Bending damage behavior of 3D-C/C-TiC-Cu composite based on acoustic emission technology

In order to improve the matrix brittleness of carbon fiber reinforced ceramic matrix composites (CMCs), a new type of 3D-C/C-TiC-Cu CMC material is prepared by introducing high toughness Ti-Cu alloy. This study uses acoustic emission (AE) technology to investigate the damage process of the material under graded cyclic bending loading in order to study the mechanical properties of materials in parallel needling and vertical needling directions. Firstly, AE parameters are used to characterize the damage evolution process. Then, Felicity ratio and dissipated energy are used to characterize the internal damage of the composite during different loading–unloading cycles. Finally, RA-AF analysis based on the k-medoids algorithm is explored to reveal the effect of different needled fiber bundle directions on the cracking pattern of the composite. The results show that the AE count and the accumulated AE energy increase gradually with increasement of the number of loading cycles. Both the Felicity ratio and the dissipated energy of each loading–unloading cycle characterize the damage state of the material, and show that the damage in parallel needling specimens is more severe than in the vertical needling specimen. In addition, the tensile performance in parallel needling direction is lower than that in its vertical direction by the ratio of tensile and shear cracks obtained through RA-AF analysis. Thus, 3D-C/C-TiC-Cu material has better flexibility and tensile strength in the vertical needling direction. In practical application, the fiber direction of the material can be arranged according to the stress condition.