Progressive Damage Accumulation Process of CFRP Cross-Ply Laminates during the Early Fatigue Life

The present work aims at investigating the progressive damage accumulation process of CFRP laminates in an interactive scheme, with a special focus on the early fatigue life where mainly matrix-dominant damage accumulates and stiffness degrades significantly. An in-situ damage monitoring system, containing edge observation, digital image correlation and acoustic emission techniques, was established to characterize and quantify the accumulation of transverse cracks and delamination. Two cross-ply configurations ([0/902]s and [02/904]s) and different stress levels were involved in the experimental campaign. Dependent crack ratio was proposed to reflect the interaction among transverse cracks, and saturated crack density was used to represent the interactive level between transverse cracks and delamination. Results showed that generation of transverse cracks and their interaction govern the early fatigue damage accumulation of the [0/902]s laminates, while not only the interaction among cracks but also the interaction between both damage mechanisms were observed for the [02/904]s laminates