STRESS-STRAIN RELATIONSHIPS IN ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE FIBERS UNDER BALLISTIC LOADING

Ultra-high molecular weight polyethylene (UHMWPE) fibers are commonly used in body armor systems, alone or in combination with ceramic inserts, as ballistic protection against high-velocity projectiles. Under dynamic loading conditions, the fibers are extremely strong in tension, but the extreme pressures created at impact by ogive-shaped projectiles can cause premature failure before additional fibers can be recruited to distribute the force. A light gas gun was used to launch 9.525 mm steel spherical projectiles into a sample of 20 layered UHMWPE uniaxial fiber sheets (at 90-degree offset between layers) to examine the stress/strain behavior of the fabric over time. Load cells (4.4 kN) were used to measure uniaxial forces along the fibers. Two high-speed video cameras were used to measure both the in-plane and out-of-plane fiber deflection. Using numerical calculations of the total strain, stress was derived from published stress-strain curves and compared to the measured load cell force data, in both X and Y directions.http://archive.org/details/stressstrainrela1094559614Major, Canada ArmyApproved for public release; distribution is unlimited