On an orthotropic model for progressive degradation

Progressive degradation in orthotropic materials is modelled from a smear-out point of view, and physical measurable quantities are used as the describing parameters. Evolution of stiffness and evolution of strength are kept uncoupled. For plane problems the stiffness evolution is modelled by the longitudinal moduli (in orthogonal directions), the shear modulus and the Poisson's ratio. The relative evolutions of these moduli are controlled by a principle of maximum energy dissipation.

Strength evolution is modelled by four normal strength parameters (two orthogonal directions with different values in tension and compression) and one shear strength. A simple principle of minimum necessary change of a strength surface avoids the practical problem of evolution for a multiplicity of strength parameters. A number of numerical examples are shown. The suggested model is presented in its most simple form and many extensions/modifications are possible. These should be based on physical experiments. (C) 1999 Elsevier Science Ltd. All rights reserved.