Interference optical measurement during continous and discontinous crack propagation in fatigue loaded polymers

Continuous and discontinuous fatigue crack propagation behaviour have been investigated in PMMA and PVC, respectively, using the optical interference method. Thus craze zone sizes at the crack tip have been measured as functions of cycle number and relative stress intensity factor during crack propagation and between crack jumps. The results obtained give new and improved information on the material behaviour in the micro-region at the crack tip and also lead to modifications of a previously proposed model on crack and craze propagation behaviour during fatigue