Evaluation of Modal Damping in FRP Based Laminated Composites through Modal Testing

The main source of damping in laminated composite materials arises from the inelastic nature of the matrix \nand the relative slipping at the fiber/matrix interfaces. Damping in laminated composite materials is usually a \nfunction of many parameters including the volume fraction of the fibers, fiber diameter and fiber orientation \nrelative to the axis of loading.Also the magnitude and frequency of the applied load and many environmental factors should be mentioned. Since the complex phenomenon of damping is difficult to incorporate into the structural dynamic analysis of laminated plates, a modal damping approximation is employed here. \nVarious methods have been presented to obtain the modal damping of a laminated composite.In this paper, classical modal testing of bi-woven laminates under various boundary conditions and analysis of the damping \nis carried out. Laminates made of Glass and Graphite fibers with epoxy resin as matrix is used in modal testing. Traditional “Strike Method” is adopted which consists of impulse hammer and accelerometer with 4-channel FFT analyzer to obtain the response of the specimen under test. Results obtained from both \nlaminates are compared and it is observed that damping properties of graphite is more dominant than glass laminates.