In the present study, a new methodology of using free-free beam method coupled with circle-fit approach is used to determine damping of Mg-SiC composites. This technique is based on classical vibration theory, by which the geometry and material properties of the metal matrix composites are related to resonant frequency and structural damping of the test specimen. Using the fact that the ratio of the vibration response to the applied force fits to a circle in the Argand plane for each resonant frequency of the test specimen, the damping factor and natural frequency is predicted accurately for the test specimen. An attempt is made to rationalize the increase in damping capability of the composites when compared against the monolithic specimen in terms of increase in dislocation density and presence of plastic zone at the particulate-matrix interface. (C) 2002 Elsevier Science Ltd. All rights reserved.