Analysis and Experiments on Interlaminar Fracture Toughness in Resin Matrix Composites.

Abstract : This final report summarizes the objectives, accomplishments and proposed new direction of research on mode II interlaminar fracture in resin matrix composites. A mode II interlaminar fracture specimen, test and analysis method for interpreting results have been successfully developed and demonstrated for the AS4/3502 material system. Experimental data have been obtained under both net tensile and compressive loading. Of considerable importance are the findings that the AS4/3502 material system show increasing resistance to crack growth in tension, 2) interlaminar fracture under compression is a totally unstable process, and 3) tension and compression behaviors are considerably different. The findings and the conclusions that are drawn from them point to new, promising directions. Complementary experiments on low cycle fatigue in tension and compression and on mode I suppression in tension have been performed. The former basically confirm the static findings. The latter illustrate the potential effectiveness of mode I suppression technology and help to clarify mixed mode fracture.