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

Abstract

The need for accurate material models to simulate the deformation, damage, and failure of polymer matrix composites under impact conditions is becoming critical as these materials are gaining increased use in the aerospace and automotive communities. To attempt to improve the predictive capability of composite impact simulations, a next generation material model is being developed for incorporation within the commercial transient dynamic finite element code LS-DYNA. The material model, which incorporates plasticity, damage, and failure, utilizes experimentally based tabulated input to define the evolution of plasticity and damage and the initiation of failure as opposed to specifying discrete input parameters such as modulus and strength. The plasticity portion of the composite constitutive model is based on an extension of the Tsai-Wu composite failure model into a generalized yield function. For the damage model, a strain equivalent formulation is used to allow for the uncoupling of the deformation and damage analyses. For the failure model, a tabulated approach is utilized in which a stress- or strain-based invariant is defined as a function of the location of the current stress state in stress space to define the initiation of failure. Failure surfaces can be defined with any arbitrary shape, unlike traditional failure models where the mathematical functions used to define the failure surface impose a specific shape on the failure surface. In the current paper, the complete development of the failure model is described and the generation of a tabulated failure surface for a representative composite material is discussed.

Improving failure sub-models in an orthotropic plasticity-based material model

“…Note that the failure angle is expressed in terms of r 22 and r 12 as in unidirectional composites, the stress in the 1-direction, r 11 , is usually of a magnitude higher than r 22 and r 12 . Using r 11 in the computation of the failure angle 8 instead of using r 12 may make the points on the failure surface agglomerate as illustrated in Figure 3 where most of the data points are concentrated at h IP values of À1808, 08 and 1808. This result is not desirable since the interpolation between unequally spaced points may yield inaccurate equivalent failure strain values.…”

“…In this paper, some of the shortcomings of PFC are discussed and modifications to the theory and implementation are introduced especially with respect to post-peak/post-failure simulation so that a stable post-peak behavior can be achieved. In addition, a (new) second failure model, the Generalized Tabulated Failure Criterion (GTFC) 8 as implemented in MAT_213, is discussed. This model is built with user input that define the two modes of failure -in-plane and out-of-plane modes.…”

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

“…While several failure theories (principal strain, Tsai-Wu, Generalized Tabulated Failure Criterion, 35 Puck) are supported in MAT213, only PFT 14,15,36 is discussed in this article. Puck's failure model is an action-plane-based model for transversely isotropic UD fiber-reinforced composite lamina.…”