Application of the variational asymptotic method for unit cell homogenization in the prediction of mechanical properties for microcellular plastics

This study presents the application of the micromechanical variational asymptotic method for unit cell homogenization (VAMUCH) with a three-dimensional unit cell structure and a coupled, macroscaled finite element analysis for analyzing and predicting the effective elastic properties of microcellular injection-molded plastics. A series of injection-molded plastic samples, which include polylactic acid, low-density polyethylene, polypropylene, polystyrene, and thermoplastic polyurethane, with microcellular-foamed structures were produced and their mechanical properties were compared with predicted values. The results showed that, for most material samples, the numerical prediction was in fairly good agreement with experimental results, which suggests the applicability and reliability of VAMUCH in analyzing the mechanical properties of porous materials. Other findings were that the material characteristics (e.g. brittleness and ductility) influenced the predicted results and that VAMUCH prediction could be improved when the unit cell structure was more representative of the real composition.