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Forming simulation of textile composites using LS-DYNA

The primary focus of this paper is on FE modeling and simulations performed to capture the material behaviors during a textile preform and a thermoplastic pre-preg forming manufacturing using LS-DYNA. Although an out-of-plane bending stiffness of textile reinforcement is often ignored as it is very low compared to in-plane stiffness, more accurate simulation, especially prediction of wrinkles, is achievable by considering out-of-plane bending stiffness in forming simulation. We propose a hybrid model which consists of a membrane and shells that can describe out-of-plane bending stiffness which is independent from in-plane behavior. In order to extend the textile reinforcement model to a thermoplastic pre-preg model for thermoforming simulation, temperature dependent stress contribution of thermoplastic is added to the textile reinforcement by applying Reuss model which can take the volume fraction of fiber into account. At first, hemispherical forming simulations of textile reinforcement are conducted under the two different forming conditions, with and without blank-holder. Wrinkle shapes predicted by the proposed model are verified by comparing with those of meso-scale model as reference in order to showcase the capability of the method. The results using this proposed model are in good agreement with the meso-scale model results in both forming conditions. As the next step, a model of thermoplastic pre-preg which can consider the temperature dependent in-plane and out-of-plane properties is constructed based on the results of three-point bending and bias-extension experiments which are conducted in the range of the process temperature. S-rail thermoforming simulations are performed and compared to experimental results. Simulated outline and shear angle are in good agreement with experimental results. Moreover, sensitivity study analysis suggests that the effect of the temperature plays a dominant role in deformation during thermoforming processes.