晶须与颗粒混合增强陶瓷基复合材料的相平均应力及微区应力分布特征分析

ANALYSIS OF PHASE AVERAGE STRESSES AND THE DISTRIBUTION FEATURES OF LOCAL-STRESS ON THE HYBRID CERAMIC COMPOSITES REINFORCED WITH WHISKERS AND PARTICLE

采用三维有限元法在MSC-MARC软件中模拟不同性质的晶须和颗粒混合增强陶瓷基复合材料时微区应力分布特征,并计算增强相及基体平均应力。结合Eshelby夹杂理论和Mori-Tanaka方法推导增强相及基体的平均应力的理论公式,将两种方法所得的结果进行比较。结果表明,理论模型与有限元法得到的各相平均应力非常吻合,不同形状的增强相分担的应力差异很大,晶须增强相能够分担大部分的平均应力,对降低基体应力、提高多相混合增强陶瓷基复合材料的强度起主要作用。数值模拟结果同时给出微区应力场分布特征,显示晶须位置变化和晶须弹性模量变化对微区应力分布均有一定影响,有利于对多相增强复合材料进行失效分析。颗粒增强相具有调节晶须分布位置,有效改善微区应力分布特征的作用。

The distribution features of local-stress for ceramic composites reinforced by the whiskers and particle with different mechanical properties are simulated by the 3-dimensional finite element method （FEM） （MSC-MARC） , and the phase average stresses are calculated. For the purpose of comparison, a theoretical formula （effective Mori-Tanaka theory, EMT） combining the Eshelby＇ s theory with Mori-Tanaka method is derived to calculate the phase average stress. The results show that the phase average stresses obtained by EMT are in good agreement with those by FEM, and there is an obvious difference to share the average stress among reinforcements with different shapes and different mechanical properties. The whiskers are prior to the spherical particles to bear high stress, and to decrease the stress in the matrix, and to improve the strength of multi-phase hybrid ceramic composites. The results from FEM also show the influences of the change of positions, and the change of elastic modulus for whiskers on the distribution features of local stress, and it is beneficial to make a failure analysis for multi-phase hybrid ceramic composites. The spherical particles are effective to improve the distribution of local stress by adjusting the positions of the whiskers.