Flexural Strength Analysis of Continuous Fiber Reinforced Ceramic Matrix Composites

摘要

Experimental researches reveal that bulk density determines the porosity in CMCs structure, which may reduce the effective load bearing area and elastic modulus of the composites, and meanwhile induce stress concentrations. However, the carbon interface with appropriate thickness can adjust the stress distribution in fiber and relieve stress concentration, consequently increase the flexural strength. In this paper, the tensile and flexural properties of a 2D-C/SiC composite were studied by experimental method. The load-displacement curve of the composite under bending load is nearly linear before fracture happens, while the uniaxial tensile stress-strain behavior is obviously non-linear. The measured data shows that the three-point-bending strength is higher than the uniaxial tensile strength. Meanwhile, based on the above analysis, a flexural strength model was presented for fiber reinforced CMCs by applying statistic theory. shear lag theory, and the rule of mixture. Effects of material density and carbon interphase on the mechanical properties of the composites were considered. The predictions are in good agreement with experimental results.