In-Situ Co-Extrusion: Additive Manufacturing of Continuous Reinforced Thermoplastic Composites

Abstract

A novel co-extrusion system for continuous fiber reinforced thermoplastic composites was designed, fabricated, and tested. This process, called In-Situ Co- Extrusion, is a combination of pultrusion and extrusion that impregnates continuous dry fiber reinforcement tows in-situ with thermoplastic for applications ranging from additive manufacturing using robotic manipulation to automated fiber placement. The performance goal was to design a co-extrusion system that directly uses raw materials (thermoplastic pellets and rolls of carbon fiber tow) instead of ‘prepreg’ tow in an effort to streamline and cut costs in advanced composites manufacturing and deliver fully customizable fiber orientation. The working coextrusion system has been tested with multiple exit geometries and degrees of fiber spreading. Microscopy techniques were employed to estimate the degree of impregnation and fiber volume fraction based on cross sections of the resulting composite tow. FEA modeling was conducted to evaluate the temperature uniformity of the extruder die design and the placement of cartridge heaters. Future work includes testing the extrusion system with different material systems and deposition using a robotic or CNC platform to demonstrate feasibility for additive manufacturing.