Effect of Polyurethane Colloid Content on the Ballistic Performance of Prepreg PBO Fiber Composite Laminates

To address the issue of weak interfacial bonding and insufficient ballistic performance in poly-p-phenylene ben-zobisoxazole (PBO) fiber composites caused by the chemically inert fiber surface, the waterborne polyurethane impregnation followed by a hot-pressing process was employed to fabricate PBO composite laminates with varying resin mass fractions (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 through quasi-static tensile testing, ballistic experiments, and X-ray computed tomography (CT). The results indicate that this process can effectively improve the formability and protective performance of the PBO fiber composite laminates. In comparison with the specimen exhibiting a resin mass fraction of 20.45%, the 30-layer specimen with a resin mass fraction of 18.40% demonstrated a 14.86% increase in tensile strength and a 28.33% increase in elastic modulus. The ballistic limit increases with resin content. The ballistic limit of the 10-layer and 20-layer specimens with a resin mass fraction of 20.45% increases by 9.9% and 5.3%, respectively. However, the increasing effect diminishes with a greater number of layers. For the 30-layer specimens, the difference in resin mass fraction between the two resins was less than 1%. 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. Efficiency of the energy absorption decreases with increasing impact velocity, while it increases with the number of layers under the same impact velocity. The effect of colloid content diminishes significantly for numerous layers. The study can provide a reference for the design of ballistic protection using PBO fiber composites.