Characterization of deformation mechanism of open cell polymeric foams based on in situ X-ray computed tomography compression tests and image-based finite element method

Open cell polyurethane foams, with their unique interconnected cell structure, have a wide range of properties and are suitable for many applications exploiting their microporous structure. Their three-dimensional spatial arrangement allows flow of liquids and solids through the material; they can be used as sound absorbing materials, catalyst carriers, and drug delivery materials. In this paper, in-situ X-ray computed tomography (CT) was used to characterize the deformational behavior and the related changes of an open cell polyurethane (PU) foam microstructure during compression. The CT images of the microstructure were taken at different strain levels almost up to incipient densification. These images allowed to reconstruct the geometry of the foam and to create 3D finite element models by applying level-set method (LSM) and Delaunay Triangulation (DT) algorithms. The foam morphological features at different strain levels were identified, with a quantitative evaluation of several geometric parameters including strut length, strut thickness and strut orientation. Afterwards, finite element analysis was performed using these models and compared with experimental tests to describe active deformation mechanisms and microstructural changes during compression. A good agreement was observed between simulation and experiments which verified the effectiveness of the proposed image-based finite element analysis method. Qualitative and quantitative analysis of simulation and experimental data provided an insightful description of the microstructure evolution of the foams under compression.