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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, 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. [ABSTRACT FROM AUTHOR]

This work focuses on the evolution of interlayer fracture toughness properties of fiber-reinforced, semi-crystalline polymers in the extrusion deposition additive manufacturing (EDAM) process. Further, this work bridges the gap between the additive process conditions (time-temperature history) and the effective layer-to-layer fracture properties developed within a printed component. This is the first step to predict delamination that can occur during printing, during cooling to room temperature after printing, and during service performance of an additively manufactured geometry. A phenomenological model is developed for fusion bonding of semi-crystalline polymer matrix composites by coupling the interdiffusion of polymer chains with the evolution of polymer crystallinity. While the interdiffusion is captured by reptation theory of polymer dynamics, the evolution of crystallinity is modeled by phenomenological crystallization kinetics and crystal melting dynamics. Further, a methodology is developed to determine the critical strain energy release rate, G I C of the interlayer interface and experiments are conducted utilizing the double cantilever beam fracture test geometry. Predictions of G IC as a function of thermal history are compared with experiments. [Display omitted] [ABSTRACT FROM AUTHOR]

Shape compensation of tooling for stamp forming of carbon fiber thermoplastic laminated composites is described as a process wherein the virtual twin, FORM3D is utilized to determine the tooling geometry required to produce the desired part geometry in a single step process. FORM3D is a physics-based virtual twin that incorporates anisotropic phenomena including transient heat transfer, thermoviscoelasticity, thermoelastic and crystallization shrinkage, and polymer crystallization and melting kinetics. This procedure for determining the compensated tool geometry is illustrated for a composite laminate constructed of AS4/PEKK prepreg, supplied by Solvay Thermoplastic Composites, for a quasi-isotropic layup of variable thickness and double curvature: major radius of curvature of 1556.7 mm and minor radius of curvature of 75.7 mm. The resulting, compensated shape was shown to agree with the desired geometry within ±0.25 mm. [Display omitted] • Shape compensation for stamp forming • Compensated tool geometry • Tool compensation validated within 0.25 mm. [ABSTRACT FROM AUTHOR]