Prediction of Material Damping in Randomly Oriented Short Fiber Polymer Matrix Composites

Abstract

The objective of this manuscript is to determine analytically the material damping of randomly oriented short fiber composites. The analytical solution was carried out by using the extension of a force-balance model established earlier by the authors [1-3] for undirectional aligned and off-axis aligned short fiber composites. We first applied an averaging procedure to the six off-axis reduced stiffnesses Qv with respect to the angle θ between the fiber orientation and the applied load. The result indicated that only two of the six moduli were independent. This implied, as expected, that randomly oriented short fiber composites are planar isotropic media in the macroscopic scale. The internal damping was then derived by applying the elastic-viscoelastic correspondence principle and separating the real and imaginary parts of the Young's and shear moduli ER and GR , respectively.