【摘要】 综合采用偏光显微镜(PLM),X射线衍射仪(XRD),扫描电子显微镜(SEM),高分辨透射电子显微镜(HRTEM)等分析方法,逐层研究了2500℃高温石墨化(HTT)处理前后双层热解炭基2D C/C复合材料的不同织构以及纤维-基体界面的变化。结果表明:HTT处理后,d002值减小,石墨化度显著提高;内层低织构热解炭的断口微观形貌与晶格条纹几乎没有变化,而外层高织构热解炭晶格条纹更加平直,尤其是发现层间裂纹密度明显增大,使得处理后的高织构热解炭在受力时,裂纹易于在层间扩展和偏转,因此可有效提高材料的韧性;同时,纤维-基体界面发生弱化也是提高材料韧性的另一机制。HTT处理前后试样的三点弯曲力学性能试验结果证实了以上机制。更多还原

【Abstract】 X-ray diffraction(XRD),scaning electron micrsocopy and transmission electron microscopy were used to study the changes of the pyrolytic carbon microstructure and fiber-matrix interface of binary layer textured 2D C/C composites before and after heat treatment.The XRD results show that the d002 decreased and the graphitization degree increased significantly with the increase of heat treatment temperature.No obvious change of the fracture surface morphology and lattice fringes of the inner layer,which correspond to low textured pyrolytic carbon,was observed.However,the lattice fringes of the outer layer(high textured pyrolytic carbon) are regularly parallel,and the density of microcracks in the outer layer increases obviously after heat treatment.These microcracks make cracks propagate and deviate easily,leading to an increase of the toughness of the C/C composites.Moreover,the weakening of the fiber-matrix interface bonding is another mechanism for the toughness enhancement.The results of three point bending tests confirmed the proposed mechanism.更多还原