弯曲载荷下纯净光滑层热解炭基2D-C/C复合材料的断裂机制

摘要

Using natural gas as carbon source, 2D needle felt as preform, 2D-C/C composites were prepared by thermal gradient chemical vapor infiltration. Their microstructures were observed under polarized light microscope (PLM) and scanning electron microscope (SEM), and the flexural behaviors before and after heat-treatment were studied with a universal mechanical testing machine. The fracture mechanism of the composites was discussed in detail. The results show that, carbon matrix exhibits pure smooth laminar (SL) characteristic including numerous wrinkled layered structures and some inter-laminar micro-cracks. With the decreasing density, the strength of the composites decreases and the toughness increases slightly;after 2500 °C heat-treatment, the inter-laminar micro-cracks in matrix increase, the strength decreases, and the toughness obviously increases. The fracture mode of the composites changes from brittle to pseudo-plastic characteristic due to more crack deflections in SL matrix.%　　以天然气作为碳源，以2D针刺碳毡作为预制体，采用热梯度化学气相渗透工艺制备2D-C/C复合材料。采用偏光显微镜(PLM)和扫描电子显微镜(SEM)观察材料的显微组织，采用万用力学试验机测试热处理前后材料的弯曲行为，讨论材料的断裂机制。结果表明，热解炭基体表现为纯净光滑层(SL)特征，包含大量褶皱层片结构和一些层间微裂纹。随着材料密度的降低，材料强度降低，断裂韧性略有提高；经过2500°C热处理后，基体中层间微裂纹数量大量增加，在加载过程中 SL基体中发生了更多的裂纹偏转，材料强度大幅度降低，其断裂韧性明显升高，从沉积态时的脆性断裂转变为理想的假塑性断裂。