## Chapter 8: Recommendations

Autodyn contains many options for the modelling of composite materials. These options are described in detail in this report. However, in using these complex models the problems are often two fold; knowing which options/models to use and how/where to obtain the required material properties.

In Orthotropic Constitutive Models, the various models are described in detail. It is important to take a pragmatic view of them rather than simply selecting the most complex. For example, if the application being modelled is only subjected to a relatively low speed impact then using an orthotropic material model with a linear equation of state is sufficient. In this case relatively simple experiments are required to obtain the directional strength properties or manufactures material data may be sufficient.

If the application is at ballistic velocities or higher then shock effects are most likely to be important and using a nonlinear equation of state is recommended. However, this requires additional experiments as described in Equation of State Properties: Inverse Flyer Plate Tests, in addition to the directional strength properties.

Whether or not the hardening option is required depends only upon the material being modeled. Some materials, such as carbon-epoxy composites have been observed to exhibit a very linear behavior [14]. Other composite materials, like Kevlar-epoxy, are highly nonlinear and significant hardening is observed [2]. In this case it is imperative to have the stress-strain data obtained from the experiments of Directional Strength Properties so that the plasticity parameters can be calculated as outlined in Plasticity Parameters. Since the tension tests are usually performed to ultimate failure, this experimental data will also indicate whether or not softening is significant.

Release 18.2 - © ANSYS, Inc. All rights reserved.