Characterization and finite element modeling of coupled properties during polymer composites forming processes

The ability to predict wrinkles and prevent them during the forming process is highly desirable for process design in industrial environments. This ability to predict requires a multifaceted characterization of textile reinforced composites, material properties and implementation in forming simulations. The deformation mechanisms during the actual forming process are coupled, implying that the coupled shear, tension, friction, and bending modes of prepreg ply could lead to a change in the effective material properties. Consequently, this paper studies the coupling effect of shear and ply-ply friction on bending properties during the forming process. A series of experimental approaches for providing the required information on those combined properties is presented. Moreover, a systematic approach for a finite element (FE) prediction of bending behavior, considering such coupling effect, is developed. The combination of numerical results and experimental observations demonstrates the significance of considering these coupled deformation modes to yield meaningful outcomes in future forming simulations. Simultaneously, this study provides fundamental knowledge on how the bending stiffness of uncured prepreg is influenced by the sample's shear angle and the friction between plies.