EFFECTS OF ORIENTATION DISTRIBUTION OF PARTICLES OR FIBERS ON ELASTIC REINFORCEMENT OF COMPOSITES

Elastic reinforcement theories for particle-filled composites and for fiber composites are reviewed, and compared with the extended equivalent inclusion method proposed by the authors. The equivalent inclusion method formulated by Eshelby can be applied uniformly to the fillers including spheres, disks and fibers by approximating each shape as an ellipsoid. Although the matrix must be isotropic, the fillers may be anisotropic. The applicability of the equivalent inclusion method, however, is limited to the composites in which fillers are oriented uniaxially. The authors have extended the method to be applicable to the composite in which fillers are of arbitrary orientation distribution. The extended equivalent inclusion method predicts the elastic moduli of composites rationally. However, it exhibits some inconsistencies in the prediction of the thermal expansion coefficients in the case where the fillers are anisotropic and of orientation distribution.