Examining the Relationship Between Ballistic and Structural Properties of Lightweight Thermoplastic Unidirectional Composite Laminates

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°/90°]) and X Hybrid architectures, at an areal density target ~27% lighter (7.8 kg/m 2 ) 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°/90°] 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.