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

The mechanical properties of low density 2-D planar-random carbon-carb on composites with densities in the range 0.17-0.40 Mgm(-3) were deter mined by 3-point bend and tensile testing and correlated with the micr ostructure. Three-point bend and tensile specimens fractured in a brit tle manner, with the former failing through a flexural failure for spa n-to-depth ratios from two to eight. Tensile strength and elastic modu lus values were lower than the respective flexural values. This was th ought to be due to the increased volume under stress, and to the deriv ation of the flexural modulus equation, not taking into account the sh ear component of the beam deflection, respectively. Mechanical propert ies 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 fo r by the reduction in microstructural anisotropy, in particular, assoc iated with the increasing proportion of recycled material.