Ballistic performance of UHMWPE-based laminated composites reinforced with Ti–6Al–4V alloy sheets

ABSTRACT The development of lightweight ballistic armor capable of providing high protection against rifle threats while minimizing weight remains a major challenge for personal protective systems. This study investigates the ballistic performance of hybrid ultra-high-molecular-weight polyethylene (UHMWPE) laminates reinforced with a 1-mm Ti-6Al-4V sheet under NIJ Level III conditions using 7.62 × 51 mm FMJ ammunition. Two commercial UHMWPE prepregs (HB212 and ST-HB13) were comparatively evaluated through fiber tensile testing, FTIR, DSC, TGA, SEM, ballistic resistance, backface signature (BFS), and ballistic limit (V 50 -type) testing. Thermal analyses confirmed that the hot-pressing cycle preserved the integrity of both prepregs without significant degradation, while microscopy and tensile testing revealed markedly superior mechanical properties for HB212 fibers (1844 MPa) compared with ST-HB13 fibers (964 MPa). Ballistic testing demonstrated that eight of the twelve laminate configurations successfully satisfied the NIJ Level III BFS requirement (<44 mm). HB212-based laminates exhibited the highest specific energy absorption and the lowest BFS values, whereas ST-HB13 hybrid laminates showed superior resistance to projectile penetration within the investigated velocity range, with some configurations resisting impacts approaching 960 m s -1 . The incorporation of the Ti-6Al-4V sheet enabled the replacement of up to 30% of the UHMWPE prepreg while maintaining ballistic resistance to rifle threats at approximately 95% of the NIJ reference velocity. High-speed imaging further indicated that the titanium layer primarily promotes projectile deformation and fragmentation, whereas the UHMWPE laminate dissipates most of the kinetic energy through progressive fiber stretching, delamination, and fracture. These findings demonstrate that hybrid UHMWPE/Ti-6Al-4V laminates provide an effective lightweight design strategy for advanced ballistic protection and establish a direct relationship between fiber tensile properties and ballistic energy absorption.