Mechanical behavior of low density polymeric foams under multiple loading and unloading

Abstract

In this thesis, mechanical behavior and energy absorption characteristics of low density polymeric foams under multiple loading and unloading are investigated for uniaxial and hydrostatic compression, uniaxial tension, simple shear, and cylinder and block indentation. Constitutive models and energy absorption diagrams available in literature for uniaxial compressive loading are reviewed. A new phenomenological constitutive model for accurate calculation of load, deformation, and absorbed energy is proposed for multiple loading and unloading. Results of the available and the new models are compared to those of experiments for expanded polystyrene (EPS) and polyethylene (PE) foams. A design procedure for multiple compressive loading and unloading is presented. A drop test rig for measuring uniaxial compressive behavior of foams at high loading speed and a hydrostatic compression test setup to study the mechanical behavior of foams under multiple hydrostatic loading and unloading are built. Tools to be used with Zwick Z020 universal tensile testing machine are prepared for uniaxial tension, simple shear, and cylinder and block indentation tests. Stressstrain results are presented for EPS and PE foam specimens. Finite element simulations of EPS and PE foam specimens under multiple loading and unloading for uniaxial and hydrostatic compression, uniaxial tension, simple shear, and cylinder and block indentation are performed using Abaqus finite element package for volumetric and isotropic hardening. The results of finite element simulations are compared to those of experiments.