X-ray computed tomography-based modeling of polymeric foams : the effect of finite element model size on the large strain response

A hybrid numerical-experimental approach is used to characterize the macroscopicmechanical behavior of polymeric foams. The method is based on microstructural characterizationof foams with X-ray computed tomography (CT) and conversion of the datato finite element (FE) models. 2D models are created from a 3D close-celled foam andsubjected to compression loads. Since the large strain regime is explored, contact betweenelements is incorporated. It is shown that for calculating the effective Young’s modulus,a model consisting of at least 11^2-12^2 cells in the model should be used, whereas for thelarge strain regime 12^2-14^2 cells in the model are needed. Discretization had a significantinfluence on the results, where relatively coarse elements caused loss of connectivity in thecell walls and thickening of the cell walls. It is shown that at least 3-4 elements should betaken over the thickness of the cell walls for these structures. Finally, a good qualitativeagreement is observed between the deformations found with the FE models and in-situcompression experiments of an open-celled foam during X-ray CT.