Effect of thickness on the damage tolerance of glass/epoxy laminates subject to repeated impacts

To evaluate the influence of layer and laminate thickness on the repeated impact response of E-glass/epoxy laminates, two types of cross-ply stacking sequences ([0/90](3n) and [0(3)/90(3)](n)), with two different thicknesses (4mm and 8mm), were analyzed. The investigation, led by running quasi-static perforation tests and repeated impact tests, outlined the better performance of [0(3)/90(3)](n) laminates. Experimental results were analyzed through a macroscopic damage variable (damage index DI) and by microscopic observation and digitalized profiles of impacted specimens. The higher damage tolerance of [0(3)/90(3)](n) laminates was found to depend on the capability of spreading the damage over a more extended area and of tolerating a higher permanent deflection. For both laminate types, the end of the steady damage accumulation phase was observed to correspond to through-thickness transverse cracking.