Experimental and simulation study of the effect of cut-out defect in carbon fibres twill weave composite

Abstract

The automated fibre placement (AFP) is an effective manufacturing process that produces a large complex structure with high quality at low secondary waste. Although, the AFP is highly accurate and reproducible and very common in the aerospace application, break and cut-out defect in the plies are inevitable. In this study, we have investigated 4 different types of geometrical cut-out defect that have an equal area (38.4 mm2) that cut from identical locations in the specimen plies. The effect of triangular, rectangular, square and circular cut-out defect has been investigated and compared to a virgin material that has no flaw or cut-out defect in the plies. It has been observed and hence reported that the circle induced flaw has caused 73% reduction in the impact strength due its 360° distortion of carrying stress. The failure mode of the circular cut-out defect specimens was proven to be matrix crack due to miscarriage of the stresses in the fibre, while a pull-out fibres failure mode has been observed in the virgin specimen. The experimental work has been validated using FEA analysis that identically simulate the boundary condition of both bending and impact test.