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采用不同界面强度的2种2D-C/SiC试件,在空气环境中进行700℃无应力氧化试验。通过扫描电镜(SEM)分析发现:材料表面的氧化机制为反应控制,纤维均匀变细;内部的氧化机制为扩散控制,被氧化的纤维产生了缺口或者局部缩颈现象。纤维氧化使有效承载面积减小,导致材料的模量和强度下降。强界面材料模量高而强度低,断口整齐;弱界面材料模量低而强度高,纤维拔出较长。基于以上SEM分析结果,建立了细观力学模型,对起始模量进行模拟计算,获得了与试验值比较吻合的结果。
Two kinds of 2D-C / SiC specimens with different interfacial strength were used to carry out stress-free oxidation test at 700 ℃ in air. Scanning electron microscopy (SEM) analysis shows that the oxidation mechanism on the surface of the material is controlled by the reaction, the fibers are uniformly thinned, the internal oxidation mechanism is controlled by diffusion, and the oxidized fibers are notched or partially constricted. Fiber oxidation reduces the effective carrying area, resulting in a decrease in the modulus and strength of the material. Strong interface material with high modulus and low strength, fracture neat; weak interface material with low modulus and high strength, fiber pull out longer. Based on the above SEM results, a mesomechanical model was established and the initial modulus was simulated and the results were in good agreement with the experimental values.