Lightweight Armor Material

Abstract

This disclosure concerns a lightweight armor material which includes a woven fabric of glass and nylon fibers, wherein the individual glass fibers are interlaced with individual nylon fibers so as to provide an interwoven relationship between the glass fibers and the nylon fibers. A woven fabric of this character is especially suitable for use in body armor and may be employed in multiple layers arranged in superposed relation, either with or without a binding resin, to provide a structural material affording protection against a high energy particle, such as a projectile or fragments therefrom. The structural material has a high resistance to the penetration of a high energy particle in relation to its weight which is superior to the penetration resistance of a comparable structure of the same weight but including woven fabric layers of either glass fibers or nylon fibers alone. A hard outer surface plate of a ceramic material may be included as a component of the structural material in one embodiment thereof, enabling the structural material to successfully withstand the direct impact of certain types of projectiles thereagainst by preventing the penetration of these projectiles and thereby protecting personnel from injury and/or equipment from damage.

Description

This invention relates to a non-metallic armor material formed to provide exceptional impact resistance, thereby affording an exceptional penetration resistance-to-weight ratio.

The present invention contemplates the provision of armor plate formed of the novel material which, however, may be utilized for other purposes. The following description of the application of the material to the production of armor is given by way of illustration only.

Body armor has previously been formed of reinforced plastic materials, such as low pressure glass-polyester laminates. Such armor, however, is subject to delamination about the area of missile impact with consequent reduction in strength of the armor, and in effectiveness in case of a second impact.

It is therefore an object of this invention to provide a composite material suitable for use as armor which is more efficient on a weight basis in stopping high velocity fragmentation projectiles or ogive shaped projectiles, than any of the individual materials of which it is composed, or any other material generally accepted for this use.

Another object of this invention is to provide a non-metallic laminated material suited for use both as body armor and for armor purposes in aircraft, personnel carriers and the like.

Still further objects of the present invention will become more fully apparent as the description proceeds when taken in connection with the accompanying drawings, in which:

FIG. 1 is a greatly enlarged plan view of a woven fabric comprising a lightweight armor material and including interlaced glass and nylon fibers in accordance with the present invention;

FIG. 2 is a sectional view of a laminated armor member including a plurality of layers of woven fabric of the type illustrated in FIG. 1 impregnated with a resin and bonded together into a composite laminate structure;

FIG. 3 is a perspective view of body armor made of woven fabric of the type illustrated in FIG. 1;

FIG. 4 is a perspective view, partially broken away, showing a laminated armor member having a hard outer surface plate as a component thereof in accordance with the present invention; and

FIG. 5 is a sectional view taken along the line 5--5 of FIG. 4.

A great deal of time and effort has been expended on the development and determination of the lightest weight armor for use against fragmentation type projectiles. One of the most widely used and successful to date is Doron or Doron II, a laminate composed of unidirectional glass fabric such as 143 cloth and a polyester resin in a fairly low concentration. Notably higher weights than for Doron are required to stop the same projectile under the same conditions with nylon fabric, either bonded or unbonded; steel; aluminum; or titanium armor alloy, as will be shown hereinafter.

I have found that by interweaving glass and nylon fibers into one fabric, a substantially more projectile-resistant material results which has been found to be better than a fabric woven of either glass fibers or nylon fibers alone. Thus, FIG. 1 shows a woven fabric 10 constructed in accordance with the present invention so as to include individual glass fibers 11 interlaced with individual nylon fibers 12 to provide an interwoven relationship between the glass fibers 11 and the nylon fibers 12 comprising the woven fabric 10. In one embodiment, as shown in FIG. 2, a series of woven fabric layers 10 in which glass fibers 11 and tough, flexible fibers 12, such as nylon, are interwoven with the glass fibers 11, is impregnated with resin 13 and bonded into a multi-ply laminate 14. The superior performance of this laminate member 14 as an armor material in comparison to that of comparable laminate members employing resin-impregnated fabric layers woven of only, glass or nylon fibers alone is totally unexpected since it would normally be thought that the test results of the laminate member 14 of FIG. 2 would lie somewhere between the test results obtained from laminate members respective employing woven glass fabric layers and woven nylon fabric layers. While the theoretical aspects of the woven fabric 10 of FIG. 1 and the laminate member 14 of FIG. 2 have not been fully developed, it is believed that there is an interaction between the two types of fibers comprising the woven fabric 10. The glass fiber 11 is thought to serve the function of the strong member and preferably is composed of roving, rather than twisted fibers, while the lighter-weight nylon fiber 12 is believed to function as both a supporting structure and elongating or stretching member. Thus, both high strength and stiffness and high elongation are obtained in one interwoven material. The optimum ratio of glass to nylon has been determined to lie within the range from about 90 parts glass and 10 parts nylon to 10 parts glass and 90 parts nylon, by weight.

The resin binder 13 may be a cured polyester or epoxy resin or preferably a rubber-phenolic resin so that resin elongation, between 10 and 400 percent is obtained, permitting the nylon -glass fabric 10 to move further without delamination. These resins are applied to the woven fabric layers in an uncured state, after which the impregnated fabric layers are combined to make the desired configuration and thickness, and then cured in that state.

Comparative date demonstrating the notably higher weights required for other armor materials to stop the same projectile under the same conditions is shown in tabular form below.

TABLE I

APPROXIMATE EQUIVALENT WEIGHT FOR A V.sub.50 OF 1600 FT/SEC FOR 0.50 CAL. FRAGMENT SIMULATOR AT 0.degree. OBLIQUITY

Material (1bs/sq ft) New nylon-glass, satin weave, about 50/50 volume basis, with resin binder 5.6 Doron II (unidirectional (Style 143) glass with resin binder) 6.1 All nylon fabric, with resin binder 6.3 2024 T-4 Aluminum 7.7 Titanium (6al. 4V) 6.4 Steel, rolled homogenous 7.2

TABLE II

APPROXIMATE EQUIVALENT WEIGHT FOR A V.sub.50 OF 1300 FT/SEC FOR 0.50 CAL. FRAGMENT SIMULATOR AT 0.degree. OBLIQUITY

Material (1bs/sq ft) Doron II 4.5 New nylon-glass, square weave, about 50/50 volume basis, with resin binder 3.8

The armor produced by this invention has superior penetration resistance to fragments-per-unit weight of armor, and resists delamination under missile impact. It is especially suitable for use in body armor, although it can find use in the protection of personnel carriers or aircraft such as helicopters, for example, which may be, and commonly are, required to operate at low altitude, bringing them within range of rifle fire from the ground.

However, this combination of fibers, may also be used by itself, i.e., without a binding resin, so that it can follow a moving contour such as a body. Thus, FIG. 3 illustrates body armor 15 made of layers of the woven fabric 10 of FIG. 1. When the binding resin 13 is used with the layers of woven fabric 10, the resulting laminate member 14 of FIG. 2 is rigid and semi-structural. The layers of woven fabric 10 may also be combined with a very hard surface plate 16, such as alumina, a hard ceramic material, as shown in FIGS. 4 and 5. When used without the hard surface plate 16, the laminate member 14 is effective in stopping metal fragments, as from the air burst of an anti-aircraft weapon. With the hard outer surface 16 of alumina, the composite laminate member 14' of FIGS. 4 and 5 is effective in stopping ball and armor piercing bullets, such as .30 cal. and 7.62 mm rifle bullets, even when such projectiles directly import thereagainst. In all three embodiments, this woven fabric 10 has been proven to be more effective as an armor material from a weight standpoint than either an all glass fabric or an all nylon fabric.

While I have designated alumina as the material of the outer surface plate 16 in the embodiment illustrated in FIGS. 4 and 5, any material having a hardness and compressive strength substantially equal to or greater than that for hard steel will also serve. The ideal material for the outer surface plate 16 has compressive strengths above 100,000 psi and hardnesses above Rockwell C-50. Ceramics type materials, such as glass, aluminum oxide (alumina), boron carbide and silicon carbide or the like are ideal.

The described use of the woven fabric 10 for armor material enables a very considerable saving in weight to be obtained in providing protective armor for specific purposes. Preferred embodiments of the invention have been described by way of example, but should not be considered as limiting the invention since various changes in the described embodiments may be made by those skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

I claim:

1. A lightweight impact and delamination resistant, non-metallic armor member for providing protection against high energy particles, such as projectiles, said armor member comprising:

an outer surface layer of material having a hardness and compressive strength substantially equal to or greater than that of hard steel,

a plurality of layers of fibrous material arranged in stacked superposed relation behind said outer surface layer,

each of said layers of fibrous material comprising a woven fabric of glass and nylon fibers, individual glass fibers in each woven fabric layer being interlaced with individual nylon fibers in the same woven fabric layer so as to provide an interwoven relationship between the glass fibers and the nylon fibers in the same fabric layer, and

each of said plurality of layers of woven fabric being impregnated with resin so as to be bonded together with said outer surface layer to define a laminated composite plate-like structure having a high resistance to the penetration of a high energy particle in relation to its weight which is superior to the penetration resistance of a comparable structure of the same weight but including woven fabric layers of either glass fibers or nylon fibers alone.

2. A lightweight impact and delamination resistant, non-metallic armor member as set forth in claim 1 wherein said glass fibers are roving material.

3. A lightweight impact and delamination resistant, non-metallic armor member as set forth in claim 1 wherein said nylon fibers have lower unit weight than said glass fibers.

4. An armor material for providing protection against high energy particles, such a projectiles, said armor material comprising:

an outer surface layer of material having a hardness and compressive strength substantially equal to or greater than that of hard steel,

a woven fabric of glass and nylon fibers,

individual glass fibers in said woven fabric being interlaced with individual nylon fibers in said woven fabric so as to provide an interwoven relationship between the glass fibers and the nylon fibers in said woven fabric, and

a resinous material coating said glass and nylon fibers and filling the interstices among them so as to form a semistructural fabric material bonded to said outer surface layer and having a high resistance to the penetration of a high energy particle in relation to its weight which is superior to the penetration resistance of a comparable structure of the same weight but including a woven fabric comprising either glass fibers or nylon fibers alone.

5. A lightweight impact and delamination resistant, non-metallic armor member for providing protection against high energy particles, such as projectiles, said armor member comprising:

an outer surface layer of material having a hardness and compressive strength substantially equal to or greater than that of hard steel,

a plurality of layers of fibrous material arranged in stacked superposed relation behind said outer surface layer,

each of said layers of fibrous material comprising a woven fabric of glass and nylon fibers, individual glass fibers in each woven fabric layer being interlaced with individual nylon fibers in the same woven fabric layer so as to provide an interwoven relationship between the glass fibers and the nylon fibers in the same fabric layer,

a resinuous material coating said glass and nylon fibers of each of said layers of woven fabric and filling the interstices among said fibers so as to bond said plurality of layers of woven fabric together with said outer surface layer,

the relative proportions of glass and nylon fibers in each of said layers of woven fabric lying between 90 parts of glass to 10 parts of nylon and 10 parts of glass to 90 parts of nylon, by weight, and

said outer surface layer and said plurality of layers of woven fabric bonded together therewith defining a laminated composite plate-like structure having a high resistance to the penetration of a high energy particle in relation to its weight which is superior to the penetration resistance of a comparable structure of the same weight but including woven fabric layers of either glass fibers or nylon fibers alone.

6. A lightweight impact and delamination resistant, non-metallic armor member as set forth in claim 5 wherein the material of said outer surface layer has a compressive strength substantially equal to or above 100,000 psi and a hardness substantially equal to or above Rockwell C-50.

7. A lightweight impact and delamination resistant, non-metallic armor member as set forth in claim 5, wherein the material of said outer surface layer is selected from the group consisting of glass, alumina, boron carbide, or silicon carbide.