Determination of the fracture strength of porous materials by considering stress concentrations

The influence of stress concentrations on the mechanical strength of porous materials has been theoretically and experimentally investigated. The investigation was limited to closed pores and low porosities (<40%). A spheroidal model allows the determination of the stress concentration factor as a function of the shape (axial ratio) and orientation of the pores, using previous results of the three dimensional elasticity theory. The theoretical approach was verified using experimental values for the bending strength of model porous materials. With this aim gypsum (plaster of Paris) and sintered glass samples with artificial well-defined porosities were fabricated. The approach shows a way for considering the stress concentrations originated by the pores for the determination of the fracture strength of porous bodies.