Effect of fibre volume fraction on mechanical performances of C/C composites

C/C composites were prepared by needled felt with fibre volume fraction of 40%, 30% and 25% densifying through chemical vapour infiltration for three times. The graphitization degree of C/C composites at different high treatment temperatures was studied by means of X-ray diffraction .The effect of fibre volume fraction on the mechanical performances of C/C composites was investigated by measuring the flexural,shear,parallel compressive and vertical compressive stress. And the fracture mechanism was analyzed by observing the fracture surface morphologies through scanning electron microscope. The results show that C/C composites with 30% fiber volume fraction have the highest strength value than the other C/C composites with 40% and 25% fiber volume fraction; the strength decreases when the samples undergo high temperature treatment; the fracture mechanism changes from brittleness into toughness when the samples experience high temperature treatment; the higher the heat treatment temperature, the lower the value of strength.