Experimental investigation on damage evolution in cross-ply laminates subjected to quasi-static and fatigue loading

In this paper an experimental investigation on damage evolution in cross-ply glass fiber reinforced plastic (GFRP) laminates under quasi-static and fatigue loading is presented. Four configurations of lay-up ([02/904]s, [02/902]s, [0/904]s and [0/903/0/903]s) with different thicknesses of cracking plies were selected to study the in-situ behavior in the damage initiation, evolution and saturation. Combined with the imaging features of different damages and the characteristic of damage evolution in the laminates, light transmission method was employed to observe the damage state and to record matrix crack density. In fatigue tests, eight stress levels were chosen for each configuration of laminates, including four lower stress levels below the stress level corresponding to the first transverse crack initiation. A conclusion was drawn from the comparison of the results that the fatigue loading with lower stress level accelerates the process of damage evolution and generates damages more thoroughly at failure.