Fabrication of thermoplastic polymer composite ribbon

Abstract

The goal of this research was to develop a controllable process to convert a thermoplastic powder-coated carbon-fiber towpreg into uniform and consolidated ribbon. The approach comprised four primary activities. (1) The patent and processing literature was studied to evaluate the state of the art. (2) A functional ribbon fabrication technique was developed by scaling-up, in a novel configuration, hardware components found in the literature. (3) The ex parte ribbonizing process was characterized by calibrating equipment, determining steady state and studying cause and effect between process parameters and ribbon quality. (4) Process design and control methods were derived from heat transfer and pulling force analyses. The ex parte ribbonizer process comprises a material handling system, a preheat region, a heated stationary bar assembly, and a cooled nip roller assembly. Appropriate timing of important contacts is key to fabricating quality ribbon. Process characterization and analyses revealed key flow mechanisms. Ribbon microstructure changes most at the bars. Ribbon macrostructure changes most at the nip. An isothermal bar contact is a practical processing constraint for ensuring uniform squeeze flow bar spreading. All bar drag force is attributed to shear stress in the interfacial viscous boundary layer between the towpreg and the stationary bar surface. Continually sensing pulling force is a good indication of process control. The research goal was achieved because the ex parte ribbonizer can be used to convert polymer powder towpreg into uniform and fully-consolidated ribbon in a controllable manner