Static and dynamic flexural strength of 99.5% alumina: Relation to porosity

Advanced ceramic materials are widely implemented in a variety of cutting edge engineering applications. Their dynamic flexural strength is an important property under impact loading conditions. Therefore, this work reports a systematic comparison of static and dynamic flexural strength results for 99.5% commercial alumina, obtained using a recently reported adaptation of the 1-point impact experimental technique. Specimens of the same size and surface roughness conditions were used in this study, in a large sample batch, thus allowing for estimation of basic statistical parameters for the evaluated material. The main observation is that the flexural strength of this material is distinctly rate-sensitive, a point that was explained by fracture surface porosity levels corresponding to the different loading regimes. During static loading the crack apparently selects a weaker path, by connecting between pores, with a resulting lower strength values and rougher fracture surface. Under dynamic loading conditions, the fracture surface is smoother and the crack path connects only the larger pores, accompanied by an increase in dynamic flexural strength.

► We measure the dynamic tensile (flexural) strength of commercial alumina.
► We report a noticeably higher dynamic strength.
► A systematic fractographic study is reported.
► The role of material defects (porosity) is related to the mechanical properties.