Design and destroying mechanism of stitching joint 3-D braided composites

Targeting at the design of the jointing of 3-D braided composites,a strength proof and parameter design formula were established and internal force response of the joint part was drawn based on studies of manufacture process.Tensile tests were conducted on 3-D stitching joint braided composites with different overlap lengths and stitching densities.The results showed that there are 3 patterns of fracture,namely,broken at one or two ends of the overlap area;delaminated in the stitching part;broken as well as delaminated in the stitching section.Analysis of destroying mechanisms indicated that the fracture mode is determined by stitching parameters,also related to the internal force distribution and stress concentration.The joint modes can be designed flexibly for actual loading conditions.