Closed-form Solutions for the Overall Coefficient of Thermal Expansion of n-phase Fiber Composites with Arbitrary Fiber Orientation

The coefficient of thermal expansion (CTE) is an important physical property of fiber composites. In the past, researchers have provided closed-form expressions for CTE for 2D and 3D random fiber composite structures. In this study, closed-form solutions for the overall CTE of n-phase fiber composites with arbitrary fiber orientation angles are derived based on the volume-weighted averaging equation. The overall unidirectional (fully aligned fibers) thermoelastic properties are developed using the transformation field analysis (TFA) method. In addition, the mechanical concentration factors are estimated using the Eshelby-Mori-Tanaka (EMT) theory. The proposed model allows for varying the fiber volume fraction, aspect ratio, geometry of the fibers, and fiber orientations while designing to meet different criteria. The results obtained using the derived equations are compared and validated with the results published in the literature. Also, a numerical study for an epoxy/graphite composite structure with a range of orientation angles is presented.