Fabrication of 2D C/C-SiC composites using PIP based hybrid process and investigation of mechanical properties degradation under cyclic heating

Abstract 2D C/C-SiC composites were fabricated using PIP process by repeated impregnations of porous C/C composite preforms with polycarbosilane followed by pyrolysis. Effect of cyclic heating on flexural and shear strength of these composites was studied by exposing the test specimens to oxyacetylene flame for 20 s and cooling by a blast of air. The cyclic heating tests were repeated up to five times. Average flexural and shear strength of the as fabricated composites were about 330 MPa and 14.5 MPa respectively. After five heating and cooling cycles, average flexural and shear strength were reduced to 120 MPa and 5.5 MPa respectively. SEM, XRD, EDAX and XPS studies were also carried out to investigate the causes of strength reduction. Oxidation started preferentially at carbon matrix through the cut ends of the weft fibers. Oxidative damage due to repeatedly heating cooling was found to be much smaller in through-thickness direction due to passive oxidation of SiC matrix while severe damage was observed parallel to the fabric layers.