Brittle material strength and fracture toughness estimation from four-point bending test

The failure stress under four-point bending cannot be considered as an intrinsic material property because of the well-known size effect increasing maximum flexural with decreasing specimen size. In this work, tests are analyzed coupled criterion for different sample sizes. only tends towards tensile strength provided height is large enough compared to characteristic length. that case, mainly driven by a criterion. Failure smaller specimens both energy and conditions, thus depending on fracture toughness. Regardless mechanical properties, we show variation ratio function length follows master curve, which propose analytical expression. Based relation, procedure post-processing allows determining illustrated based experiments three gypsum at porosity fractions.