Strain and hysteresis by stochastic matrix cracking in ceramic matrix composites
Strain and hysteresis by stochastic matrix cracking in ceramic matrix composites
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DOI：
10.1016/s0022-5096(96)00081-6
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发表时间：
1997-02
影响因子：
5.3
通讯作者：
B. Ahn;W. Curtin
中科院分区：
文献类型：
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作者：
B. Ahn;W. Curtin
提出了一种预测单向纤维增强陶瓷基复合材料（CMCs）多基体裂纹扩展过程中应力应变关系和卸载/再加载滞后行为的理论。该理论基于单纤维复合材料中多基体开裂和纤维断裂之间的相似性，并确定裂纹和应变演化作为材料中初始缺陷的统计分布、界面滑动阻力τ和复合材料中热残余应力的函数。该模型适当地包括所有长度的基体碎片，从小于当前滑移长度δ（σ）到大于2δ（σ）的长度，在施加的应力σ下，并解释了它们对复合材料的总体应变和滞后行为的各自和不同的贡献。实验应力/应变和滞后数据可以被解释为获得的界面剪切应力，热应力，和内在的矩阵缺陷分布值的程序进行了讨论。实际的物理裂纹间距只需要在一个载荷水平下确定，如断裂后，这大大简化了数据采集和分析。几个详细的例子，并与广泛使用的方法，其中裂纹间距被假定为常数，等于直接从实验中获得的平均间距的结果进行比较。以前和现在的理论之间的差异是明显的，在一个不正确的估计界面滑动，但只有约10%。在不改变基体缺陷或界面滑动阻力的情况下，研究了温度变化和残余应力的影响。
A theory is presented to predict the stress/strain relations and unload/reload hysteresis behavior during the evolution of multiple matrix cracking in unidirectional fiber reinforced ceramic matrix composites (CMCs). The theory is based on the similarity between multiple matrix cracking and fiber fragmentation in a single fiber composite, and determines the crack and strain evolution as a function of the statistical distribution of initial flaws in the material, the interfacial sliding resistance τ, and the thermal residual stresses in the composite. The model properly includes matrix fragments of all lengths, from lengths smaller than the current slip length δ(σ) to larger than 2δ(σ), at applied stress σ, and accounts for their respective and differing contributions to the overall strain and hysteresis behavior of the composite. The procedure by which experimental stress/strain and hysteresis data can be interpreted to derive values for the interfacial shear stress, thermal stresses, and intrinsic matrix flaw distribution is discussed. The actual physical crack spacing needs only to be determined at one load level, such as post-fracture, which greatly simplifies the data acquisition and analysis. Several detailed examples are presented, and the results compared with a widely-used approach in which the crack spacing is assumed constant and equal to the average spacing obtained directly from experiment. The discrepancy between the previous and present theories is manifest in an incorrect estimate for the interfacial sliding, but only by approximately 10%. The effect of changing temperature, and hence residual stresses, without changing either matrix flaws or interfacial sliding resistance, is studied.