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.