FIBER-REINFORCED COMPOSITES, LAMINATES INCLUDING THE SAME, AND SYSTEMS AND METHODS FOR MAKING SUCH LAMINATES

Abstract

This disclosure includes fiber-reinforced composites, laminates including the same, and systems and methods for making such laminates.

Claims

1. A method for forming a laminate from at least first and second fiber-reinforced composites, the method comprising: placing the first fiber-reinforced composite onto a substrate using an end effector of a robotic arm at least by translating and/or rotating the end effector relative to the substrate; placing the second fiber-reinforced composite onto the substrate using the end effector at least by translating and/or rotating the end effector relative to the substrate, wherein the placing the second fiber-reinforced composite is performed such that the second fiber-reinforced composite overlies or is adjacent to the first fiber-reinforced composite; and bonding the second fiber-reinforced composite to the first fiber-reinforced composite at least by: heating the second fiber-reinforced composite; and/or applying pressure to the second fiber-reinforced composite; wherein at least one of the first and second fiber-reinforced composites comprises: a matrix material including a thermoplastic material; and a non-woven fibrous region comprising a plurality of continuous fibers dispersed in the matrix material; wherein the width and the length of the non-woven fibrous region are substantially equal to the width and the length, respectively, of the fiber-reinforced composite; and wherein the non-woven fibrous region has a mean relative fiber area coverage (RFAC) (%) of from 65 to 90 and a coefficient of variance (COV) (%) of from 3 to 20.

2. The method of claim 1, wherein at least one of the first and second fiber-reinforced composites comprises first and second polymeric-rich regions that are disposed on opposing sides of the fiber-reinforced composite, each having less than 10% fibers by volume, wherein: the width and the length of each of the polymeric-rich regions are substantially equal to the width and the length, respectively, of the fiber-reinforced composite; and the sum of the thicknesses of the polymeric-rich regions is from 15% to 25% of the thickness of the fiber-reinforced composite.

3. The method of claim 1, comprising: capturing, with one or more sensors, data indicative of one or more of the following: a color of the second fiber-reinforced composite; a composition of a matrix material of the second fiber-reinforced composite; a thickness of the second fiber-reinforced composite; and a width of the second fiber-reinforced composite; and adjusting, using a processor and based, at least in part, on the data captured by the one or more sensors, a translational and/or rotational speed of the end effector relative to the substrate, a heat provided to the second fiber-reinforced composite, and/or a pressure applied to the second fiber-reinforced composite.

4. A method for forming a laminate from at least first and second fiber-reinforced composites, the method comprising: placing the first fiber-reinforced composite onto a substrate using an end effector of a robotic arm at least by translating and/or rotating the end effector relative to the substrate; placing the second fiber-reinforced composite onto the substrate using the end effector at least by translating and/or rotating the end effector relative to the substrate, wherein the placing the second fiber-reinforced composite is performed such that the second fiber-reinforced composite overlies or is adjacent to the first fiber-reinforced composite; and bonding the second fiber-reinforced composite to the first fiber-reinforced composite at least by: heating the second fiber-reinforced composite; and/or applying pressure to the second fiber-reinforced composite; wherein at least one of the first and second fiber-reinforced composites comprises first and second polymeric-rich regions that are disposed on opposing sides of the fiber-reinforced composite, each having less than 10% fibers by volume, wherein: the width and the length of each of the polymeric-rich regions are substantially equal to the width and the length, respectively, of the fiber-reinforced composite; and the sum of the thicknesses of the polymeric-rich regions is from 15% to 25% of the thickness of the fiber-reinforced composite.

5. The method of claim 4, wherein at least one of the first and second fiber-reinforced composites comprises: a matrix material including a thermoplastic material; and a non-woven fibrous region comprising a plurality of continuous fibers dispersed in the matrix material; wherein the width and the length of the non-woven fibrous region are substantially equal to the width and the length, respectively, of the fiber-reinforced composite; and wherein the non-woven fibrous region has a mean relative fiber area coverage (RFAC) (%) of from 65 to 90 and a coefficient of variance (COV) (%) of from 3 to 20.

6. The method of claim 4, comprising: capturing, with one or more sensors, data indicative of one or more of the following: a color of the second fiber-reinforced composite; a composition of a matrix material of the second fiber-reinforced composite; a thickness of the second fiber-reinforced composite; and a width of the second fiber-reinforced composite; and adjusting, using a processor and based, at least in part, on the data captured by the one or more sensors, a translational and/or rotational speed of the end effector relative to the substrate, a heat provided to the second fiber-reinforced composite, and/or a pressure applied to the second fiber-reinforced composite.

7. The method of any of claims 1-6, wherein substantially all of the fibers of at least one of the fiber-reinforced composites are substantially parallel with one another.

8. The method of any of claims 1-6, wherein a matrix material of at least one of the fiber-reinforced composites comprises a thermoplastic material.

9. The method of any of claims 1-6, wherein the heating is performed using a heat source comprising a laser, an infrared heat source, and/or an ultrasonic welder.

10. The method of claim 9, wherein the heat source is coupled to the end effector.

11. The method of any of claims 1-6, wherein: the applying pressure is performed using a pressing element coupled to the end effector; and optionally, the pressing element comprises a roller.

12. The method of any of claims 1-6, wherein the substrate comprises a mold.

13. The method of any of claims 1-6, wherein the substrate comprises a part.

14. The method of claim 13, wherein the part comprises an aircraft or automobile part.

15. The method of any of claims 1-6, wherein the first and second fiber-reinforced composites are supplied to the end effector via one or more flexible conduits.

16. A system for forming a laminate from one or more fiber-reinforced composites, each comprising fibers dispersed within a matrix material, the system comprising: a heat source configured to provide heat to at least one of the one or more fiber-reinforced composites; one or more sensors configured to capture data indicative of at least one of: a color of at least one of the one or more fiber-reinforced composites; a composition of the matrix material of at least one of the one or more fiber-reinforced composites; a composition of the fibers of at least one of the one or more fiber-reinforced composites; a thickness of at least one of the one or more fiber-reinforced composites; and a width of at least one of the one or more fiber-reinforced composites; and a processor configured to vary a heat provided by the heat source based, at least in part, on data captured by the one or more sensors.

17. The system of claim 16, wherein the heat source comprises a laser, an infrared heat source, and/or an ultrasonic welder.

18. The system of claim 16, comprising a robotic arm having an end effector configured to place at least one of the one or more fiber-reinforced composites onto a substrate at least by translating and/or rotating relative to the substrate.

19. The system of claim 18, wherein the heat source is coupled to the end effector.

20. The system of claim 18, wherein the processor is configured to vary a translational and/or rotational speed of the end effector relative to the substrate based, at least in part, on data captured by the one or more sensors.

21. The system of any of claims 18-20, wherein: the end effector comprises a pressing element configured to apply pressure to at least one of the one or more fiber-reinforced composites; and optionally, the pressing element comprises a roller.

22. The system of claim 21, wherein the processor is configured to vary a pressure applied by the pressing element based, at least in part, on data captured by the one or more sensors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The following drawings illustrate by way of example and not limitation. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which that structure appears. Identical reference numbers do not necessarily indicate an identical structure. Rather, the same reference number may be used to indicate a similar feature or a feature with similar functionality, as may non-identical reference numbers. The figures are drawn to scale (unless otherwise noted), meaning the sizes of the depicted elements are accurate relative to each other for at least the embodiment(s) depicted in the figures.

[0064] FIG. 1 includes cross-sectional images of prior art unidirectional fiber-reinforced composites.

[0065] FIG. 2 is a cross-sectional confocal microscope image of a unidirectional fiber-reinforced composite of the present disclosure.

[0066] FIG. 3 is a schematic of a unidirectional fiber-reinforced composite of the present disclosure, where a length, width, and thickness of the composite may be measured along axes E.sub.1, E.sub.2, and E.sub.3, respectively.

[0067] FIG. 4A is a schematic of a stack or lay-up of three unidirectional fiber-reinforced composites, with fibers of the three composites being substantially parallel to each other.

[0068] FIG. 4B is a cut-away schematic of a stack or lay-up of two unidirectional fiber-reinforced composites, with fibers of the two composites being oriented in differing directions.

[0069] FIG. 4C is a schematic of a stack or lay-up of unidirectional fiber-reinforced composites, including a protective coating.

[0070] FIG. 5 is a schematic of a system for making unidirectional fiber-reinforced composites of the present disclosure.

[0071] FIG. 6A is a perspective view of a spreading unit of the present disclosure.

[0072] FIG. 6B is a cross-sectional side view of the spreading unit of FIG. 6A, taken along line 6B-6B of FIG. 6A.

[0073] FIGS. 6C-6G are side, top, bottom, front, and back views, respectively, of the spreading unit of FIG. 6A.

[0074] FIG. 7A is a perspective view of a spreading element of the present disclosure.

[0075] FIG. 7B is a cross-sectional end view of the spreading element of FIG. 7A, taken along line 7B-7B of FIG. 7A.

[0076] FIGS. 7C-7F are front, top, bottom, and perspective views, respectively, of the spreading element of FIG. 7A.

[0077] FIGS. 8A-8C are schematics of fiber bundle(s) being spread using spreading elements of the present disclosure.

[0078] FIGS. 8D and 8E are perspective views of fiber bundles being spread using a spreading unit of the present disclosure.

[0079] FIG. 9 is a schematic depicting one embodiment for processing spreaded fiber layer(s) to form a unidirectional fiber-reinforced composite.

[0080] FIGS. 10A and 10B are perspective and front views, respectively, of a rubbing element of the present disclosure.

[0081] FIG. 11 is a schematic depicting one embodiment for processing spreaded fiber layer(s) to form a unidirectional fiber-reinforced composite.

[0082] FIG. 12 is a schematic exploded view of a laminate that can be formed using one or more of the present fiber-reinforced composites.

[0083] FIG. 13 is a schematic of a press that may be suitable for forming some of the present laminates.

[0084] FIG. 14 is a schematic of a system including a robotic arm that may be suitable for forming some of the present laminates.

[0085] FIG. 15 is a schematic of a robotic arm end effector that may be suitable for use in some of the present systems.

[0086] FIG. 16 is a schematic showing the relative placement of fiber-reinforced composites pursuant to some of the present methods for forming a laminate.

[0087] FIGS. 17-19 are cross-sectional confocal microscope images of unidirectional fiber-reinforced composites of the present disclosure.

[0088] FIGS. 20-22 are cross-sectional confocal microscope images of unidirectional fiber-reinforced composites that are comparative to those of the present disclosure.

[0089] FIGS. 23 and 24 are front and side views, respectively, of test samples, each including a laminate formed from unidirectional tapes of the present disclosure.

[0090] FIG. 25 depicts an apparatus suitable for testing the test samples of FIGS. 23 and 24.

[0091] FIGS. 21 and 22 depict the test samples of FIGS. 23 and 24, after testing.

DETAILED DESCRIPTION

[0092] Currently available fiber-reinforced composites may suffer from non-uniform arrangements of fibers and voids that can render the composites weak and susceptible to cracks and breakage that can ultimately lead to the failure of parts, components, devices, and the like including such composites. By comparison, fiber-reinforced composites of the present disclosure include a non-woven fibrous region having a substantially uniform density as defined by a mean relative fiber area coverage (RFAC) (%) and a coefficient of variance (COV) (%). Composites of the present disclosure have improved structural characteristics when compared with currently available composites.

[0093] Conventional apparatuses for spreading and/or impregnating fibers suffer from an inability to provide for sufficiently even spacing of the fibers and/or an inability to sufficiently prevent the fibers from moving during impregnation. Such uneven spacing and fiber movement can result in non-uniform fiber arrangement and voids in a resulting composite. In contrast, the spreading unit and the impregnation unit of the present disclosure can be used to prepare fiber-reinforced composites having substantially uniform densities, as described above.

[0094] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. Fiber-Reinforced Composites

[0095] Fiber-reinforced composites of the present disclosure can have a thermoplastic or thermoset polymeric matrix and a non-woven fibrous region comprising a plurality of continuous fibers dispersed in the polymeric matrix. Typically, the width and the length of the non-woven fibrous region are substantially similar to the width and the length, respectively, of the fiber-reinforced composite. Such fiber-reinforced composites can include, by volume, at least 35 to 70% of the plurality of continuous fibers.

[0096] Such a non-woven fibrous region can have a substantially uniform density as defined by a mean relative fiber area coverage (RFAC) (%) of from 65 to 90 and a coefficient of variance (COV) (%) of from 3 to 20, preferably a mean RFAC (%) of from 69 to 90 and a COV (%) of from 3 to 15, and most preferably a mean RFAC (%) of from 75 to 90 and a COV (%) of from 3 to 8.

[0097] 1. Determining Density Uniformity

[0098] The density uniformities of the composites of the present disclosure are determined by using the following procedure: [0099] 1. A cross-sectional image of a thermoplastic or thermoset fiber-reinforced tape/composite is obtained via optical microscopy (e.g. confocal microscopy). The cross-sectional image is taken perpendicularly to the longitudinal axis of the fibers and has a length of at least 1500 m and a width (e.g., measured along a thickness of the tape/composite) of at least 160 m. In the Examples, a Keyence VK-X200 Camera with a 50 lens (Keyence VK-X200, Elmwood, N.J., USA) was used; however, other cameras or imaging devices can be used. [0100] 2. Cross hairs are drawn that bisect the length and the width of the cross-sectional image. [0101] 3. A first square box is drawn centered on the cross hairs and having sides equal to 40% of the thickness of the tape/composite. [0102] 4. Two sets of 5 adjacent square boxes, each square box having the same dimensions as the first square box, are drawn such that each set is on a respective side of the vertical or width-wise cross hair, adjacent to the first square box, and centered on the horizontal or length-wise cross-hair. A total of 11 boxes will be present, thereby offering 11 data points. [0103] 5. Fiber surface area, or the area occupied by fibers, in each of the 11 square boxes is measured and, for each square box, is represented as a percentage of the total area of the square box, referred to as area coverage (AC) (%). [0104] 6. A relative fiber area coverage (RFAC) (%) for each of the 11 square boxes is determined by dividing AC for the square box by the theoretical maximum possible AC, which may assume close packing of circular filaments, and multiplying by 100. A mean RFAC (%) is determined by averaging the RFACs of the 11 square boxes. [0105] 7. A coefficient of variance (COV) (%) is determined by dividing the standard deviation (a) of the ACs by the average of the ACs and multiplying by 100.

[0106] The above procedure was used in the Examples section to calculate the mean RFAC and COV values of fiber-reinforced composites of the present disclosure and three comparative, commercially available composites.

[0107] 2. Fiber-Reinforced Composite Dimensions

[0108] FIGS. 2 and 3 depict a unidirectional fiber-reinforced composite 200. Fiber-reinforced composites (e.g., 200) can have any width (e.g., measured along axis E.sub.2) and any length (e.g., measured along axis E.sub.1). For example, fiber-reinforced composites (e.g., 200) can have a width of up to 6 m or larger, or from 0.01 to 6 m, 0.5 to 5 m, or 1 to 4 m, or any range therebetween, and a length of up to 10,000 m or larger, or from 5 to 1,000 m, 10 to 100 m, or any range therebetween. The width of a composite (e.g., 200) can be 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0 m, or larger. The length of a composite (e.g., 200) can be 1, 10, 100, 500, 1,000, 1,500, 2,000, 2,500, 3,000, 3,500, 4,000, 4,500, 5,000, 5,500, 6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500, 10,000 meters, or larger.

[0109] 3. Fibrous Region

[0110] Fiber-reinforced composite 200 includes a non-woven fibrous region 202 dispersed in a polymer matrix 204. Non-woven fibrous region 202 includes a plurality of fibers 206, which are unidirectionally oriented and substantially parallel to a first axis (e.g., axis E.sub.1, FIG. 3). Fibers (e.g., 206) of a composite (e.g., 200) make up, by volume, 35 to 70%, preferably 40 to 65%, more preferably 45 to 55%, or any range therebetween, of the composite. Fibrous region 202 can be formed from a first flattened fiber layer and a second flattened fiber layer that have been pressed into a matrix material (e.g., as shown in and described with respect to FIG. 9). Fibers 206 can be glass fibers, carbon fibers, aramid fibers, polyethylene fibers, polyester fibers, polyamide fibers, ceramic fibers, basalt fibers, or steel fibers, or a combination thereof. Fibers 206 can have an average filament cross-sectional area of from 7 m.sup.2 to 800 m.sup.2, which, for circular fibers, equates to an average filament diameter of from 3 to 30 microns.

[0111] Fibers (e.g., 206) of a composite (e.g., 200) may be provided in bundles (e.g., bundles of carbon, ceramic, carbon precursor, ceramic precursor, glass, and/or the like fibers). Such bundles may include any number of fibers, such as, for example, 400, 750, 800, 1,375, 1,000, 1,500, 3,000, 6,000, 12,000, 24,000, 50,000, 60,000, or more fibers. Fibers in a bundle can have an average filament diameter of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or more microns (e.g., from 5 to 24 microns, 10 to 20 microns, 12 to 15 microns, or any range therebetween). Fibers can be provided with a coating (e.g. a coating of an organic polymer, such as an organosilane), a pigment, and/or the like.

[0112] Glass fiber bundles (e.g., fiber glass yarn bundles) are commercially available from PPG Industries (Pittsburgh, Pa., USA) under the trade name HYBON, Jushi Group Co., Ltd. (CHINA), and Kripa International (INDIA). Glass fiber bundles can have an average filament diameter of 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 microns, or larger (e.g., from 10 to 24 microns, 12 to 20 microns, 13 to 15 microns, or any range therebetween). Carbon fiber or modified carbon fiber bundles (e.g., carbon fiber tows) are commercially available from ACP Composites (Livermore, Calif., USA), Toray Industries, Inc. (JAPAN), and ZOLTEK (Bridgeton, Mo., USA) under the trade name Panex. Carbon fiber bundles can have an average filament diameter of from 3 to 8 microns, from 6 to 7 microns, or any range therebetween.

[0113] Aramid fiber bundles (e.g., aramid fiber yarn bundles) are sold by DuPont (Wilmington, Del., USA) under the trade name KEVLAR. Ceramic fiber bundles (e.g., metal oxide fiber bundles) are commercially available from 3M (United States) under the trade name 3M Nextel Continuous Ceramic Oxide Fibers. Basalt fiber bundles are commercially available from Kamenny Vek (Moscow, RUSSIA) under the trade name Basfiber or from Sudaglass Fiber Technology under the trade name Sudaglass (RUSSIA). Polyester fiber bundles, polyamide fiber bundles, polypheylene sulfide fiber bundles, and polypropylene fiber bundles are commercially available from Toray Industries under the trade name TORAYCA. Without wishing to be bound by theory, it is believed that physical properties of fibers do not substantially change when the fibers are processed to form a fiber-reinforced composite using methods and apparatuses of the present disclosure.

[0114] A polymer matrix (e.g., 204) can comprise any suitable material, such as, for example, a thermoplastic polymer and/or a thermoset polymer. Non-limiting examples of such thermoplastic polymers include polyethylene terephthalate (PET), polycarbonates (PC), polybutylene terephthalate (PBT), poly(1,4-cyclohexylidene cyclohexane-1,4-dicarboxylate) (PCCD), glycol modified polycyclohexyl terephthalate (PCTG), poly(phenylene oxide) (PPO), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polymethyl methacrylate (PMMA), polyethyleneimine or polyetherimide (PEI) or derivatives thereof, thermoplastic elastomers (TPE), terephthalic acid (TPA) elastomers, poly(cyclohexanedimethylene terephthalate) (PCT), polyethylene naphthalate (PEN), a polyamide (PA), polysulfone sulfonate (PSS), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), acrylonitrile butyldiene styrene (ABS), polyphenylene sulfide (PPS), co-polymers thereof, or blends thereof. Non-limiting examples of such thermoset polymers include unsaturated polyester resins, polyurethanes, bakelite, duroplast, urea-formaldehyde, diallyl-phthalate, epoxy resin, epoxy vinylesters, polyimides, cyanate esters of polycyanurates, dicyclopentadiene, phenolics, benzoxazines, co-polymers thereof, or blends thereof.

[0115] Fibrous region 202 has a substantially uniform density as defined above. As shown, composite 200 has a volume fraction of voids that is less than 5%, such as, for example, less than 4, 3, 2, or 1%, from 0 to 5%, from 0.1 to 4%, or from 1 to 3%. Some fiber-reinforced composites, such as composite 200, can be substantially free of voids. In contrast, the prior art composites of FIG. 1 have fibrous regions that, while including consistent density portions 102, have inconsistent density portions 104 and voids 106.

[0116] 4. Polymeric-Rich Regions

[0117] As shown, non-woven fibrous region 202 is positioned between a first polymeric-rich region 208 and a second polymeric-rich region 210. Polymeric-rich regions 208 and 210 include less than 10%, by volume, of fibers 206. Polymeric-rich regions (e.g., 208, 210, and/or the like) can comprise less than 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1%, by volume, of fibers (e.g., 206). The width and the length of each of first and second polymeric-rich regions, 208 and 210, are substantially similar to the width and the length, respectively, of fiber reinforced composite 200. For fiber-reinforced composite 200, a sum of the thickness of first polymeric-rich region 208 and the thickness of second polymeric-rich region 210 is from 15 to 25% of the thickness of the composite. First and second polymeric-rich regions, 208 and 210, have substantially the same thickness (e.g., the thicknesses are within 10% of each other); however, in other embodiments, polymeric-rich regions (e.g., 208 and 210) may have differing thicknesses (e.g., thicknesses that vary by more than 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more % with respect to each other). Each of first and second polymeric-rich regions, 208 and 210, can have a substantially uniform density throughout the polymeric-rich region. Such polymer-rich regions (e.g., 208 and 210) may enhance composite (e.g., 200) strength by providing sufficient polymeric matrix (e.g., 204) to hold fibers (e.g., 206) in position, as well as facilitate handling of the composite (e.g., by overlying and containing fibers within the composite) and bonding of the composite to other composites or structures.

[0118] 5. Fiber-Reinforced Composites Made from Plies

[0119] FIGS. 4A-4C are schematics of stacks or lay-ups of fiber-reinforced composites of the present invention, which may be used to form laminates. Such stacks or lay-ups can include two or more (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) fiber-reinforced composites (e.g., 200), and such fiber-reinforced composites can be oriented relative to one another within the stack or lay-up in any suitable fashion. For example, stack 400 of FIG. 4A includes three UD fiber-reinforced composites, 200, 402, and 404. As shown, fibers 406 of each UD composite 200, 402, and 404 are substantially parallel to one another and with axis E.sub.1 (e.g., stack 400 may be characterized as a UD stack). For further example, stack 400 of FIG. 4B includes two UD fiber-reinforced composites, 200 and 402. As shown, fibers 206 of UD composite 200 are angularly disposed (e.g., at 90 degrees) relative to fibers 406 of UD composite 402. Composites, plies, stacks, and laminates may be provided with protective coating(s). For example, FIG. 4C depicts a stack of two UD fiber-reinforced composites, 408 and 410, having protective coatings or layers 412 and 414. Lay-ups or stacks having non-fibrous or non-UD layer(s), plie(s), or film(s) are also contemplated. Examples of such layer(s), plie(s), or film(s) include neat thermoplastic resin, compounded thermoplastic polymer with various additives, and/or the like.

[0120] 6. Additives

[0121] The disclosed polymeric compositions and matrices can further comprise one or more optional additive components, including for example, one or more additives selected from the group consisting of: a coupling agent to promote adhesion between a matrix material and fibers, an antioxidant, a heat stabilizer, a flow modifier, a flame retardant, a UV stabilizer, a UV absorber, an impact modifier, a cross-linking agent, a colorant, or a combination thereof. Non-limiting examples of coupling agents suitable for use as an additive component in the disclosed compositions include Polybond 3150 maleic anhydride grafted polypropylene, commercially available from Chemtura, Fusabond P613 maleic anhydride grafted polypropylene, commercially available from DuPont, maleic anhydride ethylene, or combinations thereof. An exemplary flow modifier suitable for use as an additive component in the disclosed compositions can include, without limitation, CR20P peroxide masterbatch, commercially available from Polyvel Inc. A non-limiting exemplary stabilizer suitable for use as an additive component in the disclosed compositions can include, without limitation, Irganox B225, commercially available from BASF. In a still further aspect, neat polypropylene can be introduced as an optional additive. Non-limiting examples of flame retardants include halogen and non-halogen-based polymer modifications and additives. Non-limiting examples of UV stabilizers include hindered amine light stabilizers, hydroxybenzophenones, hydroxyphenyl benzotriazoles, cyanoacrylates, oxanilides, hydroxyphenyl triazines, and combinations thereof. Non-limiting examples of UV absorbers include 4-substituted-2-hydroxybenzophenones and their derivatives, aryl salicylates, monoesters of diphenols, such as resorcinol monobenzoate, 2-(2-hydroxyaryl)-benzotriazoles and their derivatives, 2-(2-hydroxyaryl)-1,3,5-triazines and their derivatives, or combinations thereof. Non-limiting examples of impact modifiers include elastomers/softblocks dissolved in matrix-forming monomer(s), such as, for example, bulk HIPS, bulk ABS, reactor modified PP, Lomod, Lexan EXL, and/or the like, thermoplastic elastomers dispersed in matrix material by compounding, such as, for example, di-, tri-, and multiblock copolymers, (functionalized) olefin (co)polymers, and/or the like, pre-defined core-shell (substrate-graft) particles distributed in matrix material by compounding, such as, for example, MBS, ABS-HRG, AA, ASA-XTW, SWIM, and/or the like, or combinations thereof. Non-limiting examples of cross-linking agents include divinylbenzene, benzoyl peroxide, alkylenediol di(meth)acrylates, such as, for example, glycol bisacrylate and/or the like, alkylenetriol tri(meth)acrylates, polyester di(meth)acrylates, bisacrylamides, triallyl cyanurate, triallyl isocyanurate, allyl (meth)acrylate, diallyl maleate, diallyl fumarate, diallyl adipate, triallyl esters of citric acid, triallyl esters of phosphoric acid, or combinations thereof.

B. Systems, Methods, and Apparatuses for Making Fiber-Reinforced Composites

[0122] FIG. 5 is a schematic of a system 500 for making fiber-reinforced composite 200 of the present disclosure. System 500 can include spools of fiber bundles 502, an unwinding unit 504, a fiber preparation section 506, a spreading section 508, an impregnation section 510, a shaping unit 512, and a winder 514. Spools of fiber bundles 502 can be positioned on unwinding unit 504, which can unwind fiber bundles 516 from the spools such that the fiber bundles can be provided to fiber preparation section 506. In some instances, a wound fiber bundle may be provided (e.g., from a supplier) without a spool; in such instances, a spool may be inserted into the wound fiber bundle before positioning the wound fiber bundle on unwinding unit 504. Fiber bundles 516 may be fiber bundles that have not been subjected to any fiber spreading operation. Fiber preparation section 506 can include units known in the art to prepare fiber bundles 516 for spreading. For example, fiber preparation section 506 may include one or more tensioners (e.g., a dancer tension control system, one or more rollers, and/or the like) for tensioning, stabilizing, and, in some instances, guiding fiber bundles 516. Such tensioner(s) may provide tension to fiber bundles 516 during contact with spreading elements 604A-604D, which may help maintain the fiber bundles in position during spreading or flattening of the fiber bundles. In some instances, unwinding unit 504 may be spaced from fiber preparation section 506 and/or spreading section 508 (e.g., by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more m), such that, for example, a weight of fiber bundles 516 serves to tension the fiber bundles. For further example, fiber preparation section 506 may be configured to heat fiber bundles 516 and/or spray the fiber bundles (e.g., to remove any coating that may be present on the fiber bundles).

[0123] In spreading section 508, fiber bundles 516 can be spread or flattened into spreaded fiber layers 518 (as described in more detail below). Spreaded fiber layers 518 may be provided to impregnation section 510, where the fiber layers can be dispersed into a matrix material to form a fiber-reinforced composite 520 (e.g., fiber-reinforced composite 200 in FIG. 2). Impregnation section 510 can include an extruder, a bath, a coating system, and/or the like. Fiber-reinforced composite 520 can enter shaping unit 512, where the fiber-reinforced composite may be formed into a tape 522 or sheet. Tape 522 may be provided to winder 514, which may wind the tape around a spool (e.g., to facilitate storage, transportation, and/or the like of the tape).

[0124] 1. Spreading Section

[0125] Spreading section 508 may include one or more spreading units 600, each configured to spread one or more fiber bundles 516 into one or more spreaded fiber layers 518. Spreading section 508 may also include one or more rollers, motors, electrical connections, and/or the like needed to operate spreading unit 600.

[0126] i. Spreading Unit

[0127] Referring to FIGS. 6A through 6G, spreading unit 600 is depicted. As will be described in more detail below, spreading unit 600 can include various components, such as, for example, one or more holding elements (e.g., 602A-602D), one or more spreading elements (e.g., 604A-604D), one or more heat sources (e.g., such as heated spreading element(s)), and, optionally, one or more rollers (e.g., 606). Components of spreading unit 600 can be made of materials that are resistant to corrosion and/or to materials used in making fiber layers or fiber-reinforced composites (e.g., fibers, matrix materials, and/or the like), such as, for example, stainless steel, other alloys, and/or the like. Components of spreading unit 600 can be coupled to a frame 608. One or more components of spreading unit 600 can be removably coupled to frame 608, to, for example, facilitate maintenance and/or reconfiguration of the spreading unit (e.g., via replacing spreading elements with other spreading elements having differing lobes, replacing holding elements with other holding elements having differing fiber holding sections, radii, and/or the like, and/or the like). Frame 608 can include wheels or other features to enhance portability of spreading unit 600.

[0128] ii. Holding Elements

[0129] Holding elements 602A-602D each include a fiber holding section 610 disposed between holding element end sections 612 (FIG. 6F). For each holding element, fiber holding section 610 may be characterized as including a plurality of grooves 614 or a plurality of projections 616. As shown, each fiber holding section 610 includes seven (7) grooves 614; however, in other embodiments, a fiber holding section (e.g., 610) may include any number of grooves (e.g., 614), and the number of grooves may be selected based on a number of fiber bundles (e.g., 516) to be spread by a spreading unit (e.g., 600), a number of spreaded fiber layers (e.g., 518) to be produced by the spreading unit, and/or the like. Grooves 614 of a fiber holding section 610 may each have dimensions (e.g., width and depth) that are the same as, substantially similar to, or different than one another. Holding elements 602A-602D each comprise a bar (e.g., the holding elements are rod-shaped); however, in other embodiments, a holding element (e.g., 602A-602D) may comprise a plate.

[0130] Holding elements 602A-602D may each be configured to reduce undesired lateral movement of a plurality of fibers (e.g., in a fiber bundle 516 or a spreaded fiber layer 518) as the plurality of fibers enters the spreading unit, passes over spreading element(s), exits the spreading unit, and/or the like. For example, for a fiber holding section 610, grooves 614 may each have a width (e.g., measured along a longitudinal axis of the respective holding element) that corresponds to a width of a plurality of fibers that the fiber holding section is configured to receive. Grooves 614 of holding elements 602A and 602C, which are configured to receive fiber bundles 516, may each have a smaller width than a width of grooves 614 of holding elements 602B and 602D, which are configured to receive spreaded fibers from spreading elements 604A and 604C. More particularly, grooves 614 of holding elements 602A and 602C can each have a width of 4 to 8 mm, preferably about 6 mm, and grooves 614 of holding elements 602B and 602D can each have a width of 8 to 12 mm, preferably about 10 mm.

[0131] Spreading unit 600 includes four (4) holding elements 602A-602D and four (4) spreading elements 604A-604D. Each spreading element can be paired with a holding element and, for each pair, the holding element can be positioned upstream of the spreading element.

[0132] iii. Spreading Elements

[0133] Referring additionally to FIGS. 7A-7F, shown is a spreading element 604, which may be representative of spreading elements 604A-604D. Spreading element 604 is configured to spread a plurality of fibers into a spreaded fiber layer 518 (e.g., whether spreading fibers in a fiber bundle 516 or further spreading fibers in a spreaded fiber layer 518). Spreading element 604 includes a profile taken perpendicularly to a longitudinal axis of the spreading element, a first surface 626 that defines a convex portion of the profile, and a second surface 628 that defines a straight or concave portion of the profile. First surface 626 can be ellipsoidal and/or second surface 628 can be planar or concave. First surface 626 and second surface 628 can meet at an edge 630, which may be rounded (e.g., the edge may be filleted) to mitigate snagging or tearing of fibers as they pass over the edge. In these ways and others, as a plurality of fibers passes over spreading element 604 (e.g., approaching the spreading element in a direction indicated by arrow 632), the fibers may transition from first surface 626 to second surface 628 (e.g., across edge 630, if present), thereby spreading the fibers. Spreading element 604 is generally straight; for example, the longitudinal axis of the spreading element extends through spreading element end sections 622 as well as a portion of the spreading element that is halfway between the longitudinal end sections. Spreading element 604 comprises a bar (e.g., is rod-shaped); however, in other embodiments, a spreading element (e.g., 604A-604D) may comprise a plate.

[0134] Spreading element 604 includes two or more lobes 620 disposed along the longitudinal axis of the spreading element. Each lobe 620 can include a first surface 626 and a second surface 628 (e.g., as described above). Lobes 620 can be disposed along the longitudinal axis of the spreading element such that second surfaces 628 of the two or more lobes are contiguous. As shown, spreading element 604 includes 7 lobes; however, in other embodiments, a spreading element (e.g., 604) can include any suitable number of lobes (e.g., 620), such as, for example, from 1 to 100, 2 to 50, 3 to 25, 5 to 20 lobes, with 5, 6, 7, 8, 9, or 10 lobes being preferred.

[0135] Spreading elements 604A-604D can each be movable relative to a plurality of fibers being spread by spreading unit 600 in a direction that is substantially perpendicular to a long dimension of the fibers (e.g., generally in a direction indicated by arrow 605), which may enhance spreading of the fibers. For example, each of spreading elements 604A-604D may be coupled to frame 608 such that the spreading element is movable relative to the frame in a direction that is substantially aligned with the longitudinal axis of the spreading element. In some embodiments, an entire spreading unit (e.g., 600), including a frame (e.g., 608) and spreading elements (e.g., 604A-604D), may be configured to move relative to a plurality of fibers being spread by the spreading unit.

[0136] More particularly, spreading elements 604A-604D may be configured to oscillate relative to a plurality of fibers being spread by spreading unit 600. Such oscillation can be at any suitable amplitude, such as, for example, of from 0.1 to 20 mm, 0.1 to 10 mm, 0.5 to 8 mm, 1 to 5 mm, or 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 mm. Such oscillation can be at any suitable frequency, such as, for example, of from 0.1 to 5 Hz, 0.5 to 2 Hz, or 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 Hz. Such oscillation of spreading elements 604A-604D may assist in juxtaposing a plurality of fibers as the fibers pass over the spreading elements. Each of spreading elements 604A-604D can be oscillated at a same or different amplitude and/or frequency.

[0137] Spreading elements 604A-604D can each be rotatable about the longitudinal axis of the spreading element and relative to a plurality of fibers being spread by spreading unit 600. For example, spreading elements 604A-604D are each coupled to frame 608 such that the spreading element is rotatable relative to the frame about the longitudinal axis of the spreading element. Through such rotation of a spreading element, the location where a plurality of fibers makes contact with the spreading element (e.g., along first surface 626 or second surface 628 or at edge 630) can be adjusted to provide for optimum spreading of the fibers. In some embodiments, such rotation of a spreading element may be cyclical or oscillating.

[0138] Movement (e.g., translation and/or rotation) of spreading elements (e.g., 604A-604D) can be accomplished in any suitable fashion. For example, spreading element ends 622 of each spreading element 604A-604D include coupling elements, 618A-618D, respectively, each configured to be coupled to a motor or drive (not shown).

[0139] Referring additionally to FIG. 8A, methods for producing a spreaded fiber layer are shown. A fiber bundle 802 having an initial width (W.sub.i) may enter spreading unit 600 and, in some instances, pass over a holding element (e.g., 602A-602D). Fiber bundle 802 may make contact with spreading element 604A (e.g., travelling in a direction indicated by arrow 607), which may be oscillating, at first surface 626 and transition to second surface 628 (e.g., across edge 630), thereby being spread into a spreaded fiber layer 804. Spreaded fiber layer 804 can, in some instances after passing over a holding element (e.g., 602A-602D), make contact with spreading element 604B, which may be oscillating, at first surface 626 and transition to second surface 628 (e.g., across edge 630), thereby being spread into a spreaded fiber layer 806, having a width (W.sub.1) that is larger than the initial width of fiber bundle 802.

[0140] While not shown, a (e.g., major and/or minor) radius of first surface 626 of spreading element 604B (e.g., of lobe 620C) can be larger than a corresponding radius of first surface 626 of spreading element 604A (e.g., of lobe 620A). Such a configuration may facilitate spreading element 604B in further spreading spreaded fiber layer 804 from spreading element 604A. A radius of first surface 626 of spreading element 604B can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more % larger than a corresponding radius of first surface 626 of spreading element 604A. In some embodiments, a first surface (e.g., 626) of a first spreading element (e.g., 604A) can have a radius of from 10 to 50 mm, 20 to 40 mm, 25 to 35 mm, or about 30 mm and a first surface (e.g., 626) of a second spreading element (e.g., 604B) that is downstream of the first spreading element can have a radius of from 50 to 100 mm, 50 to 90 mm, 55 to 65 mm, or about 60 mm.

[0141] In some embodiments, more than one fiber bundle (e.g., 516) can be used to make a single spreaded fiber layer (e.g., 518). For example, and referring additionally to FIGS. 8B-8E, fiber bundles 802 and 808 may be spread by spreading unit 600 into spreaded fiber layers 806 and 810, respectively (e.g., in a same or similar fashion as described above for fiber bundle 802). As shown, spreading elements 604A and 604B, and more particularly lobes 620A-620D thereof, may be positioned relative to one another such that spreaded fiber layers 806 and 810 form a single spreaded fiber layer 812. Spreaded fiber layer 812 can have a width that is equal to or greater than a sum of the width of spreaded fiber layer 806 and a width (W.sub.2) of spreaded fiber layer 810. Similarly, a spreaded fiber layer 812 can be formed from fiber bundles 816 and 818 (FIG. 8C). In some instances, spreaded fiber layer 812 from fiber bundles 802 and 808 may be combined with spreaded fiber layer 812 from fiber bundles 816 and 818 to form a spreaded fiber layer 812 having fibers from fiber bundles 802, 808, 816, and 818.

[0142] Such spreaded fiber layers (e.g., 806, 810, 812, and/or the like) may be produced at any suitable rate, such as, for example, of from 1 to 50 m/min, 2 to 25 m/min, or 8 to 15 m/min. Spreaded fiber layers (e.g., 806, 810, 812, and/or the like) from spreading section 508 may be provided to impregnation section 510 to be dispersed into a matrix material.

[0143] 2. Impregnation Section

[0144] Impregnation section 510 may include an extruder 906, one or more pressing elements (e.g., 908, 914, 918, 922, 923, and/or the like), one or more rubbing elements (e.g., 916, 920, 924, and/or the like), one or more heat source(s) (e.g., 915, heated pressing element(s), heated rubbing element(s), and/or the like), and/or the like. Impregnation section 510 may also include one or more rollers, motors, electrical connections, and/or the like needed to operate the impregnation section. At least some components of impregnation section 510 may be referred to collectively as an impregnation unit, even though such components may not be physically attached to one another.

[0145] Referring to FIG. 9, spreaded fiber layer(s) from spreading section 508 may be guided to impregnation section 510 by one or more rollers 606 (e.g., which, if present, may be considered a component of the spreading section and/or a component of the impregnation section) wherein the spreaded fiber layer(s) may be dispersed within a matrix material. For example, impregnation section 510 comprises an extruder 906 configured to supply a sheet or film of matrix material to the spreaded fiber layer(s); however, in other embodiments, a matrix material may be provided to spreaded fiber layer(s) using any suitable structure.

[0146] Impregnation section 510 includes one or more pressing elements (e.g., 908, 914, 918, 922, 923, and/or the like), each disposed downstream of extruder 906 and configured to press at least one of the spreaded fiber layer(s) into the matrix material. For example, each pressing element can include a convex surface configured to press at least one of the spreaded fiber layer(s) into the matrix material as the spreaded fiber layer, when in contact with the matrix material, is passed under tension over the convex surface. A pressure applied by a pressing element to the spreaded fiber layer(s) can be varied by adjusting an angle at which the spreaded fiber layer(s) approach or leave the pressing element, a tension of the spreaded fiber layer(s), and/or the like. Pressing elements (e.g., 908, 914, 918, 922, 923, and/or the like) may be heated, in some instances, to differing temperatures. In these ways and others, such pressing elements may provide sufficient pressure and/or temperature to press the one or more spreaded fiber layers into the matrix material. In some instances, a heat source 915, such as, for example, an infrared heat source, may be provided to facilitate the pressing process (e.g., by heating the matrix material and/or spreaded fiber layer(s)). Pressing elements (e.g., 908, 914, 918, 922, 923, and/or the like) may comprise any suitable structure, such as, for example, a bar, plate, roller (e.g., whether stationary or rotating), and/or the like. In instances where a rotating pressing element is usedor any other rotating element that contacts fibersa guard, barrier, or blade may be positioned against the rotating element to prevent fibers from wrapping around the rotating element.

[0147] Impregnation section 510 includes one or more rubbing elements (e.g., 916, 920, 924, and/or the like) configured to facilitate dispersion of the one or more spreaded fiber layers within the matrix material. FIGS. 10A and 10B depict a rubbing element 1200, which may be representative of rubbing elements 916, 920, and 924. Rubbing element 1200 includes two or more convexities 1206 disposed along a longitudinal axis 1204 of the rubbing element. Due to convexities 1206, rubbing element 1200 can have a profile, taken parallel to longitudinal axis 1204, that includes curved portions, which can collectively form a larger portion of the profile that may be characterized as fluctuating and/or undulating (e.g., in distance from the longitudinal axis). Convexities 1206 of rubbing element 1200 each include an ellipsoidal surface; however, convexities (e.g., 1206) of a rubbing element (e.g., 1200) may have any suitable shape. Rubbing element 1200 comprises a bar (e.g., the rubbing element is rod-shaped); however, in other embodiments, a rubbing element may comprise a plate.

[0148] One or more rubbing elements (e.g., 916, 920, 924, and/or the like) may each be movable relative to spreaded fiber layer(s) being processed by impregnation section 510 in a direction that is substantially perpendicular to a long dimension of the spreaded fiber layer(s). For example, impregnation section 510 can include a frame to which the one or more rubbing elements may be coupled, and each of the rubbing element(s) can be movable relative to the frame in a direction that is substantially aligned with the longitudinal axis of the rubbing element. Rubbing elements may be configured to oscillate, for example, at any of the amplitudes and frequencies described above for spreading elements 604A-604D. Each rubbing element (e.g., 916, 920, 924, and/or the like) is configured to contact at least one of the one or more spreaded fiber layers after the spreaded fiber layer has been pressed into the matrix material.

[0149] As shown in FIG. 9, spreaded fiber layers 901 and 902 can be guided by rollers 606, if present, to extruder 906. Spreaded fiber layers 901 and 902 can include the same or differing types of fibers and can have the same or differing widths. Extruder 906 may supply a sheet or film of matrix material to at least one of spreaded fiber layers 901 and 902, such as, for example, to an upper surface of spreaded fiber layer 902 to form a coated spreaded fiber layer 910. Spreaded fiber layer 901 may be brought into contact with coated spreaded fiber layer 910 and may be pressed into the matrix material by passing over pressing element 908. Coated spreaded fiber layer 910 may be pressed into the matrix material by passing over pressing element 914. The spreaded fiber layers, coupled by the matrix material, may be passed over rubbing element 916, which may be oscillating, to facilitate dispersion of the spreaded fiber layers into the matrix material. In this example, the coupled spreaded fiber layers may be further passed over pressing element 918, over rubbing element 920, over pressing element 922, over rubbing element 924, and over pressing element 923. In some instances, the coupled spreaded fiber layers can be passed over a plate 925 and/or be directed to a pressing device 926 including one or more consolidation rollers 928. A fiber-reinforced composite 200 from impregnation section 510 can be processed by shaping unit 512 and/or provided to winder 514. In some embodiments, only one spreaded fiber layer (e.g., 901 or 902) is processed by impregnation section 510.

[0150] Referring now to FIG. 11, in some embodiments, an impregnation section 510 includes a matrix material bath 1002. As shown, spreaded fiber layer 902 can be passed through matrix material bath 1002, which can be facilitated by stationary or rotating rollers (e.g., 1004, 1006, and/or the like), to form coated spreaded fiber layer 1008. Coated spreaded fiber layer 1008 may be consolidated, for example, by pressing (e.g., via consolidation rollers 1010) to form fiber-reinforced composite 200. Fiber-reinforced composite 200 may be passed through a solvent recovery bath 1004 to remove any free matrix material, which can be facilitated by stationary or rotating rollers (e.g., 1012 and/or the like).

C. Laminates including Fiber-Reinforced Composites and Systems and Methods for Making the Same

[0151] FIG. 12 is a schematic exploded view of a laminate 1300 that can be formed using one or more of the present fiber-reinforced composites. For example, laminate 1300 can include one or more fiber-reinforced composites (e.g., 1304a-1304f), each comprising fibers 1308 dispersed within a matrix material 1312. Each of the fiber-reinforced composite(s) of laminate 1300 can be a fiber-reinforced composite of the present disclosure or another fiber-reinforced composite.

[0152] Provided by way of example, laminate 1300 can include a fiber-reinforced composite 1304a having fibers 1308 aligned in a first direction 1316a and a fiber-reinforced composite 1304b having fibers 1308 aligned in a second direction 1316b that is angularly disposed relative to the first direction. A smallest angle 1320 between first direction 1316a and second direction 1316b can be approximately 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 85, or 90 degrees. More particularly, laminate 1300 can include six (6) fiber-reinforced composites, 1304a-1304f, each having fibers 1308 that are angularly disposed at approximately 0, 45, 45, 45, 45, and 0 degrees, respectively, relative to a long dimension of the fiber-reinforced composite and/or the laminate. Other laminates can include any suitable number of fiber-reinforced composite(s), each having fibers that are angularly disposed at any suitable angle relative to a long dimension of the fiber-reinforced composite and/or the laminate, such as, for example, approximately 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, and/or 90 degrees. While fiber-reinforced composites 1304a-1304f of laminate 1300 each comprise a unidirectional fiber-reinforced composite (e.g., in which substantially all of fibers 1308 are substantially parallel to one another), other laminates can include fiber-reinforced composite(s) that have fibers defining a woven structure (e.g., a plane, twill, satin, basket, leno, mock leno, or the like weave). Fiber-reinforced composite(s) (e.g., 1304a-1304f) of a laminate (e.g., 1300) can be stacked in a symmetric (e.g., FIG. 12) or asymmetric configuration.

[0153] Some laminates (e.g., 1300) can include fiber-reinforced composite(s) (e.g., 1304a-1304f) having polymeric-rich region(s) (e.g., 208, 210, and/or the like). A fiber-reinforced composite (e.g., 1304a-1304f) including such polymeric-rich region(s) (e.g., disposed on one or both sides of the fiber-reinforced composite) may be particularly suited for use in forming a laminate (e.g., 1300). To illustrate, such polymeric-rich region(s) can facilitate bonding of the fiber-reinforced composite to another fiber-reinforced composite or to a structure (e.g., substrate 1508, described below) by, for example, providing an increased amount of matrix material (e.g., 1312) on one or both sides of the fiber-reinforced composite. To further illustrate, such polymeric-rich region(s) can facilitate handling of the fiber-reinforced composite by, for example, overlying and containing fibers (e.g., 1308) within the fiber-reinforced composite, which, if dislocated, can injure workers, become tangled in and/or clog fiber-reinforced composite handling equipment (e.g., spool 1516, conduit 1520, end effector 1512, and/or the like, described below), weaken the fiber-reinforced composite, and/or the like.

[0154] Laminates (e.g., 1300) of the present disclosure can be formed in any suitable manner. For example, FIG. 13 depicts a press 1400 for forming a laminate (e.g., 1300) from one or more fiber-reinforced composites (e.g., 1304a-1304f). Press 1400 can include two or more press portions (e.g., 1404a and 1404b), each defining a pressing surface 1408. Press 1400 can be movable, via relative movement of the press portions, between an open position and a closed position in which pressing surfaces 1408 cooperate to press fiber-reinforced composite(s) that are disposed between the pressing surfaces. To illustrate, in press 1400, press portion 1404a can be moved relative to press portion 1404b (e.g., in a direction indicated by arrow 1406) to move the press between the open and closed positions. Each of pressing surfaces 1408 can include planar, angled, convex, concave, and/or the like portion(s) and can be selected based on a desired shape for a laminate formed by press 1400. Movement of press 1400 between the open and closed positions can be facilitated via, for example, one or more hydraulic, electric, pneumatic, and/or the like actuators 1410.

[0155] Press 1400 can include and/or can be used in conjunction with a heat source 1412. For example, in press 1400, heat source 1412 comprises a heating element configured to heat at least one of the press portions. Nevertheless, a heat source (e.g., 1412) can comprise any suitable heat source, such as, for example, a laser, an infrared heat source, and/or the like. Such a heat source (e.g., 1412) can facilitate laminate formation by, for example, softening and/or melting the matrix material of one or more fiber-reinforced composites used to form the laminate.

[0156] To illustrate, while a press (e.g., 1400) is in an open position (e.g., FIG. 13), one or more fiber-reinforced composites (e.g., 1304a-1304f) can be placed on one or more pressing surfaces (e.g., 1408) of the press. Placement of the fiber-reinforced composite(s) on the pressing surface(s) can be performed by a worker, a robotic arm (e.g., 1504, described below), and/or the like. The press can then be moved to a closed position, thereby pressing the fiber-reinforced composite(s) between the pressing surfaces to form a laminate (e.g., 1300) from the fiber-reinforced composite(s). The fiber-reinforced composite(s) can be heated (e.g., using heat source 1412) before, during, and/or after movement of the press from the open position to the closed position.

[0157] For further example, FIG. 14 depicts a system 1500 for forming a laminate (e.g., 1300) from one or more fiber-reinforced composites (e.g., 1304a-1304f). More particularly, system 1500 can include a robotic arm 1504 having an end effector 1512 configured to place the fiber-reinforced composite(s) onto a substrate 1508 to form the laminate. A fiber-reinforced composite can be placed onto a substrate by being placed into contact with the substrate or by being placed into contact with one or more other fiber-reinforced composites that are in contact with the substrate. Substrate 1508 can comprise a mold, form, platform, surface and/or the like from which the laminate can be removed, or the substrate can remain with the laminate such that the substrate and the laminate form a part (e.g., an automobile, aircraft, and/or the like part) (e.g., such that the laminate can be placed to locally re-inforce the part).

[0158] System 1500 can include a spool 1516 around which a fiber-reinforced composite (e.g., 1304a-1304f) can be wound. Spool 1516 can be located within a temperature-controlled housing 1518 in order to reduce the risk of premature softening and/or melting of the fiber-reinforced composite that might otherwise cause the fiber-reinforced composite to stick to itself or component(s) of system 1500. System 1500 can include a conduit 1520 configured to convey the fiber-reinforced composite from spool 1516 to end effector 1512. Conduit 1520 can be flexible to, for example, facilitate movement of the fiber-reinforced composite from spool 1516 to end effector 1512 during movement of the end effector relative to substrate 1508. Conduit 1520 can be (e.g., air- and/or liquid-cooled), which can provide benefits similar to those provided by housing 1518. Referring additionally to FIG. 15, end effector 1512 can include one or more rollers 1524 configured to draw the fiber-reinforced composite from conduit 1520.

[0159] System 1500 can be configured to tension the fiber-reinforced composite. To illustrate, spool 1516 can be configured to resist unwinding of the fiber-reinforced composite from the spool, via, for example, the spool being resistant to rotation. Such resistance of spool 1516 to rotation can be provided through friction, a motor coupled to spool 1516, and/or the like. To further illustrate, system 1500 can be configured to allow control over rotational position and/or speed of spool 1516 and at least one of roller(s) 1524 (e.g., via motors coupled to the spool and the at least one roller), which can be adjusted to tension the fiber-reinforced composite. Tensioning of the fiber-reinforced composite can reduce the risk of the fiber-reinforced composite buckling, becoming jammed, and/or the like within system 1500.

[0160] End effector 1512 can include a pressing element 1528 configured to press the fiber-reinforced composite against substrate 1508. The fiber-reinforced composite can be directed through end effector 1512 to pressing element 1528 by one or more rollers, pins, conduits, and/or the like of the end effector. In end effector 1512, pressing element 1528 comprises a roller; however, in other embodiments, a pressing element (e.g., 1528) can comprise a pin, a (e.g., curved) plate, and/or the like. Such a pressing element (e.g., 1528) can comprise a flexible material to, for example, facilitate pressing of a fiber-reinforced composite against curved portion(s) of a substrate (e.g., 1508).

[0161] System 1500 can include a heat source 1532, which can be coupled to end effector 1512, configured to heat the fiber-reinforced composite. In system 1500, heat source 1532 comprises a laser; however, in other embodiments, a heat source (e.g., 1532) can comprise a heating element configured to heat a pressing element (e.g., 1528), an infrared heat source, an ultrasonic welder, and/or the like. By pressing the fiber-reinforced composite against substrate 1508 and/or another fiber-reinforced composite that is coupled to the substrate and/or heating the fiber-reinforced composite, the fiber-reinforced composite can be bonded to the substrate and/or to the other fiber-reinforced composite.

[0162] End effector 512 can be movable relative to substrate 1508 such that the end effector can place the fiber-reinforced composite at a desired location on the substrate and in a desired direction along the substrate. For example, in system 1500, end effector 1512 can rotate about and/or translate along axes 1536a, 1536b, and/or 1536c relative to substrate 1508 (e.g., in six degrees of freedom). Such movement of end effector 1512 relative to substrate 1508 can be accomplished in any suitable fashion, and the following description is provided only by way of illustration. Robotic arm 1504 can include a base 1540 and one or more arms (e.g., 1544a, 1544b, and/or the like) coupled between the base and end effector 1512. Movement of end effector 1512 can be effectuated via movement (e.g., rotation and/or translation) of at least a portion of base 1540 relative to a floor above which robotic arm 1504 is disposed, movement (e.g., rotation and/or translation) of at least a portion of one or more of the arm(s) relative to at least a portion of the base, and/or movement (e.g., rotation and/or translation) of at least a portion of end effector 1512 relative to at least a portion of one or more of the arm(s). Such relative movement of base 1540, the one or more arms, and/or end effector 1512 can be facilitated by, for example, electric, hydraulic, pneumatic, and/or the like actuators. In some embodiments, a substrate (e.g., 1508) can be movable (e.g., rotatable and/or translatable) relative to a floor above which the substrate is disposed (e.g., to facilitate placement of a fiber-reinforced composite at a desired location on the substrate and in a desired direction along the substrate).

[0163] End effector 1512 can include a cutter 1548 configured to cut the fiber-reinforced composite to, for example, allow a desired length of the fiber-reinforced composite to be placed onto substrate 1508. To illustrate, end effector 1512 can apply a first length of the fiber-reinforced composite onto substrate 1508, cutter 1548 can cut the fiber-reinforced composite, and the end effector can apply a second length of the fiber-reinforced composite onto the substrate (e.g., in a different location on and/or in a different direction along the substrate). Once the fiber-reinforced composite has been cut, the separated sections of the fiber-reinforced composite are referred to as separate fiber-reinforced composites (e.g., a first and a second fiber-reinforced composite).

[0164] While system 1500 is described with respect to a single fiber-reinforced composite feed (e.g., from a single spool 1516), other embodiments can comprise any suitable number of fiber-reinforced composite feeds and can comprise a corresponding number of spools (e.g., 1516), conduits (e.g., 1520), rollers (e.g., 1524), pressing elements (e.g., 1528), heat sources (e.g., 1532), cutters (e.g., 1548), and/or the like.

[0165] For example, some embodiments of the present methods comprise placing a first fiber-reinforced composite onto a substrate (e.g., 1508) using an end effector (e.g., 1512) of a robotic arm (e.g., 1504) and placing a second fiber-reinforced composite onto the substrate using the end effector. As shown in FIG. 16, such placement can be such that the second fiber-reinforced composite overlies the first fiber-reinforced composite (e.g., fiber-reinforced composite 1304h overlies fiber-reinforced composite 1304g) and/or such that the second fiber-reinforced composite is adjacent to the first fiber-reinforced composite (e.g., fiber-reinforced composite 1304h is adjacent to fiber-reinforced composite 1304i). The first and second fiber-reinforced composites can come from the same or different fiber-reinforced composite feeds. Some embodiments comprise bonding the first and second fiber-reinforced composites by heating (e.g., using heat source 1532) at least one of the first and second fiber-reinforced composites and/or applying pressure (e.g., using pressing element 1528) to at least one of the first and second fiber-reinforced composites.

[0166] System 1500 can include one or more sensors 1556 configured to capture data indicative of fiber-reinforced composite propert(ies), such as, for example, color, matrix material composition, fiber composition, thickness, width, and/or the like. Such sensor(s) (e.g., 1556) can comprise any suitable sensor, such as, for example a color sensor (e.g., an RBG, RBGC, and/or the like color sensor), a light-based sensor (e.g., a camera, a laser-, infrared-, and/or the like based sensor), an ultrasonic sensor, and/or the like. In system 1500, sensor(s) 1556 are disposed on end effector 1512; however, in other embodiments, sensor(s) (e.g., 1556) can be disposed at any suitable location, such as, for example, on or proximate to a spool (e.g., 1516), a conduit (e.g., 1520), and/or the like.

[0167] System 1500 can include a processor 1560 configured to control system component(s) based, at least in part, on data captured by sensor(s) 1556. For example, processor 1560 can control heat source 1532 to vary a heat provided by the heat source to a fiber-reinforced composite based, at least in part, on data captured by sensor(s) 1556 indicative of propert(ies) of the fiber-reinforced composite. To illustrate, processor 1560 can control heat source 1532 to provide less heat to fiber-reinforced composites having darker colors than to fiber-reinforced composites having lighter colors (e.g., darker fiber-reinforced composites may reflect less energy than lighter fiber-reinforced composites), more heat to fiber-reinforced composites having matrix materials with higher melting points than to fiber-reinforced composites having matrix materials with lower melting points, more heat to thicker and/or wider fiber-reinforced composites than to thinner and/or narrower fiber-reinforced composites (e.g., thicker and/or wider fiber-reinforced composites may comprise more matrix material than thinner and/or narrower fiber-reinforced composites), and/or the like. Processor 1560 can control heat source 1532 to vary a heat provided by the heat source based, at least in part, on a translational and/or rotational speed of end effector 1512 relative to substrate 1508, a pressure applied by pressing element 1528, and/or the like.

[0168] For further example, processor 1560 can be configured to vary a translational and/or rotational speed of end effector 1512 relative to substrate 1508 (e.g., via control of robotic arm 1504 actuator(s)) based, at least in part, on data captured by sensor(s) 1556 indicative of propert(ies) of a fiber-reinforced composite being placed by the end effector onto substrate 1508. To illustrate, processor 1560 can be configured to translate and/or rotate end effector 1512 relative to substrate 1508 more slowly when the end effector is placing thicker and/or wider fiber-reinforced composites than when the end effector is placing thinner and/or narrower fiber-reinforced composites, when the end effector is placing fiber-reinforced composites having matrix materials with higher melting points than when the end effector is placing fiber-reinforced composites having lower melting points, and/or the like. Processor 1560 can be configured to vary a rotational and/or translational speed of end effector 1512 relative to substrate 1508 based, at least in part, on a heat provided by heat source 1532, a pressure applied by pressing element 1528, and/or the like.

[0169] For yet further example, processor 1560 can be configured to vary a pressure applied by pressing element 1528 to a fiber-reinforced composite (e.g., via control of robotic arm 1504 actuator(s)) based, at least in part, on data captured by sensor(s) 1556 indicative of propert(ies) of the fiber-reinforced composite. To illustrate, processor 1560 can be configured to apply more pressure to fiber-reinforced composites having matrix materials with higher melting points than to fiber-reinforced composites having lower melting points, more pressure to thicker and/or wider fiber-reinforced composites than to thinner and/or narrower fiber-reinforced composites, and/or the like. Processor 1560 can vary a pressure applied by pressing element 1528 based, at least in part, on a heat provided by heat source 1532, a translational and/or rotational speed of end effector 1512 relative to substrate 1508, and/or the like.

[0170] Some embodiments of the present methods comprise adjusting a translational and/or rotational speed of an end effector (e.g., 1512) relative to a substrate (e.g., 1508), a heat provided (e.g., by heat source 1532) to a fiber-reinforced composite, and/or a pressure applied (e.g., by pressing element 1528) to the fiber-reinforced composite, based, at least in part, on one or more of the following: a color of the fiber-reinforced composite, a composition of the matrix material of the fiber-reinforced composite, a composition of the fibers of the fiber-reinforced composite, a thickness of the fiber-reinforced composite, and a width of the fiber-reinforced composite. Such adjustment(s) can be made (e.g., in real time) by a processor (e.g., 1560) (e.g., considering data captured by sensor(s) 1556) and/or can comprise system parameter(s) that are entered (e.g., manually).

EXAMPLES

[0171] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results.

Example 1

Sample Tapes of the Present Disclosure and Comparative Tapes

[0172] Unidirectional glass fiber tapes of the present disclosure (samples 1-3 or S1-S3) were prepared using the spreading and impregnation units described above. For S1-S3, the glass fibers have an average diameter of 17 m. For S1, the polymer used to form the matrix was polypropylene, for S2, the polymer used to form the matrix material was high-density polyethylene, and, for S3, the polymer used to form the matrix material was polyamide 6 (Aegis H8202NLB). FIGS. 17-19 are cross-sectional confocal microscope images of S1, S2, and S3, respectively, the images being obtained by a Keyence VK-X200 camera with a 50 lens.

[0173] Three comparative commercially available glass fiber tapes (comparatives 1-3 or C1-C3) were also analyzed. Sample C1 has an average filament diameter of 13 m, and samples C2 and C3 have an average filament diameter of 17 m. FIGS. 20-22 are cross-sectional confocal microscope images of C1, C2 and C3, respectively.

[0174] The uniform densities of S1-S3 and C1-C3 were determined in the manner outlined above in the section of the specification titled Determining Density Uniformity. For S1, the RFAC (%) and COV (%) values are 82.3 and 4.0, respectively. For S2, the RFAC (%) and COV (%) values are 80.4 and 7.0, respectively. For S3, the RFAC (%) and COV (%) values are 69.7 and 8.0, respectively. For C1, the RFAC (%) and COV (%) values are 47.3 and 25.3, respectively. For C2, the RFAC (%) and COV (%) values are 65.7 and 32.4, respectively. For C3, the RFAC (%) and COV (%) values are 55.5 and 9.2, respectively.

[0175] Tables 1-3 provide the data points for S1-S3, respectively, and tables 4-6 provide the data points for C1-C3, respectively. The theoretical maximum possible coverage, assuming close packing of circular filaments within a square, is 78.5%, which is calculated as the area of the circular filaments divided by the area of square. For example, for a circular filament with a radius r within a square having a side 2r, the coverage equals r.sup.2/(2r).sup.2.

TABLE-US-00001 TABLE 1 (Sample S1 Data Points) Fiber Area Square Area Fiber Percent Box Fiber Count (cm.sup.2) (cm.sup.2) Coverage* 1 30 6.8094E05 0.0001 68.1 2 30 6.8094E05 0.0001 68.1 3 29 6.58242E05 0.0001 65.8 4 29 6.58242E05 0.0001 65.8 5 27 6.12846E05 0.0001 61.3 6 27 6.12846E05 0.0001 61.3 7 28 6.35544E05 0.0001 63.6 8 28 6.35544E05 0.0001 63.6 9 27 6.12846E05 0.0001 61.3 10 29 6.58242E05 0.0001 65.8 11 29 6.58242E05 0.0001 65.8 *Average of boxes 1 to 11 is 64.6. Therefore, (64.6/78.5) 100 = an RFAC of 82.3. Standard deviation for boxes 1 to 11 is 2.6. Therefore, (2.6/64.4) 100 = a COV of 4.0.

TABLE-US-00002 TABLE 2 (Sample S2 Data Points) Fiber Area Square Area Fiber Percent Box Fiber Count (cm.sup.2) (cm.sup.2) Coverage* 1 27 6.12846E05 0.0001 61.3 2 28 6.35544E05 0.0001 63.6 3 29 6.58242E05 0.0001 65.8 4 28 6.35544E05 0.0001 63.6 5 27 6.12846E05 0.0001 61.3 6 30 6.80940E05 0.0001 68.1 7 26 5.90148E05 0.0001 59.0 8 29 6.58242E05 0.0001 65.8 9 27 6.12846E05 0.0001 61.3 10 31 7.03638E05 0.0001 70.4 11 24 5.44752E05 0.0001 54.5 *Average of boxes 1 to 11 is 63.1. Therefore, (63.1/78.5) 100 = an RFAC of 80.4. Standard deviation for boxes 1 to 11 is 4.4. Therefore, (4.4/63.1) 100 = a COV of 7.0.

TABLE-US-00003 TABLE 3 (Sample S3 Data Points) Fiber Area Square Area Fiber Percent Box Fiber Count (cm.sup.2) (cm.sup.2) Coverage* 1 25 5.6745E05 0.0001 56.7 2 26 5.90148E05 0.0001 59.0 3 27 6.12846E05 0.0001 61.3 4 24 5.44752E05 0.0001 54.5 5 22 4.99356E05 0.0001 49.9 6 25 5.67450E05 0.0001 56.7 7 26 5.90148E05 0.0001 59.0 8 24 5.44752E05 0.0001 54.5 9 23 5.22054E05 0.0001 52.2 10 22 4.99356E05 0.0001 49.9 11 21 4.76658E05 0.0001 47.7 *Average of boxes 1 to 11 is 54.7. Therefore, (54.7/78.5) 100 = an RFAC of 69.7. Standard deviation for boxes 1 to 11 is 4.4. Therefore, (4.4/54.7) 100 = a COV of 8.0.

TABLE-US-00004 TABLE 4 (Comparative Sample C1 Data Points) Fiber Area Square Area Fiber Percent Box Fiber Count (cm.sup.2) (cm.sup.2) Coverage* 1 32 4.25E05 0.0001 42.5 2 17 2.26E05 0.0001 22.6 3 24 3.19E05 0.0001 31.9 4 31 4.11E05 0.0001 41.1 5 37 4.91E05 0.0001 49.1 6 31 4.11E05 0.0001 41.1 7 21 2.79E05 0.0001 27.9 8 17 2.26E05 0.0001 22.6 9 33 4.38E05 0.0001 43.8 10 35 4.65E05 0.0001 46.5 11 30 3.98E05 0.0001 39.8 *Average of boxes 1 to 11 is 37.2. Therefore, (37.2/78.5) 100 = an RFAC of 47.3. Standard deviation for boxes 1 to 11 is 9.4. Therefore, (9.4/37.2) x 100 = a COV of 25.3.

TABLE-US-00005 TABLE 5 (Comparative Sample C2 Data Points) Fiber Area Square Area Fiber Percent Box Fiber Count (cm.sup.2) (cm.sup.2) Coverage* 1 28 6.36E05 0.0001 63.6 2 16 3.63E05 0.0001 36.3 3 30 6.81E05 0.0001 68.1 4 11 2.5E05 0.0001 25.0 5 21 4.77E05 0.0001 47.7 6 28 6.36E05 0.0001 63.6 7 29 6.58E05 0.0001 65.8 8 25 5.67E05 0.0001 56.7 9 29 6.58E05 0.0001 65.8 10 23 5.22E05 0.0001 52.2 11 10 2.27E05 0.0001 22.7 *Average of boxes 1 to 11 is 51.6. Therefore, (51.6/78.5) 100 = an RFAC of 65.7. Standard deviation for boxes 1 to 11 is 16.7. Therefore, (16.7/51.6) 100 = a COV of 32.4.

TABLE-US-00006 TABLE 6 (Comparative Sample C3 Data Points) Fiber Area Square Area Fiber Percent Box Fiber Count (cm.sup.2) (cm.sup.2) Coverage* 1 21 4.77E05 0.0001 47.7 2 21 4.77E05 0.0001 47.7 3 19 4.31E05 0.0001 43.1 4 18 4.09E05 0.0001 40.9 5 17 3.86E05 0.0001 38.6 6 18 4.09E05 0.0001 40.9 7 17 3.86E05 0.0001 38.6 8 22 4.99E05 0.0001 49.9 9 19 4.31E05 0.0001 43.1 10 21 4.77E05 0.0001 47.7 11 18 4.09E05 0.0001 40.9 *Average of boxes 1 to 11 is 43.5. Therefore, (43.5/78.5) 100 = an RFAC of 55.5. Standard deviation for boxes 1 to 11 is 4.0. Therefore, (4.0/43.5) 100 = a COV of 9.2.

Example 2

Process to Make S1

[0176] Samples S1-S3 were prepared using the spreading and impregnation units described above. The following includes a non-limiting explanation of the procedure used to make sample S1.

[0177] A desired number of fiber bundles are introduced into the UD tape production line. Fibers from the fiber bundles are continuously pulled through the production line by a pulling station located at the end of the production line. The fibers are separated into two groups, one of which is processed by the lower section of the spreading unit to produce a lower spreaded fiber layer and the other of which is processed by the upper section of the spreading unit to produce an upper spreaded fiber layer. A polymer matrix material is brought into contact with the top surface of the lower spreaded fiber layer. The upper and lower spreaded fiber layers are combined and pressed into the matrix material by passing over a series of pins. The combined spreaded fiber layers are consolidated into a UD tape, which is wound around a spool. Line speed used to make sample S1 was 8 m/s.

Example 3

Testing of Laminates Comprising Tapes of the Present Disclosure

[0178] Referring now to FIGS. 23-27, compression testing of laminates comprising tapes of the present disclosure was performed. Four test samples 1104 were prepared, each including a UD laminate 1120 having fibers aligned with a long dimension of the laminate. Each laminate 1120 was formed from a 4 mm thick lay-up of UD tapes of the present disclosure, each having glass fibers dispersed within a polypropylene matrix material. Each laminate 1120 was cut to a length of 140 mm and a width of 12 mm using a water jet cutter. To prepare each laminate 1120 for testing, aluminum tabs 1116 were adhered to the laminate at opposing laminate ends 1112 using 3M Scotch-Weld DP8005. Prior to adhesion of aluminum tabs 1116, each laminate end 1112 was scuffed and degreased. For each test sample 1104, a gage section 1108 was defined between opposing sets of aluminum tabs 1116.

[0179] Samples 1104 were compression tested until failure using a Zwick 250 kN testing apparatus 1124 (FIG. 25). The mean compression strength of samples 1104 was 456 MPa, with a standard deviation of 45.4 MPa. As shown in FIGS. 26 and 27, for each sample 1104, failure occurred at one of laminate ends 1112 rather than at gage section 1108, which may be attributed to de-bonding between the laminate end and respective aluminum tab(s) 1116. It is anticipated that, through use of more robust tabs (e.g., forming the tabs with the laminate, molding the tabs onto the laminate, welding the tabs to the laminate, and/or the like), higher compression strength test results could be achieved.

[0180] The above specification and examples provide a complete description of the structure and use of illustrative embodiments. Although certain embodiments have been described above with a certain degree of particularly, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention. As such, the various illustrative embodiments of the methods and systems are not intended to be limited to the particular forms disclosed. Rather they include all modifications and alternatives falling within the scope of the claims, and embodiments other than the one shown may include some or all of the features of the depicted embodiment. For example, elements may be omitted or combined as a unitary structure and/or connections may be substituted. Further, where appropriate, aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples having comparable or different properties and/or functions, and addressing the same or different problems. Similarly, it will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments.

[0181] The claims are not intended to include, and should not be interpreted to include, means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) means for or step for, respectively.