Mechanical properties and failure mechanism of 3D needle-punched Cf/SiC-Al composites

Tensile behaviour and failure mechanism of 3D needle-punched Cf/SiC-Al composites were studied in detail. Cf/ SiC-Al composites were prepared by precursor infiltration pyrolysis (PIP) and vacuum pressure infiltration processes. The bulk density and open porosity of the as-fabricated Cf/SiC-Al composites were tested by drainage method. The as-cut samples were subjected to tensile tests in air at room temperature and the stress-displacement response was analyzed. The cross-section and fracture regions of tested samples were analyzed by SEM in order to understand microstructure-property relationships. It was observed that Al alloy was successfully prepared between carbon fiber bundles which resulted in the low porosity (5.5%). Cf/SiC-Al composites showed higher values of tensile strength (159 +/- 10 MPa) and modulus as compared to Cf/SiC composites. Failure mechanism of Cf/SiC-Al composites was analyzed combining the stress-displacement response and fracture morphology. Fracture mode of the 0 degrees fiber bundle, the 90 degrees fiber bundle and the needle fiber bundle were significantly different which had an important influence on the failure mechanism of Cf/SiC-Al composites. Fracture surface of the 0 degrees fiber bundle was relatively flat, and there was no sign of fiber pulled-out which showed the characteristics of brittle fracture. Toughening mechanism such as interface debonding and fiber pulled-out exhibited in the 90 degrees fiber bundle.