Finite element analysis of thermoplastic composite plates in forming temperature

An implicit mixed finite element formulation is developed based on the plate theory to analyze thermoforming process of thermoplastic plates reinforced with unidirectional continuous fibers. The plate thickness variations and the rotation of transverse planes are considered using Reissner-Mindlin approximation in order to model the predominated deformation mechanisms of the transverse fiber flow and intra-ply shear in these highly kinematical constrained materials. The kinematical constrains due to material incompressibility and fiber inextensibility are considered in the plate theory formulations and taken into account in the finite element method by introducing penalty numbers. A new analytical approach is developed to analyze the forming procedure of a composite plate on the single curvature geometry to compare the numerical results with analytical approach. The forming of thermoplastic plates to the hemispherical configuration is also studied by means of finite element technique. The geometry of panel in blank holder region is estimated considering both the effect of blank holder normal pressure and the viscous layers in die contact surfaces. The finite element results show that the geometry and defects due to wrinkling during the shaping procedure may be conventionally predicted using the derived formulations.