Morphological optimization of process parameters of randomly oriented carbon/carbon composite

Abstract

A microstructure analysis is carried out to optimize the process parameters of a randomly oriented discrete length hybrid carbon fiberreinforced carbon matrix composite. The com-posite is fabricated by moulding of a slurry into a preform, followed by hot-pressing and carbonization. Heating rates of 0.1, 0.2, 0.3, 0.5, 1, and 3.3°C/min and pressures of 5, 10, 15, and 20 MPa are applied during hot-pressing. Matrix precursor to reinforcement weight ra-tios of 70:30, 50:50, and 30:70 are also considered. A microstructure analysis of the carbon/carbon compacts is performed for each variant. Higher heating rates give bloated compacts whereas low heating rates give bloating-free, finemicrostructure compacts. The compacts fabricated at higher pressure have displayed side oozing of molten pitch and discrete length carbon fibers.The microstructure of the compacts fabricated at low pressure shows a lack of densification.The compacts with low matrix precursor to reinforcement weight ratios have insufficientbonding agent to bind the reinforcement whereas the higher matrix precursor to reinforcement weight ratio results in a plaster-like structure. Based on the microstructure analysis, a heating rate of 0.2°C/min, pressure of 15 MPa, and a matrix precursor to rein-forcement ratio of 50:50 are found to be optimum w.r.t attaining bloating-free densificationand processing time.