A systematic investigation for mode-I fracture properties of stitched composites

Three-dimensional stitched composite (3DSC) is one kind of 3D textile structural composite with higher per-formance on the interlaminated properties. This work demonstrates a systematic analysis of the Mode I fracture behavior of the 3DSC by designing the stitch pitch and fineness of the stitch yarn in the experiments. In the finite element model, a mixed model combining the homogeneous and microstructural parts was developed to reveal the mechanism of stitch pitch and fineness of the stitch yarn on the mode I fracture behavior of the 3DSC. The results show that the effect of the stitch pitch on the mode I fracture behavior of the 3DSC is related to the crack propagation length of the first stitch yarn, which is also dependent on the tension properties of the stitch yarn. The thickness of stitch yarn can significantly improve the fracture toughness of the 3DSC. However, the relative improvement efficiency of the stitch yarn gradually decreases with the rise of the yarn fineness. According to this phenomenon, this work proposed an optimized design to improve the mode I fracture properties of the 3DSC.