Bridging the macro to the mesoscale: Developing tensorial damage models for anisotropic materials
Fluids and Materials Seminar
16th July 2018, 2:00 pm – 3:00 pm
Two of the most challenging problems which arise in continuum damage mechanics are firstly the selection of variables to describe the internal damage and secondly the difficulty in modelling materials with significant initial anisotropy such as composites or sedimentary rocks. A severe limitation imposed by many continuum damage mechanics models is the assumption of initial isotropy in many anisotropic damage models. This may place unrealistic assumptions about the material being modelled or restrict the application of continuum damage mechanics to materials without significant anisotropy. It remains a challenge to use continuum damage mechanics to model common rocks and materials with significant initial anisotropy, for example sedimentary rocks or brittle composite materials. Many theories have been proposed and various types of damage variables ranging from scalar to vector to tensor quantities have been used.
In this talk we consider anisotropic damage and the most general form for damage by using a fourth order tensor for the damage variables. We demonstrate how experimentally measured quantities can be related to the internal tensorial damage variables. We have developed methods to identify the directionality and magnitude of the introduced damage using experimental ultrasonic measurements of damaged elastic moduli. We apply this analysis to experiments of initially isotropic or anisotropic solids becoming anisotropic (with a change of symmetry class or magnitude of anisotropy) under loading. This analysis provides a robust way to validate and advance models of general anisotropic damage evolution based on continuum damage mechanics. This represents a significant advance in the development of anisotropic damage models based on continuum damage mechanics which until now have not been able to be experimentally verified and tested.