Abstract
Foam core sandwich panel structures are an excellent structural concept to realize full potential capabilities of composite materials owing to its high strength to weight and high stiffness to weight ratio together with suitable formability for integral structures. However, degradation of strength due to the interfacial crack initiated from the damaged area is one of serious problems of this concept. Authors proposed the interfacial crack suppression method named the crack arrester. This concept is to install materials with higher stiffness on the crack propagation path and induce the redistribution of the load between the foam core area near the crack tip and the leading edge of the crack arrester in order to decrease the energy release rate at the crack tip less than the interfacial fracture toughness. A crack suppression effect of the crack arrester were analytically estimated and experimentally validated under mixed mode of mode I and mode II, and mode III type loading conditions. As for the analyses, it was confirmed that the energy release rates at crack tip decreased as the crack tip approached the leading edge of the arrester under constant loadings. In the experimental validation, fracture toughness tests were conducted and the apparent fracture toughness increased as crack tip approached the leading edge of the arrester. Based on the acquired apparent fracture toughness derived from test data, a crack onset judgement method was proposed and a crack onset judgement diagram was prepared in order to apply this concept to structural designs
