To address the issue of weak interfacial bonding and insufficient ballistic performance in poly(p-phenylene benzobisoxazole) (PBO) fiber composites caused by the chemically inert fiber surface, this study employed waterborne polyurethane impregnation followed by a hot-pressing process to fabricate PBO composite laminates with varying resin contents (18.40% and 20.45%) and numbers of fiber layers (10, 20, and 30 layers). The tensile properties, ballistic limit, failure modes, and energy absorption mechanisms of the composites were investigated using quasi-static tensile testing, ballistic experiments, and X-ray computed tomography (CT). The results indicate that this process effectively improves the formability and protective performance of PBO fiber composite laminates. Compared to the specimen with a resin content of 20.45%, the 30-layer specimen with a resin content of 18.40% exhibits a 14.86% increase in tensile strength and a 28.33% increase in elastic modulus. The ballistic limit increases with resin content; for the 10-layer and 20-layer specimens, the ballistic limit of the specimens with a resin content of 20.45% increases by 9.9% and 5.3%, respectively. However, this increasing effect diminishes with a greater number of layers, with the difference between the two resin contents being less than 1% for the 30-layer specimens. The primary failure modes of the composite laminates include fiber shear fracture, matrix cracking and delamination, and fiber tensile fracture. Energy absorption is achieved through the synergistic mechanisms of fiber compressive deformation, shear, and tensile fracture. The energy absorption efficiency decreases with increasing impact velocity, while it increases with the number of layers at the same impact velocity. The influence of resin content on energy absorption becomes less pronounced for laminates with a higher number of layers. This study provides a reference for the design of ballistic protection using PBO fiber composites.
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