Abstract In this paper, a systematic study on the effect of flaws on flexural strength of ultra-high temperature ceramics (UHTCs) was carried out by using three typical materials (i.e., ZrB2, ZrB2-SiC and ZrB2-SiC-G ceramics) containing micro-sized flaws with controllable sizes, shapes as well as orientations. Depending on the flaw sizes and orientations, different fracture modes were analyzed by SEM observation and theoretical calculation. Based on Emmerich’s hole/strength model and the maximum strain-energy release-rate mixed-mode fracture criterion, a universal flaw/strength model was developed to describe the flexural strength of flawed UHTCs after taking both material properties and flaw’s geometries into account, and compared well with the experimental data in both mode I and mixed-mode conditions. Prediction results of the proposed model have further verified that substantially consistent with the flexural strength reports of UHTCs in the literature as well as the theoretical strengths calculated from the elastic modulus, which means that the proposed model has a great potential in guiding the design of high-strength ceramics in full-scale (from atomic-scale to macro-scale).

中文翻译：

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基于飞秒激光法的超高温陶瓷缺陷/强度响应定量研究

摘要 本文采用三种典型材料（即ZrB2、ZrB2-SiC和ZrB2-SiC-G陶瓷），系统研究了缺陷对超高温陶瓷（UHTCs）抗弯强度的影响。具有可控尺寸、形状和方向的微型缺陷。根据缺陷尺寸和方向，通过SEM观察和理论计算分析了不同的断裂模式。基于 Emmerich 的孔/强度模型和最大应变-能量释放率混合模式断裂准则，在考虑材料特性和缺陷几何形状后，开发了通用缺陷/强度模型来描述有缺陷的 UHTC 的弯曲强度，并且与模式 I 和混合模式条件下的实验数据进行了很好的比较。