A phenomenological approach to decompose geometrical and constitutive aspects of failure induced anisotropy

Classic anisotropic material descriptions require very sophisticated calibr ation techniques to uniquely identify the constitutive parameters. The pres ented approach identifies the fracture induced anisotropy as an evolution o f individual, geometrically oriented failure mechanisms. Thus, only the cal ibration of a generic fracture mechanism has to be performed - and the evol ving anisotropy is an automatic result of the calculation. The possibility for Mode I fracture and the transition to Mode II failure via Mixed Mode fr acture is incorporated in the framework, including the proper energetic arg uments. Multiple, intersecting fracture processes are accounted for and the ir individual contribution to the overall degradation and the evolution of the specific anisotropic softening behaviour is demonstrated. Comparisons w ith classic isotropic formulations clearly point out the range of applicabi lity and the limitations of the proposed model in the analysis of the aniso tropic residual strength capacity of partially damaged structures. (C) 1998 Elsevier Science B.V. All rights reserved.