LOW-VELOCITY IMPACT BEHAVIOR OF PRESTRESSED COMPOSITE LAMINATES

Composite materials remain extremely vulnerable to out-of-plane impact loads, which may lead to severe degradation in strength and stiffness . Many researchers have studied in this field, however, most of their papers only discussed the impact behavior of the specimens without in- plane forces. In reality, the aircraft parts made of composites were s ubjected to in-plane stresses during flight. In this study, an investi gation was undertaken to evaluate the effect of in-plane stresses on t he impact behavior of composite laminates. The low velocity drop-weigh t impact was conducted on T-300/976 quasi-isotropic graphite/epoxy lam inates. Impacted composite specimens were examined by C-scanning ultra sonic inspection to quantify the damage size. The contact force during impact was measured with a piezoelectric force transducer and a digit al oscilloscope. The experimental results showed that the impact behav ior was highly related to birth pretension and precompression. Moreove r, the pretension may induce the severe effect for impacted composite laminates.