Indentation modelling of heterogeneous materials

The computational modelling of the indentation response of heterogeneous ma terials is studied using the finite element method. The material system con sists of hard particles embedded within a soft matrix. Two material models with exactly the same overall stress-strain characteristics are simulated: one specifically incorporating dispersed elastic particles in an elastic-pl astic matrix and the other a simple elastic-plastic continuum having a homo genized constitutive response of the particle-containing material. The mate rial model with particles explicitly included shows a harder response than that of the homogenized model, even when the particle size is much smaller than the indent size. This is primarily due to the local increase in partic le concentration directly underneath the indentation, which cannot be easil y accounted for in the homogenized model. As a consequence, treating a hete rogeneous material as a simple continuum in a straightforward manner appear s to be an invalid approach in indentation modelling.