A photoelastic study of an angle crack specimen subject to mixed mode I–III displacements

A methodology, incorporating the use of an automated polariscope together with three-dimensional photoelasticity, is described and employed to determine mode III stress intensity factors. A series of angled cracks in a modified compact tension specimen were examined. The cracks were at an angle to the face of the specimen so that mode I and III displacements were produced. The results of the experiments were compared with the standard expressions for K_I and K_III, and some recent modifications to the expressions. The results support the findings of recent finite element analyses and fracture work by others that the expressions are not accurate and that the stress intensity factors vary along the crack front.