Multiscale description of polymeric foam behavior : a new approach based on discrete element modeling
Résumé
The mechanical behavior of polymeric foams depends on several parameters, such as temperature, material density, and strain rate. The studied foams are multiscale materials; agglomerated beads (bead scale is millimetric) are composed of microscopic closed cells (a few tens of microns). The response of the material to dynamic loading consists of three regions: an elastic phase, a plastic phase, and densification. The first part of this work has been the identification of the behavior of these multiscale foams in terms of density and strain rate. Some results are presented in this paper. From these first dynamic results, the second step has been the observation and the analysis of the physical phenomena initiated during the yield plateau. Buckling of the bead and cell wall and strong damage localization were studied with several devices and techniques such as high-speed camera, SEM, and microtomography. The final objective is the development of a model adapted to the multiscale structure of the foam. The first step of this numerical approach consists in the modeling of the microstructure. Due to the microscopic discrete aspect of the foam, a Discrete Element Model has been developed to study the relationship between microscopic properties and the macroscopic behavior of foam.