Interfacial Properties of Stitched Three-Dimensional Woven Composite/Titanium Alloy Hybrid Board

The effects of stitching types (trajectory of stitching), stitch fiber materials, and the twist of stitches on interfacial shear, short-beam strength, and interlaminar fracture toughness of three-dimensional (3D) woven composite/titanium alloy hybrid broad were investigated experimentally. The results revealed that when considering interlaminar shear properties: stitching types have little effect on interlaminar shear properties of hybrid laminates; the difference of ultimate load and strength is great when different stitch fiber materials are used, and aramid fiber are the most; the ultimate load and strength can also be greatly increased by twisting the stitches, and the maximum load and ultimate strength of the stitches with twist of 30m\(^{-1} \) are the highest, but excessive twisting will lead to the decrease of the ultimate load and strength of the structure. When considering the strength performance of the short beam: the maximum load and the strength of the short beam do not change significantly with the change of stitching types, stitch fiber materials, and the twist of stitches. When the interlaminar fracture toughness is considered: the interlaminar fracture toughness is increased by stitching, and the delamination resistance of the sample strengthened by carbon fiber stitch is stronger; over-twisting of stitches results in a decrease in the delamination resistance. The results revealed that the failure mode of the interlaminar shear test specimens is all shear failure of stitches. The failure mode of short-beam strength specimens is the interlaminar shear failure of 3D braided laminates. And there are three failure modes in the interlaminar fracture toughness test: the three-dimensional braided plate laminated fracture at the precrack tip; part of the stitches are tensile fracture, and the three-dimensional braided plate was layered fracture; all the stitches were tensile fracture, and the 3D braided laminates were peeled off from the titanium alloy plates. The formation of the three modes was mainly related to the stitch fiber materials and the degree of twist.