Numerical analysis on viscoelastic creep responses of aligned short fiber reinforced composites

Micro-mechanics analysis using the Representative Volume Element (RVE) approach implemented with the Finite Element Method has been widely used for computing material properties of unidirectional fibrous polymer matrix composites. However, little attention has been given to viscoelastic RVEs of discontinuous fiber reinforced composites. This paper develops a RVE-based Finite Element algorithm for evaluating the effective viscoelastic creep behaviors of aligned short fiber composites. A parametric study including considerations of fiber volume fraction, fiber aspect ratio and fiber packing geometry is performed through the proposed algorithm. Computed results indicate that increasing the fiber volume fraction decreases the mechanical compliance of the overall compound, and the effect of fiber reinforcements is particularly significant in the direction of fiber alignment. Additionally, increasing the fiber aspect ratio reduces the creep compliance coefficient along the direction of fiber alignment more than coefficients along other directions. The fiber packing geometry affects the values of axial compliance properties at low fiber volume fraction and its impacts become less as the fiber volume fraction increases. We also provide an application to simulate the equivalent viscoelastic creep response out of the RVE approach through ABAQUS user defined material subroutine, and the maximum absolute error between the two sets of data is only 1%.