Development of Simplified Methods to Characterize Plasticity Parameters for LS-DYNA MAT213

Abstract

A material model which incorporates several key capabilities which have been identified as lacking in currently available composite material models has been developed. The material model utilizes experimentally based tabulated input to define the evolution of plasticity, damage, and failure as opposed to specifying discrete input parameters (such as modulus and strength). It has been implemented into the commercially available transient dynamic finite element code LS-DYNA® as MAT 213. The model can simulate the nonlinear deformation, damage and failure that take place in a composite under dynamic loading conditions. One challenge that has been encountered by users of MAT 213 is that several of the parameters in the orthotropic plasticity model are extremely difficult to characterize experimentally or data may not be available to characterize them. To simplify this process, a toolset and methodology are being developed which can be implemented as a stand-alone in MATLAB® application. A key part of this toolset will utilize a simplified version of the orthotropic plasticity model. Specifically, the orthotropic plasticity model utilized in MAT 213 has been simplified to simulate the stress-strain response of a composite ply with an arbitrary fiber orientation subjected to uniaxial loading or the shear response of a composite ply subject to pure shear loading. These simplified models will allow a user to simultaneously simulate the longitudinal and transverse tensile and compressive stress-strain responses, the shear stress-shear strain responses, and the off-axis tensile (or compressive) stress-strain responses of a composite ply in a highly efficient manner. By using this toolset, particularly when combined with a suitable optimizer, a user can quickly determine the required plasticity model parameters required for a MAT 213 analysis.⋅