HEATED COMPRESSION TESTING TO REDUCE CALIBRATION COSTS IN THE ONBOARDING OF FIBERREINFORCED FEEDSTOCKS FOR LARGE AREA ADDITIVE MANUFACTURING VIA THERMOPLASTIC EXTRUSION

Large Area Additive Manufacturing (LAAM) has been an emerging area of interest in the composites industry, enabling the rapid prototyping and fabrication of structural components and systems. Increasingly larger platforms for LAAM extrusion have been developed for both research and development as well as commercial end-use purposes, with some available extruder capacities reaching up to 225 kg/hr and print bed platforms up to 29 m in length. Although similar in concepts to smaller scale thermoplastic extrusion equipment, the nuances associated with LAAM extrusion platforms present unique challenges, which are often particular to an individual piece of LAAM equipment. One of the primary challenges associated with LAAM extrusion methods includes the onboarding and calibration of fiber-reinforced feedstocks. Processing settings, such as screw speeds and material melt temperatures, are often found to be unique to a particular piece of extrusion equipment or bead geometry and are not easily translatable between disparate use cases. The University of Maine’s Advanced Structures and Composites Center has been developing methods to minimize time, effort, and material costs associated with the onboarding and calibrating of fiber-reinforced pellet feedstocks for LAAM thermoplastic extrusion. Compression testing, based on ASTM D695, of injection molded coupons was performed within a heated environmental chamber to determine maximum temperatures at which a LAAM extruded bead of the same material would retain loading capacity to self-support additional print layers. When combined with an on-tool infrared pyrometer to monitor deposition and substrate temperatures, reductions in costs associated with the non-value-added process of onboarding material feedstocks were observed. Initially performed using a pelletized PA12-glass fiber feedstock on a Cincinnati BAAM, work is currently underway to extend this process to LAAM extrusion efforts using other material systems.