DAMPING OF FLUID INFILTRATED NANOPOROUS MEDIA - PART I - LOSS TANGENT

Mechanical damping behavior of Coming Vycor porous glass, code 7930, f ully and partially saturated with water, was studied. This porous glas s had 28% volume porosity, 2.3 nm average pore radius, and 207 m(2)/g internal surface area. The relaxation strength appears consistent with the damping mechanism in which the infiltrated water flows from the c ompressive region to the tensile region inside the glass specimen unde rgoing a three-point bending vibration. The effect of water content in partially saturated specimens suggests that only about 40% of the abs orbed water is free to flow under pressure gradients and the rest (60% ) of the absorbed water or about three monomolecular layers were adsor bed on the internal surfaces. Such adsorbed water does not seem to con tribute to the relaxation strength but appears to increase the damping background. The behavior of the loss tangent of the porous glass part ially saturated with water implies that some pores are full and others are empty except for the adsorbed layer.