EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Short fiber reinforced plastics are important materials in many fields of lightweight construction, especially in transport application. Their advantage is that they can be processed in a rather economic manner by the standard methods for processing of polymeric materials. Therefore, they are suitable for all kinds of industrial scale production. Nevertheless, a major challenge is the lack of validated precise material models for the numerical prediction of their mechanical response considering their complex fatigue damage and degradation behavior.

The present contribution is concerned with the definition of a continuum damage mechanics model for this class of materials. The model is based on the assumption of anisotropic linear elasticity in conjunction with a Tsai-Hill type failure approach. In contrast to the standard Tsai Hill approach assuming failure once the failure envelope is reached by the stress or strain state, a continuum damage formulation is proposed, using the distance of the respective stress point to the failure envelope as the damage driving quantity. Employing the concept of microplasticity, a damage evolution equation for fatigue damage development is derived. The model is implemented as a user-defined subroutine into a commercial finite element program.

The numerical development is complemented by an experimental study on fatigue of short fiber composites using an injection molded glass fiber reinforced PA66 as a reference material. The material is characterized in different directions throughout the relevant temperature range for automotive or similar transport applications. The experimental results are employed for both, material parameter identification and validation of the mathematical formulation of the material model.