Patent Description:
<CIT> discloses an energy absorbing member comprising a polymeric material which is formed from a thermoplastic composition containing a continuous phase including a matrix polymer. <CIT> discloses a composite panel comprising a single composite layer which includes a thermoplastic resin matrix, reinforcing fiber and nano-filler particles. <NPL>) discloses high strain compression responses of woven Kevlar reinforced polypropylene composites.

A ballistic-resistant composite accordingly to the invention includes at least one layer that has a network of ballistic fibers and a resin matrix. The resin matrix includes maleic anhydride-grafted polypropylene (MA-g-PP). The resin matrix additionally includes polyurethane. The resin matrix includes, by weight, <NUM>% to <NUM>% of the MA-g-PP, the MA-g-PP has, by weight, <NUM>% to <NUM>% of maleic anhydride, the MA-g-PP has a molecular weight of <NUM>,<NUM> to <NUM>,<NUM>, and the at least one layer has a single layer that has an areal density of <NUM> grams per square meter to <NUM> grams per square meter.

In a further embodiment of any of the foregoing embodiments, the maleic anhydride-grafted polypropylene is maleic anhydride-grafted polypropylene block copolymer.

In a further embodiment of any of the foregoing embodiments, the polyurethane includes a blocked isocyanate composed of isocyanate bonded with a blocking agent selected from the group consisting of wherein the blocking agent is selected from the group consisting of phenol, nonyl phenol, β-dicarbonyl compounds, methylethylketoxime, alcohols, ε-caprolactam, amides, imidazoles, pyrazoles, and combinations thereof.

In a further embodiment of any of the foregoing embodiments, the at least one layer includes, by weight, from <NUM>% to <NUM>% of the resin matrix.

In a further embodiment of any of the foregoing embodiments, the network of ballistic fibers includes polyethylene fibers.

In a further embodiment of any of the foregoing embodiments, the network of ballistic fibers includes ultra-high molecular weight polyethylene fibers.

In a further embodiment of any of the foregoing embodiments, the at least one layer includes two of the layers laminated together.

In a further embodiment of any of the foregoing embodiments, the MA-g-PP has, by weight, <NUM>% to <NUM>% of maleic anhydride.

<FIG> schematically illustrates a representative portion of a ballistic-resistant composite <NUM> in the form of a layer <NUM>. The layer <NUM> may be fabricated to desired sizes but typically will be produced as a thin sheet that can be divided into ply pieces. The layer <NUM> includes a network of ballistic fibers <NUM> and a resin matrix <NUM>. The resin matrix <NUM> includes maleic anhydride-grafted polypropylene (MA-g-PP), represented at <NUM>. The "grafted" indicates that the maleic anhydride is covalently bonded to the polypropylene.

A "fiber" as used herein is an elongated body that is significantly longer than it is wide. The form of the "fiber" or "fibers" is not particularly limited and may be a monofilament, multifilament, ribbon, strip, yarn, or tape, and may be continuous or discontinuous, with a regular or irregular cross-section.

A "ballistic fiber" refers to a high-performance fiber that is engineered for ballistic resistance. A ballistic fiber may also be considered to be a "high tenacity fiber" that has a tenacity of about <NUM>/d (grams per denier) or more. Even higher tenacities may facilitate performance enhancement, such as greater than <NUM>/d, greater than <NUM>/d, greater than <NUM>/d, greater than <NUM>/d, or greater than <NUM>/d. A ballistic fiber may further have a tensile modulus of about <NUM>/d or more (ASTM <NUM>), and in some examples a modulus of <NUM>/d or more, and an energy-to-break of about <NUM> J/g (Joules per gram) or more (ASTM D2256).

In the illustrated example, the network of ballistic fibers <NUM> are ultra-high molecular weight polyethylene (UHMWPE) ballistic fibers. Although UHMWPE ballistic fibers are useful for high performance ballistic resistance, it is to be understood that the network of ballistic fibers <NUM> is not limited thereto. Other examples of the network of ballistic fibers <NUM> include, but are not limited to, highly oriented high molecular weight polyolefin fibers, high modulus or high tenacity polyethylene fibers and polypropylene fibers, aramid fibers, aromatic heterocyclic co-polyamide fibers, terpolyaramide fibre, polybenzazole fibers, polyvinyl alcohol fibers, polyacrylonitrile fibers, liquid crystal copolyester fibers, polyamide fibers, polyester fibers, glass fibers, graphite fibers, carbon fibers, basalt or other mineral fibers, rigid rod polymer fibers, and mixtures and blends thereof.

The polymers forming the network of ballistic fibers <NUM> may be high-strength, high tensile modulus fibers. Examples include polyolefin fibers, including high density and low density polyethylene, extended chain polyolefin fibers, such as highly oriented, high molecular weight polyethylene fibers, such as ultra-high molecular weight polyethylene fibers, and polypropylene fibers, such as ultra-high molecular weight polypropylene fibers. Additional examples include para-aramid fibers, polyamide fibers, polyethylene terephthalate fibers, heterocyclic co-polyamide fibers, terpolyaramide fibre, polyethylene naphthalate fibers, extended chain polyvinyl alcohol fibers, extended chain polyacrylonitrile fibers, polybenzazole fibers, such as polybenzoxazole (PBO) and polybenzothiazole (PBT) fibers, liquid crystal copolyester fibers and other rigid rod fibers such as pyridobisimidazole-<NUM>, <NUM>-diyl (<NUM>,<NUM>-dihydroxy-p-phenylene) (e.g.,M5(R) fibers by Magellan Systems International of Richmond, Va. or as disclosed in <CIT>, <CIT>, <CIT>, or <CIT>). Additional examples include copolymers, block polymers and blends of the above materials. Example polyethylenes are extended chain polyethylenes having molecular weights of at least <NUM>,<NUM>, at least one million, or between two million and five million. In some examples, the fibers are high-performance fibers such as extended chain polyethylene fibers, poly-para-phenylene terephthalamide fibers, which may also be referred to as aramid fibers (e.g., by DuPont (Kevlar®), Teijin (Twaron®), Kolon (Heracron®), or Hyosung Aramid), aromatic heterocyclic co-polyamides, which may also be referred to as modified para-aramids (e.g., Rusar®, Autex®), ultra-high molecular weight polyethylene (UHMWPE)(e.g., by Honeywell, DSM, and Mitsui under the trade names Spectra®, Dyneema®, and Tekmilon®, respectively, as well as Pegasus® yarn), poly(p-phenylene-<NUM>,<NUM>-benzobisoxazole) (PBO) (e.g., by Toyobo under the name Zylon®), and/ or polyester-polyarylate yarns (e.g., liquid crystal polymers produced by Kuraray under the trade name Vectran®). In some embodiments, industrial fibers such as nylon, polyester, polyolefin-based yarns (including polyethylene and polypropylene), could also be used.

The resin matrix <NUM> is continuous in the illustrated example and fully or substantially fully embeds the network of ballistic fibers <NUM>. The form, however, of the resin matrix <NUM> is not limited but the resin matrix <NUM> is at least in contact with the network of ballistic fibers <NUM>. In this regard, the resin matrix <NUM> may be a continuous or discontinuous layer on the network of fibers <NUM>, which as above may in the form of monofilaments, multifilaments, ribbons, strips, yarns, or tapes. For instance, as shown in <FIG>, the resin matrix <NUM> is a continuous layer on the network of fibers <NUM>. The resin matrix <NUM> may be applied to the network of fibers <NUM> by any suitable technique, including but not limited to, spraying, dipping, roller coating, hot-melt coating, powder scatter coating, or as a cast thin film that is laminated to the network of ballistic fibers <NUM>.

The ballistic-resistant composite <NUM> is comprised of, by weight percent based on the total weight of the composite <NUM>, about <NUM>% to about <NUM>% of the resin matrix <NUM>. More typically, the ballistic-resistant composite <NUM> will be comprised of about <NUM>% to about <NUM>% of the resin matrix <NUM>, or about <NUM>% to about <NUM>% of the resin matrix <NUM>.

As indicated above, the resin matrix <NUM> includes MA-g-PP, of which a proposed example chemical structure is shown in <FIG>. In the illustrated example, the Ma-g-PP is of a homopolymer variety in that polypropylene is the only polymer of the backbone polymer chain. The backbone includes polypropylene that has no grafted maleic anhydride and polypropylene that has grafted maleic anhydride. The maleic anhydride is atactic, although the stereochemistry will change, as discussed later in this disclosure. Alternatively, the MA-g-PP is a block copolymer, as shown for example in <FIG>. Here, the backbone again includes polypropylene that has no grafted maleic anhydride and polypropylene that has grafted maleic anhydride. In the block copolymer, the backbone additionally includes blocks of isobutylene. The chemical structure may vary in accordance with the number average molecular weights "m," "n," and "x. " As non-limiting examples, "m" may be <NUM> to <NUM>,<NUM>, "n" may be <NUM> to <NUM>,<NUM>, and "x" may be <NUM> to <NUM>. The term "the MA-g-PP" thus may refer herein to either the homopolymer or the block copolymer.

The molecular weight of the MA-g-PP is <NUM>,<NUM> to <NUM>,<NUM>. The MA-g-PP has, by weight, <NUM>% to <NUM>% of maleic anhydride. In a further example, the MA-g-PP has <NUM>% to <NUM>% maleic anhydride.

The MA-g-PP is used in mixture with polyurethane. For example, the resin matrix <NUM> includes, by weight, <NUM>% to <NUM>% of the MA-g-PP, and the remainder is the polyurethane.

In an additional example, the polyurethane includes a blocked isocyanate that is composed of isocyanate bonded with a blocking agent. For instance, the blocking agent is selected from phenol, nonyl phenol, β-dicarbonyl compounds, methylethylketoxime, alcohols, ε-caprolactam, amides, imidazoles, pyrazoles, and combinations thereof.

The bonding between the isocyanate and the blocking agent is reversible in dependence on temperature. Thus, the isocyanate is blocked (i.e., the blocking agent is bonded with the isocyanate) at relatively low temperatures, deblocked (i.e., the blocking agent is not bonded to the isocyanate) at relatively high temperatures, and can be cycled between the blocked and deblocked states by adjusting the temperature. When the blocking agent is bonded with the isocyanate the blocking agent prevents the isocyanate from reacting (i.e., the blocked isocyanate is inert in the resin matrix <NUM>), and when the blocking agent is not bonded to the isocyanate the isocyanate is reactive (i.e., the isocyanate is reactive in the resin matrix <NUM>).

In general, the temperature at which initial deblocking is observed from the blocked state is called the deblocking temperature. Deblocking temperatures can be found in general literature and used as guidance in selecting useful blocked isocyanates for a particular implementation. Additionally, or alternatively, deblocking temperatures can be readily experimentally determined through a known measurement technique. Deblocking temperatures may be given in the literature as temperature ranges in order to encompass variations. Such ranges or variations do not hinder the understanding or practice of this disclosure, at least because ranges or variations in combination with the teachings of this disclosure will permit selection of one or more blocked isocyanates for a given implementation.

The resin matrix <NUM> may be cross-linkable by heating to a temperature that causes the isocyanate to liberate from the blocking agent and the liberated isocyanate to reactively cause cross-linking of the resin matrix <NUM>. Such a temperature is equal to or above the deblocking temperature of the selected blocked isocyanate but will not be so high as to damage the network of fibers <NUM> or other constituents in the ballistic resistant composite <NUM>, if present. At a minimum, the temperature will be below a temperature at which the network of fibers <NUM> degrades in the implemented process conditions (time, temperature, pressure, etc.).

In an example process for forming a layer <NUM> and a laminate, the network of fibers <NUM> is initially coated with the resin matrix <NUM>. The coating can be applied using known techniques, such as impregnation, lamination, or powder coating. In some examples, the resin matrix <NUM> is applied as an aqueous medium, as a solvent-based medium, as a cast film-form, or as hot-melt granules. An example aqueous medium may include fillers, viscosity modifiers, and the like and have a solids content from about <NUM>% to about <NUM>% by weight, with the remaining weight being water. As an example, a single one of the layers <NUM> has an areal density of <NUM> grams per square meter to <NUM> grams per square meter.

Multiple layers <NUM> may be laminated together under heat and pressure to produce a laminate. For unidirectional arrangements of the fibers <NUM> in each layer <NUM>, the layers <NUM> may be cross-plied in the lamination step, such as a <NUM>°/<NUM>° configuration. The total number of layers <NUM> that are laminated together may depend on the end use article to be produced, but will typically be from two to <NUM> of the layers <NUM>, such as only two layers <NUM>, up to <NUM> layers <NUM>, up to <NUM> layers <NUM>, or up to <NUM> layers <NUM>. The thickness of the layers <NUM> will typically be from <NUM> micrometers to <NUM> meters. Two or more laminates are consolidated under heat and pressure to form a laminate armor. Except for the resin matrix <NUM>, this process is otherwise known and those skilled in the art will thus recognize appropriate process conditions in view of this disclosure.

Aspects of the present disclosure are based on the concept that ballistic improvement in fiber-reinforced composite armor is achievable by modifying the sonic velocity of the ballistic panel "as a whole. " Work relating to improving composite ballistic armor performance has focused not on this, but rather on optimizing the theoretical ballistic potential of the high-performance yarns within the composite, by optimizing the composite construction - i.e., via yarn spreading or via lower resin content construction and by via optimizing the surface interaction or the yarn with resin matrix.

The ballistic theory behind aspects of the present disclosure is as follows. If two identical fiber-reinforced composite armor panels were produced from orthogonal UD fabric using the same high-performance yarn, at the same fiber-fraction volume, and only differed in that the resin matrix of one had a higher sonic velocity than the other; it is predicted that that the one with the higher sonic velocity will ballistically outperform the other. This is established mathematically by van Heerden in <CIT>, which can be used to predict the theoretical ballistic performance of a high-performance yarn constrained within a fiber-reinforced composite armor made from continuous unidirectional fibers. The ballistic performance of a yarn is a function of both its own elastic modulus and density and the sonic modulus and density of the resin matrix itself. This makes sense as the speed of sound through an anisotropic composite material will be some average of both the sound speed in the yarn and the sound speed in the resin.

Further, given the extremely high elastic moduli of ballistic yarns (e.g. ~<NUM> GPa for Kevlar <NUM>) relative to most standard composite resin matrices (<NUM> GPa for LDPE), van Heerden also shows that resin matrix typically has a negative impact on the theoretical ballistic performance of the "constrained" yarn that the "negative impact" of the resin matrix can be minimized by:.

Aspects of the present disclosure address factor B above by incorporating of the relatively low density MA-g-PP. Since polypropylene has a density of only <NUM>/cm<NUM> it effectively lowers the density of a resin matrix compared to more traditional polyurethane resins systems, with respective densities of greater than <NUM>/cm<NUM>. The reduction in resin density consequently increases the sonic velocity of the resin matrix given by the equation:
<MAT>.

The increase in sonic velocity facilitates improved ballistic performance for the ballistic resistant composite armor by increasing the speed at which longitudinal strain waves travel along the ballistic yarns thereby increasing the armor's ability to absorb and dissipate the kinetic energy of a ballistic projectile.

Aspects of the present disclosure are also based on the concept that ballistic improvement in fiber-reinforced composite armor is achievable by selectively increasing the level of adhesion between a resin matrix and ballistic fibers. This is counter-intuitive to ballistic composite design in that the paradigm is to have relatively low matrix-fiber adhesion. Thus, simply maximizing matrix-fiber adhesion is unlikely to yield better ballistic performance. Moreover, in practicality, effectively increasing matrix-fiber adhesion for improved ballistic performance is challenging, especially for non-polar, low surface energy fibers, such as UHMWPE.

Increased matrix-fiber adhesion is accomplished herein by the use of the MA-g-PP, which serves as a coupling agent to the ballistic fibers, while at the same time bonding effectively to the polyurethane. The mechanism of adhesion varies depending on the chemistry of the ballistic fiber. For non-polar ballistic fibers, such as UHMWPE, the maleic anhydride on the MA-g-PP modifies the chemical nature of different melt point/molecular weight (MP/MW) polypropylenes and/or polypropylene-block copolymers to increase their polarity. Although not wishing to be bound, the theory is that by grafting polypropylene with maleic anhydride, the non-polar (somewhat amorphous) polypropylene molecule becomes more polar and more crystalline. Hence, the nonpolar portion of the polymer can orient towards, and bond with, a nonpolar, low energy surface of a ballistic fiber. The polar groups can orient away from the ballistic fiber and may serve to bond with polar groups of polyurethane. In that case, the MA-g-PP in essence serves as a coupling agent to bond the polyurethane to the ballistic fibers where previously there was no chemical bonds. For polar ballistic fibers, such as para-aramid fibers, free hydrogen and double bonded oxygen groups on the fiber surfaces form hydrogen bonds with the maleic anhydride, thus coupling the polypropylene of the MA-g-PP to the fibers.

<FIG> shows the MA-g-PP of <FIG> after it has undergone hydrolysis. In the hydrolyzed state, the maleic anhydride is maleic acid and is functional for chemical bonding. Notably, the maleic acid groups also re-orient into an isotactic stereochemistry via rotation about the carbon-carbon bonds. This structural change makes the MA-g-PP polar, with the negatively charged maleic acid groups orientating to one side of the molecule and more crystalline (isotactic) in nature with all the of uncharged methyl groups of the polypropylene molecules orientating to the other side of the molecule.

<FIG> shows how MA-g-PP block copolymer serves to form strong bonds with the polar reactive polyurethane and how the hydrocarbons of the MA-g-PP orient toward the non-polar hydrocarbons of the ballistic fiber. Although Van Der Waals forces are generally relatively weak, at high molecular weights, such as over <NUM>,<NUM> MW of the non-polar hydrocarbon ballistic fiber, there is a relatively high number of Van Der Waals bonds. Thus, even though a single bond is relatively weak, the many bonds of the long MW length serve to provide a combined bond strength that is substantial. In <FIG> only hydrogen bonding of the maleic anhydride is shown, but ester linkages may also be present via functional alcohol groups (e.g., on polyurethane).

The Van Der Waals strength effect is similar to the effect that is responsible for high strength in UHMWPE. UHMWPE derives strength from the length of its individual molecules and the relatively weak Van Der Waals bonds between the molecules. This occurs because it is made up of extremely long chains of polyethylene that align such that each chain is bonded to the adjacent chains with so many Van Der Waals bonds that the whole system can support great tensile loads.

It is also possible that with enough heat the MA-g-PP will melt-bond to the surface of the ballistic fibers. Even below the melting point of either the fiber or the MA-g-PP, amorphous regions of each polymer may open such that the polymers locally intermix.

The maleic anhydride components of the MA-g-PP may also react with the aforementioned blocked isocyanates to crosslink and form chemical bonds. Such partial crosslinking further increases sonic modulus and tensile strength and thereby increases ballistic performance. Cross-linking also results in ballistic armor panels that are stiffer and more environmentally stable.

An experiment was designed to compare the relative ballistic performance of different resin matrices. This experiment entailed making comparative hard composite armor panels out of <NUM>-ply non-woven orthogonal UD fabric where only the resin matrix itself was varied. These composite panels were then ballistically tested to quantitatively compare their V<NUM> ballistic performances, and subsequently the relative ballistic efficiency of each resin system.

In this example, a two-ply non-woven composite was formed from layers of unidirectionally oriented 780dtex (700den) high tenacity UHMWPE yarn with a tenacity of <NUM>/den (<NUM>. 11GPa) and a modulus of <NUM>/den (<NUM>. Unitapes were prepared by passing the fibers from a creel and through a combing station to form a unidirectional network. The fiber network was then placed on a carrier web and the fibers were coated separately with five different water-based resins:.

The coated fiber network was then passed through an oven to evaporate the water in the composition and was wound onto a roller, with a carrier web. The resulting structure contained about <NUM>% by weight of the resin matrix, based on the total weight of the composite. Two continuous rolls of unidirectional fiber prepregs, of each resin chemistry, A, B, C, D and E were prepared in this manner, and the corresponding unitapes were cross plied, along with the removal of the carrier webs to form <NUM>°/<NUM>° consolidated UD orthogonal fabric rolls at a target areal density of 82gsm. Panels of these five materials measuring <NUM> x <NUM> (<NUM>"x15. <NUM>") were stacked into <NUM>-layer panels and pressed at <NUM> (<NUM>°F), at 214bar (3000psi) for <NUM> respectively to form rigid consolidated hard armor ballistic composite panels. These flat panels were also cooled to room temperature under pressure prior to removal from the press. The resulting <NUM>-layer panels had an approx. areal density of <NUM>/m<NUM> (<NUM>. 0psf) and were tested, clamped in a frame, air-backed, against 44gn (30cal) fragment simulating projectiles (FSPs) according to Mil-STD-662F. The ballistic results were then normalized to an areal density of <NUM>/m<NUM> (<NUM>. 0psf) and were as follows:.

In this example the three of the <NUM>°/<NUM>° consolidated UD orthogonal fabrics, with different resin matrices, from Example <NUM> were used to compare the relative ballistic efficiency of each resin system when pressed under different pressures vs. 17gn FSP projectiles.

In this example the three resin systems tested were Resin B, Resin C, and Resin E from Example <NUM>. Each of these UD orthogonal fabrics was cut into <NUM> x <NUM> (<NUM>"x15. <NUM>") sheets, stacked into <NUM>-layer panels and pressed at <NUM> (<NUM>°F), at both <NUM>. 6bar (400psi) and 214bar (3000psi) for <NUM> respectively to form rigid consolidated hard armor ballistic composite panels. These flat panels were also cooled to room temperature under pressure prior to removal from the press. The resulting <NUM>-layer panels had an approx. areal density of <NUM>/m<NUM> (<NUM>. 50psf) and were tested, clamped in a frame, air-backed, against 17gn (22cal) fragment simulating projectiles (FSPs) according to Mil-STD-662F. The ballistic results were then normalized to an areal density of <NUM>/m<NUM> (<NUM>. 50psf) and were as follows:.

Resin E, which combined MA-g-PP block copolymer with the base TPU resin, therefore had the best V50 ballistic performance, <NUM>% better than TPU without M MAg-PP block copolymer added, and exhibited the biggest V<NUM> performance improvement of <NUM>% when comparing the V<NUM> performance of panels pressed at relatively low (<NUM> psi) pressure, and identical panels pressed at relatively high pressures (i.e. <NUM> psi). This testing also seems to indicate that resin matrices with blocked isocyanate crosslinker perform better than those without when pressed at lower pressures <400psi.

In the following examples a number of new resin matrices analogous to Resin E in the above examples were formulated and made into consolidated UD orthogonal fabrics in an attempt to determine a preferred version of this invention. These resins differed in the amount of MA-g-PP block copolymer used in the formulation, in the molecular weight of the MA-g-PP block copolymer used in the formulation and the in the weight percentage of maleic anhydride used to make the MA-g-PP block copolymer.

In this example a <NUM>-ply non-woven composite was formed from layers of unidirectionally oriented 1650dtex (1485den) high tenacity UHMWPE yarn with a tenacity of <NUM>/den (<NUM>. 43GPa) a modulus of <NUM>/den (<NUM>. 3GPa) and a % elongation of <NUM>%. Unitapes were prepared by passing the fibers from a creel and through a combing station to form a unidirectional network. The fiber network was then placed on a carrier web and the fibers were coated separately with <NUM> different water-based resins:.

The coated fiber network was then passed through an oven to evaporate the water in the composition and was wound onto a roller, with a carrier web. The resulting structure contained about <NUM>% by weight of the resin matrix, based on the total weight of the composite. Two continuous rolls of unidirectional fiber prepregs, of each resin chemistry, E and F were prepared in this manner, and the corresponding unitapes were cross-plied, along with the removal of the carrier webs to form <NUM>-layer <NUM>°/<NUM>° UD orthogonal fabrics, which were then laminated to themselves to form <NUM>-layer <NUM>°/<NUM>°/<NUM>°/<NUM>° consolidated UD orthogonal fabric rolls at a target areal density of 160gsm. Panels of these two materials measuring <NUM> x <NUM> (<NUM>"x15. <NUM>") were stacked into both <NUM>-layer panels and <NUM>-layer panels. These panels were then pressed at <NUM> (<NUM>°F), at 214bar (3000psi) for <NUM> and <NUM> respectively to form rigid consolidated hard armor ballistic composite panels. These flat panels were also cooled to room temperature under pressure prior to removal from the press. The resulting <NUM>-layer panels had an approx. areal density of <NUM>/m<NUM> (<NUM>. 50psf) and were tested, clamped in a frame, air-backed, against 17gn (22cal) fragment simulating projectiles (FSPs) according to Mil-STD-662F. The resulting <NUM>-layer panels had an approx. areal density of <NUM>/m<NUM> (<NUM>. 44psf) and were tested, clamped in a frame, air-backed, against <NUM>. 62x39mm, Type <NUM> Ball, FMJ MSC, <NUM> grains (<NUM> caliber) rifle rounds according to Mil-STD-662F. The ballistic results were then normalized to <NUM>/m<NUM> and <NUM>/m<NUM> respectively and were as follows:.

Hence the higher maleic acid formulation showed a <NUM> to <NUM>% ballistic improvement over one with only <NUM>% maleic acid by weight.

Then identical to Example <NUM> above, <NUM>-layer, 160gsm, <NUM>°/<NUM>°/<NUM>°/<NUM>° consolidated UD orthogonal fabric rolls were made using these two new resins systems and from these, ballistic panels were then constructed. The resulting <NUM>-layer, Resin G and Resin H panels had an approx. areal density of <NUM>/m<NUM> (<NUM>. 50psf) and were tested, clamped in a frame, air-backed, against 17gn (22cal) fragment simulating projectiles (FSPs) according to Mil-STD-662F. The resulting <NUM>-layer, Resin G and Resin H panels had an approx. areal density of <NUM>/m<NUM> (<NUM>. 44psf) and were tested, clamped in a frame, air-backed, against <NUM>. 62x39mm, Type <NUM> Ball, FMJ MSC, <NUM> grains (<NUM> caliber) rifle rounds according to Mil-STD-662F. The ballistic results were then normalized to <NUM>/m<NUM> and <NUM>/m<NUM> respectively and were as follows:.

The lower molecular weight MA-g-PP block copolymer resin (Resin G) exhibited much better ballistic performance vs. the higher molecular weight MA-g-PP block copolymer formulation (Resin H) when tested against high-energy (~<NUM> Joule) rifle rounds that require the composite armor panels to deform significantly (due to tensile strain and cone formation) as part of its energy absorption/energy dissipation mechanism. No significant difference however was noted between the two resin systems, G and H, when tested against relatively low energy <NUM> caliber (~<NUM> Joule) FSP's. The rationale for this, is that composite panels impacted by small, low energy FSP's undergo a different energy absorption/energy dissipation mechanism than those impacted by high energy projectiles. Some of the better performance exhibited by Resin G panels can also be attributed to this formulation's slightly higher maleic anhydride content.

Then identical to Example <NUM> above, <NUM>-layer, 160gsm, <NUM>°/<NUM>°/<NUM>°/<NUM>° consolidated UD orthogonal fabric rolls were made using these three resins systems and from these, ballistic panels were constructed. The resulting <NUM>-layer, Resin E, Resin I and Resin J panels had an approx. areal density of <NUM>/m<NUM> (<NUM>. 50psf) and were tested, clamped in a frame, air-backed, against 17gn (22cal) fragment simulating projectiles (FSPs) according to Mil-STD-662F. The resulting <NUM>-layer Resin E, Resin I and Resin J panels had an approx. areal density of <NUM>/m<NUM> (<NUM>. 44psf) and were tested, clamped in a frame, air-backed, against <NUM>. 62x39mm, Type <NUM> Ball, FMJ MSC, <NUM> grains (<NUM> caliber) rifle rounds according to Mil-STD-662F. The ballistic results were then normalized to <NUM>/m<NUM> and <NUM>/m<NUM>, respectively. The results of this testing found there to be no significant difference in the ballistic performance of these three resins systems despite their varying levels of MA-g-PP block copolymer. All of the to <NUM>/m<NUM> panels had V<NUM> result in the range of <NUM>/s vs. 17gn FSP's and all the <NUM>/m<NUM> panels had V<NUM> result in the range of <NUM>/s vs. the <NUM>. 62x39mm rifle rounds. This indicates that even small amounts of MA-g-PP block copolymer added to a TPU formulation can be beneficial; also, that the resin system is not particularly sensitive, from a ballistic efficiency standpoint, to the amount of compatible MA-g-PP block copolymer in resin matrix.

Claim 1:
A ballistic-resistant composite comprising:
at least one layer including a network of ballistic fibers and a resin matrix, the resin matrix including maleic anhydride-grafted polypropylene (MA-g-PP),
wherein the resin matrix additionally includes polyurethane, the resin matrix includes, by weight, <NUM>% to <NUM>% of the MA-g-PP, the MA-g-PP has, by weight, <NUM>% to <NUM>% of maleic anhydride, the MA-g-PP has a molecular weight of <NUM>,<NUM> to <NUM>,<NUM>, and the at least one layer has a single layer that has an areal density of <NUM> grams per square meter to <NUM> grams per square meter.