A variational constitutive model for elastic-viscoplastic materials subjected to plastic damage and hydrolytic degradation

Paulo Bastos de Castro¹; Thiago André Carniel¹; Jan-Michel Colombo Farias¹; Eduardo Alberto Fancello¹

¹ Universidade Federal de Santa Catarina

doi:10.20906/CPS/CILAMCE2015-0879

Resumo

In this article, a variational constitutive model is presented in order to propose a suitable description for the elastic-viscoplastic behavior of materials subjected to coupled plastic-hydrolytic damage. Such characteristics are usually associated with polymers, namely bioabsorbable ones, which are materials with distinguished properties among those currently used in medical applications. A remarkable feature of bioabsorbable materials is related to hydrolytic degradation. The study and modeling of such a phenomenon is far to be completely understood, being open to investigation and development of new constitutive models. Aiming at the formulation of a constitutive model, an approach based on variational principles may present attractive characteristics like its mathematical structure and its natural association with the description of physical problems. Thus, in this work, the authors present a model based on the framework of the so-called variational constitutive updates in which incremental stress-strain relations can be derived from a pseudo-elastic strain-energy density. The general structure of this method is outlined and then the model formulation is described. Preliminary results obtained by means of standard tests show the viability and the potential of this model to predict the typical mechanical behavior of bioabsorbable materials. Advantages, difficulties and proposals for future work are then discussed.

Palavras-chave: variational constitutive updates; viscoplasticity; plastic-hydrolytic damage; finite elements