Bimodal strength distributions and flaw populations of ceramics and fibres

For the evaluation of the fracture strength data of brittle materials such as ceramics or ceramic fibres, the Weibull statistics has been widely applied. If the materials show a bimodal distribution of fracture strength values, different models (multiplicative bimodal, additive bimodal Weibull distributions and Gamma distributions) were used. With the preliminary assumption of the validity of weakest link and Griffith's law, this work intends to show the different flaw probability and flaw probability density distributions, which are described by the respective models. These model descriptions are compared to two experimental examples, a ceramic material (recrystallized silicon carbide) and a carbon fibre.