Optical high dynamic range acquisition of crack density evolution in cyclic loaded GFRP cross-ply laminates affected by stitching

The fatigue crack density evolution in a cross-ply laminate where edge finish and stitching are taken into account is investigated. Diamond saw and water jet cutting are used to produce the test specimens and some of the specimens are polished afterwards. The crack density evolution and crack initiations are tracked automatically. It is shown that the number of cracks initiating at the edges for non-polished specimens are similar, whereas the diamond saw cut and polished specimens have fewer cracks at the edges, and the water jet cut and polished specimens have even fewer. In addition it is shown that the crack density is higher in the stitching areas than in the rest for polished specimens. This indicates that the stitching is highly governing of where cracks initiate and propagate in the specimens with limited edge defects. The same applies to real composite structures, which are negligibly affected by edge defects.