Measurement of dynamic interlaminar fracture toughness of FRP laminates using dynamic displacement measuring apparatus

Dynamic mode II and mixed-mode interlaminar fracture toughnesses of CFRP laminates were measured using an instrumented impact testing system at a low impact speed (0.9 m/s). The system consisted of an instrumented drop weight impact tester and dynamic displacement measuring apparatusconstructed from an optical fiber, position sensing detector and laser light source. The results showed that if dynamic interlaminar fracture toughness is estimated on the basis of load data obtained from a strain gage signal measured on the falling dart, the dynamic toughness could be overestimated, resulting in an erroneous understanding of the experimental results. It was also shown that the dynamic toughness can be evaluated accurately on the basis of the displacement data measured by the dynamic displacement measuring apparatus. It is thus concluded that the displacement-based analysisis more accurate and reliable than the load-based analysis in the measurement of the dynamic interlaminar fracture toughness of FRP laminates.