THE RESPONSE OF FIBROUS COMPOSITES TO IMPACT LOADING

The response of advanced composites to low‐velocity projectile loading was investigated. The impact failure mechanisms of composites containing various fibers with different strength and ductility were studied by a combination of static indentation testing, instrumented falling dart impact testing, acoustic emission monitoring, and scanning electron microscopy (SEM). The composites containing fibers with both high strength and high ductility (eg., polyethylene (PE) fibers) demonstrate a superior impact resistance as compared to those containing fibers with high strength (eg., graphite fibers) or high ductility (eg., nylon fibers) but not both. Upon impact loading, the composites containing PE fibers usually exhibited a great degree of plastic deformation and some level of delamination. These mechanisms acted to dissipate a significant amount of strain energy prior to the penetration phase of the impact process. No through penetration was observed in all the samples containing more than three layers of PE fabric except when loaded at relatively high rates and low temperatures. Although certain levels of delamination also took place in other composite systems, very little plastic deformation occurred, allowing ready penetration of the projectile. The stacking sequences in the hybrid laminates studied were found to play a critical role in triggering or inhibiting the processes of plastic deformation and delamination and, therefore, controlling their energy absorption capability. The penetration resistance of composites appeared to be dictated by the fiber toughness. The later property must be measured in a simulated high‐rate condition. Copyright © 1990 Society of Plastics Engineers