Owing to many advantages compared to conventional metallic materials,composite materials have been widely used in many areas of engineering applications,especially in aerospace applications.Their excellent strength-to-weight ratios,resistance to fatigue/corrosion and flexibility in design are particularly attractive for high performance light weight aircraft structures.However,a major concern that has to be considered following the widespread implementation of composites is their safety during service.Impact usually causes inner damages in composite material which in general cannot be found easily.