Examining the effect of dilation angle on the flexural response of amorphous polymers using finite element analysis

Purpose The primary objective of this study was to evaluate the influence of the dilation angle on the flexural response of amorphous polymers through finite element analyses employing the linear Drucker-Prager plasticity model, alongside presenting a rigorous and systematic procedure for determining the constitutive model parameters. Design/methodology/approach The parameters of the linear Drucker-Prager material model, including the friction angle, were initially determined based on tensile and compressive test data obtained at identical strain rates for 3D-printed amorphous Acrylonitrile-Styrene-Acrylate (ASA). Subsequently, three-point bending simulations were performed in the Abaqus/Standard software, initially assuming the friction angle equal to the dilation angle, following the associated flow rule. The simulations were then repeated with dilation angles greater and smaller than the friction angle, following the non-associated flow rule, to rigorously assess the impact of the dilation angle on the flexural response of ASA. Findings The simulation results revealed that while the dilation angle does not affect the initial bending stiffness, it significantly enhances the post-yield stiffness of ASA. Comparative finite element analyses demonstrated that employing a non-associated flow rule with dilation angles smaller than the friction angle provides more accurate peak load predictions compared to cases where the dilation angle exceeds the friction angle, which resulted in substantially larger prediction errors. These findings suggested that the associated flow rule where the dilation angle equals the friction angle may be conservatively adopted for reliable modeling in the absence of sufficient experimental data to determine the dilation angle. Originality/value The originality of this study is to address critical knowledge gaps by quantifying dilation angle effects on amorphous polymers' flexural response, presenting a clear procedure to determine linear Drucker-Prager constitutive parameters, and resolving flow rule selection challenges.