Vibration Characteristics of Automotive Composite Materials

This paper describes measurements of dynamic stiffness and internal damping (that is, the complex moduli) of automotive fiber-reinforced plastics over the frequency range 10 to 1000 Hz at maximum strain amplitudes up to 0.0017. Three types of chopped E-glass fiber-reinforced polyester composites and two types of hybrid chopped/continuous fiber-reinforced polyester composites are tested, along with neat resin samples. Complex moduli are measured by using a forced flexural vibration technique. Materials having the greatest stiffness are generally found to have the lowest damping, and vice versa. The complex moduli of all materials are found to be essentially independent of frequency and amplitude within the ranges investigated. Damping in the composites is at least one order of magnitude greater than the damping in an aluminum calibration specimen.