碳/碳复合材料疲劳损伤失效试验研究

Test research on fatigue damage failure of C/C composites

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。

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.