ABSTRACT
It can be important to test composite laminates’ resistance to hard objects impacting at low velocity. As documented in numerous investigations (see, e.g., Cantwell and Morton 1991 and Abrate 1998), impact damage may not be visible to the naked eye, although its effect on the residual strength and reliability is important. Several failure modes have been identified, such as matrix permanent deformation (indentation), matrix cracking and delamination, and in severe cases fiber failures. When a laminate contains interlaminar damage, it is compressive strength that can be expected to be degraded because individual plies or groups of plies are free to exhibit local instabilities. Therefore, to simulate the action of lateral impact of foreign objects and subsequent delaminations, it has been common practice to conduct dropweight testing of composite panels and subsequently conduct compressionafter-impact (CAI) testing on the impacted panel to determine the damage tolerance of the material. Both these tests are American Society for Testing and Materials (ASTM) standards. The falling-weight impact test is designated ASTM D7136 (2012), and the CAI test is ASTM D7137 (2012). This chapter describes these two tests and provides examples of test results.
