Hyperelastic Modelling Approaches to Polymeric Foams

Gargı, Yasin
In this study, we present a comprehensive investigation into the mechanical behaviour of closed-cell EPDM (ethylene propylene diene monomer) foams through material modelling and experimental validation. Our research primarily focuses on identifying the parameters of the Ogden compressible foam and Blatz-Ko material models, which are employed to accurately represent the mechanical behaviour of the foam under various loading conditions. Three distinct foam densities were chosen for assessment: EPDM100, EPDM130, and EPDM180. Uniaxial tension and confined compression experiments were conducted to identify the mechanical behaviour of the materials. The Ogden compressible foam 1st order and 3rd order and the Blatz-Ko material models were employed to capture the complex mechanical behaviour of the closed-cell EPDM foam. Material parameters for each model were identified by simultaneously fitting the experimental data of uniaxial tension and confined compression experiments. The optimisation process was carried out using the MATLAB "fmincon" nonlinear optimisation function, resulting in parameter sets that best described the foam's response under these loading scenarios. We employed the parameters identified from our MATLAB code to simulate uniaxial tension and confined compression using unit elements within ANSYS. The results exhibited an exact correspondence with our MATLAB code outputs. Consequently, this process validated our MATLAB code's accuracy and reliability. A non-homogeneous uniaxial compression experiment was performed to validate the results of the material parameters obtained through the simultaneous utilisation of uniaxial tension and confined compression experiments under different deformation conditions. Finite element analysis was conducted under conditions precisely replicated from the non-homogeneous uniaxial compression experiment. Subsequently, a comparison was performed between the force-displacement curves obtained from the analyses and experiments, allowing for a comprehensive examination of the results.
Citation Formats
Y. Gargı, “Hyperelastic Modelling Approaches to Polymeric Foams,” M.S. - Master of Science, Middle East Technical University, 2023.