碳/碳复合材料疲劳损伤失效试验研究

对单向碳/碳复合材料纵向拉-拉疲劳特性及面内剪切拉-拉疲劳特性进行了试验研究; 对三维四向编织碳/碳复合材料的纵向拉-拉疲劳特性及纤维束-基体界面剩余强度进行了试验研究。使用最小二乘法拟合得到了单向碳/碳复合材料纵向及面内剪切拉-拉疲劳加载下的剩余刚度退化模型及剩余强度退化模型, 建立了纤维束-基体界面剩余强度模型。结果显示: 单向碳/碳复合材料在87.5%应力水平的疲劳载荷下刚度退化最大只有8.8%左右, 在70.0%应力水平的疲劳载荷下, 面内剪切刚度退化最大可达30%左右; 三维四向编织碳/碳复合材料疲劳加载后强度及刚度均得到了提高; 随着疲劳循环加载数的增加, 三维四向编织碳/碳复合材料中纤维束-基体界面强度逐渐减弱。 

Test research on fatigue damage failure of C/C composites

The longitudinal tensile-tensile fatigue characteristics and in-plane shear tensile-tensile fatigue characteristics of unidirectional C/C composites and the longitudinal tensile-tensile fatigue characteristics of three-dimensional and four-directional braided C/C composites were researched through tests. The interface residual strength between fiber bundle and matrix was measured. The residual stiffness degradation model and the residual strength degradation model under longitudinal and in-plane shear tensile-tensile fatigue loading of unidirectional C/C composites were fitted by the least square method, and the interface residual strength model between fiber bundle and matrix was established. The results show that the biggest stiffness degradation of the unidirectional C/C composites at the fatigue load stress level of 87.5% is only about 8.8%, whereas, the biggest in-plane shear stiffness degradation goes to about 30% at the fatigue load stress level of 70.0%. The strength and stiffness of three-dimensional and four-directional braided C/C composites are both improved after fatigue loading. The interface strength between fiber bundle and matrix of the three-dimensional and four-directional braided C/C composites decrease gradually with the increase of fatigue loading cycles.