Experimental and finite element simulation of natural rubber foams using real 3D structures

Natural rubber (NR) foams were prepared via a one-step foaming process, the effect of density and morphology on micro-level and macro-level mechanical properties was studied. In particular, experimental data were used to validate different numerical models based on actual three-dimensional (3D) foam structures built using a combination of 2D scanning electron microscopy (SEM) images. Then the uniaxial compression behavior was simulated at two levels (micro-scale and macro-scale) with finite element methods (FEM). The FEM results were finally compared with experimental data and different hyper-elastic models. SEM images showed that increasing the relative foam density from 0.3 to 0.5 led to a 55% decrease in cell size and a 1000% increase in cell number. The real 3D structures showed that foams with higher density have a more homogenous structure with lower structural defects or cell connections. The results also revealed that FEM at the macroscopic level is in good agreement with experimental results, especially for high density foams. On the other hand, FEM at the microscopic level showed that the maximum stress concentration and related micro-strain substantially decreased with increasing foam density.