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.