High toughness fiber reinforced polymer composites are adopted for applications such as bulletproof shields, helmets and hard body armor that require high impact resistance as well as sufficient structural stiffness and strength. However, the impact energy absorption of fully-infused stiff composites made of Kevlar fibers and matrix is not as good as that of dry Kevlar fabrics. This study proposes a partially-infused Kevlar thermoplastic composite with significantly improved impact resistance. Unlike conventional Kevlar fiber reinforced laminates where the resin is fully infused into the fiber yarns, the fabrication process of partially-infused laminates is controlled such that only the exterior of the Kevlar fiber yarns is infused with thermoplastic resin. Consequently, the Kevlar fibers at the core of each fiber yarn are unrestricted during impact, thus, dissipating more energy. The infused exterior of Kevlar fiber yarns forms tough interlaminar interfaces that resist delamination during out-of-plane loading. The partially-infused laminate has similar static indentation resistance and slightly lower bending resistance when compared to conventional fully-infused Kevlar reinforced thermoplastic laminates, but dissipated 318% more energy in ballistic penetration tests performed with a 12 mm diameter steel spherical projectile.
Source : A new partially-infused fiber reinforced thermoplastic composite for improving impact resistance – ScienceDirect