Validation of shape change predictions for stamp forming of carbon fiber thermoplastic composite laminates

Stamp forming with thermoplastic composites provides high-rate production of structural components. A series of physical phenomena develops concurrently as a blank of fiber reinforced thermoplastic is consolidated, reheated, stamp formed, and cooled within the tool, and released from the tool in the stamp forming process. Transient phenomena contributing to the residual deformation of continuous fiber-reinforced thermoplastics processed by stamp forming were described and characterized in this work. The transient phenomena considered included anisotropic heat transfer, anisotropic shrinkage, thermoviscoelastic behavior, and semi-crystalline polymer melting and crystallization kinetics. A comprehensive experimental characterization of the material properties required to model the phenomena involved in shape change is summarized in this work. The digital twin of this process, termed FORM3D and based on the finite element solvers ABAQUS and ANIFORM, has been constructed with the goal of describing the important phenomena in thermoplastic stamp forming, particularly to predict shape change. Shape change predictions made with FORM3D were validated against experimental measurements for a double curvature geometry made with a quasi-isotropic stacking sequence. The double curvature geometry developed both spring-in and spring-out deformations in the minor and major radii of curvature, respectively. FORM3D predictions were in excellent agreement with the experiments in both magnitude and distribution of the deformation. The same correlation was observed for three repetitions of the stamp formed experiment carried out in this work.