Thermoforming Simulation of Organosheet Materials

For the construction of lightweight components in the automotive and aerospace industries, continuous fiber reinforced materials (or so-called organo sheets), which can be thermoformed in short cycle times, are becoming more frequently used. Continuous fiber preforms can also be individually constructed in such a way that the optimal fiber orientation results after the forming process, achieving the necessary structural properties while saving material. During the forming process, shearing of the reinforcement structure in the organo sheet results in a local adjustment of the fiber orientation. The resulting fiber orientation can be influenced by positioning the blank and selecting suitable retention systems (e.g. retention pins or spring systems). In order to avoid a costly experimental trial-and-error process, it makes sense to model the process of thermoforming via simulation. From a simulation point of view, it is a great challenge to model the shaping of a custom constructed organo sheet material. Existing continuum mechanical models are unfortunately not yet able to accurately represent the deformation of ordinary organo sheet materials, and not flexible enough to deal with the individual characteristics of an application-oriented semi-finished product. In this project, the FEM software LS-DYNA® is used to model organo sheets by means of a modular principle consisting of beam and shell elements. By suitably selecting the contact and boundary conditions, as well as the material models, it is possible to separate the in-plane and out-of-plane properties of the multilayer system and to consider the individual material properties of the yarns. The outcome of the simulation is information about the resulting fiber orientation and distribution, the elastic and plastic stretching of the yarns and temperature distribution, as well as any resulting defects such as wrinkling, delamination or tearing of the preform sheet.

The aim of this project is to predict the forming behaviorof continuous fiber reinforced thermoplastics in the thermoforming process and to make statements about resulting fiber orientation, final contour, and wrinkling.