ ,

-(CH2)nOR ⁹ , where R ⁹ is hydrogen or a halogen substituted hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms and n is 0, 1 , 2, 3 or more. The presence of internal halogen groups, such as CI and Br, can assist in providing flame retardancy to the articles without the need to include a separate flame retardant. In other instances, each of R ¹ , R ² , R ³ and R ⁴ of formula (I) and R ¹ and R ⁴ of formula (II) may independently be hydrogen or

-(CH2)nR ¹⁰ , where R ¹⁰ is Si(R ^u ) _q R ¹² where R ¹¹ is a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms, R ¹² is a halogen, and n and q are each 0, 1 , 2 or 3 or more. In other embodiments, each of R ¹ , R ² , R ³ and R ⁴ of formula (I) and R ¹ and R ⁴ of formula (II) may independently be hydrogen, -(O=C-0- C=0)-, -(0=C-NR ¹⁴ -C=0), where R ¹⁴ is a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms or 1 to 2 carbon atoms. In some embodiments, the groups of R ¹ , R ² , R ³ and R ⁴ of formulae (I) and (II) are independently selected from the groups listed herein and so no polar groups are present in the reactant molecule. For example, the groups can be selected such that no oxygen, nitrogen or other centers are present in the reactant molecule. As described herein, such polar groups can poison certain catalysts. Where it is desired to use reactants with polar groups, catalysts can be selected that are not poisoned by the groups present in the reactant molecules.

[0045] In some examples, the compound of formula (II) may be a derivative com rising the structure shown in formula III)

where R ¹ and R ⁴ of formula (III) may each independently be hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbon atoms. In some embodiments, each of R ¹ arid R ⁴ is independently hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 6 carbon atoms. In other embodiments, each of R ¹ and R ⁴ is independently hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 4 carbon atoms. In some embodiments, each of R ¹ and R ⁴ is independently hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 3 carbon atoms. In some embodiments, each of R ¹ and R ⁴ is independently hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 or 2 carbon atoms. In further embodiments, each of R ¹ and R ⁴ is independently hydrogen and a methyl group. In some embodiments, each of R ¹ and R ⁴ is hydrogen to provide dicyclopentadiene. In some examples, R ¹ and R ⁴ of formula (III) may each independently be -(CH ₂ )nCOOR ⁶ , -(CH2)nOCOR ⁶ , -(CH2)„OR ⁶ , where R ⁶ is hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms and n is 0, 1 , 2, or 3 or more. In other embodiments, Rl and R ⁴ of formula (III) may each independently be hydrogen or -(CH2)nCN where n is 0, 1 , 2, 3 or more. In some embodiments, R ¹ and R ⁴ of formula (III) may be hydrogen or-(CH2)nCONR ⁷ R ⁸ , where R ⁷ and R ⁸ are independently hydrogen or a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms or 1 to 2 carbon atoms and n is 0, 1 , 2 or 3 or more. In some embodiments, R ¹ and R ⁴ of formula (III) may independently be hydrogen,

-<CH ₂ )nCOOR ⁹ , -(CH2)„COCOR ⁹ , -(CH2)nOR ⁹ , where R ⁹ is hydrogen or a halogen substituted hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms or 1 to carbon atoms and n is 0, 1, 2, 3 or more. In some embodiments, R ¹ and R ⁴ of formula (III) may each independently be hydrogen or-(CH2) _n R ¹⁰ , where R ¹⁰ is Si(R' ')qR ¹² where R ^{1 1} is a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms, R ¹² is a halogen, and each of n and q is independently 0, 1, 2 or 3 or more. In some embodiments, R ¹ and R ⁴ of formula (III) may independently be hydrogen, -(0=C-0-C=0)-, -(0=C-NR ¹⁴ -C=0), where R ¹⁴ is a hydrocarbon group (saturated or unsaturated and linear or cyclic) comprising 1 to 10 carbons atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms. In some embodiments, the groups of R ¹ and R ⁴ of formula (III) may independently be selected from the groups listed herein and so no polar groups, e.g., oxygen or nitrogen, are present in the reactant molecule.

[0046] In some embodiments, the resins described herein may be produced by reacting at least one compound having formula (I), formula (II), or formula (III) in the presence of a catalyst. In some embodiments, the resins described herein may be produced by reacting two compounds having formula (I) with each other in the presence of a catalyst. The compounds of formula (I) may be the same or may be different. Similarly, two or more different or similar compounds having the general formula of formula (II) may be mixed together and polymerized by ROMP. Additionally, two or more different or similar compounds having the general formula of formula (III) may be mixed together and polymerized by ROMP. In some embodiments, one reactant is a compound of formula (I) and the other reactant is a compound of formula (II). In some embodiments, one reactant is a compound of formula (I) and the other reactant is a compound of formula (III). In some embodiments, one reactant is a compound of formula (II) and the other reactant is a compound of formula (III). The binary mixtures may further comprise a catalyst, solvents, rate limiters or controllers or other additives or compounds as desired. For example, as described herein, it may be desirable to cure the resins at two different temperatures, and a rate controller may be present such that polymerization does not complete at the first temperature. Where different compounds are present in a binary mixture of reactants, the compounds may be present in a 50/50 mixture (50% by weight/50% by weight), 40/60 mixture, 30/70 mixture, 20/80 mixture, 10/90 mixture, 5/95 mixture or other suitable ratios between these illustrative ratios. In some embodiments, one of the compounds of the binary mixture is either norbornene or dicylopentadiene and the other compound is independently selected from compounds of formulae (I)-(III). In some embodiments, polymerization may be permitted to occur for some period in the presence of a first compound and a second, different compound may be added after the first period to permit polymerization in the presence of the second compound.

[0047] In some embodiments, the resins described herein may be produced by reacting three compounds having formulae (I), (II) and (III) with each other in the presence of a catalyst. For example, three different compounds all having a formula of formula (I) can be combined to provide a ternary mixture and polymerized using ROMP. In some

embodiments, two compounds of formula (I) may be reacted with a compound of formula (II). In some embodiments, two compounds of formula (I) may be reacted with a compound of formula (III). In some embodiments, one compound of formula (I) is reacted with two compounds of formula (II). In some embodiments, one compound of formula (I) is reacted with two compounds of formula (III). In some embodiments, three compounds of formula (III) are reacted with each other and polymerized by ROMP. In some embodiments, two compounds of formula (II) are reacted with one compound of formula (III). In further instances, three compounds of formula (III) are reacted with each other and polymerized by ROMP. In some embodiments, a compound of formula (I) is reacted with one compound of formula (II) and another compound of formula (HI). Where ternary mixtures of reactants are used, the ternary mixtures may further comprise a catalyst, solvents, rate limiters or controllers or other additives or compounds as desired. Where different compounds are present in a ternary mixture of reactants, the compounds may be present in a (l/3)/(l/3)/(l/3) mixture (33.33% by weight of each compound), a 40/40/20 mixtures, a 50/30/20 mixture, a 60/20/20 mixture, a 70/10/20 mixture, a 75/5/20 mixture, a 50/40/10 mixture, a 55/40/5 mixture, a 60/30/10 mixture, a 80/10/10 mixture, a 90/5/5/ mixture a 95/2.5/2.5 mixture, a 95/4/1 mixture or other illustrative weight percentage ratios between these illustrative ratios. In some embodiments, one of the compounds of the ternary mixture is either norbornene or dicylopentadiene and the other two compounds are independently selected from compounds of formulae (I)-(III).

[0048] In some embodiments, specific norbornene compounds and derivatives suitable for use include, but are not limited to, norbornene, dicyclopentadiene, 5-methyl-2- norbonene, 5-ethyl-2-norbornene, 5-ethylene-2-norbornene, 5-propyl-2-norbonene, 5-butyl-2- norbonene, 5-pentanyl-2-norbonene, 5-hexyl-2-norbonene, 5-cyclohexyl-2-norbonene, 5- septyl-2-norbonene, 5-octyl-2-norbonene, 5-nonyl-2-norbonene, 5-decyl-2-norbonene, 5- ethylene-5-chloro-2-norbornene, 5-propyl-5-chloro-2-norbonene, 5-butyl-5-chloro-2- norbonene, 5-pentanyl-5-chloro-2-norbonene, 5-hexyl-5-chloro-2-norbonene, 5-cyclohexyl- 5-chloro-2-norbonene, 5-septyl-5-chloro-2- norbonene, 5-octyl-5-chloro-2-norbonene, 5- nonyl-5-chloro-2-norbonene, 5-decyl-5-chloro-2- norbonene, 5-methyl-5-bromo-2- norbornene, 5-ethylene-5-bromo-2-norbornene, 5-propyl-5- bromo-2-norbonene, 5-butyl-5- bromo-2-norbonene, 5-pentanyl-5-bromo-2-norbonene, 5-hexyl-5-bromo-2-norbonene, 5- cyclohexyl-5-bromo-2-norbonene, 5-septyl-5-bromo-2-norbonene, 5- octyl-5-bromo-2- norbonene, 5-nonyl-5-bromo-2-norbonene, 5-decyl-5-bromo-2-norbonene, methyl 5- norbornene-2-carboxylate, ethyl 5-norbornene-2-carboxylate, phenyl 5-norbornene-2- carboxylate, methyl 2-methyl-5-norbornene-2-carboxylate, butyl 3-phenyl-5-norbornene-2- carboxylate, dimethyl 5-norbornene-2,3-dicarboxylate, cyclohexyl 5-norbornene-2- carboxylate, allyl 5-norbornene-2-carboxylate, 5-norbornene-2-yl acetate, 5-norbornene-2- nitrile, 3-methyl-5- norbornene-2-nitrile, 2,3-dimethyl-5-norbornene-2,3-dinitrile, 5- norbornene-2-carboxylic acid amide, N-methyl-5-norbornene-2-carboxylic acid amide, N ,N- diethyl-5-norbornene-2-carboxylic acid amide, N,N,N',N'-tetramethyl-5-norbornene-2,3- dicarboxylic acid diamide, 5-chloro-2- norbornene, 5-bromo-2-norbornene, 5-fluoro-2- norbornene, 5-methyl-5-chloro-2-norbornene, chloroethyl 5-norbornene-2-carboxylate, dibromopropyl 5-norbornene-2-carboxylate, dichloropropyl 5-norbornene-2-carboxylate, monochlorophenyl 5-norbornene-2-carboxylate, monobromophenyl 5-norbornene-2- carboxylate, tribromophenyl 5-norbornene-2-carboxylate, 2,3-dichloro-5-norbornene, 2-bromo-5 -norbornene, 2-bromomethyl-5-norbornene, tribromobenzyl 5-norbornene-2- carboxylate, 5-norbornene-2,3-dicarboxylic anhydride, 2,3- dimethyl-5-norbornene-2,3- dicarboxylic anhydride, 5-norbornene-2,3-dicarboxylic acid imide, N-phenyl-2-methyl-5- norbornene-2,3-dicarboxylic acid imide, 2-trichlorosilyl-5-norbornene, 2-(dimethylmethoxysilyl)-5-norboraene, 2-(dimethylacetylsilyl)-5-norbornene, and

2-trimethylsilyl-5-norbornene.

[0049] In some embodiments, one of more of the compounds of formulae (I)-(III) can be combined with either norbornene or dicyclopentadiene in an amount of about 85-95 weight percent norbornene or dicyclopentadiene with the remaining 5-15 weight percent from the other compounds of formulae (I)-(III). In some embodiments, the mixture may comprise about 85-95 weight percent norbornene with the remaining 5-15 weight percent from dicyclopentadiene. In some embodiments, the mixture may comprise about 85-95 weight percent dicyclopentadiene with the remaining 5-15 weight percent from norbornene. In some embodiments, the resin can be 100 weight percent norborene. In other embodiments, the resin can be 100 weight percent dicclopentadiene.

[0050] In some embodiments, the monomers described herein can be used in combination with other materials. For example, one or more additional materials may be present in the resins produced using the monomers described herein. Illustrative additional materials include, but are not limited to, pigments, carbon black, natural rubber, silicone rubber, urethane rubber, a urethane, a polyurethane, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, and their copolymers with acrylic acid or acrylic acid esters or other vinyl ester monomers, fluoropolymers, including fluoroplastics (such as PTFE, FEP, TFA, ETFE, THV, etc.) and fluoroelastomers, some other polymeric material, or blends thereof. Where fluoropolymers are present, monomers of chlorotrifluoroethylene (CTFE) and vinylidene fluoride (VF2), either as homopolymers, or as copolymers with TFE, HFP, PPVE, PMVE and ethylene or propylene can be used. Additionally, the fluoropolymer may comprise a peril uoropolymer such as homopolymers and copolymers of tetrafluoroethylene (TFE), hexafluoropropylene (HFP) and fluorovinyl ethers, including perfluoropropyl and perfluoromethyl vinyl ether.

[0051] Applicants have discovered that using VARTM in combination with the cyclic olefin resins disclosed herein can produce a cured article with lower dielectric constant, lower loss tangent, lower moisture absorption, lighter weight, and higher mechanical properties such as tensile strength than those cured articles previously developed.

Curing Substrate to Form Composite Substrates

[0052] After the substrates have been fully impregnated with resin, the impregnated substrates can be cured. The impregnated substrates described herein may be cured using many different suitable methods. For example, the impregnated substrates may be subjected to heat to polymerize the resin and harden the substrates to form a composite substrate. The exact curing temperature used can depend on the particular cyclically strained alkene(s) resin selected, but illustrative curing temperatures include, but are not limited to about 80°C to about 100°C or about 150°C to about 200°C. In some embodiments, the cyclically strained alkenes selected for use in the resin may be bi-curable resins that are cured in two or more different temperature steps. In some embodiments, the impregnated substrates can be cured by dwelling at about 40°C for one hour and then increasing the temperature up to about 180°C with a ramping rate of about 1-2 °C/min and then stay at about 180°C for one hour. In some embodiments, the cyclically strained alkenes may be combined with a catalyst and first cured at a temperature of about 70-1 10°C, about 75-90, about 75-85, or about 85°C for a first period. In some embodiments, the first period can be about 0.25-5 hours, about 0.5-2 hours, about 0.75-1.5 hours, or about 1 hour. The resin may then be cured for a second period at a higher temperature, e.g., about 125-200°C, about 125-175°C, about 140-160°C, about 145- 155°C, or about 150°C for a second period. In some embodiments, the second period can be about 0.25-5 hours, about 0.5-4 hours, about 1-3 hours, about 1.5-2.5 hours, or about 2 hours. If desired, a third curing temperature higher than the first and second may also be used.

[0053] In some embodiments, it may be desirable to include a rate-limiting compound with the resin to limit the degree of polymerization during the first curing temperature. For example, phosphines such as triphenylphosphine or other suitable rate limiters may be added to ensure that polymerization is not complete during the first curing temperature. In other instances, the bi-curing temperatures can be selected to provide a resin (or final, cured article) with a glass transition temperature that is greater than a comparable resin produced using a single curing step. In some embodiments, the glass transition temperature of the resin can be about 100-300°C, about 125-275°C, about 150-250°C, about 175-225°C, or about 176-205°C.

[0054] In some embodiments, the impregnated substrates can be cured while they are still in the vacuum bag and in the mold. Accordingly, the vacuum applied can be maintained during the curing step. If desired, the curing may be performed in a substantially inert environment devoid of oxygen or other gases, or an inert gas, e.g., nitrogen, may be introduced into the curing apparatus if desired. In some instances, curing may

simultaneously be accompanied by forming of the plies or layers of the substrate into a desired shape for use in an article such as, for example, a radome. For example, where the plies or layers of the substrate are used to form a radome, the plies or layers can be coupled to each other to form a dome or truncated sphere in a mold. Each individual ply or layer can be formed into a desired size and thickness and then coupled to other pieces to provide the radome structure. The curing can then form a composite substrate which includes the plies or layers in the desired shapes.

|0055] After curing, the vacuum bag can be removed while the cured article remains in the mold. The cured article can then be removed from the mold. In addition, the cured article can be trimmed to eliminate any waste or surface blemishes. Furthermore, a desired finish or additional hardware can be applied to the cured article.

[0056] As previously stated, Applicants have discovered that using the VARTM process described herein with the specific resin compositions also described herein can form a cured article with low dielectric constant, low loss tangent, low moisture absorption, light weight, and high mechanical properties such as tensile strength.

|0057] In some embodiments, the cured article can have a dielectric constant less than or equal to about 4, about 3, about 2.7, about 2.6, about 2.5, about 2.4, about 2.3, about 2.2, about 2.1, or about 2. In some embodiments, the cured article can have a dielectric constant of about 0.5-4, about 1-4, about 1.5-3.5, about 2-3.5, about 2-3, about 2-2.46, or about 2.46. A low dielectric constant can provide a more transparent material to an applied electric field and can enable higher data transmission. A higher dielectric constant may create more interference with microwave frequency.

[0058] Another important aspect of the permittivity of a radome can be the loss tangent (i.e., dielectric loss). As the polarization of a material under an applied electric field varies, some of the field energy can be dissipated due to charge migration (i.e., induction) or conversion into thermal energy (i.e., molecular vibrations). This can also be referred to as the dissipation factor due to the loss tangent's definition as the ratio of the resistive power loss to applied field power with the capacitor. In some embodiments, the cured article can have a loss tangent less than or equal to about 0.004, about 0.003, about 0.00275, about 0.0025, about 0.00225, about 0.00215, about 0.0021, about 0.002, or about 0.0019. These low loss tangents can have a much lower effect on microwave frequency.

[0059] In some embodiments, the cured article can have a water (moisture) absorption of less than or equal to about 1.5%, about 1.4%, about 1.3%, about 1.2%, about 1.1%, about 1%, about 0.75%, about 0.7%, about 0.65%, about 0.6%, about 0.55%, about 0.5%, about 0.45%, about 0.4%, about 0.35%, about 0.3%, about 0.25%, about 0.2%, about 0.15%, about 0.1%), or about 0.05%. These moisture absorption can provide an electrical and mechanical benefit on a cured article. The weight gain of water can be measured after the cured article was immersed into a water chamber at 60°C for seven weeks.

[0060] Low adhesion strength can cause delamination and low impact resistance in sandwich cured articles. Accordingly, high adhesion strength can provide structural integrity to a sandwich cured article. In some embodiments, the a sandwich cured article can have an adhesion strength greater than or equal to about 5 lbs., about 5.5 lbs., about 6 lbs., about 6.1 lbs., about 6.2 lbs., about 6.3 lbs., about 6.4 lbs., or about 6.5 lbs. In some embodiments, the adhesion strength can be about 5-10 lbs., about 5.5-8 lbs., about 6-7 lbs., about 6.1 -6.5 lbs., or about 6.3-6.4 lbs.

[0061] Structural integrity of a sandwich cured article can also be judged by the tensile strength. Without a high tensile strength, the sandwich cured article will suffer from poor mechanical performance. In some embodiments, the sandwich cured article can have a tensile strength greater than or equal to about 200 psi, about 250 psi, about 275 psi, about 300 psi, about 315 psi, about 325 psi, about 330 psi, or about 350 psi. In some embodiments, the tensile strength can be about 200-500 psi, about 250-450 psi, about 300-400 psi, or about 325-350 psi.

[0062] In some embodiments, the cured article can have a thickness depending on the intended use of the cured article. In some embodiments, the cured article can have a thickness that is about 0.01-0.5 inches thick, about 0.01 to about 0.2 inches thick, or about 0.07 to about 0.15 inches thick.

[0063] In addition, the cured article can be a lighter weight than a cured article formed using an epoxy resin TC250 commercially produced by Tencate. The TC250 resin has a glass transition temperature of 130°C and a density of 1.21 g/cm ³ . For example, the cured article disclosed herein can save at least about 2 wt%, about 2.5 wt%, about 3 wt%, about 3.25 wt%, about 3.5 wt%, about 3.75 wt%, about 4 wt%, about 4.25 wt%, about 4.5 wt%, about 4.75 wt%, or about 5 wt% when compared to an identical cured article except that an epoxy resin TC250 commercially produced by Tencate was used instead of the resins disclosed herein.

[0064] Referring to figure 2, system 200 comprises radome 202 constructed and arranged to protect antenna 204. Antenna 204 is mounted on support structure 206 which may include a power source and electronics (not shown) such as a controller or processor, if desired, or may be electrically coupled to a controller or processor positioned below support structure 206. During use of system 200, antenna 204 is covered by radome 202 which is also supported on support structure 206. Antenna 204 could alternately be located on a building, could be ground-based, could be coupled to an aircraft, recreational vehicle, train, bus, subway, automotive vehicle, or other devices which may themselves be mobile.

Radome 202 comprises a suitable structure formed using a resin transfer method and one or more of the resins described herein to protect antenna 204 from environmental elements without causing significant interference to the signals to be transmitted and received by antenna 204. For example, radome 202 may be produced using the VARTM in combination with a low viscosity cyclic olefin resin described herein to provide a final radome structure that has a dielectric constant less than or equal to about 4, about 3, about 2.7, about 2.6, about 2.5, about 2.4, about 2.3, about 2.2, about 2.1, or about 2; a loss tangent less than or equal to about 0.004, about 0.003, about 0.00275, about 0.0025, about 0.00225, about 0.00215, about 0.0021, about 0.002, or about 0.0019; a water (moisture) absorption of less than or equal to about 1.5%, about 1.4%, about 1.3%, about 1.2%, about 1.1%, about 1%, about 0.75%, about 0.7%, about 0.65%, about 0.6%, about 0.55%, about 0.5%, about 0.45%, about 0.4%, about 0.35%, about 0.3%, about 0.25%, about 0.2%, about 0.15%, about 0.1%, or about 0.05%. In some embodiments, the radome can be a sandwich radome that has an adhesion strength greater than or equal to about 5 lbs., about 5.5 lbs., about 6 lbs., about 6.1 lbs., about 6.2 lbs., about 6.3 lbs., about 6.4 lbs., or about 6.5 lbs and/or a tensile strength greater than or equal to about 200 psi, about 250 psi, about 275 psi, about 300 psi, about 315 psi, about 325 psi, about 330 psi, or about 350 psi. In addition, the final radome can be a lighter weight than a radome formed using an epoxy resin TC250 commercially produced by Tencate. For example, the final radome can save at least about 2 wt%, about 2.5 wt%, about 3 wt%, about 3.25 wt%, about 3.5 wt%, about 3.75 wt%, about 4 wt%, about 4.25 wt%, about 4.5 wt%, about 4.75 wt%, or about 5 wt% when compared to an identical radome except that an epoxy resin TC250 commercially produced by Tencate was used instead of the resins disclosed herein.

[0065] In some embodiments, radome 202 is produced using the VARTM process in combination with a cyclically strained alkene effective to undergo ring opening metathesis polymerization in the presence of a catalyst to provide the resin. In some instances, the cyclically strained alkene may be norbornene or a norbornene derivative as described in reference to formulae (I)-(III).

[0066] In some embodiments, although an antenna within a dish is shown under radome 202 in Figure 2, the antenna may be part of a larger system or other electronic devices may instead be present under radomes. For example, antenna 204 may be a high frequency radar antenna. In other instances, antenna 204 may be a phased array or a dish (such as a parabolic dish, or a split cylinder dish) and may be rotating or non-rotating. In some instances, antenna 204 and radome 202 may be part of a number of different types of radar system assemblies. For example, radome 202 can be used in conjunction with weather radar systems and airport radar systems. In certain examples, instead of using a radar antenna, system 200 can include other antennas. One example of such an antenna can be a satellite communications antenna. In other instances, radome 204 may be used as part of a cellular communications system to protect underlying antennas from weather. In some embodiments, the radome may be part of a wireless communications device, e.g., an outside Wi-Fi or Bluetooth system, that can provide communication between devices. For example, the radome and Wi-Fi device may be part of a mobile communications system that permits users to access broadband communications devices through mobile devices such as cellular phones, laptops, tablets, etc. The Wi-Fi device/radome system may be mounted on a mobile vehicle or a non-mobile structure, e.g., a telephone pole, wall of a building, etc. In some embodiments, the communications system may comprise a first system configured to operate as a radar system and a second system configured to provide wireless access. For example, a single radome of an aircraft or ship may house a radar system and a Wi-Fi system to permit users on the aircraft or ship to have wireless communication through the mobile devices and the Wi-Fi system.

[0067] In some examples, the radomes may be present on a vehicle such as an automotive vehicle, truck, bus, train, subway, plane, a ship, a submarine or the like. For example, the radome may be integrated into (or attached to) a front or rear bumper (or both) of a vehicle and protect an underlying antenna that may transmit and receive waves for proximity detection. In other instances, the radome may be part of the vehicle to send and receive communications from and to the vehicle, e.g., may be part of a cellular

communications network or wireless communications system such as those found on ships, planes, and trains. Where the radome is part of a ship, plane, or train, it may take an aerodynamic shape to not increase drag to a substantial degree. Where the radome is present in underwater applications, e.g., on a submarine for protecting a sonar system or in an underwater communications system, the radome may be sealed to a permanent structure so a fluid tight seal is present between the radome and the structure to protect any underlying antenna or other communications devices. Where the communication devices are deployed, e.g., from a submerged vessel to a surface, the radome may be buoyant to permit it to float on the surface without the need for an external bladder or other flotation device. The low moisture absorption of the radomes described herein permit use of the radomes in salt water and other moist environments without any substantial interference of the transmission to and from electronic devices within the radome.

[0068] In some embodiments, the radomes described herein may be integral to an electronic device to protect the electronic device while at the same time permitting the electronic device to receive and/or send signals. For example, a cellular phone may comprise an integral radome with an embedded microantenna. If desired, the microantenna can be configured to rotate or move to increase the overall signal receiving capabilities of the phone. A touch screen can be electrically or wirelessly coupled to the cellular phone to permit the user to access the phone's features. In some embodiments, the radome may be integral to a structural component of a vehicle, e.g., a bumper, emergency lights, nose cone, or other components of vehicles such that the radome takes the general shape of the structural part of the vehicle. In addition, the radome can be located on a nose, dorsal, or tail mounted.

[0069] In some embodiments, the radomes described herein may be used for military operations communications or emergency operations communications. For example, military personnel, police vehicles, emergency centers, and the like may wish to use dedicated radio bands outside normal over-the-air scanning frequencies to communicate with each other. A conventional handheld scanner may scan frequencies from about 29 MHz to about 1.3 GHz. These frequencies are generally referred to as very high frequencies (VHF) for frequencies from 30 MHz to about 330 MHz or ultra-high frequencies (UHF) for frequencies from about 330 MHz to about 2.9 GHz. Although the radomes described herein can be used in VHF and UHF bands, emergency operations communications transmitted at these frequencies may be received and heard by anyone with a handheld scanner. To avoid reception by the public, the radomes described herein can be used in combination with a transmitter/receiver to transmit or receive signals in the S band (2-4 GHz), C band (4-8 GHz), X band (8-12 GHz), _u band (12-18 GHz), band (18-26.5 GHz), Ka band (26.5-40 GHz), Q band (30-50 GHz), U band (40-60 GHz), V band (50-75 GHz), E band (60-90 GHz), W band (75-1 10 GHz), F band (90- 140 GHz), or D band (1 10-170 GHz). In particular, bands such as the K _a band and Q band can be used in satellite communications. For example, a satellite may include a radome and underlying transmitter/receiver configured to transmit/receive signals in the 20-50 GHz range. In addition, frequencies of 20-50 GHz may be used in nose cone radar systems (or radar systems positioned in areas other than in the nose) of aircraft for close-range targeting of targets. If desired, the geometry of the radome on aircraft may be constructed to provide stealth-like capability, e.g., the radome does not comprise a shape at any portion that would readily reflect radar waves and permit detection of the aircraft by enemy personnel. The satellites may take the form of communication satellites, e.g., those with geostationary orbits, elliptical orbits, or other orbits, or other types of satellites or similar devices, e.g., weather satellites, military satellites, astronomical satellites, navigational satellites, reconnaissance satellites, earth observation satellites on space stations or other devices that orbit the earth. In other instances, the resins and articles described herein can be used to cover sonar systems, e.g., those used by the Navy that are typically designed to detect low frequencies in the 100- 500 Hz or 1 kHz- 10 kHz range. The sonar systems may be fixed, e.g., positioned on the ocean floor, or may be part of a vessel such as a ship or submarine.

[0070] In some embodiments, the radome may comprise an inner insulation layer, if desired, to insulate an electronic device from the elements or to prevent thermal loss from inside the radome where an air conditioner (not shown) provides cooled air to any electronic devices within the radome. While the exact thickness of the radome may vary depending on the intended use of the radome, in some instances, the thickness is about 0.01 inches thick to about 0.5 inches thick, about 0.01 inches thick to about 0.2 inches thick, or about 0.07 inches thick to about 0.15 inches thick. In addition, due to the VARTM process, the thickness of the cured article can be substantially uniform or uniform unlike traditional cured articles made using hand lay-up processes. The electronic device may take many forms as described herein and may include an antenna or transmitter/receiver that can send and receive signals. In some embodiments, the electronic device may be part of a radar system, a sonar system, or a communications system, e.g., Wi-Fi systems, Bluetooth systems, radio systems, cellular communication systems, satellite systems, or other suitable systems. In some embodiments, the substrates (and composite substrates) and resins described herein may be used to construct thin-plate radomes. While the exact configuration may vary, a thin-plate radome can be thin in comparison to the wavelength at the operating frequency. In other instances, the radome may be constructed as a half-wavelength radome, where the radome has a thickness equivalent to about one-half the wavelength. Other variations such as quarter- wavelength radomes and the like may also be produced using the methods, materials, and substrates described herein.

|0071] Although some aspects of radome production are known, the specific combination and advantages realized by the methods and components described herein provide an advancement in radome fabrication.

EMBODIMENTS

[0072] The following embodiments, numbered consecutively from 1 through 89 provide various non-limiting embodiments described herein.

[0073] Embodiment 1 : A method for making a radome, comprising: inserting a dry substrate into a mold assembly; impregnating the dry substrate using a vacuum with a resin produced from a cyclically strained alkene that has undergone ring opening metathesis polymerization in the presence of a catalyst; and heating the impregnated substrate to cure the resin to form the radome, wherein the radome has a dielectric constant of less than 3, has a loss tangent of less than 0.00215, and has a moisture absorption of less than 1%.

[0074] Embodiment 2: The method of embodiment 1 , wherein the dry substrate comprises a plurality of layers coupled together.

[0075] Embodiment 3 : The method of any one of embodiments 1-2, wherein the plurality of layers are coupled together by adhesives or stitching.

[0076] Embodiment 4: The method of any one of embodiments 1-3, wherein the dry substrate is a single substrate formed by 3-D knitting.

[0077] Embodiment 5: The method of any one of embodiments 1-4, wherein the dry substrate comprises glass.

[0078] Embodiment 6: The method of embodiment 5, wherein the glass comprises E- glass.

[0079] Embodiment 7: The method of embodiment 5, wherein the glass comprises quartz.

[0080] Embodiment 8: The method of any one of embodiments 1-7, wherein the cyclically strained alkene is a compound of formula (I)

wherein R ¹ , R ² , R ³ and R ⁴ of formula (I) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms.

[0081] Embodiment 9: The method of embodiment 8, wherein each of R ¹ , R ² , R ³ and R ⁴ of formula (I) is hydrogen.

[0082] Embodiment 10: The method of any one of embodiments 1-9, wherein the cyclically strained alkene is a compound of formula (II)

wherein R ¹ and R ⁴ of formula (II) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms arid R ⁵ may be -Cth, oxygen, a secondary amine or a tertiary amine.

[0083] Embodiment 11 : The method of embodiment 10, wherein each of R ¹ and R ⁴ of formula (II) is hydrogen and R ⁵ is -CH2.

[0084] Embodiment 12: The method of any one of embodiments 1-11, wherein the cyclically strained alkene is a compound of formula (III)

wherein R ¹ and R ⁴ of formula (III) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms. [0085] Embodiment 13: The method of embodiment 12, wherein each of R ¹ and R ⁴ of formula (III) is hydrogen.

[0086] Embodiment 14: The method of any one of embodiments 1-13, wherein the resin comprises two different cyclically strained alkenes each effective to undergo ring opening metathesis polymerization in the presence of a catalyst to provide the resin.

[0087] Embodiment 15: The method of embodiment 14, wherein one of the cyclically strained alkenes is a norbornene derivative and the other cyclically strained alkene is dicyclopentadiene.

[0088] Embodiment 16: The method of embodiment 14, wherein one of the cyclically strained alkenes is a 5-ethylene-2-norbornene and the other cyclically strained alkene is dicyclopentadiene.

[0089] Embodiment 17: The method of any one of embodiments 1-16, further comprising applying a release agent to the mold prior to adding the substrate.

[0090] Embodiment 18: The method of embodiment 17, wherein the release agent comprises a polytetrafluoroethylene (PTFE) film.

[0091] Embodiment 19: The method of any one of embodiments 1-18, further comprising applying a peel ply to the substrate.

[0092] Embodiment 20: The method of any one of embodiments 1-19, further comprising applying a flow media to the substrate.

[0093] Embodiment 21 : The method of any one of embodiments 1-20, further comprising adding at least one resin inlet port to the mold assembly and at least one vacuum outlet port to the mold assembly.

[0094] Embodiment 22: The method of any one of embodiments 1-21, further comprising enclosing the dry substrate with a vacuum bag.

[0095] Embodiment 23: The method of embodiment 22, wherein the vacuum bag is sealed to itself or to the mold assembly using sealant tape.

[0096] Embodiment 24: The method of any one of embodiments 1-23, wherein the radome has a moisture absorption of less than 0.5%. [0097] Embodiment 25: The method of any one of embodiments 1-24, wherein the radome has a dielectric constant of 2-3.

[0098] Embodiment 26: A method for making a radome, comprising: inserting a first dry substrate into a mold assembly; applying a foam core to a side of the first dry substrate; applying a second dry substrate to a side of the foam core opposite the first dry substrate; impregnating the first dry substrate and the second dry substrate using a vacuum with a resin produced from a cyclically strained alkene that has undergone ring opening metathesis polymerization in the presence of a catalyst; and heating the impregnated substrate to cure the resin to form the radome, wherein the radome has a dielectric constant of less than 2.4, has a loss tangent of less than 0.00215, has a moisture absorption of less than 1%, has an adhesion strength greater than 6 lbs, and has a tensile strength greater than 300 psi.

[0099] Embodiment 27: The method of embodiment 26, wherein the first dry substrate comprises a first plurality of layers coupled together and the second dry substrate comprises a second plurality of layers coupled together.

[00100] Embodiment 28: The method of embodiment 27, wherein the first and second plurality of layers are coupled together by adhesives or stitching.

[00101] Embodiment 29: The method of any one of embodiments 26-28, wherein the first and second dry substrates are single substrates formed by 3-D knitting.

[00102] Embodiment 30: The method of any one of embodiments 26-29, wherein the first and second dry substrate comprise glass.

[00103] Embodiment 31 : The method of embodiment 30, wherein the glass comprises E-glass.

[00104] Embodiment 32: The method of embodiment 30, wherein the glass comprises quartz.

[00105] Embodiment 33: The method of any one of embodiments 26-32, wherein the foam core 13 a clo3cd-ccll foam core.

[00106] Embodiment 34: The method of any one of embodiments 26-33, wherein the foam core comprises polyphenylsulfone (PPSU). [00107] Embodiment 35: The method of any one of embodiments 26-34, wh cyclically strained alkene is a compound of formula (I)

wherein R ¹ , R ² , R ³ and R ⁴ of formula (I) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms.

[00108] Embodiment 36: The method of embodiment 35, wherein each of R ¹ , R ² , R ³ and R ⁴ of formula (I) is hydrogen.

[00109] Embodiment 37: The method of any one of embodiments 26-36, wherein the cyclically strained alkene is a compound of formula (II)

wherein R ¹ and R ⁴ of formula (II) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms and R ⁵ may be -CH2, oxygen, a secondary amine or a tertiary amine.

[00110] Embodiment 38: The method of embodiment 37, wherein each of R ¹ and R ⁴ of formula (II) is hydrogen and R ⁵ is -CH2.

100111] Embodiment 39: The method of any one of embodiments 26-38, wherein the cyclically strained alkene is a compound of formula (III)

(III)

herein R ¹ and R ⁴ of formula (III) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms.

[00112] Embodiment 40: The method of embodiment 39, wherein each of R ¹ and R ⁴ of formula (III) is hydrogen.

[00113] Embodiment 41 : The method of any one of embodiments 26-40, wherein the resin comprises two different cyclically strained alkenes each effective to undergo ring opening metathesis polymerization in the presence of a catalyst to provide the resin.

[00114] Embodiment 42: The method of embodiment 41 , wherein one of the cyclically strained alkenes is a norbornene derivative and the other cyclically strained alkene is dicyclopentadiene.

[00115] Embodiment 43: The method of embodiment 41 , wherein one of the cyclically strained alkenes is a 5-ethylene-2-norbornene and the other cyclically strained alkene is dicyclopentadiene.

[00116] Embodiment 44: The method of any one of embodiments 26-43, further comprising applying a release agent to the mold assembly prior to adding the first dry substrate.

[00117] Embodiment 45: The method of embodiment 44, wherein the release agent comprises a polytetrafluoroethylene (PTFE) film.

[00118] Embodiment 46: The method of any one of embodiments 26-45, further comprising applying a peel ply to the second dry substrate.

[00119] Embodiment 47: The method of any one of embodiments 26-46, further comprising applying a flow media to at least one of the first or second dry substrate.

[00120] Embodiment 48: The method of any one of embodiments 26-47, further comprising applying a flow media to both the first and second dry substrate.

[00121] Embodiment 49: The method of any one of embodiments 26-48, further comprising adding at least one resin inlet port to the mold assembly and at least one vacuum outlet port to the mold assembly.

[00122] Embodiment 50: The method of any one of embodiments 26-49, further comprising enclosing the dry substrate with a vacuum bag. [00123] Embodiment 51 : The method of embodiment 50, wherein the vacuum bag is sealed to itself or to the mold assembly using sealant tape.

[00124] Embodiment 52: A radome, comprising: a composite substrate comprising a cured resin, wherein the radome has a dielectric constant of less than 3, has a loss tangent of less than 0.00215, and has a moisture absorption of less than 1%.

[00125] Embodiment 53: The radome of embodiment 52, wherein the cured resin is produced from a cyclically strained alkene that has undergone ring opening metathesis polymerization in the presence of a catalyst.

[00126] Embodiment 54: The radome of any one of embodiments 52-53, wherein the composite substrate comprises a plurality of layers coupled together.

[00127] Embodiment 55: The radome of embodiment 54, wherein the plurality of layers are coupled together by adhesives or stitching.

[00128] Embodiment 56: The radome of any one of embodiments 52-55, wherein the composite substrate is a single composite substrate formed by 3-D knitting.

[00129] Embodiment 57: The radome of any one of embodiments 52-56, wherein the composite substrate comprises glass.

[00130] Embodiment 58: The radome of embodiment 57, wherein the glass comprises E-glass.

[00131] Embodiment 59: The radome of embodiment 57, wherein the glass comprises quartz.

[00132] Embodiment 60: The radome of embodiment 53, wherein the cyclically strained alkene is a compound of formula (I)

wherein R ¹ , R ² , R ³ and R ⁴ of formula (I) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms. [00133] Embodiment 61 : The radome of embodiment 60, wherein each of R ¹ , R ² , R ³ and R ⁴ of formula (I) is hydrogen.

[00134] Embodiment 62: The radome of embodiment 53, wherein the cyclically strained alkene is a compound of formula (II)

wherein R ¹ and R ⁴ of formula (II) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms and R ⁵ may be -CH2, oxygen, a secondary amine or a tertiary amine.

[00135] Embodiment 63: The radome of embodiment 62, wherein each of R ¹ and R ⁴ of formula (II) is hydrogen and R ⁵ is -CH2.

[00136] Embodiment 64: The radome of embodiment 53, wherein the cyclically strained alkene is a compound of formula (III)

wherein R ¹ and R ⁴ of formula (III) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms.

[00137] Embodiment 65: The radome of embodiment 64, wherein each of R ¹ and R ⁴ of formula (III) is hydrogen.

[00138] Embodiment 66; The radome of embodiment 53, wherein the cured resin comprises two different cyclically strained alkenes each effective to undergo ring opening metathesis polymerization in the presence of a catalyst to provide the resin. [00139] Embodiment 67: The radome of embodiment 66, wherein one of the cyclically strained alkenes is a norbornene derivative and the other cyclically strained alkene is dicyclopentadiene.

[00140] Embodiment 68: The radome of embodiment 66, wherein one of the cyclically strained alkenes is a 5-ethylene-2-norbornene and the other cyclically strained alkene is dicyclopentadiene.

[00141] Embodiment 69: The radome of any one of embodiments 52-68, wherein the radome has a moisture absorption of less than 0.5%.

[00142] Embodiment 70: The radome of any one of embodiments 52-69, wherein the radome has a dielectric constant of 2-3.

[00143] Embodiment 71 : A radome, comprising: a first composite substrate comprising a cured resin; a foam core on a side of the first composite substrate; and a second composite substrate comprising the cured resin on a side of the foam core opposite the first composite substrate; wherein the radome has a dielectric constant of less than 2.4, has a loss tangent of less than 0.00215, has a moisture absorption of less than 1%, has an adhesion strength greater than 6 lbs, and has a tensile strength greater than 300 psi.

[00144] Embodiment 72: The radome of embodiment 71, wherein the cured resin is produced from a cyclically strained alkene that has undergone ring opening metathesis polymerization in the presence of a catalyst.

[00145] Embodiment 73: The radome of any one of embodiments 71-72, wherein the first composite substrate comprises a first plurality of layers coupled together and the second composite substrate comprises a second plurality of layers coupled together.

[00146] Embodiment 74: The radome of embodiment 73, wherein the first and second plurality of layers are coupled together by adhesives or stitching.

[00147] Embodiment 75: The radome of any one of embodiments 71-74, wherein the first and second composite substrates are single composite substrates formed by 3-D knitting.

[00148] Embodiment 76: The radome of any one of embodiments 71-75, wherein the first and second composite substrate comprise glass. (00149] Embodiment 77: The radome of embodiment 76, wherein the glass comprises E-glass.

[00150] Embodiment 78: The radome of embodiment 76, wherein the glass comprises quartz.

[00151] Embodiment 79: The radome of any one of embodiments 71-78, wherein the foam core is a closed-cell foam core.

[00152] Embodiment 80: The radome of any one of embodiments 71-79, wherein the foam core comprises polyphenylsulfone (PPSU).

[00153] Embodiment 81 : The radome of embodiment 72, wherein the cyclically strained alkene is a compound of formula (I)

wherein R ¹ , R ² , R ³ and R ⁴ of formula (I) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms.

[00154] Embodiment 82: The radome of embodiment 81, wherein each of R ¹ , R ² , R ³ and R ⁴ of formula (I) is hydrogen.

[00155] Embodiment 83: The radome of embodiment 72, wherein the cyclically strained alkene is a compound of formula (II)

wherein R ¹ and R ⁴ of formula (II) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms and R ⁵ may be -CH2, oxygen, a secondary amine or a tertiary amine. [00156] Embodiment 84: The radome of embodiment 83, wherein each of R ¹ and R ⁴ of formula (II) is hydrogen and R ^s is -CH2.

[00157] Embodiment 85: The radome of embodiment 72, wherein the cyclically strained alkene is a compound of formula (III)

wherein R ¹ and R ⁴ of formula (III) may each independently be hydrogen or a hydrocarbon group comprising 1 to 10 carbon atoms.

[00158] Embodiment 86: The radome of embodiment 85, wherein each of R ¹ and R ⁴ of formula (III) is hydrogen.

[00159] Embodiment 87: The radome of embodiment 72, wherein the cured resin comprises two different cyclically strained alkenes each effective to undergo ring opening metathesis polymerization in the presence of a catalyst to provide the resin.

[00160] Embodiment 88: The radome of embodiment 87, wherein one of the cyclically strained alkenes is a norbornene derivative and the other cyclically strained alkene is dicyclopentadiene.

[00161] Embodiment 89: The radome of embodiment 87, wherein one of the cyclically strained alkenes is a 5-ethylene-2-norbornene and the other cyclically strained alkene is dicyclopentadiene.

EXAMPLES

Flat Panels of Neat Resin

[00162] Two flat panels of neat resin can be made by casting into a mold with a circular disk shape. The samples can have a 1/8" x 2.5" diameter. The resin used to produce the first flat panel can be a ROMP DCPD resin Expl768 commercially produced by Materia. The resin used to produce the second flat panel can be an epoxy resin BT250E-1 commercially produced by Tencate. The following Table 1 includes the various properties of the neat resin.

TABLE 1

Monolithic Flat Panels with Substrates

[00163] The dielectric constant, loss tangent, and weight savings values were compared for various monolithic flat panels. First, these values were compared between a monolithic flat panel formed using the VARTM process disclosed herein with a 12 layer 7781 Glass substrate and a DCPD resin Expl768 commercially produced by Materia and a monolithic flat panel formed using a hand lay-up process with a 7781 Glass substrate and an epoxy resin TC250 commercially produced by Tencate. Next, these values were compared between a monolithic flat panel formed using the VARTM process disclosed herein with a 4581 Quartz substrate and a DCPD resin Expl 768 commercially produced by Materia and a monolithic flat panel formed using a hand lay-up process with a 4581 Quartz substrate and an epoxy resin TC250 commercially produced by Tencate.

[00164] The DCPD/7781 Glass and DCPD/4581 Quartz panels were formed by placing a PTFE release film on an aluminum mold, placing twelve plies of 7781 Glass fabric or 4581 Quartz fabric on the release film, placing a peel ply layer down, placing a media flow down, forming a vacuum bag with a resin inlet and a vacuum outlet, inducing resin by the VARTM process, and curing in an oven.

[00165] The values for dielectric constant and loss tangent for the DCPD/7781 Glass and DCPD/4581 Quartz cured articles were modelled based on individual data of DCPD, 7781 Glass, and 4581 Quartz. In addition, the values for weight savings were calculated based on individual density data for the various components in the cured articles. Lastly, the dielectric constant and loss tangent for the Epoxy/7781 Glass and Epoxy /4581 Quartz samples were averaged from the TC250 data sheet. The results are shown in Tables 2, 3, and 4 below. TABLE 2

TABLE 4

[00166] The DCPD/7781 Glass and Epoxy/7781 Glass monolithic flat panels described above were also tested for water absorption. Both monolithic flat panels were immersed in water at 60°C. The weight gain (i.e., water absorption) was measured over a period of days. A chart illustrating the results of the water absorption test is shown in figure 3.

Sandwich Panels with Substrates and Core Layer

|Ul>167J Mechanical properties such as adhesion strength and tensile strength were compared for various sandwich flat panels. First, the mechanical properties were compared between a sandwich flat panel formed using a first 7781 Glass substrate, a PPSU foam core, a second 7781 Glass substrate, and a DCPD resin Exp 1768 commercially produced by Materia and a sandwich flat panel formed using hand lay-up with a first 7781 Glass substrate, a honeycomb core, a second 7781 Glass substrate, and an epoxy resin TC250 commercially produced by Tencate. Next, the mechanical properties were compared between a sandwich flat panel formed using a first 7781 Glass substrate, a PPSU foam core, a second 7781 Glass substrate, and a DCPD resin Expl 768 commercially produced by Materia and a sandwich flat panel formed using hand lay-up with a first 7781 Glass substrate, a PEI foam core, a second 7781 Glass substrate, and an epoxy resin TC250 commercially produced by Tencate.

[00168] The DCPD composite / PPSU foam / DCPD composite sandwich panel was formed by placing a PTFE release film on an aluminum mold, placing two plies of 7781 Glass fabric on the release film, placing 0.25 inch PPSU foam on the two plies, placing an additional two plies of 7781 Glass fabric, placing a peel ply layer down, placing a media flow down, forming a vacuum bag with a resin inlet and a vacuum outlet, inducing resin by the VARTM process, and curing in an oven.

[00169] The mechanical values for adhesion strength and tensile property for the various sandwich flat panels are shown in Table 5 below.

TABLE 5

Testing Methods

[00170] Unless otherwise specified herein, reference to any of the following characteristics below in the description above and the claims appended hereto refer to values obtained using the following tests: [00171] Dielectric constant can be measured by ASTM 2520 at 10 GHz. Although described more specifically in the ASTM 2520 protocol, the dielectric strength can be generally measured using cavity perturbation methods and a rectangular waveguide. For example, the sample was placed between plates of the waveguide to measure the dielectric properties.

[00172] Loss tangent can be measured by ASTM 2520.

[00173] Glass transition temperature can be measured by ASTM D3418-03.

[00174] Density can be measured by ASTM D794.

[00175] Moisture or water absorption values can be measured using ASTM D570-98. Although described more specifically in the ASTM D570-98 protocol, the moisture absorption can be generally measured by drying disk specimens in an oven for a specified time and at a specified temperature and then placing them in a desiccator to cool.

Immediately upon cooling the specimens can be weighed. The material can then be submerged in water at a specified temperature, e.g., 23°C for 24 hours or until equilibrium. Specimens can removed, patted dry with a lint-free cloth, and weighed to determine the amount of water absorbed.

[00176] The adhesion strength can be measured using the adhesion peel test according to ASTM D3167.

[00177] The tensile strength can be measured using the tensile property test according to ASTM C297.

[00178] This application discloses several numerical ranges in the text and figures. The numerical ranges disclosed inherently support any range or value within the disclosed numerical ranges, including the endpoints, even though a precise range limitation is not stated verbatim in the specification because this disclosure can be practiced throughout the disclosed numerical ranges.

[00179] The description above is presented to enable a person skilled in the art to make and use the disclosure, and is provided in the context of a particular application and its requirements. Various modifications to the preferred embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the disclosure. Thus, this disclosure is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. Finally, the entire disclosure of the patents and publications referred to in this application is hereby incorporated herein by reference.