Modeling of hyperelasticity in polyamide 12 produced by selective laser sintering

Polyamide 12 (PA12) is a core material in many 3D-printing techniques, including selective laser sintering (SLS), and its mechanical characterization helps to better understand behaviors of additively manufactured parts made from this polymer. In this paper, the elastic response of SLS-produced PA12 is shown to be nonlinear. Standard test samples with different orientations with regard to the scanning direction are 3D-printed with the use of PA2200 powder, and their elastic response is investigated under uniaxial tension at different strain rates. Mooney-Rivlin hyperelastic models are proposed to address the observed nonlinear elasticity of the samples. Cyclic response of the specimens is shown to be stabilized after a few transient cycles so the material parameters are determined for trained samples after shakedown in their response. The obtained parameters are found to depend on the loading speed; thus, a rate-dependent hyperelastic constitutive model is presented for PA12 produced by selective laser sintering. This model is validated by comparing its numerical prediction with empirical responses under simple tension tests.