Verification and Validation of a Three-Dimensional Orthotropic Plasticity Constitutive Model Using a Unidirectional Composite

Abstract

Abstract:A three-dimensional constitutive model has been developed for modeling orthotropic composites subject to impact loads. It has three distinct components-a deformation model involving elastic and plastic deformations; a damage model; and a failure model. The model is driven by tabular data that is generated either using laboratory tests or via virtual testing. A unidirectional composite-T800/F3900, commonly used in the aerospace industry, is used in the verification and validation tests. While the failure model is under development, these tests indicate that the implementation of the deformation and damage models in a commercial finite element program, LS-DYNA, is efficient, robust and accurate.

Implementation of a tabulated failure model into a generalized composite material model

“…The details of this “convex correction” have been extensively discussed in earlier studies. 2,21,22 This parameter adjustment results in a stiffer “modified” off-axis response than is actually observed in the experiments. The modified stress interaction terms were also used to generate the failure surfaces used for these analyses, leading to artificially inflated failure stresses under multi-axial loading conditions.…”

“…20 The deformation and damage response of this composite have been extensively simulated using the developed material model in earlier efforts, which are described, along with the various input parameters required for the code, in several references. 21–23…”

“…To construct the required failure surfaces (and the modified radius versus angle plots described earlier in this paper), the normal and shear failure stresses measured from the various characterization tests described in earlier studies 21–23 were used to construct nominal failure surfaces using the Tsai-Wu failure criteria. These surfaces were then converted into the required radius versus angle plots using the procedures described above.…”

Implementing deformation, damage, and failure in an orthotropic plastic material model

“…MAT213 has three sub-models with the primary sub-model for deformation that can work in conjunction with the submodels for damage and for failure, at the request of the user. Details of the deformation [28][29][30][31] and damage 32,33 sub-models can be found in our earlier publications. The salient features are presented here for completeness.…”

“…Third, the final three terms, H 44 , H 55 , and H 66 , are computed by fitting the shear curves with the master curve in the effective stress versus plastic strain space. 30 Assuming strain compatibility in the true (damaged) and effective (undamaged) stress spaces makes it possible to decouple damage and plasticity. This allows the deformation model, governed by a plasticity algorithm, to account for both elastic and inelastic deformations while the reduction of elastic stiffness in the PMDs and principal material planes is handled by the damage model.…”