纤维体积分数对炭/炭复合材料力学性能的影响

以40%,30%和25%3种不同纤维体积分数的针刺整体毡为坯体,经3次化学气相浸渗后制备C/C复合材料;测定其未经热处理与经不同温度热处理后的石墨化度,抗弯、抗剪、垂直与平行抗压强度;在偏光下观察其微观结构;采用扫描电子显微镜对其断口形貌进行观察;研究纤维体积分数与C/C复合材料的力学性能的关系及不同热处理条件下C/C复合材料的断裂机理.研究结果表明:在不同热处理状态下,当纤维体积分数为30%时炭/炭复合材料的抗弯、抗压和抗剪强度均最高;经热处理后的试样,其力学性能降低,断裂方式由脆性断裂转变为韧性断裂;热处理温度越高,其力学性能降低的程度越大.

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.