Water in confined geometry, an approach to the behaviour of fluids in boundary lubrication

Abstract The viscoelastic properties of porous media are studied as a function of their moisture content; Water content can be divided in two classes. Free water at high moisture content which acts only as a dead weight and bound water at low water content which greatly influences the viscoelastic properties of the materials. On hydrophilic surfaces, the water film sticks to the inner pores and increases the stiffness of the sample. On hydrophobic surfaces the reverse is true. The water films damp the materials. During transients, the damping factor exhibits large maxima. This is related to the mechano-sorptive effect. A discussion on the subject is presented.