Hyperelastic strain measurements and constitutive parameters identification of 3D printed soft polymers by image processing

To realize the full potential of 3D Printing technology in the design of materials and structures, it is indispensable to characterize and predict the mechanical response of 3D Printing materials to external stimuli. This study is focused on hyperelastic strain measurements and constitutive parameters identification of 3D printed soft polymers undergoing uniaxial deformation. A simple method using an optical camera in conjunction with an image processing tool is proposed to accurately measure the average strain experienced by rubbery polymers during a tensile test. The potential of the method is demonstrated through tensile tests of 3D printed soft polymer by accurately determining the stress–strain response and the Poisson's ratio without using extensometers. Influence of printing direction on the anisotropic behavior of 3D printed polymer is investigated by applying the proposed test method to specimens printed in two different directions. The Neo-Hookean constitutive parameters of the soft polymer are determined from the experimentally obtained stress–strain data. The method is validated and a technique to conveniently determine associated error-margins is presented. Moreover, finite element analysis (FEA) of the soft polymer is performed to show that the constitutive parameters determined can predict the mechanical response of the tested polymer accurately if used in commercial FEA packages.