Examining the Relationship Between Ballistic and Structural Properties of Lightweight Thermoplastic Unidirectional Composite Laminates
Abstract : The pursuit for lightweight personal protection (helmets, body armor, etc.) has been a key issue for the Army in recent years. Previous efforts have shown that the variation of orientation and architecture in ultra-high molecular weight polyethylene (UHMWPE) composite panels can significantly affect ballistic performance characteristics. In our experiments, an architecture now referred to as ARL X Hybrid emerged as the clear leader in the compromise between ballistic performance and back face deformation (BFD). For this work, thermoplastic unidirectional materials (both aramid and polyethylene based) were evaluated using 17 grain FSP V50 and 9 mm BFD testing in both typical ([0 deg/90 deg]) and X Hybrid architectures, at an areal density target 27% lighter (7.8 kg/sq m) than the currently fielded state of the art. Digital Image Correlation (DIC) was employed to characterize the materials during testing and to help elucidate the panel response as a function of architecture. Polyethylene materials in the X Hybrid architecture were shown to retain 96-99% of the [0 deg/90 deg] architecture's V50 ballistic performance, while also reducing the BFD by 36-41%. Higher fiber involvement, increased interaction area, and increased membrane stress and through-thickness compression are proposed as factors for this phenomenon.
Molecular influence in high-strain-rate microparticle impact response of poly(urethane urea) elastomers
Abstract The dynamic deformation response of select model poly(urethane urea) elastomers (PUU) at high strain rates is investigated via an all-optical laser-induced projectile impact test (LIPIT). LIPIT measurements allow the direct visualization of the impact of micro-projectiles (silica spheres) on substrates and in-situ characterization, including depth of penetration and the extent of rebound of the micro-projectiles. PUUs are proven to be robust and the silica spheres are observed to rebound from them upon impact. In addition, for PUUs a strong correlation was noted between the coefficient of restitution and the maximum depth of penetration. Also, the coefficient of restitution data is comparable to that of glassy polycarbonate (PC), which is in great contrast to the comparison of the corresponding ambient storage modulus data obtained via dynamic mechanical analysis at 1 Hz. We hypothesize that high-rate deformation-induced glass transition is a plausible molecular relaxation mechanism towards macroscopic, dynamic stiffening/strengthening in PUUs.
Ballistic materials and penetration mechanics
Ballistic materials and penetration mechanics , Ballistic materials and penetration mechanics , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی