In-situ thermoplastic impregnation of a dry composite fiber tow for additive manufacturing

Abstract

The goal of this research is to develop an open-source deposition head design for impregnating continuous dry fiber reinforcement tows in-situ with thermoplastic resin as the matrix for non-planar additive manufacturing and other automated composites manufacturing processes (e.g., mandrel wrapping, automated fiber placement). The deposition head design used for demonstrating the concept consists of a heated plunger system to meter molten plastic (although an extruder is envisioned for future work) into an impregnation chamber through which the fiber passes and is impregnated upon exiting. It is unlike the current commercial systems on the market (Markforged), which uses pre-impregnated fiber, but is similar to two systems in development (Arevo Labs, Orbital Composites) in that dry fiber and matrix in pellet form is used. Based on early experiments and literature models, it was determined that the rate and quality of fiber impregnation at least depends on the resin viscosity, chamber pressure and exposure time. Using the designed deposition head, test samples of carbon fiber tow (3K) are infused with several thermoplastics resins (Polyethylene, Nylon, and Polycarbonate) for a range of pressure, temperature and fiber feed rate. To test the quality of impregnation of test samples, i.e. the degree of impregnation, Microscopy techniques were used. Experimental results and lessons learned will be used for a 2nd generation deposition head design and actual additive manufacturing builds.