Abstract
ABSTRACT Carbon fibers reinforced ceramic matrix nanocomposites were fabricated through the slurry infiltration method and pulse chemical vapor infiltration (PCVI) route. Multiple impregnations were applied to fill the large voids within the composites. In order to achieve a highly densified composite, the PCVI process was applied to deposit the SiC matrix onto the pore surface within the composites. The objectives of this work are to investigate the influences of the nanosize powder and the fabrication parameters of the PCVI processes on the physical properties, mechanical properties, and microstructure of the nanocomposites. In the processing for forming ceramic nanocomposite, the SiC nanosize powder are added to the matrix precursor (Si powder mixed with phenolic resin) follows the impregnation of the slurry into the preform. The system is then placed into a high temperature environment to pyrolysis (1100℃) the polymer precursor into carbon. Further heat treatment at 1450℃converts carbon and silicon powder into silicon carbide matrix of the carbon fiber reinforced composites. Further densification is required to enhance the density of the fabricated composites for engineering applications. In the PCVI process, the mixture of TMS vapor phase mixed with carrier gas is channeled into the reactor and vacuumed periodically. During the pyrolysis process, the deposition of solid product onto the pore surface within the composites to enhance the density of the composites can be achieved. In this work, the densification process under various precursor concentration, pulse number, and holding time will be studied. The physical properties (matrix distribution, density, open porosity), mechanical properties (interlaminar shear strength) and morphologies of the fracture surface of the fabricated nanocomposites at different processing conditions will be investigated.