Experiment investigation on biaxial tensile strength of 3D in-plane braided C/C composites

Biaxial tensile experiments of 3D in-plane braided C/C composites were carried out by cruciform specimen under different loading ratios and loading directions. The loading ratios were 1:1 and 1:2 in X-Y plane and 1:1 in X-Z plane. The results show that all of the specimens fail in the gage section and represent brittle fracture. The failure modes of specimen in X-Y plane are matrix cracking and fiber bundle breakage. The direction of fracture plane is 60° with respect to one loading direction. The failure modes of specimen in X-Z plane are dominated by the fiber rod pulling breakage. The C/C composites strengths under biaxial loading become lower than that under uniaxial results. The parameters of Tsai-WU criterion are determined by experimental data, which may be helpful to the strength design and evaluation of the 3D in-plane braided C/C composites structures.