1. Field of the Invention
The invention relates to lightweight, ballistic resistant structures. More particularly, the invention pertains to armor structures incorporating two or more spaced apart, ballistic resistant panels, having superior impact and ballistic performance at a light weight.
2. Description of the Related Art
Ballistic resistant articles containing high strength fibers that have excellent properties against projectiles are well known. High strength fibers conventionally used include polyolefin fibers, such as extended chain polyethylene fibers, and aramid fibers, such as para- and meta-aramid fibers. For many applications, the fibers may be used in a woven or knitted fabric. For other applications, the fibers may be encapsulated or embedded in a matrix material to form non-woven rigid or flexible fabrics.
Various ballistic resistant constructions are known that are useful for the formation of hard or soft armor articles such as helmets, structural panels and ballistic resistant vests. For example, U.S. Pat. Nos. 4,403,012, 4,457,985, 4,613,535, 4,623,574, 4,650,710, 4,737,402, 4,748,064, 5,552,208, 5,587,230, 6,642,159, 6,841,492, 6,846,758, all of which are incorporated herein by reference, describe ballistic resistant composites which include high strength fibers made from materials such as extended chain ultra-high molecular weight polyethylene. These composites display varying degrees of resistance to penetration by high speed impact from projectiles such as bullets, shells, shrapnel and the like.
For example, U.S. Pat. Nos. 4,623,574 and 4,748,064 disclose simple composite structures comprising high strength fibers embedded in an elastomeric matrix. U.S. Pat. No. 4,650,710 discloses a flexible article of manufacture comprising a plurality of flexible layers comprised of high strength, extended chain polyolefin (ECP) fibers. The fibers of the network are coated with a low modulus elastomeric material. U.S. Pat. Nos. 5,552,208 and 5,587,230 disclose an article and method for making an article comprising at least one network of high strength fibers and a matrix composition that includes a vinyl ester and diallyl phthalate. U.S. Pat. No. 6,642,159 discloses an impact resistant rigid composite having a plurality of fibrous layers which comprise a network of filaments disposed in a matrix, with elastomeric layers there between. The composite is bonded to a hard plate to increase protection against armor piercing projectiles.
Current armor structures are fabricated and installed as a single sheet of fabric armor material with optional steel or ceramic plate facings. As increasing ballistic resistance requirements are met, significant weight is typically added to such armor structures as the materials are made thicker to enhance the ballistic resistance properties. There is a need in the art for a means to increase ballistic resistance properties of armor without adding significant weight to the structure. The present invention provides a solution to this need. Particularly, the invention provides armor structures including two or more connected but spaced apart, ballistic resistant panels, having superior impact and ballistic performance at a light weight. When a high speed projectile hits the first armor panel, the projectile is deformed and slowed down prior to reaching the second armor panel. When the second armor panel is hit, the projectile is either slowed down further, or stopped. The spaced configuration reduces backface deformation compared to a configuration where multiple panels are directly bonded together. Also, an improvement in ballistic resistance allows lower weight structures to be used to maintain the superior ballistic resistance properties achieved with higher weight materials.