Examination and clarification of R ratio in fatigue delamination growth analysis of composite laminates with fiber bridging

Abstract

Combined experimental and comprehensive analytical approaches were used to investigate the correctness of various R ratio parameters in fatigue delamination growth analysis of composite laminates with fiber bridging. The investigation results indicated that the widely used displacement or load ratio is not the correct R ratio parameter, since correlation with Paris law and Hartmann and Schijve crack growth equations can produce up to three orders of magnitude difference in fatigue delamination growth rate. Consequently, the correct R ratio parameter based on the similitude principle of fracture mechanics was identified and used successfully to eliminate the significant errors which is very significant for both academic research and engineering applications.