The damping property of glass fiber reinforced polymer matrix composites with two different strand/fiber diameters, their different orientations and layups are investigated. It is found that the damping can be improved at the negligible expense of stiffness, by generating more number of interfaces, i.e.,reducing the fiber diameter from 27.2 mm to 18.3 mm without compromising the dimensions of the composite specimen and the volume fraction of the fiber in the specimens. The natural frequencies and loss factors have been evaluated from experimental results, using the impulse technique. The same properties have also been evaluated theoretically by performing modal analysis, using Blevins' “Formulas
for Natural Frequency and Mode Shape”, and the three phase damping analysis using Ni and Adams's “the Specific Damping Capacity (SDC) model” and Gu et al. 's “the interfacial adhesion model” in the energy dissipation relationship. A good agreement exists between the experimental and theoretical
values.