WO2017015422A1 - Strain-relieved armor - Google Patents

Abstract

Provided are a strain-relieved ply, a strain-relieved panel including the strain-relieved ply, articles of armor including the strain-relieved ply and the strain-relived panel, and corresponding methods of use. For example, the strain-relieved ply may include a plurality of yarns characterized by a periodic variation in yarn direction along a yarn axis. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis may be effective to facilitate transmission of impact energy away from a site impacted by a projectile. The strain-relieved ply may be independent of a viscoelastic layer.

Description

STRAIN-RELIEVED ARMOR

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. Prov. Pat. App. No. 62/195,288, filed on July 21, 2015, which is incorporated by reference herein in its entirety.

BACKGROUND

[0002] Although soft armor woven from modern high strength fibers greatly reduces the risk of death from high-impact projectiles, such armor can restrict motion and be very cumbersome to wear. Non-woven textile fiber armor was developed to increase flexibility, enhance breathability, and reduce weight of fiber armor. Armors made of non-woven textile fibers, or "unidirectional" (UD) armors, may include one or more plies each configured as an array of straight, parallel fibers. The UD arrangement may offer greater ultimate strength and flexibility compared to woven armors. The greater ultimate strength of UD arranged fibers may allow impact energy to dissipate with increased efficiency due to a larger strain-to-failure value as well as a higher speed of sound, which may be evidenced by the increase in elastic modulus of the UD ply. Further, non-woven armor may be inherently stronger than woven armor, as the fiber crossings characteristic of woven designs are avoided. In woven armor, such fiber crossings may concentrate ballistic forces of an impact or otherwise present weak points in the woven armor compared to non-woven armor.

[0003] It is known that certain energy-absorbing structural laminates may be formed from a set of fiber plies held together with a corresponding set of interspersed viscoelastic layers. The viscoelastic layers may function to distribute shear strains throughout such energy-absorbing structural laminates and dampen or resist the transmission of vibrational energy. Such energy- absorbing structural laminates may be formed into devices, e.g., sports racquets. Such energy- absorbing structural laminates may enhance the comfort or performance of such devices by dampening or resisting unwanted vibration. However, such energy-absorbing structural laminates would be unsuited for armor use as the energy of a ballistic impact would be absorbed and concentrated at an impact site, leading to unwanted ballistic damage or failure.

[0005] The present application appreciates that developing fiber-based armor may be a challenging endeavor.

SUMMARY

[0004] In one embodiment, a strain-relieved ply is provided. The strain-relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The strain- relieved ply may be independent of a viscoelastic layer. The periodic variation in yarn direction of the plurality of yarns may be effective to facilitate transmission of impact energy away from a site impacted by a projectile.

[0005] In one embodiment, a strain-relieved panel is provided. The strain-relieved panel may include at least one strain-relieved ply. Each strain-relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy away from a site impacted by a projectile. The strain-relieved panel may be independent of a viscoelastic layer.

[0006] In one embodiment, an article of armor is provided. The article of armor may include at least one strain-relieved panel. Each strain-relieved panel may include at least one strain- relieved ply. Each strain-relieved ply may include a plurality of yarns. Each of the plurality of yarns may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The article may be effective to facilitate transmission of impact energy away from a site impacted by a projectile.

[0007] In one embodiment, a method of protection from impact is provided. The method may include providing a subject or object to be protected from impact. The method may include positioning a strain-relieved ply with respect to the subject or object to be protected. The strain- relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy away from a site impacted by a projectile.

[0008] In one embodiment, a method of protection from impact is provided. The method may include providing a subject or object to be protected from impact. The method may include positioning a strain-relieved panel with respect to the subject or object to be protected. The strain-relieved panel may include at least one strain-relieved ply. Each strain-relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy away from a site impacted by a projectile.

[0009] In one embodiment, a method of protection from impact is provided. The method may include providing a subject or object to be protected from impact. The method may include positioning an article of armor with respect to the subject or object to be protected. The article of armor may include at least one strain-relieved ply. Each strain-relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy away from a site impacted by a projectile.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying figures, together with the detailed description provided below, describe examples and data to support embodiments of the claimed invention.

[0011] FIG. 1 illustrates fiber configuration (straight) in unidirectional plies and panels.

[0012] FIG. 2A illustrates an example fiber configuration (sinusoidal) for strain-relieved plies and panels.

[0013] FIG. 2B illustrates terminology used to describe an example fiber configuration (sinusoidal) for strain-relieved plies and panels.

[0014] FIG. 3A illustrates an example strain-relieved ply including fibers in a sinusoidal configuration.

[0015] FIG. 3B illustrates an example strain-relieved ply including fibers in a sinusoidal configuration.

[0016] FIG. 4 illustrates an example strain-relieved panel including two strain-relieved plies stacked in a 0°/90° orientation.

[0017] FIG. 5A illustrates data representing V50 testing of unidirectional panels and simulation testing of unidirectional panels.

[0018] FIG. 5B illustrates data representing residual velocity simulation testing of unidirectional panels and V50 testing of unidirectional panels.

[0019] FIG. 6A illustrates data representing V50 testing of sinusoidal panels and simulation testing of sinusoidal panels.

[0020] FIG. 6B illustrates data representing residual velocity simulation testing of sinusoidal panels and V50 testing of sinusoidal panels.

[0021] FIG. 7 illustrates data representing amplitude:wavelength simulation studies of sinusoidal panels in comparison to unidirectional panel performance.

[0022] FIG. 8 illustrates data representing residual velocity and amplitude:wavelength simulation studies of sinusoidal panels at 625 m/s impact velocity. [0023] FIG. 9 illustrates data representing residual velocity and amplitude:wavelength simulation studies of sinusoidal panels at 650 m/s impact velocity.

DETAILED DESCRIPTION

[0024] In various embodiments, a strain-relieved ply is provided. The strain-relieved ply may include a plurality of yarns. Each yarn may each include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The yarn axis and the periodic variation in yarn direction may lie within the strain-relieved ply. The strain-relieved ply may define or lie within a plane. The strain-relieved ply may be independent of a viscoelastic layer. The periodic variation in yarn direction of the plurality of yarns may be effective to facilitate transmission of an impact wave from a site impacted by a projectile. The periodic variation in yarn direction of the plurality of yarns may be effective to relieve the stress at the impact site.

[0025] In many embodiments, the strain-relieved ply may be independent of a viscoelastic layer. Being independent of a viscoelastic layer, the periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy, e.g., vibrational energy, away from a site impacted by a projectile. This independence from viscoelastic layers is distinct from known energy absorbing structural laminates that require fiber plies held together with a corresponding set of interspersed viscoelastic layers.

[0026] A strain-relieved ply may include a thickness of about 0.05 mm. A strain-relieved ply may include a thickness of less than about 0.05 mm. A strain-relieved ply may include a thickness greater than about 0.05 mm. A strain-relieved ply may include a thickness in millimeters of one or more of: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, 0.44, 0.46, 0.48, and 0.50. A strain-relieved ply may include a thickness in millimeters between any of the preceding values, for example, between about 0.03 and about 0.07, or between about 0.05 and about 0.30, and the like. A strain-relieved ply may include a thickness greater than about 0.50 mm.

[0027] Each yarn may include a plurality of spun fibers, e.g., in the form of spun yarn. Spun yarn may include a single type of fiber or may include twisting of different fibers together, e.g., in the form of a blended yarn. Alternatively, each yarn may include a single fiber, e.g., in the form of a filament yarn. The plurality of yarns may include one or more of: spun yarn, blended spun yarn, and filament yarn. [0028] The plurality of yarns may include one or more types of polyaramid fibers. Polyaramid fibers may include, for example, any grade or denier of one or more of: KEVLAR® (DuPont, Wilmington, Delaware, US), NOMEX® (DuPont, Wilmington, Delaware, US), CO EX® (Teijin Limited, Osaka, JP), ARAWIN® (Toray Chemical Korea, Inc., KR), NEW STAR® (Yantai Tahyo, CN), X-FIPER® (SRO Group, CN), KERMEL® (Kermel, FR), TWARON® (Teijin Limited, Osaka, JP), TEIJINCONEX® (Teijin Limited, Osaka, JP), GOLD FLEX® (Honeywell, Colonial Heights, Virginia, US), GOLD SHIELD® (Honeywell, Colonial Heights, Virginia, US), a combination thereof, and the like. The plurality of yarns may include poly(phenylene-benzobisoxazole) or poly( -phenylene-2,6-benzobisoxazole) (PBO) fibers, such as ZYLON® (Toyobo Co., Osaka, JP). The plurality of yarns may include poly(hydroquinone- diimidazopyridine) fibers, such as M5® (Magellan Systems International, Chesterfield, Virginia, US). The plurality of yarns may include polyethylene fibers and/or ultra-high molecular weight (UHMW) polyethylene fibers. UHMW polyethylene fibers may include, for example, one or more of: DYNEEMA® (DSM Dyneema, Heerlen, Netherlands), SPECTRA® (Honeywell, Colonial Heights, Virginia, US), SPECTRA SHIELD® (Honeywell, Colonial Heights, Virginia, US), a combination thereof, and the like. The plurality of yarns may include carbon fibers or carbon fiber composites. Carbon fibers may include carbon nanotubes. The plurality of yarns may include one or more types of fibers, for example, one or more of: polyaramid fibers, poly(phenylene-benzobisoxazole) fibers, poly(phenylene-diimidazopyridine) fibers, poly(hydroquinone-diimidazopyridine) fibers, UHMW polyethylene fibers, carbon fibers, a combination thereof, and the like. The plurality of yarns may include, for example, one or more of: KEVLAR®, NOMEX®, CONEX®, ARAWIN®, NEW STAR®, X-FIPER®, KERMEL®, TWARON®, TEIJINCONEX®, GOLD FLEX®, GOLD SHIELD®, ZYLON®, M5®, DYNEEMA®, SPECTRA®, SPECTRA SHIELD®, spider silk, BIOSTEEL® (AMsilk, Germany), silk, carbon fibers, carbon nanotubes, a combination thereof, and the like.

[0029] The plurality of yarns may be coated, submersed, adhered to, or suspended in non- Newtonian fluids, such as a dilatant or shear thickening material. For example, the plurality of yarns may be combined with silica nanoparticles, ARMOURGEL® (Uhlststem, Ltd., Taichung City, TW), D3o® (Design Blue, Ltd., GB), ACTIVE PROTECTION SYSTEM® (Dow Corning, Midland, Michigan, US), and the like.

[0030] The plurality of yarns may be characterized by a periodic variation in yarn direction along yarn axis. A periodic variation may include the plurality of yarns arranged in any repeating or wave-like configuration, e.g., a sinusoidal configuration. An example sinusoidal configuration is illustrated in FIG. 2A, which may be compared to the unidirectional (UD) configuration including an array of straight and parallel fibers, as illustrated in FIG. 1. A periodic variation in yarn direction may include the plurality of yarns arranged in a pattern made up of corners defined by angles which trace a path between two parallel lines, such as a zigzag- type configuration. A periodic variation in yarn direction may include the plurality of yarns arranged in any repetitive pattern that may be characterized by an amplitude (e.g., Al plus A2; see FIG. 2B) and a wavelength (e.g., Wl, W2, W3, and/or W4; see FIG. 2B), or a plurality of amplitudes and wavelengths. A yarn direction (e.g., YD; see FIG. 2B) may describe a vector path along which the yarn propagates the patterned configuration.

[0031] The plurality of yarns characterized by a periodic variation in yarn direction (YD) may be characterized by a wavelength and an amplitude, as illustrated in FIGS. 2A and 2B, in contrast to the unidirectional configuration including an array of straight and parallel fibers, as illustrated in FIG. 1. A wavelength may be defined as the distance (Wl) between successive apexes (or (W2) between successive troughs). Alternatively, a wavelength may be defined as the distance (W3) between successive downward-facing inflection points (e.g., IP; see FIG. 2B) (or (W4) successive upward-facing inflection points). An amplitude may be defined as the shortest vertical distance between the highest point of an apex and a lowest point of a trough along a yarn axis (e.g., YA; see FIG. 2B) bisecting the inflection points (IP). The amplitude may be defined as the distance Al plus the distance A2. As used herein, a wavelength is the length of one full period or repeat unit within the pattern of the periodic variation.

[0032] The plurality of yarns may be characterized by a wavelength in millimeters of at least about one or more of: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, and 40, e.g., about 5, 10, 20, 25, 30, 35, or 40. The plurality of yarns may include a wavelength in millimeters between any two of the preceding values, for example, between about 5 and about 15, between about 5 and about 40, and the like. In some embodiments, the plurality of yarns may include a wavelength greater than about 40 mm. In some embodiments, the plurality of yarns may include a wavelength less than about 1 mm. The plurality of yarns may be characterized by a non-uniform wavelength that varies along the yarn direction. The plurality of yarns may include a wavelength that varies in millimeters between any two of the preceding wavelength values, for example, between about 5 and about 15, between about 5 and about 40, and the like. For example, the plurality of yarns may include a wavelength of 15 mm toward an outer edge of the strain-relieved ply and transition to a wavelength of 5 mm toward an inner portion of the strain-relieved ply after some distance. For example, the plurality of yarns may include a wavelength of 15 mm at both outer edges of the strain-relieved ply while an inner portion of the strain-relieved ply may include a wavelength of 5 mm, and the like. [0033] In some embodiments, shorter or longer wavelengths may extend over certain areas for enhanced ballistic resistance. For example, in body armor, shorter wavelengths may be located to overlay vital organs.

[0034] The plurality of yarns may be characterized by an amplitude in millimeters of at least about one or more of: 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, and 16. The plurality of yarns may include an amplitude in millimeters in a range between any two of the preceding values, for example, between about 1 and about 16, between about 1 and about 8, between about 1 and about 5, between about 2 and about 10, and the like. The amplitude may be greater than about 16 mm. In some embodiments, the amplitude may be less than about 1 mm. The plurality of yarns may include or be characterized by a uniform amplitude.

[0035] The plurality of yarns may include or be characterized by a non-uniform amplitude that varies along the yarn direction. The plurality of yarns may include an amplitude in millimeters that varies between any two of the preceding amplitude values, for example, between about 1 and 16, about 1 and 8, about 1 and 5, about 2 and 10, and the like. For example, the plurality of yarns may include an amplitude of about 4 mm toward an outer edge of the strain- relieved ply and transition to an amplitude of about 2 mm toward an inner portion of the strain- relieved ply, and the like.

[0036] In many embodiments, the plurality of yarns may be characterized by an amplitude to wavelength (amplitude:wavelength) ratio. The plurality of yarns may include an amplitude:wavelength ratio of at least about one or more of: 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, 0.90, 0.95, and 1.0. The plurality of yarns may include an amplitude:wavelength ratio in a range between any of the preceding values, for example, between about 0.05 and about 0.20, between about 0.10 and about 0.50, between about 0.2 and 0.4, and the like. For example, yarns including a wavelength of about 5 mm may have an amplitude of between about 1 mm and about 2 mm. For example, yarns including an amplitude of about 3 mm may have a wavelength of between about 7.5 mm and about 15 mm. The plurality of yarns may include or be characterized by a uniform amplitude:wavelength ratio.

[0037] In some embodiments, the plurality of yarns may include or be characterized by a non-uniform amplitude to wavelength (amplitude:wavelength) ratio that varies along the yarn direction. For example, the plurality of yarns may include an amplitude:wavelength ratio that varies in a range between any of the preceding values, for example, between about 0.05 and about 0.20, between about 0.10 and about 0.50, between about 0.2 and 0.4, and the like. For example, the plurality of yarns may include an amplitude:wavelength ratio of about 0.40 toward an outer edge of the strain-relieved ply and transition to an amplitude :wavelength ratio of about 0.20 toward an inner portion of the strain-relieved ply, and the like.

[0038] The plurality of yarns 301 arranged in a sinusoidal configuration may be viewed in FIGs. 3A and 3B. Plurality of yarns 301 may be non-woven. As used herein, "non-woven" means that the plurality of yarns are arranged without substantial weaving or interlacing. As used herein, "without substantial weaving or interlacing" means that the plurality of yarns may be secured as described herein with an amount of securing fibers equal to or less than about 5% by weight compared to the weight of fiber content of the plurality of yarns.

[0039] Adjacent yarns in plurality of yarns 301 may be nested. For example, each apex and trough of the periodic variation in yarn direction may nest within adjacent yarn apexes and troughs. Plurality of yarns 301 may be arranged such that each yarn may be flush with adjacent yarns.

[0040] Alternatively, plurality of yarns 301 may be separated by a distance to afford a gap between adjacent yarns (not shown). A portion of plurality of yarns 301 may be nested while a portion of plurality of yarns 301 may be separated by a gap. The gap may be vacant. The gap may be occupied by a material. For example, the gap may be occupied by a resin or polymer, such as an epoxy resin.

[0041] Plurality of yarns 301 characterized by a periodic variation in yarn direction may be aided by a securement. The securement may include a laminate backing 302, as shown in FIG. 3B. Laminate backing 302 may include a thermoplastic laminate, such as an epoxy resin, for example. Laminate backing 302 may contact at least one surface of plurality of yarns 301. The securement may include securing fibers 303, as shown in FIGs. 3A and 3B. Securing fibers 303 may include any type of fiber, including fibers previously described. For example, securing fibers 303 may include one or more fibers described herein, e.g., polyaramid fibers such as KEVLAR® fibers, or other conventional fibers such as nylon fibers, polyester fibers, polyethylene fibers, and the like.

[0042] Securing fibers 303 may be adhered to, woven, or interlaced through plurality of yarns 301, e.g., perpendicular to the yarn axis, parallel to the yarn axis, and the like. Securing fibers 303 may be woven over and under each of the adjacent yarns in any conventional weaving pattern. For example, securing fibers 303 may be woven over and under every two of the consecutive yarns. Securing fibers 303 may be woven over and under multiple adjacent yarns, for example, over three yarns and under two yarns, and the like.

[0043] As described herein, securing fibers 303 may be present in an amount equal to or less than about 5% by weight compared to the fiber content of plurality of yarns 301. Plurality of yarns 301 may still be considered "non-woven" when securing fibers 303 may be present in an amount of equal to or less than about 5% by weight.

[0044] Securing fibers 303 may be separated by a distance in millimeters along the yarn axis of at least about one or more of: 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Securing fibers 303 may be separated by a distance in millimeters along the yarn axis between any of the preceding values, for examples between about 1 and about 2, or between about 2 and about 5. The securing fibers may be separated by a distance along the yarn axis less than about 1 mm. Securing fibers 303 may be separated by a distance along the yarn direction greater than about 10 mm.

[0045] Securing fibers 303 may be separated by a distance in millimeters along a direction perpendicular to the yarn axis of at least about one or more of: 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Securing fibers 303 may be separated by a distance in millimeters along a direction perpendicular to the yarn axis between any of the preceding values, for examples between about 1 and about 2, or between about 2 and about 5, and the like. Securing fibers 303 may be separated at by a distance along a direction perpendicular to the yarn axis less than about 1 mm. Securing fibers 303 may be separated by a distance along a direction perpendicular to the yarn axis greater than about 10 mm.

[0046] Securing fibers 303 may be separated at a non-uniform distance. A non-uniform distance may vary along the yarn axis and/or perpendicular to the yarn axis. For example, a plurality of securing fibers 303 may be spaced at a distance of about 2 mm in one area, whereas a plurality of securing fibers 303 may be spaced at a distance of about 4 mm in another area.

[0047] Securing fibers 303 may occupy one or more specific points along the periodic configuration. For example, securing fibers 303 may span the apexes and/or troughs, for example, in a sinusoidal configuration. For example, securing fibers 303 may span the inflection points. For example, securing fibers 303 may span areas other than the apexes, troughs, or inflection points. Securing fibers 303 may span one or more of: apexes; troughs; inflection points; and areas other than the apexes, troughs, and inflection points.

[0048] The strain-relieved ply may be contacted with a matrix. The matrix may be selected to facilitate transmission of impact energy away from a site impacted by a projectile. Such a matrix may exclude viscoelastic layers. In some embodiments, the matrix may include the laminate backing. The strain-relieved ply may be impregnated with the matrix. The matrix may include a cross-linked or cross-linkable material. The matrix may include a polymer, a polymeric composition or composite. The matrix may include a cured polymer. The matrix may include a resin. The matrix may include a cured resin. The matrix may include one or more of: an epoxy resin, a phenolic resin, a polyurethane resin, a vinyl ester resin, a styrene block copolymer, a polyester resin, polyvinyl butyral (PVB), and additives, such as an amino silane. The matrix may include a dilatant or non-Newtonian fluid, such as a silica nanoparticle dispersion, ARMOURGEL®, D3o®, ACTIVE PROTECTION SYSTEM®, and the like. The matrix may include a ceramic or a ceramic composite. The matrix may include steel. The matrix may include carbon fibers. The matrix may include carbon nanotubes.

[0049] A strain-relieved ply may be configured for use as an article of armor. The strain- relieved ply may be configured for soft ballistic armor and/or hard ballistic armor, e.g. as a strain-relieved panel. The strain-relieved ply may be configured as a small arms protective plate. The strain-relieved ply may be configured as a backing material for a trauma plate. The strain- relieved ply may be configured for an armor vest designed for a human and/or dog. The strain- relieved ply may be configured for a helmet. The strain-relieved ply may be configured as a fabric or textile. The strain-relieved ply may be configured as a shield. The strain-relieved ply may be configured for a ballistic blanket. The strain-relieved ply may be configured for vehicle panels. The strain-relieved ply may be configured for a crash barrier, for example, barriers surrounding race tracks. The strain-relieved ply may be configured for explosive containment systems or barriers surrounding explosive containment systems. The strain-relieved ply may be configured for containment systems or barriers surrounding high speed equipment, such as flywheels, grinding wheels, and the like. The strain-relieved ply may be configured for high- impact sporting equipment, such as hockey equipment, baseball equipment, and football equipment.

[0050] In various embodiments, a strain-relieved panel is provided. The strain-relieved panel may include at least one strain-relieved ply. Each strain-relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy away from a site impacted by a projectile. The strain-relieved panel may be independent of a viscoelastic layer.

[0051] In many embodiments, the at least one strain-relieved panel may be independent of a viscoelastic layer. Being independent of a viscoelastic layer, the periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy, e.g., vibrational energy, away from a site impacted by a projectile. This independence from viscoelastic layers is distinct from known energy-absorbing structural laminates that require fiber plies held together with a corresponding set of interspersed viscoelastic layers. [0052] The strain-relieved ply included in the strain-relieved panel may include any aspect of the strain-relieved ply as described herein.

[0053] The strain-relieved panel may include a plurality of strain-relieved plies. For example, the strain-relieved panel may include a number of strain-relieved plies of at least about one or more of: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 110, 120, 130, 140, 140, 160, 180, and 200, e.g., 10, 20, 50, or 100. A strain-relieved panel may include a number of strain-relieved plies between any of the preceding values, for example, between about 30 and about 52, or between about 50 and about 100, and the like.

[0054] A strain-relieved panel may include a thickness in millimeters of at least about one or more of: 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.3, 0.4, 0.5, 0.6 0.7, 0.8, 0.9, 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, and 50, e.g., about 2.5, about 5, and the like. A strain-relieved panel may include a thickness in millimeters between any two of the preceding values, for example, between about 2.5 and about 5.

[0055] A strain-relieved panel may include a plurality of strain-relieved plies. The plurality of strain-relieved plies may be stacked. The plurality of strain-relieved plies may be oriented such that the yarn axes of adjacent strain-relieved plies may be aligned or superimposed, e.g., at a 0° rotation relative to adjacent plies.

[0056] The strain-relieved plies may be oriented such that the plurality of yarns characterized by a periodic variation in yarn direction along the yarn axis are not aligned or superimposed. For example, the yarn axis of a ply may be rotated, e.g., by an angle greater than 0° and up to about 90°, e.g., 90° orientation, relative to the yarn axis of an adjacent ply. Adjacent plies may further be stacked in an alternating pattern between 0° and 90°, in another repeating pattern, and the like. The plies may be stacked in a uniform orientation or pattern throughout the strain-relieved panel, e.g., the yarn axes of all plies may be aligned. The plies may be stacked in a random orientation or a non-uniform set of patterns throughout the strain-relieved panel.

[0057] FIG. 4 illustrates a strain-relieved panel 400 showing fibers of two strain-relieved plies stacked in a 0°/90° orientation. Fibers 401 may be arbitrarily assigned as a 0° configuration. Fibers 402 may be assigned as a 90° configuration with respect to fibers 401. Fibers 401 may overlay fibers 402. Fibers 401 may be free of interlacing or weaving with fibers 402. Strain-relieved panel 400 may be effective to defeat a projectile 403 from penetration upon impact.

[0058] One or more of the strain-relieved plies may be configured such that the plurality of yarns characterized by a periodic variation in yarn direction along the yarn axis are offset by less than a wavelength. This offset may alternatively be referred to as a phase shift. For example, yarns of adjacent plies may be offset or phase-shifted by half of a wavelength. In this example, a crest of a ply may align with a trough of an adjacent stacked ply. Yarns of adjacent strain- relieved plies may be offset or phase-shifted by one or more of: 1/10, 1/8, 1/6, 1/4, 1/3, 1/2, 2/3, 3/4, 4/5, 6/7, 7/8, and 9/10 of a wavelength. Adjacent strain-relieved plies may include yarns offset or phase-shifted between any of the preceding values, for example, between about 1/10 of a wavelength and about 1/6 of a wavelength, or between about 1/2 of a wavelength and about 4/5 of a wavelength, and the like. Adjacent strain-relieved plies may include yarns offset by less than 1/10 of a wavelength. Adjacent strain relieved plies may be offset by more than 9/10 of a wavelength. Adjacent strain-relieved plies may be aligned or superimposed, with an offset or phase shift of zero.

[0059] For strain-relieved panels including strain-relieved plies stacked at a 0°/90° orientation, one or more of the strain-relieved plies may be configured such that the plurality of yarns characterized by a periodic variation in yarn direction along the yarn axis are offset by less than a wavelength with respect to a preceding or succeeding ply of the same orientation, e.g., 0° orientation or 90° orientation. For example, in a strain-relieved panel including strain-relieved plies stacked in an alternating 0°/90° orientation, one or more strain-relieved plies at, e.g., 0° orientation, may be offset with respect to another strain-relieved ply at 0° orientation. In general, yarns of strain-relieved plies of the same orientation may be offset or phase-shifted by one or more of: zero, 1/10, 1/8, 1/6, 1/4, 1/3, 1/2, 2/3, 3/4, 4/5, 6/7, 7/8, and 9/10 of a wavelength. Strain-relieved plies may include yarns of the same orientation, offset or phase-shifted between any of the preceding values, for example, between about 1/10 of a wavelength and about 1/6 of a wavelength, or between about 1/2 of a wavelength and about 4/5 of a wavelength, and the like. Strain-relieved plies of the same orientation may include yarns offset by less than 1/10 of a wavelength. Strain relieved plies of the same orientation may be offset by more than 9/10 of a wavelength. Strain-relieved plies of the same orientation may be aligned or superimposed, e.g. zero.

[0060] Yarns of strain-relieved plies may be offset or phase-shifted randomly within the strain-relieved panel. For example, a strain-relieved panel including strain-relieved plies stacked in an alternating 0°/90° orientation may include strain-relieved plies 1, 3, 5, 7, etc. (0° orientation), where ply 3 is offset by 1/2 of wavelength with respect to ply 1, ply 5 is offset by 1/3 of a wavelength with respect to ply 1, and ply 7 is offset by 7/9 of a wavelength with respect to ply 3, and the like. Furthermore, strain-relieved plies 2, 4, 6, 8, etc. (90° orientation) may also be randomly offset. Alternatively, strain-relieved plies 2, 4, 6, 8, etc. (90° orientation) may be aligned, uniformly offset, or patterned offset, for example, such as each ply being offset by 5/6 of a wavelength with respect to an adjacent ply.

[0061] The strain-relieved plies of a strain-relieved panel including fibers randomly offset may be referred to as asymmetric plies, and the corresponding strain-relieved panel may be referred to as an asymmetric panel. Asymmetric plies and asymmetric panels may collectively be referred to as having an asymmetric configuration. Conversely, strain-relieved plies having an aligned configuration (zero offset) may be referred to as symmetric plies. The corresponding strain-relieved panel having aligned strain-relieved plies may be referred to as a symmetric panel. Symmetric plies and symmetric panels may collectively be referred to as having a symmetric configuration.

[0062] The strain-relieved panel may include a plurality of strain-relieved plies characterized by a range of different wavelengths. For example, one strain-relieved ply may include a plurality of yarns having a wavelength of about 5 mm, whereas another strain-relieved ply may include a plurality of yarns having a wavelength of about 15 mm. One or more of the strain-relieved plies may include a plurality of yarns having a non-uniform wavelength, as described herein.

[0063] One or more of the strain-relieved plies may include a plurality of yarns having a different amplitude. For example, one strain-relieved ply may include an amplitude of about 1 mm, whereas another strain-relieved ply may include a plurality of yarns having an amplitude of about 2 mm. For example, one strain-relieved ply may include an amplitude of about 1 mm, whereas another strain-relieved ply may include a plurality of yarns having a non-uniform amplitude ranging from about 1 mm to about 2 mm. One or more of the strain-relieved plies may include a plurality of yarns having a non-uniform amplitude, as described herein.

[0064] A strain-relieved panel may include a plurality of strain-relieved plies. One or more of the strain-relieved plies may include a plurality of yarns having a different amplitude:wavelength ratio, as described herein. For example, one strain-relieved ply may include an amplitude: wavelength ratio of about 0.20, whereas another strain-relieved ply may include an amplitude:wavelength ratio of about 0.40.

[0065] One or more of the strain-relieved plies may include a plurality of yarns having a non-uniform amplitude:wavelength ratio, as described herein. For example, one strain-relieved ply may include an amplitude: wavelength ratio of about 0.20, whereas another strain-relieved ply may include a non-uniform amplitude: wavelength ratio ranging from about 0.20 to about 0.40.

[0066] The strain-relieved ply may be contacted with a matrix. The strain-relieved panel may be contacted with a matrix. The matrix may include a laminate backing. The strain- relieved ply may be impregnated with a matrix. The strain-relieved panel may be impregnated with a matrix. A matrix may include a polymerized or polymerizable material. A matrix may include a polymer, a polymeric composition or composite. The matrix may include a cured polymer. The matrix may include a resin. The matrix may include a cured resin. The matrix may include one or more of: an epoxy resin, a phenolic resin, a polyurethane resin, a vinyl ester resin, a styrene block copolymer, a polyester resin, polyvinyl butyral (PVB), and additives, such as an amino silane. The matrix may include a dilatant or non-Newtonian fluid, such as a silica nanoparticle dispersion, ARMOURGEL®, D3o®, ACTIVE PROTECTION SYSTEM®, and the like. The matrix may include a ceramic or a ceramic composite. The matrix may include steel. The matrix may include carbon fibers. The matrix may include carbon nanotubes.

[0067] A strain-relieved panel may be configured for use as an article of armor. The strain- relieved panel may be configured for soft ballistic armor and/or hard ballistic armor. The strain- relieved panel may be configured as a small arms protective plate. The strain-relieved panel may be configured as a backing material for a trauma plate. The strain-relieved panel may be configured for an armor vest designed for a human and/or dog. The strain-relieved panel may be configured for a helmet. The strain-relieved panel may be configured as a fabric or textile. The strain-relieved panel may be configured as a shield. The strain-relieved panel may be configured for a ballistic blanket. The strain-relieved panel may be configured for vehicle panels. The strain-relieved panel may be configured for a crash barrier, for example, barriers surrounding race tracks. The strain-relieved panel may be configured for explosive containment systems or barriers surrounding explosive containment systems. The strain-relieved panel may be configured for containment systems or barriers surrounding high speed equipment, such as flywheels, grinding wheels, and the like. The strain-relieved panel may be configured for high- impact sporting equipment, such as hockey equipment, baseball equipment, and football equipment.

[0068] In various embodiments, an article of armor is provided. The article of armor may include at least one strain-relieved panel. Each strain-relieved panel may include at least one strain-relieved ply. Each strain-relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The article may be effective to facilitate transmission of impact energy away from a site impacted by a projectile.

[0069] In several embodiments, the strain-relieved ply included in the article of armor may include any aspect of the strain-relieved ply, as described herein. In some embodiments, the strain-relieved panel included in the article of armor may include any aspect of the strain- relieved panel, as described herein.

[0070] The article of armor may be configured for soft ballistic armor and/or hard ballistic armor. The article of armor may be configured as a small arms protective plate. The article of armor may be configured as a backing material for a trauma plate. The article of armor may be configured for an armor vest designed for a human and/or dog. The article of armor may be configured for a helmet. The article of armor may be configured as a fabric or textile. The article of armor may be configured as a shield. The article of armor may be configured for a ballistic blanket. The article of armor may be configured for vehicle panels. The article of armor may be configured for a crash barrier, for example, barriers surrounding race tracks. The article of armor may be configured for explosive containment systems or barriers surrounding explosive containment systems. The article of armor may be configured for containment systems or barriers surrounding high speed equipment, such as flywheels, grinding wheels, and the like. The article of armor may be configured for high-impact sporting equipment, such as hockey equipment, baseball equipment, and football equipment.

[0071] In various embodiments, a method of protection from impact is provided. The method may include providing a subject or object to be protected from impact. The method may include positioning a strain-relieved ply with respect to the subject or object to be protected. The strain-relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy away from a site impacted by a projectile. In several embodiments of the method, the strain-relieved ply may include any aspect of the strain- relieved ply as described herein.

[0072] In various embodiments, a method of protection from impact is provided. The method may include providing a subject or object to be protected from impact. The method may include positioning a strain-relieved panel with respect to the subject or object to be protected. The strain-relieved panel may include at least one strain-relieved ply. Each strain-relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy away from a site impacted by a projectile. In several embodiments of the method, the strain-relieved ply may include any aspect of the strain-relieved ply as described herein. In some embodiments of the method, the strain-relieved panel may include any aspect of the strain-relieved panel as described herein.

[0073] In various embodiments, a method of protection from impact is provided. The method may include providing a subject or object to be protected from impact. The method may include positioning an article of armor with respect to the subject or object to be protected. The article of armor may include at least one strain-relieved ply. Each strain-relieved ply may include a plurality of yarns. Each yarn may include at least one fiber. The plurality of yarns may be characterized by a periodic variation in yarn direction along a yarn axis. The periodic variation in yarn direction of the plurality of yarns along the yarn axis may be effective to facilitate transmission of impact energy away from a site impacted by a projectile. In several embodiments of the method, the strain-relieved ply may include any aspect of the strain-relieved ply as described herein. In some embodiments of the method, the article of armor may include any aspect of the article of armor as described herein.

EXAMPLES

[0074] The following data illustrate the effectiveness against mid-range velocity projectiles of strain-relieved panels that include yarns arranged in a sinusoidal configuration. EXAMPLE 1A: UNIDIRECTIONAL PERFORMANCE VS. SIMULATION

[0075] Micro-scale computer simulations demonstrated mechanical properties predictions of unidirectional panels. Experimental testing on physical unidirectional panels were performed for comparison and validation of the simulation method.

[0076] Simulations employed composites including KEVLAR® 49 fibers (1420 denier),

EP3552 epoxy resin, and having an areal density of about 2.98 kg/m². Simulations were performed using the explicit solver (default) in LS-Dyna. Full Lagrangian representation of all components were employed. MAT162 material model (software) was used for composite materials.

[0077] Delamination was handled explicitly through tiebreak contact. In the region of interest and up to 2.5 cm away from the impact point, weft direction damage was also handled through tiebreak contact. Continuum damage mechanics was used where tiebreak contact was not used. The Fragment Simulating Projectiles (FSP) was simulated as mild steel using the Johnson-Crook (simplified) material model.

[0078] Unidirectional panels were prepared from KEVLAR® 49 fibers (1420 denier) and

EP3552 epoxy -resin unidirectional plies. The unidirectional panel included 52 unidirectional plies arranged in an alternating 0°/90° stacked orientation. The unidirectional panel was characterized as having a fiber content of 71.71% by volume which resulted in a unidirectional panel of about 2.98 kg/m².

[0079] The comparison showed an acceptable agreement between the simulation and experimental tests. The comparative data is illustrated in FIGs. 5 A and 5B.

[0080] FIG. 5A illustrates the results of simulation and experimental V50 testing on 0.30 caliber projectiles. The term V50 may be defined as a ballistic test where projectiles are fired at increasing velocities until they start penetrating. A V50 rating for ballistic protection is the velocity of projectiles where 50% of the projectiles do not penetrate the material, and 50% of the projectiles do penetrate the material.

[0081] Simulation testing predicted panel failure between about 540 m/s and about 550 m/s. Experimental testing determined a maximum velocity of less than about 538 m/s. At about 538 m/s, the projectile penetrated each of the two essentially identical panels tested.

[0082] FIG. 5B illustrates the results of experimental Fragment Simulating Projectiles

(FSP) testing with 0.30 caliber projectiles, where the residual velocity was measured (the velocity of the projectile after perforation). FSP testing demonstrates the action of a fragment, such as shattered casings of an artillery shell, bomb, grenade, and bullets. The simulation demonstrated a residual velocity of about 135 m/s with a projectile fired at about 525 m/s, and a residual velocity of about 200 m/s with a projectile fired at about 550 m/s.

EXAMPLE IB: STRAIN-RELIEVED PERFORMANCE VS. SIMULATION

[0083] Micro-scale computer simulations demonstrated mechanical properties predictions of strain-relieved panels. Experimental testing on physical strain-relieved panels were performed for comparison and validation of simulation method.

[0084] Simulations employed composites including KEVLAR® 49 fibers (1420 denier),

EP3552 epoxy resin, and having an areal density of about 2.98 kg/m². Simulations were performed using the explicit solver (default) in LS-Dyna. Full Lagrangian representation of all components were employed. MAT162 material model (software) was used for composite materials.

[0085] Delamination was handled explicitly through tiebreak contact. In the region of interest and up to 2.5 cm away from the impact point, weft direction damage was also handled through tiebreak contact. Continuum damage mechanics was used where tiebreak contact was not used. The Fragment Simulating Projectiles (FSP) was simulated as mild steel using the Johnson-Crook (simplified) material model.

[0086] Strain-relieved panels were prepared from KEVLAR® 49 fibers (1420 denier) and EP3552 epoxy -resin strain-relieved plies. The strain-relieved plies included KEVLAR® 49 fibers arranged in a sinusoidal configuration having a 38 mm wavelength, and a 5 mm amplitude. The strain-relieved panel included 50 asymmetric strain-relieved plies in an alternating 0°/90° orientation. The strain-relived panel was characterized as having a fiber content of 71.48% by volume which resulted in a strain-relived panel of about 2.98 kg/m².

[0087] The comparison showed an acceptable agreement between the simulation and experimental tests. The comparative data is illustrated in FIGs. 6Aand 6B.

[0088] FIG. 6A illustrates the results of simulation and experimental V50 testing on 0.30 caliber projectiles. The term V50 may be defined as a ballistic test where projectiles are fired at increasing velocities until they start penetrating. A V50 rating for ballistic protection is the velocity of projectiles where 50% of the projectiles do not penetrate the material, and 50% of the projectiles do penetrate the material.

[0089] Simulation data indicated that the point in which the projectile impacted the strain-relieved panel may influence the effectiveness of the panel (hit-point sensitivity), as well as the configuration of the plies (configuration sensitivity). For example, impact at an apex (also referred to herein as "crest" or "trough") demonstrated panel failure at about 475 m/s, whereas impact at an inflection point was successful at about 525 m/s (hit-point sensitivity).

[0090] For example, impact at an apex of a 0°/90° stacked panel with a symmetric configuration demonstrated panel failure at about 475 m/s, whereas impact at an apex of a 0°/90° stacked panel with an asymmetric configuration demonstrated panel success at about 475 m/s (configuration sensitivity). Additionally, simulations of randomized stacked panels, i.e., randomly stacked plies at 0° or 90° orientation, demonstrated panel success and failure at about 500 m/s without consideration of hit-point sensitivities. The randomized simulation provided data that closely mirrored the experimental data described below.

[0091] Experimental testing of physical strain-relieved panels demonstrated panel failure at velocities greater than about 480 m/s (Panel 1 : symmetric plies; Panel 2: asymmetric plies) without consideration to hit-point sensitivity. However, discrepancies in the results were observed between about 465 m/s and about 480 m/s, likely owing to hit-point sensitivity issues.

[0092] FIG. 6B illustrates the results of Fragment Simulating Projectiles (FSP) testing with 0.30 caliber projectiles, where the residual velocity was measured (the velocity of the projectile after perforation). FSP testing simulates the action of a fragment, such as shattered casings of an artillery shell, bomb, grenade, and may include bullets.

[0093] The simulation demonstrated a residual velocity of about 210 m/s with a projectile fired at about 490 m/s, and a residual velocity of about 400 m/s with a projectile fired at about 600 m/s. The results obtained in the study illustrated in FIG. 6B did not incorporate hit- point sensitivity data or data pertaining to random phase-shift configurations or random ply orientations.

EXAMPLE 2: AMPLITUDE: WAVELENGTH RATIO INVESTIGATION

[0094] Micro-scale computer simulations predicted the mechanical properties of strain- relieved panels including yarns of various amplitudes and wavelengths. Simulation testing with parameters mimicking KEVLAR® 49/EP3552 epoxy-resin panels, which included 50 asymmetric strain-relieved plies in an alternating 0°/90° orientation, a fiber content of 71.48% by volume, amplitudes ranging from 0.5 mm to 14.0 mm, and wavelengths of 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, and 38 mm, were conducted.

[0095] FIG. 7 illustrates the percent difference in residual velocity (V_R) of strain- relieved panels and unidirectional panels compared to various amplitude:wavelength ratios. V_R may be calculated by subtracting the residual velocity found for the corresponding strain- relieved panel from the residual velocity found for the unidirectional panel and dividing this resulting value by the residual velocity determined for unidirectional panel [V_R = ((VU_D - VS_R)/VU_D) * 100]. Values greater than 0 in the graph indicate better performance than the unidirectional panel and values less than 0 indicate worse performance than the unidirectional panel.

[0096] The graph in FIG. 7 illustrates that shorter wavelengths perform better than longer wavelengths. Amplitude:wavelength values between about 0.2 and about 0.4 show greater performance. For example, a wavelength of 5 mm and amplitude of 1.5 (amplitude:wavelength = 0.3) provides about 50% V_R difference, whereas a wavelength of 10 mm and amplitude of 3 (amplitude:wavelength = 0.3) provides about 15% V_R difference, while an wavelength of 15 mm and an amplitude of 4.5 (amplitude: wavelength = 0.3) provides about 0%> V_R difference. For example, wavelengths of greater than or equal to 20 mm at an amplitude:wavelength of 0.3 perform worse than the unidirectional panel.

EXAMPLE 3: BALLISTIC LIMITS OF STRAIN-RELIEVED PANELS

[0097] Micro-scale computer simulations predicted the mechanical properties of strain- relieved panels including yarns of various wavelengths. Simulation testing with parameters mimicking KEVLAR® 49/EP3552 epoxy-resin panels, which included 50 asymmetric strain- relieved plies in an alternating 0°/90° orientation, a fiber content of 71.48%) by volume, an amplitude:wavelength value of 0.3, and wavelengths of 5 mm, 10 mm, 15 mm, and 38 mm, were conducted. [0098] Simulations determined that increasing ballistic limits were achievable at decreasing wavelengths. Simulations show increased ballistic limit velocity of up to 160 m/s (50%).

38 mm wavelength : Ballistic limit = 350-375 m/s

UD panel : Ballistic limit = 540 m/s

15 mm wavelength : Ballistic limit = 550-600 m/s

10 mm wavelength : Ballistic limit = 625-650 m/s

5 mm wavelength : Ballistic limit = 650-700 m/s

EXAMPLE 4: 625 m/s IMPACT PERFORMANCE

[0099] Micro-scale computer simulations were used to predict the mechanical properties at an impact velocity of 625 m/s for strain-relieved panels including yarns of various wavelengths and amplitudes. Simulation testing on Kevlar 49 EP3552 epoxy-resin strain- relieved panels including 50 asymmetric strain-relieved plies in an alternating 0°/90° orientation, a fiber content of 71.48% by volume, varying amplitude: wavelength ratios, and wavelengths of 5 mm, 10 mm, and 15 mm, were conducted. The results are illustrated in FIG. 8.

[00100] FIG. 8 illustrates the residual velocities compared to amplitude:wavelength ratios for various strain-relieved panels at an projectile impact velocity of 625 m/s. In addition to determining an optimal amplitude:wavelength range of 0.2-0.4, a significant wavelength effect was observed—favoring shorter wavelengths. At a wavelength of 5 mm and an amplitude of 1 mm (amplitude: wavelength ratio = 0.2), the projectile was defeated, whereas at a wavelength of 10 mm and an amplitude of 1 mm (amplitude: wavelength ratio = 0.2), the projectile exhibits a residual velocity of about 300 m/s. At a wavelength of 10 mm and an amplitude of 4 mm (amplitude:wavelength ratio = 0.4), the projectile was defeated, whereas at a wavelength of 15 mm and an amplitude of 4 mm (amplitude: wavelength ratio = 0.4), the projectile exhibits a residual velocity of about 200 m/s.

[00101] As can further be seen by the graph in FIG. 8, the performance of all other panels, with the exception to those exhibiting an amplitude:wavelength ratio of less than 0.2, exceeded the performance of the unidirectional panel.

EXAMPLE 5: 650 m/s IMPACT PERFORMANCE

[00102] Micro-scale computer simulations were used to predict the mechanical properties at an impact velocity of 650 m/s for strain-relieved panels including yarns of various wavelengths and amplitudes. Simulation testing on KEVLAR® 49 EP3552 epoxy-resin strain- relieved panels including 50 asymmetric strain-relieved plies in an alternating 0°/90° orientation, a fiber content of 71.48% by volume, varying amplitude:wavelength ratios, and wavelengths of 5 mm, 10 mm, and 15 mm, were conducted. The results are illustrated in FIG. 9.

[00103] FIG. 9 illustrates the residual velocities compared to amplitude:wavelength ratios for various strain-relieved panels at an projectile impact velocity of 650 m/s. At a wavelength of 5 mm and an amplitude of 1 mm (amplitude: wavelength ratio = 0.2), the projectile was defeated. At a wavelength of 10 mm and an amplitude of 4 mm (amplitude: wavelength ratio = 0.4), the projectile was exhibited a residual velocity of about 300 m/s - which is more than 100 m/s less than the residual velocity exhibited by the unidirectional panel.

[00104] As can further be seen by the graph in FIG. 9, the performance of all other panels, with the exception to those exhibiting an amplitude:wavelength ratio of less than 0.2, exceeded the performance of the unidirectional panel.

[00105] To the extent that the term "includes" or "including" is used in the specification or the claims, it is intended to be inclusive in a manner similar to the term "comprising" as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term "or" is employed (e.g., A or B) it is intended to mean "A or B or both." When the applicants intend to indicate "only A or B but not both" then the term "only A or B but not both" will be employed. Thus, use of the term "or" herein is the inclusive, and not the exclusive use. See Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms "in" or "into" are used in the specification or the claims, it is intended to additionally mean "on" or "onto." To the extent that the term "selectively" is used in the specification or the claims, it is intended to refer to a condition of a component wherein a user of the apparatus may activate or deactivate the feature or function of the component as is necessary or desired in use of the apparatus. To the extent that the terms "operatively coupled" or "operatively connected" are used in the specification or the claims, it is intended to mean that the identified components are connected in a way to perform a designated function. To the extent that the term "substantially" is used in the specification or the claims, it is intended to mean that the identified components have the relation or qualities indicated with degree of error as would be acceptable in the subject industry.

[00106] As used in the specification and the claims, the singular forms "a," "an," and "the" include the plural unless the singular is expressly specified. For example, reference to "a compound" may include a mixture of two or more compounds, as well as a single compound.

[00107] As used herein, the term "about" in conjunction with a number is intended to include ± 10% of the number. In other words, "about 10" may mean from 9 to 11. [00108] As used herein, the terms "optional" and "optionally" mean that the subsequently described circumstance may or may not occur, so that the description includes instances where the circumstance occurs and instances where it does not.

[00109] As stated above, while the present application has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art, having the benefit of the present application. Therefore, the application, in its broader aspects, is not limited to the specific details, illustrative examples shown, or any apparatus referred to. Departures may be made from such details, examples, and apparatuses without departing from the spirit or scope of the general inventive concept.

[00110] The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

1. A strain-relieved ply, comprising:

a plurality of yarns, each yarn comprising at least one fiber, the plurality of yarns being characterized by a periodic variation in yarn direction along a yarn axis;

the strain-relieved ply being independent of a viscoelastic layer; and

the periodic variation in yarn direction of the plurality of yarns along the yarn axis being effective to facilitate transmission of impact energy away from a site impacted by a projectile.

2. The strain-relieved ply of claim 1, the periodic variation in yarn direction along the yarn axis being characterized by at least one wavelength along the yarn axis and at least one amplitude perpendicular to the yarn axis.

3. The strain-relieved ply of claim 2, characterized by a ratio between the at least one amplitude to the at least one wavelength of between about 0.2: 1 and about 0.4: 1.

4. The strain-relieved ply of claim 2, one or more of the at least one wavelength and the at least one amplitude varying along the yarn axis.

5. The strain-relieved ply of claim 1, the plurality of yarns being non-woven.

6. The strain-relieved ply of claim 1, the periodic variation in yarn direction along the yarn axis being characterized by a wavelength in millimeters of between about 5 and about 40.

7. The strain-relieved ply of claim 1, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration.

8. The strain-relieved ply of claim 1, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration characterized by a wavelength along the yarn axis between about 5 mm and about 15 mm.

9. The strain-relieved ply of claim 1, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration characterized by a varying wavelength along the yarn axis.

10. The strain-relieved ply of claim 9, the wavelength varying between about 5 mm and about 40 mm along the yarn axis.

11. The strain-relieved ply of claim 1, the periodic variation in yarn direction along the yarn axis being characterized by an amplitude in millimeters of between about 1 and about 16.

12. The strain-relieved ply of claim 1, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration characterized by an amplitude between about 1 mm and about 8 mm.

13. The strain-relieved ply of claim 1, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration characterized by a varying amplitude along the yarn axis.

14. The strain-relieved ply of claim 1, the plurality of yarns comprising one or more of: a plurality of spun fibers and filament fibers.

15. The strain-relieved ply of claim 1, further comprising a matrix, the strain-relieved ply being contacted or impregnated with the matrix.

16. The strain-relieved ply of claim 15, the matrix comprising one or more of: a resin a polymer, a cured resin, a cured polymer, and a ceramic.

17. The strain-relieved ply of claim 15, the matrix comprising an epoxy resin.

18. The strain-relieved ply of claim 15, the matrix being a laminate backing.

19. The strain-relieved ply of claim 1, the plurality of yarns comprising one or more of: polyaramid fiber, poly(phenylene-benzobisoxazole) fiber, poly(hydroquinone- diimidazopyridine) fiber, polyethylene fiber, ultra-high molecular weight polyethylene fiber, carbon fiber, carbon fiber composites, and carbon nanotubes.

20. The strain-relieved ply of claim 1, the plurality of yarns comprising one or more fibers of: KEVLAR®, NOMEX®, CO EX®, TECHNORA®, ARAWIN®, EWSTAR®, X- FIPER®, KERMEL®, TWARON®, TEIJINCONEX®, ZYLON®, M5®, DYNEEMA®, and SPECTRA®.

21. A strain-relieved panel comprising:

at least one strain-relieved ply, each strain-relieved ply comprising a plurality of yarns, each of the plurality of yarns comprising at least one fiber, the plurality of yarns being characterized by a periodic variation in yarn direction along a yarn axis, the periodic variation in yarn direction of the plurality of yarns along the yarn axis being effective to facilitate transmission of impact energy away from a site impacted by a projectile, and

the strain-relieved panel being independent of a viscoelastic layer.

22. The strain-relieved panel of claim 21, the periodic variation in yarn direction along the yarn axis being characterized by at least one wavelength along the yarn axis and at least one amplitude perpendicular to the yarn axis.

23. The strain-relieved panel of claim 22, the periodic variation in yarn direction along the yarn axis characterized by a ratio between the at least one amplitude to the at least one wavelength of between about 0.2: 1 and about 0.4: 1.

24. The strain-relieved panel of claim 22, one or more of the at least one wavelength and the at least one amplitude varying along the yarn axis.

25. The strain-relieved panel of claim 21, the periodic variation in yarn direction along the yarn axis being characterized by a wavelength in millimeters of between about 5 and about 40.

26. The strain-relieved panel of claim 21, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration.

27. The strain-relieved panel of claim 21, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration characterized by a wavelength along the yarn axis between about 5 mm and about 15 mm.

28. The strain-relieved panel of claim 21, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration characterized by a varying wavelength along the yarn axis.

29. The strain-relieved ply of claim 28, the wavelength varying between about 5 mm and about 40 mm along the yarn axis.

30. The strain-relieved panel of claim 21, the periodic variation in yarn direction along the yarn axis being characterized by an amplitude in millimeters of between about 1 and about 16.

31. The strain-relieved panel of claim 21, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration characterized by an amplitude between about 1 mm and about 8 mm.

32. The strain-relieved panel of claim 21, the periodic variation in yarn direction along the yarn axis comprising a sinusoidal configuration characterized by a varying amplitude along the yarn axis.

33. The strain-relieved panel of claim 32, the amplitude varying between about 1 mm and about 16 mm along the yarn axis.

34. The strain-relieved panel of claim 21, further comprising a plurality of strain-relieved plies, each strain-relieved ply stacked to form the strain-relieved panel.

35. The strain-relieved panel of claim 34, each strain-relieved ply stacked at a 90° orientation relative to an adjacent strain-relieved ply.

36. The strain-relieved panel of claim 34, each strain-relieved ply stacked at a 0° orientation relative to an adjacent strain-relieved ply.

37. The strain-relieved panel of claim 34, the plurality of strain-relieved plies stacked at a random 0°/90° orientation.

38. The strain-relieved panel of claim 34, the plurality of strain-relieved plies stacked in a patterned 0°/90°orientation.

39. The strain-relieved panel of claim 34, the periodic variation in yarn direction of the plurality of yarns in at least one of the strain-relieved plies being offset by less than a wavelength relative to an adjacent strain-relieved ply.

40. The strain-relieved panel of claim 34, the periodic variation in yarn direction of the plurality of yarns in at least one of the strain-relieved plies being offset by less than half of a wavelength relative to an adjacent strain-relieved ply.

41. The strain-relieved panel of claim 34, the plurality of yarns in each strain-relieved ply being characterized by a same wavelength.

42. The strain-relieved panel of claim 34, the plurality of yarns in at least two of the strain- relieved plies each being characterized by a different wavelength.

43. The strain-relieved panel of claim 34, the plurality of yarns in each strain-relieved ply being characterized by a same amplitude.

44. The strain-relieved panel of claim 34, the plurality of yarns in at least two of the strain- relieved plies being characterized by a different amplitude.

45. The strain-relieved panel of claim 21, the strain-relieved panel comprising between about 50 strain-relieved plies and about 100 strain-relieved plies.

46. The strain-relieved panel of claim 21, the strain-relieved panel comprising less than about 50 strain-relieved plies.

47. The strain-relieved panel of claim 21, the strain-relieved panel comprising more than 100 strain-relieved plies.

48. The strain-relieved panel of claim 21, further comprising a matrix, one or more of: the strain-relieved panel and the at least one strain-relieved ply being contacted or impregnated with the matrix.

49. The strain-relieved panel of claim 48, the matrix comprising one or more of: a resin, a polymer, a cured resin, a cured polymer, and a ceramic.

50. The strain-relieved panel of claim 48, the matrix comprising an epoxy resin.

51. The strain-relieved ply of claim 48, the matrix being a laminate backing.

52. The strain-relieved panel of claim 21, the plurality of yarns comprising one or more of: a plurality of spun fibers and filament fibers.

53. The strain-relieved panel of claim 21, the plurality of yarns being non-woven.

54. The strain-relieved panel of claim 21, the plurality of yarns comprising one or more of: polyaramid fiber, poly(phenylene-benzobisoxazole) fiber, poly(hydroquinone- diimidazopyridine) fiber, polyethylene fiber, ultra-high molecular weight polyethylene fiber, carbon fiber, carbon fiber composites, and carbon nanotubes.

55. The strain-relieved panel of claim 21, the plurality of yarns comprising one or more fibers of: KEVLAR®, NOMEX®, CO EX®, TECHNORA®, ARAWIN®, EWSTAR®, X- FIPER®, KERMEL®, TWARON®, TEIJINCONEX®, ZYLON®, M5®, DYNEEMA®, and SPECTRA®.

56. An article of armor comprising:

at least one strain-relieved panel comprising:

at least one strain-relieved ply, each strain-relieved ply comprising a plurality of yarns, each of the plurality of yarns comprising at least one fiber, the plurality of yarns being characterized by a periodic variation in yarn direction along a yarn axis, the periodic variation in yarn direction of the plurality of yarns along the yarn axis being effective to facilitate transmission of impact energy away from a site impacted by a projectile.

57. The article of armor of claim 56, configured for one or more of: hard ballistic armor, soft ballistic armor, an armor vest, a helmet, a small arms protective plate, a backing material for a trauma plate, a vehicle panel, a ballistic blanket, and a ballistic shield.

58. The article of armor of claim 56, the projectile comprising a velocity of less than about 625 m/s to about 700 m/s.

59. The article of armor of claim 56, the periodic variation in yarn direction along the yarn axis in each strain-relieved ply being characterized by at least one wavelength along the yarn axis and at least one amplitude perpendicular to the yarn axis.

60. The article of armor of claim 59, the periodic variation in yarn direction along the yarn axis characterized by a ratio between the at least one amplitude to the at least one wavelength of between about 0.2: 1 and about 0.4: 1.

61. The article of armor of claim 59, one or more of the at least one wavelength and the at least one amplitude varying along the yarn axis.

62. The article of armor of claim 56, the periodic variation in yarn direction along the yarn axis in each strain-relieved ply being characterized by a wavelength in millimeters of between about 5 and about 40.

63. The article of armor of claim 56, the periodic variation in yarn direction along the yarn axis in each strain-relieved ply being characterized by a sinusoidal configuration.

64. The article of armor of claim 56, the periodic variation in yarn direction along the yarn axis in each strain-relieved ply being characterized by a sinusoidal configuration characterized by a wavelength along the yarn axis between about 5 mm and about 15 mm.

65. The article of armor of claim 56, the periodic variation in yarn direction along the yarn axis in each strain-relieved ply being characterized by a sinusoidal configuration characterized by a varying wavelength along the yarn axis.

66. The article of armor of claim 65, the wavelength varying between about 5 mm and about 40 mm along the yarn axis.

67. The article of armor of claim 56, the periodic variation in yarn direction along the yarn axis in each strain-relieved ply being characterized by an amplitude in millimeters of between about 1 and about 16.

68. The article of armor of claim 56, the periodic variation in yarn direction along the yarn axis in each strain-relieved ply being characterized by a sinusoidal configuration characterized by an amplitude between about 1 mm and about 8 mm.

69. The article of armor of claim 56, the periodic variation in yarn direction along the yarn axis in each strain-relieved ply being characterized by a sinusoidal configuration characterized by a varying amplitude along the yarn axis.

70. The article of armor of claim 69, the amplitude varying between about 1 mm and about 16 mm along the yarn axis.

71. The article of armor of claim 56, further comprising a plurality of strain-relieved plies, each strain-relieved ply stacked to form the strain-relieved panel.

72. The article of armor of claim 71, each strain-relieved ply stacked at a 90° orientation relative to an adjacent strain-relieved ply.

73. The article of armor of claim 71, each strain-relieved ply stacked at a 0° orientation relative to an adjacent strain-relieved ply.

74. The article of armor of claim 71, the plurality of strain-relieved plies stacked at a random 0 90° orientation.

75. The article of armor of claim 71, the plurality of strain-relieved plies stacked in a patterned 0790°orientation.

76. The article of armor of claim 71, the periodic variation in yarn direction of the plurality of yarns in at least one of the strain-relieved plies being offset by less than a wavelength relative to an adjacent strain-relieved ply.

77. The article of armor of claim 71, the periodic variation in yarn direction of the plurality of yarns in at least one of the strain-relieved plies being offset by less than half of a wavelength relative to an adjacent strain-relieved ply.

78. The article of armor of claim 71, the plurality of yarns in each strain-relieved ply being characterized by a same wavelength.

79. The article of armor of claim 71, the plurality of yarns in at least two of the strain- relieved plies each being characterized by a different wavelength.

80. The article of armor of claim 1, the plurality of yarns in each strain-relieved ply being characterized by a same amplitude.

81. The article of armor of claim 71, the plurality of yarns in at least two of the strain- relieved plies being characterized by a different amplitude.

82. The article of armor of claim 56, the strain-relieved panel comprising between about 50 strain-relieved plies and about 100 strain-relieved plies.

83. The article of armor of claim 56, the strain-relieved panel comprising less than about 50 strain-relieved plies.

84. The article of armor of claim 56, the strain-relieved panel comprising more than 100 strain-relieved plies.

85. The article of armor of claim 56, further comprising a matrix that contacts or impregnates one or more of: the strain-relieved panel and the at least one strain-relieved ply.

86. The article of armor of claim 85, the matrix comprising one or more of: a resin, a polymer, a cured resin, a cured polymer, and a ceramic.

87. The article of armor of claim 85, the matrix comprising an epoxy resin.

88. The article of armor of claim 85, the matrix being a laminate backing.

89. The article of armor of claim 56, each plurality of yarns comprising one or more of: a plurality of spun fibers and filament fibers.

90. The article of armor of claim 56, each plurality of yarns being non-woven.

91. The article of armor of claim 56, each plurality of yarns comprising one or more of: polyaramid fiber, poly(phenylene-benzobisoxazole) fiber, poly(hydroquinone- diimidazopyridine) fiber, polyethylene fiber, ultra-high molecular weight polyethylene fiber, carbon fiber, carbon fiber composites, and carbon nanotubes.

92. The article of armor of claim 56, each plurality of yarns comprising one or more fibers of: KEVLAR®, NOMEX®, CONEX®, TECHNORA®, ARAWIN®, NEWSTAR®, X- FIPER®, KERMEL®, TWARON®, TEIJINCONEX®, ZYLON®, M5®, DYNEEMA®, and SPECTRA®.

93. A method of protection from impact, comprising:

providing a subject or object to be protected from impact; and

positioning a strain-relieved ply with respect to the subject or object to be protected, the strain-relieved ply comprising a plurality of yarns, each yarn comprising at least one fiber, the plurality of yarns being characterized by a periodic variation in yarn direction along a yarn axis, the periodic variation in yarn direction of the plurality of yarns along the yarn axis being effective to facilitate transmission of impact energy away from a site impacted by a projectile.

94. The method of claim 93, the strain-relieved ply comprising the strain-relieved ply of any of claims 1-20.

95. A method of protection from impact, comprising:

providing a subject or object to be protected from impact; and

positioning a strain-relieved panel with respect to the subject or object to be protected, the strain-relieved panel comprising at least one strain-relieved ply, each strain-relieved ply comprising a plurality of yarns, each of the plurality of yarns comprising at least one fiber, the plurality of yarns being characterized by a periodic variation in yarn direction along a yarn axis, the periodic variation in yarn direction of the plurality of yarns along the yarn axis being effective to facilitate transmission of impact energy away from a site impacted by a projectile.

96. The method of claim 95, the strain-relieved panel comprising the strain-relieved panel of any of claims 21-55.

97. A method of protection from impact, comprising:

providing a subject or object to be protected from impact; and

positioning an article of armor with respect to the subject or object to be protected, the article of armor comprising at least one strain-relieved ply, each strain-relieved ply comprising a plurality of yarns, each of the plurality of yarns comprising at least one fiber, the plurality of yarns being characterized by a periodic variation in yarn direction along a yarn axis, the periodic variation in yarn direction of the plurality of yarns along the yarn axis being effective to facilitate transmission of impact energy away from a site impacted by a projectile.

98. The method of claim 97, the article of armor comprising the article of armor of any of claims 56-92.