MECHANICAL-PROPERTIES IN FLEXURE AND TENSION OF LOW-DENSITY CARBON-CARBON COMPOSITES

The mechanical properties of low density 2-D planar-random carbon-carbon composites with densities in the range 0.17-0.40 Mgm(-3) were determined by 3-point bend and tensile testing and correlated with the microstructure. Three-point bend and tensile specimens fractured in a brittle manner, with the former failing through a flexural failure for span-to-depth ratios from two to eight. Tensile strength and elastic modulus values were lower than the respective flexural values. This was thought to be due to the increased volume under stress, and to the derivation of the flexural modulus equation, not taking into account the shear component of the beam deflection, respectively. Mechanical properties were isotropic within the planes, and greater than the respective out-of-plane values, and mechanical property values increased with an increasing density. However, there was a decrease in the anisotropy of mechanical properties with increasing density, which was accounted for by the reduction in microstructural anisotropy, in particular, associated with the increasing proportion of recycled material.