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, 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 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.

中文翻译：

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基于声发射技术的3D-C/C-TiC-Cu复合材料弯曲损伤行为

为了改善碳纤维增强陶瓷基复合材料（CMC）的基体脆性，引入高韧性Ti-Cu合金制备了新型3D-C/C-TiC-Cu CMC材料。本研究采用声发射（AE）技术研究材料在分级循环弯曲载荷下的损伤过程，以研究材料在平行针刺和垂直针刺方向上的力学性能。首先，利用AE参数来表征损伤演化过程。然后，利用幸福比和耗散能来表征复合材料在不同加载-卸载循环过程中的内部损伤。最后，基于k-medoids算法进行分析，揭示不同针刺纤维束方向对复合材料裂纹模式的影响。结果表明，随着加载循环次数的增加，声发射次数和累积声发射能量逐渐增加。费利西比和每次加载-卸载循环的耗散能都表征了材料的损伤状态，并表明平行针刺试件的损伤比垂直针刺试件的损伤更严重。另外，通过分析得到的拉伸裂纹与剪切裂纹之比，平行针刺方向的拉伸性能低于垂直方向的拉伸性能。因此，3D-C/C-TiC-Cu材料在垂直针刺方向上具有更好的柔韧性和拉伸强度。实际应用中，可根据应力情况安排材料的纤维方向。