Abstract: According to the distribution feature of inherent defect in ceramic composite, defect is simplified as non-stiffness ellipsoidal inclusion in transverse isotropic matrix, and relevant microstructure model is established. Cell’s equivalent stiffness is calculated based on improved interact direct derivative (IDD) estimate, assuming cells distributed randomly in ceramic, the equivalent stiffness of rod ceramic composite is obtained with the help of volume averaging approach, and the effect of inherent defect in transverse isotropic matrix is analyzed, and the effect of anisotropic property of matrix discussed either. Result indicate that effective elastic constants is reduced obviously by inherent defect and it is sensitive to defect fraction as the fraction is low; shape of defect has important influence to effective elastic constants; for a lamellar defect, thick of defect has significant influence especially while width has little influence; and the weaken effect is more obviously as the defect plane perpendicular to elastic axis of greater modulus, it is necessary to take anisotropic property of matrix into consideration.

Key words: Equivalent stiffness, Inherent defect, Interact direct derivative estimate, Transverse isotropy