3.1.2.2. Coefficients of Thermal Expansion

3.1.2.2.1. Homogenization of Unidirectional Composites

Material Designer offers two methods for the analytical homogenization of the coefficients of thermal expansion of a unidirectional composite, namely Schapery and Mori-Tanaka methods.

Schapery's Method

Consider a unidirectional composite with inclusions transversely isotropic in the x direction. In the Schapery's method [Schapery, (1968)], the thermal expansion coefficient in the longitudinal direction is computed as

(3–8)

and the thermal expansion coefficient in the transverse directions is computed as

(3–9)

Here the Young moduli and Poisson ratios of the matrix and fiber constituents are denoted by E and ν.

Note that in the Schapery's method inclusions are modeled as infinitely long cylinders.

Mori-Tanaka Method

Following the formalism in [Lu P., (2013)], the thermal expansion coefficients predicted by the Mori-Tanaka method read

(3–10)

where

(3–11)

and is the Eshelby tensor introduced in the section above, Homogenization of Unidirectional Composites.

3.1.2.2.2. Orientations Averaging

In case of a composite with misaligned fiber orientations, the orientation averaged thermal expansion coefficients are given by [Camacho et al., (1990)]

(3–12)

where

  • the constants R 1 and R 2 depend on the stiffness tensor and thermal expansion coefficients of the unidirectional composite

  • and denote the second order orientation and identity tensors in Voigt notation, respectively;

  • the orientations averaged stiffness tensor is computed as described in the section above, Orientations Averaging.