Figure 4.

Representative FEM results for the layer indentation model with top stiff (black, 20–100 kPa) and soft (gray, 1–5 kPa) inclusions on a 10 kPa bottom substrate. (A) Indentation force versus depth is shown. (B) Corresponding pointwise elastic modulus versus depth is shown; the stiff inclusion curves start high and decrease with indentation depth, whereas soft inclusion curves start low and increase with depth. The effective volume fraction versus depth for (C) stiff inclusion and (D) soft inclusion show distinct characteristics, but each family of curves behaves similarly.