Damage characterization of composites to support an orthotropic plasticity material model

Abstract

The focus of this paper is the development of test procedures to characterize the damage-related behavior of a unidirectional composite at room temperature and quasi-static loading conditions and use the resulting data in the damage sub-model of a newly developed material model for orthotropic composites. This material model has three distinct sub-models to handle elastic and inelastic deformations, damage, and failure. A unidirectional composite—T800/F3900 that was the focus of our previous work, is used to illustrate how the deformation and damage-related experimental procedures are developed and used. The implementation of the damage sub-model into LS-DYNA is verified using single-element tests and validated using impact tests. Results show that the implementation yields reasonably accurate predictions of impact behavior involving deformation and damage in structural composites.

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

“…Details of the experimental procedures including test equipment, specimen preparation, and data reduction procedures can be found in our earlier publications. 31,33,42 As expected, in each of the experiments, the failure occurred along the axis of the fibers (magnified images are shown in Figure 10(a), (c) and (e) for 10 , 15 , and 30 off-axis test, respectively). Figure 8(c) shows the longitudinal strain field just prior to failure.…”

“…The verification and validation tests were carried out using a UD T800/F3900 composite. 40 The strength properties of the composite obtained from the experiments 31,33 and used in the failure model are listed in Table 2. It should be noted that T 33 and 13 in Table 2 are not used in the failure model but are used in the discussion of the results.…”

“…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.…”

“…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. 33 The relationship between the true stress space and the effective stress space is captured in the damage sub-model as…”

“…the direction in which damage is being induced. 33 An example is shown in equation ( 5) where the damage parameters are updated when relating the true stress 22 to the effective stress eff 22 C plays in the relationship. It should be noted that the model accounts for possible differences between tensile and compressive behavior.…”