2D-C/ SiC 复合材料的宏观拉压特性和失效模式

通过拉伸、压缩实验, 从宏观上研究了平纹编织C/ SiC 复合材料在简单载荷作用下模量、残余应变及泊松比的变化。通过断口观察, 分析了材料在面内拉、压载荷作用下的损伤与失效模式。实验结果表明, 拉伸载荷作用下, 材料在低应力就开始损伤。0°纤维束表面基体开裂和层间裂纹是主要损伤形式。损伤后, 随着应力增加, 拉伸卸载模量、泊松比线性减小, 残余应变增加; 压缩应力-应变基本呈直线关系, 模量、泊松比基本不变。拉伸破坏表现为韧性断裂, 断裂机理为分层后0°纤维束的断裂、携带90°纤维束拔出; 压缩破坏形成一个与加载方向成13°的断裂平面, 破坏机理为层间裂纹、0°/ 90°纤维束之间裂纹和90°纤维束内裂纹的产生和迅速扩展、最后0°纤维束剪切断裂。

UNIAXIAL MACRO-MECHANICAL PROPERTY ANDFAILURE MODE OF A 2D-WOVEN C/ SiC COMPOSITE

The macro-mechanical behavior of 2D-woven C/ SiC composites produced with CVI technique was investigated by loading and unloading uniaxial tensile and compress test s. The changes in elastic modulus , residualst rain , and Poisson ratio were studied for further characterization of mechanical properties of the CMCs in complexst ress states. Failure mode and damage mechanisms were analyzed by SEM and optical microscope. The tensile test sshow that damage begins at a very low tensile st ress level of about 40 MPa , and that the unloading modules andPoisson ratio decrease linearly as the tensile st ress increases , while the residual st rain increases. Fractography analysis shows that mat rix cracks around the 0°fiber bundles and interlaminar cracks are the main damage mechanisms.The compress behavior is almost linear to failure. The compress modulus and Poisson ratio remain constant . Thetensile specimens break in a ductile manner , because of delamination , longitudinal bundles failure and pull out . Theglobal compress failure in a plane orient s about 13°to the loading direction , and because of cracks between bundlesand within the 90°bundles , the 0°bundles are sheared to failure.