Effect of fiber content on properties of a short carbon fiber reinforced fused silica matrix composite

Fused silica matrix composites with high content (20 vol.%, 40 vol.% and 60 vol.%) of short carbon fibers were prepared using a hot-pressing technique. Influence of fiber content on crystallization of fused silica matrix, mechanical properties, thermal expansion and oxidization resistance of the composite was studied. More fiber content seems more easily to induce crystallization of the fused silica matrix. The incorporation of short carbon fiber and its increasing content tend to devastate mechanical properties including strength and fracture toughness for the composites with relatively low content of fiber, while for the composite with 60 vol.%Cf, fracture toughness get a high regain, pseudo-plastic behavior is induced and fracture strain dramatically increased to 0.36% due to the microcracking and fiber pull-out toughening effects. Thermal expansion coefficient of the composite increases slowly at initial stage then increases dramatically with increasing carbon fiber content. Oxidization resistance of the composites is weakened by the addition of the carbon fiber, the correlation between weight loss of C/SiO₂ composite and burning time can be described by parabolic rules.