A comparison of several methods of calculating fracture toughness from composite laminate test data

Critical fracture toughness was determined by two different techniques for graphite/epoxy laminates of three stacking sequences and several thicknesses. Critical fracture toughness was determined by a finite element stress analysis of a center-cracked tension specimen which yielded the stress intensity factor as a function of specimen thickness and applied load. As an alternative approach the critical strain energy release rate was determined from the compliance calibration technique. Test results from both procedures are compared and discussed.