A 3-D ellipsoidal flaw model for brittle fracture in compression

Engineering materials are rarely free of flaws. Mode I cracking from pre-ex isting flaws is the major cause of the brittle fracture in compression of m aterials such as concrete and rock. A 3-D ellipsoidal flaw model is used to show the significant influence of flaw geometry on crack initiation in uni form uniaxial, biaxial and triaxial compression. The model shows that the g overning criterion for crack initiation may change from energy to stress wi th increasing crack size, and that for voids of similar size a spherical vo id is the most critical shape for crack initiation. The model thus provides a basis for a better understanding of both the phenomenon and the mechanis m of brittle fracture in compression. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.