考虑夹杂相互作用的复合陶瓷夹杂界面的断裂分析
INTERFACE CRACKING ANALYSIS WITH INCLUSIONS INTERACTION IN COMPOSITE CERAMIC
-
摘要: 复合材料中夹杂含量较高时,夹杂间的相互作用能显著改变材料细观应力应变场分布,基体和夹杂中的平均应力应变水平也会发生较大变化,导致复合材料强度等力学性能发生显著变化. 为修正单一夹杂模型运用在实际材料中的误差,基于相互作用直推估计法,建立一种考虑含夹杂相互作用的夹杂界面裂纹开裂模型. 首先根据相互作用直推估计法,得到残余应力和外载应力共同作用下夹杂中的平均应力,再计算无限大基体中相同的夹杂达到相同应力场时的等效加载应力,将此加载应力作为含界面裂纹夹杂的等效应力边界条件,在此边界条件下求得界面裂纹尖端的应力强度因子,进而得到界面裂纹开裂的极限加载条件,并分析了夹杂弹性性能、含量、热残余应力、夹杂尺寸等因素对界面裂纹开裂条件的影响. 结果表明,方法能够有效修正单夹杂模型运用在实际材料中的误差,较大的残余应力对界面裂纹开裂有重要的影响,夹杂刚度的影响并非单调且比较复杂;在残余应力较小时,降低柔性夹杂刚度或者增大刚性夹杂刚度都有利于提高材料强度;扩大夹杂尺寸将导致裂纹开裂极限应力显著降低,从而降低材料强度.Abstract: Micro strain and stress field and the average field is significantly influenced by the interaction of inclusions of high volume fraction, and the composite mechanical properties changes a lot by the introduced inclusions. To reduce the error of using the theoretical model with single inclusion in real multi-inclusion-material property prediction, an inclusion interface cracking model is established based on the interaction direct derivative (IDD) estimate. Average e ective stress field is obtained under applied loading and residual stress based on the IDD estimate, then the stress intensity factor (SIF) of interface arc-crack around circular inclusion under the stress boundary condition is calculated. The critical applied stress is evaluated according to the e ective stress field and the interface arc-crack SIF, and the influence of inclusion elastic modulus, volume fraction, residual stress, and inclusion size are analysed. The result indicates that the method is e ective. Residual stress has remarkable influence to interface cracking; the critical applied stress is not monotonic and complicated with the inclusion sti ness variation when the residual stress is large, while the critical applied stress is increasing with the soft inclusion decreasing the sti ness and the sti inclusion increasing the sti ness when the residual stress is small; large size inclusion decreases the critical applied stress and detrimental to composite strength.