Complex Moduli of Chopped Fiber and Continuous Fiber Composites: Comparison of Measurements with Estimated Bounds

Abstract

Measured complex moduli of two E-glass/polyester chopped fiber com posites (PPG SMC-R25 and PPG SMC-R65), of an E-glass/polyester hybrid chopped/continuous fiber composite (PPG XMC-3) and of an E-glass/ epoxy continuous fiber composite (3M Scotchply) are compared with esti mated bounds on the moduli. The measured storage moduli of the chopped fiber composites and of the hybrid composites and the storage and loss moduli of the continuous fiber composite generally fall within the bounds. However, the measured loss moduli of the chopped fiber composites and of the hybrid composites are greater than the estimated upper bounds, even when a liberal estimate of glass fiber damping is assumed in the calculation of the bounds. These results indicate that the chopped fiber composites may have other damping mechanisms in addition to those present in the resin matrix and glass fiber materials.