Density, Microstructure, and Strain-Rate Effects on the Compressive Response of Polyurethane Foams

A better understanding of the effect of density, microstructure, and strain rate on the mechanical response of polymeric foam materials is needed to improve their performance. The objective of this paper is to study the combined influence of density, microstructure, and strain-rate on the compressive stress-strain response of polymeric foams. Microstructural morphological parameters (e.g., pores sizes and wall thicknesses) have been quantified using Micro X-ray tomography and MATLAB-based techniques. Polymeric foam samples were examined under uniaxial compression loading at quasistatic (0.001 to $$0.1 s^{-1}$$ ), intermediate (1 to $$250 s^{-1}$$ ), and dynamic strain rates (3200 to $$5700 s^{-1}$$ ). All experiments were coupled with high speed cameras to measure strain using 2D digital image correlation, and to visualize deformation. The variation of the mechanical properties across alldensities (e.g., elastic modulus and collapse stress) are found to behave in a power law fashion with respect to strain rate. A comprehensive data set across a varied range of densities and strain rates, especially intermediate strain rates, is lacking in previous research, and generalized phenomenological relationships developed in this paper to predict combined influences of density, microstructure, and strain-rate over varied range of materials are important contributions of this work. The results showed that the power-law relationships act as a good predictor for the prediction of mechanical properties and elastic response, and as an indicator for damage mechanisms in these polymeric foams.