Properties and microstructure of KD-I/SiC composites by combined process of CVI/RB/PIP

3D preforms braided with KD-I SiC fibers were employed to fabricate SiC/SiC composites by a modified polymer infiltration and pyrolysis (PIP) process, using Al as active filler. Pyrocarbon (PyC) and SiC interphases were initially deposited on the fiber surface to investigate the effect of SiC thickness on the mechanical properties in the presence of Al particles. The large inter-bundle pores in the preforms were infiltrated by slurry consisting of polycarbosilane (PCS), inert SiC and active Al powders in the first infiltration process. In the reaction bonding (RB) process, carburization and nitridation of Al particles results in volume expansion and compensates the polymer shrinkage on pyrolysis. Specimens were further processed with PIP process to obtain denser composites. As a result, the developed composites exhibit excellent mechanical properties and well meet the demands of lightweight structural components at room temperature.