LIMITATIONS OF PORE-STRESS CONCENTRATIONS ON THE MECHANICAL-PROPERTIES OF POROUS MATERIALS

Severe limitations on pore-stress concentration effects on mechanical properties are shown. First, the porosity dependence of materials with dilute porosities is not consistent with significant variations in st ress concentrations with the stress state. Second, in non-dilute poros ities, pore stress concentration effects are reduced due to pore-stres s interactions as pore spacings decrease. Such reduction of stress con centrations is seen as supporting the concept of the minimum solid are a correlating with properties in porous materials, and the similarity between the porosity dependence of mechanical properties and electrica l and thermal conductivity. Finally, crack-pore interactions often lim it the effects of pore-stress concentrations, e.g. due to small pore s izes. However, some effects of pore-stress concentrations may occur du e to tensile failure from a few or an isolated pore, or more general p orosity under compressive loading, but even in these cases pore shape- stress concentration effects are significantly mitigated.