Numerical determination of elastic and viscoelastic properties of aligned continuous and discontinuous fiber reinforced composites.

Micro-mechanics analysis using the Representative Volume Element (RVE) approach implemented with the Finite Element Method (FEM) has been extensively exploited for determining material properties of unidirectional fibrous polymer composites. However, prior RVE research has primary focused on continuous fiber composites. Little attention has been given to discontinuous short fiber reinforcements, especially when viscoelastic properties are of interest. This thesis develops an RVE-based approach for composites with aligned continuous and discontinuous inclusions specifically for purposes of evaluating the effective elastic stiffness matrix, Coefficient of Thermal Expansion (CTE) and viscoelastic creep compliance coefficients of these materials. Calculated results indicate stiff inclusions decrease the thermal deformation and mechanical compliance along the direction of fiber alignment more significantly than other directions. Additionally, parametric studies shown that fiber volume fraction and packing geometry (regular array/ staggered array) have a significant influence on the composites' properties, while fiber aspect ratio has relatively little effect.