AU5675290A - Ballistic resistant composite article and method - Google Patents

Description

BALLISTIC RESISTANT COMPOSITE ARTICLE AND METHOD BACKGROUND OF THE INVENTION This invention relates to an article of manufacture for ballistic end use. The prior art is described in U.S. 4,737,401, hereby incorporated by reference. Other background patents are U.S. 4,681,792, U.S. 4,737,402, U.S. 4,748,064, U.S. 4,650,710, U.S. 4,623,574, U.S. 4,613,535, U.S. 4,501,856, U.S. 4,457,985, and U.S. 4,403,012 and copending application U.S. Serial No. 62,998 filed July 13, 1987 all hereby incorporated by reference to the extent that they are not inconsistent with the 10 teachings herein. Brief Description of the Invention

This invention is an article of manufacture for ballistic end use comprising more than one network of high modulus high strength fibers each network being first impregnated with a high modulus resin which can be cured to a rigid state, dried, then each impregnated, dried but not cured network coated with a low modulus elastomeric resin, then the networks are plied together so that the low modulus elastomeric resin acts as an adhesive between each of the networks. The plied networks are subsequently cured to form a rigid composite without cooling the mold. The method of this invention is a method to manufacture a rigid composite for ballistic end use comprising preparing multiple networks of high modulus high strength fibers, impregnating the networks with a high modulus resin, drying the high modulus resin impregnated into the networks, coating the impregnated networks with a low modulus elastomeric resin, plying the dried coated networks together to form multiple layers of the networks, then curing the high modulus resin so that it becomes rigid and so that the elastomeric resin acts as an adhesive between each layer of networks. The curing of the high modulus resin can be after plying the networks or before the coating of the impregnated networks with the elastomeric resin. Preferrably between about 2 and about 400 plies of the networks are plied together. DETAILED DESCRIPTION OF THE INVENTION This invention in detail is an article of manufacture for ballistic end use comprising more than one network of high modulus high strength fibers each network being first impregnated with a high modulus resin capable of being cured to a rigid state, dried, then each impregnated dried network is coated with a low modulus elastomeric resin, then the networks are plied together so that the low modulus elastomeric resin acts as an adhesive between each of the networks. Preferably the plied networks are subsequently cured to form a rigid composite. The preferred plies number betweem about 2 and 400, more preferrably between about 4 and about 80. The impregnated networks can be individually cured before being coated with the elastomeric resin. The high modulus high strength fiber preferrably has a modulus from about 400,000 psi to about 100 x 10 psi and a strength from 100,000 psi to 1,000,000 psi. The high modulus resin has a modulus of between about 100,000 and about 1,000,000 psi and the low modulus elastomeric resin has a modulus from between about 10 psi to about 2,000 psi.

The high modulus high strength fiber is preferrably selected from the group consisting of high molecular weight polyethylene, aramids, high molecular weight polypropylene, graphite, carbon, metals, alumina polyester, nylon and combinations thereof. The most preferred fiber is high molecular weight polyethylene.

The preferred low modulus elastomeric resin is selected from the group consisting of polybutadiene, polyisoprene, natural rubber, ethylene-propylene copolymers, ethylene-propylenediene terpolymers, polysulfide polymers, polyurethane elastomers, chlorosulfonated polyethylene, polychloroprene, plasticized polyvinylchloride, butadiene acrylonitrile elastomers, poly(isobutylene-co-isoprene) , polyacrylates, polyesters, polyethers, fluoro-elastomers, silicone elastomers, thermoplastic elastomers, copolymers of ethylene and combinations thereof. The plastizer for polyvinyl chloride can be diallyl or dioctyl phthalate or other plastizers well known in the art. The preferred elastomeric resin is a polyurethane, such as Dispercoll E-585 from Mobay.

The preferred high modulus resin is selected from the group consisting of phenolics, polyesters, epoxies, vinylesters, rigid polyurethanes, polyimides and mixtures or co-polymers thereof. The most preferred high modulus resins are vinylesters.

The method of this invention is a method to manufacture a rigid composite for ballistic end use comprising preparing a multiple networks of high modulus high strength fibers, impregnating the networks with a high modulus resin, drying the high modulus resin impregnated into the networks, coating the impregnated networks with a low modulus elastomeric resin, plying the dried coated networks together to form multiple layers of the networks and curing the high modulus resin so that it becomes rigid and so that the elastomeric resin acts as an adhesive between each layer of networks. The curing of the high modulus resin can be after plying or before coating the networks. The preferred number of plies is between about 4 and about 90 plies of the networks plied together.

By ballistic end use is meant not only civilian uses such as bullet-proof vests and mats but particularly the military applications such as helmets and armor or hulls used in aircraft, vehicles, ships and other vessels and similar high impact applications.

By network is meant fibers arranged in configurations of various types. For example, the plurality of fibers can be grouped together to form a twisted or untwisted yarn. The fibers of yarn may be formed as a felt, knitted or woven (plain, basket, satin and crow feet weaves, etc.) into a network, fabricated into a non-woven fabric, arranged in a parallel array, layered, or formed into a fabric by any of a variety of conventional techniques. For fiber herein, is meant an elongate body the length dimension of which is much greater than the transverse dimensions of width and thickness. Accordingly, the term fiber includes monofilament, multifilament, ribbon, strip, staple and other forms of chopped or cut fiber and the like having regular or irregular cross-sections. For purposes of this invention in general, a high strength high modulus fiber is a fiber having a tensile modulus of at least 20 grams per denier and tensile strength of at least about 7 grams per denier. By high modulus resin is meant a resin having a modulus of 100,000 to 1,000,000 psi. By cured is meant the transition from less rigid to more rigid state as by cross-linking with or without catalyst usually with heat. By rigid is meant stiff in that the impregnated network has structrual integrity and can stand alone. By low modulus resin is meant the elastomeric resins having a modulus of less than 2,000 psi. By adhesive is meant that the resin must be compatible with the rigid resin which was impregnated in the network and cannot effect by chemical reaction, by dissolving or otherwise the high modulus resin or its carrier. The adhesive must improve adherence between layers and maintain structural integrity of the plies. The adhesive may be soft or semi-rigid but it must achieve improved transient deformation and delamination properties. By transient deformation is meant a test as follows.

The transient deformation is measured on a soft molding clay kept at 13 mm gap behind the target. After shooting, any deformation more than the gap leaves a per enant dent on the clay. The depth of the dent is then measured by a precise gage. The deformation is calculated by adding the 13 mm and the depth of the dent.

Benefits of this invention or the prior art rigid resin composites are

1. increase bonding between networks of fibers impregnated with a rigid resin, and

2. the increased bonding of 1. above provides the critical difference in transient deformation which can mean the difference between life and death to the wearer. For example, see comparative example 2 where the transient deformation of the helmet was 29mm compared to the example of this invention, example 4, where the transient deformation was only 18mm. The gap between the composite and the head of the wearer of the helmet is greater than 18mm but less than 29mm so that a bullet or other fragment striking the helmet of this invention would cause a dent in the helmet but would not penetrate to or push against the skull of the wearer whereas using the prior art, method and article, the wearer would suffer a severe injury or death. These benefits are achieved without loss of ballistic properties as demonstrated by the data on the V_J-_Q information in examples 4 and 6. The second coat alone, the elastomeric resin, cannot be used alone because of the need to cool the mold in order to remove the result and composite. This is time consuming and becomes uneconomic on a commercial scale. The use of the method and article of this invention provides improved adhesion and yet the increased bonding is not at the detriment of ballistics performance. This is contrary to past experience. In the past whenever adhesion became better, the ballistic performance as determined by the V_ςQ data became worse. The benefit of this invention over simple composites of the prior art using only elastomeric resin is in manufacturing. There is no need for extensive time to cool the mold to remove the composite.

EXAMPLE 1 (Comparative)

SPECTRA^® 900 yarn was woven into fabric style 903

(plain weave 21 x 21). This fabric was then coated with solution which contained 45.3% by weight vinylester

Derakane 8084, 9.1% diallylphthlate, 0.134% Lupersol 256, 22.7% acetone and 22.7% acetone and 22.7% ethanol. Resin content (solids basis) of the coated fabric (prepreg) was

24%. The 29 layers of prepreg was pressed (molded) at

240°F, 400 psi for 15 minutes. The laminate had an areal density of 1.67 psf (pounds per square foot). The V_5Q of the laminate was 2010 fps for a .22 cal fsp (fragment simulator projectile). The peel strength was 433 g/inch.

Extensive delamination between plies was observed. The peel strength was obtained on an one inch width specimen and measuring the force need to separate the two individual plies at 180° angle.

EXAMPLE 2 (Comparative) Twenty-seven layers of prepreg of Example 1 were inserted into a medium size helmet mold and pressed under 180 tons at 240°F for 15 minutes. The finished helmet weighed 2.28 pounds. The V_5Q of the helmet was 2150 fps (feet per second). The transient deformation of the helmet was 29mm when tested with a .30 cal 44 grain fsp at speed of 1560 fps.

EXAMPLE 3 The same fabric as in example 1 was coated with the same manner as in example 1 and with solution which contained 22.4% vinylester Derakane 8084, 4.47% diallyl phthalate, 0.134% Lupersol 256, 36.53% acetone, and 36.53% ethanol. The resin content of the resulting prepreg was 9.9%. This prepreg was then coated again with an aqueous solution which contained 20% of Dispercoll E-585 solids. The total resin content was 23.4%. A laminate was made under identical conditions as shown in example 1. The weight of the laminate was 1.77 psf. The V_ςQ was 2067 fps. The peel strength was 1717 g/inch. Compare Example 1. EXAMPLE 4

The prepreg made as in example 3 was fabricated into a helmet with identical conditions as shown in example 2. The helmet weight was 2.31 pounds. The V_5Q was 2349 for a .22 cal 17 grain fsp. The transient deformation was 18mm when shot with a .30 cal 44 grain fsp at speed of 1559 fps. Significant improvement in delamination of plies was observed. EXAMPLE 5 (Comparative)

Kevlar 29 fabric style K29/13 from Knytex (Kevlar 29, 3000 denier, 14 oz/sq. yd., 17 x 17 plain weave) was prepreged with the same resin system as shown in example 1.

The resin content was 14.4%. The 15 layers prepreg were then pressed at 240°F, 20 minutes at 624 psi. The laminate had an areal density of 1.63 psf. The V₅₀ of the laminate was 1698 fps. The peel strength was 346 g/inch.

EXAMPLE 6

The same Kevlar fabric was formed into a prepreg and fabricated into laminate as shown in example 3. The laminate had an areal density of 1.63 psf. The V_cn was bu 1727 fps. The peel strength was 1480 g/inch. Compare

Example 5.

The following is a list further describing the compounds used in the above Examples.

Compound Trade name Source vinyl ester Derakane 8084 Dow Chemical

2.5-dimethyl 2.5-di(2-ethyl hexanoyl peroxy) hexane Lupersol 256 Pennwalt aqueous polyurethane dispersion Dispercoll E-585 Mobay

40% solids

Claims

WE CLAIM:

1. An article of manufacture for ballistic end use comprising more than one network of high modulus, high strength fibers, each network being first impregnated with a high modulus resin, said resin can be curable to a rigid state, said impregnated network dried, then each impregnated, dried network coated with a low modulus elastomeric resin, then the networks plied together so that the low modulus, elastomeric resin acts as an adhesive between each of the networks.

2. The article of claim 1 wherein said high modulus, high strength fiber has a modulus of between about 400,000 psi and 100 x 10⁶ psi and a tensile strength of between about 100,000 and 400,000 psi, said high modulus resin has a modulus of from between about 100,000 and about 1,000,000 psi, and said low modulus elastomeric resin has a modulus from between about 10 psi to about 2,000 psi.

3. The article of claim 1 wherein the ration of the thickness of each said network to the equivalent diameter of said fiber is equal to or less than about 12.8.

4. A method to manufacture a rigid composite for ballistic end use comprising preparing multiple networks of high modulus, high strength fibers impregnating said networks with a high modulus resin, drying said high modulus resin impregnated into said networks coating said impregnated networks with a low modulus elastomeric resin plying said dried, coated, networks together to form multiple layers of said networks, and curing said high modulus resin so that it becomes rigid and so that -said elastomeric resin acts as an adhesive between each layer of networks.

5. The method of claim 4 wherein the ratio of the thickness of each said network to the equivalent diameter of said fiber is equal to or less than about 12.8.