Spherical indentation of porous ceramics: Elasticity and hardness

A combined experimental and numerical approach is used to characterise the elastic and plastic deformation of a porous bulk ceramic material (La0.6Sr0.4Co0.2Fe0.8O3, LSCF) with porosities in the range 5-45 vol%, undergoing spherical indentation. The Gurson model was used in FEM simulations to describe the densification of the porous material in the plastic zone under the indenter. The simulated indentation response curves, extracted elastic modulus, hardness and densification in the plastic zone all showed good agreement with corresponding experimental observations. The results show that the hardness increases with maximum indentation depth over a representative depth that depends on porosity. In this particular ceramic the hardness, at sufficiently large penetration depth, is approximately 1.7 times the uniaxial yield stress of the porous material.