An Analytical Friction Model for Handling and Spreading of Carbon Fiber Tows for Composite Prepregging Applications

Abstract

A novel co-extrusion system for continuous fiber reinforced thermoplastic composites in filament and narrow tape format was designed, fabricated, and tested. The new modified pultrusion process, called In Situ Impregnation, impregnates continuous dry fiber reinforcement tows in-situ with thermoplastic matrix for applications ranging from 3D printing using robotic manipulation to automated fiber placement. The technical goal of the system is to directly co-extrude and impregnate a reinforcement fiber tow (carbon) with thermoplastic matrix injected by an extruder fed with thermoplastic pellets. This approach uses inexpensive materials instead of ‘prepreg’ tow in order to streamline the additive manufacturing process, cut costs for advanced composites manufacturing, and deliver fully customizable fiber orientation. The purpose of this paper is to discuss analytical modeling of friction and fiber tensioning in the system which allows for the full impregnation of the fibers. Experiments were conducted on a working pultrusion system where load was adjusted through the tensioning system to better understand the amount of friction throughout the system, the magnitude of tension in the fiber tow, and to validate the models. The resulting friction model can be used by machine designers to estimate the tension in tows, ropes, fibers, etc. in similar tensioning devices, and estimate automated system specifications such as motor requirements. A brief description of the new manufacturing process is also provided. Future work includes commercialization of the technology, automation of the manufacturing system, and further modeling work to predict fiber spreading behavior based on geometric factors.