Abstract: The effective elastic moduli and damage of materials containing orthogonal inclusions or defects are investigated in this paper. Based on Eshelby-Mori-Tanaka's theory, a simplified formula of the effective moduli for a multiphase, anisotropic composite is developed. The explicit expressions of the effective elastic compliance tensor of an orthotropic composite reinforced by three mutually perpendicular families of ellipsoidal inclusions are then derived. These expressions contain the micro-structural parame...