We report on normal contact and friction measurements of model multicontactinterfaces formed between smooth surfaces and substrates textured with astatistical distribution of spherical micro-asperities. Contacts are eitherformed between a rigid textured lens and a smooth rubber, or a flat texturedrubber and a smooth rigid lens. Measurements of the real area of contact $A$versus normal load $P$ are performed by imaging the light transmitted at themicrocontacts. For both interfaces, $A(P)$ is found to be sub-linear with apower law behavior. Comparison to two multi-asperity contact models, whichextend Greenwood-Williamson (J. Greenwood, J. Williamson, \textit{Proc. RoyalSoc. London Ser. A} \textbf{295}, 300 (1966)) model by taking into account theelastic interaction between asperities at different length scales, isperformed, and allows their validation for the first time. We find that longrange elastic interactions arising from the curvature of the nominal surfacesare the main source of the non-linearity of $A(P)$. At a shorter range, andexcept for very low pressures, the pressure dependence of both density and areaof micro-contacts remains well described by Greenwood-Williamson's model, whichneglects any interaction between asperities. In addition, in steady sliding,friction measurements reveal that the mean shear stress at the scale of theasperities is systematically larger than that found for a macroscopic contactbetween a smooth lens and a rubber. This suggests that frictional stressesmeasured at macroscopic length scales may not be simply transposed tomicroscopic multicontact interfaces.
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