Advanced hybrid composites are becoming the material of choice in the transportation industry due to its lightweight, high stiffness-to-weight ratio and good manufacturing characteristics. Consequently, there is a need to develop micromechanical mathemati­cal models to better understand and quantify the mechanical and structural properties of these materials.

In this thesis, a combined Eshelby-Mori-Tanaka Mean Field Theory (EMT) and Volume Weighted-Averaging Technique (VWA) is developed to determine the overall effective linear thermoelastic properties of n-phase hybrid composites for both the unidirectional aligned and arbitrary oriented fiber composites. The proposed method provides an effective and comprehensive mathematical model as it includes the ge­ometry of the fibers, fiber volume fraction and interaction effects between fibers to determine the overall effective properties of hybrid composites. Closed-form solu­tions for both the overall effective linear elastic properties and coefficients of thermal expansion (CTE) of an arbitrary oriented uniformly distributed fiber composite are obtained in terms of the overall unidirectional stiffness tensor components and CTE components respectively. An alternative closed-form solution for the overall CTE for unidirectional aligned fiber composite has been obtained as well. Finally, an extensive parametric study using the combined EMT-VWA theory has been carried out in or­der to examine the overall effective linear thermoelastic properties of both uniformly distributed unidirectional aligned and 2D/3D random fiber composites as a function of different fiber volume fractions, inclusion shapes, aspect ratios and void contents.