Damage initiation and growth in composite laminates during open hole compression tests

The damage initiation and growth near the edges of a circular open hole of laminated composite plates under compressive load were experimentally studied to understand the physical meaning of the open hole compression strength. Damage growth sequence was investigated mainly through optical micrographs of various sections of damaged specimens. When comparatively tough interface laminates were tested, various damages occurred following initial kink band damage in the 0° layers, such as zigzag damage composed of kink bands and transverse cracks in ±45° layers, matrix cracks in 0° layers, and delaminations above and below the 0° layers. High-speed video images showed that unstable growth of the delaminations near the surface was observed prior to the final failure, accompanying buckling of the delaminated layer. The possible sequences of the damage growth were discussed through consideration of the above damage data.