Brittle Failure Prediction of Ceramics Using a Multiscale Approach

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Abstract
Brittle failure is classically modeled by the Weibull distribution, based on a phenomenological approach. The procedure fails if the distribution of the failure‐initiating defects varies within material batches and may lead to a wrong conclusion about the predictive power of the model. The purpose of this paper is to highlight this problem, which can occur with brittle materials such as ceramics. This study, based on the results of tensile and bending tests made on silicon nitride specimens, consists of three steps: (i) micrographic and fractographic studies are performed to determine the defect‐size density in each type of specimen and the mechanical behavior of the defects, (ii) the classical modeling with a Weibull distribution is shown to fail to predict the results, and (iii) a new approach for the identification of a fracture model is developed, based on step (i). The fracture prediction is computed from the actual defectsize distribution in each material batch, so that the procedure can be adapted to changes in the defect‐size distribution caused by the manufacturing process.

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