Improving the Sustainability of Additive Manufacturing Using Fiber-reinforced Polymers

The low cost of polymer additive manufacturing, coupled with its ease of use, has advanced the technology to a point of ubiquity. Printed parts, however, often have a short useful lifespan, and many end up in the landfill. With maturation, engineers must consider sustainability and environmental impact. Polymer AM, and a trend towards pellet-fed machines, is uniquely suited for closed-loop reprocessing. This effort’s objective is to quantify the mechanical property degradation in fiber-reinforced polymers during the recycling and reprocessing of pellet feedstock for additive manufacturing. The application is pellet-fed 3D printed forming tools for sheet metal. A glass fiber reinforced polycarbonate was selected, and the raw material was processed into test coupons by injection molding to characterize the tensile, thermal, and rheological properties, as well as micro-CT analysis to quantify fiber loading, length, and orientation. Samples were then subjected to a granulating recycling process before reprocessing and recharacterizing. This cycle was repeated through four iterations. In parallel, blends of reground and virgin pellet were characterized in a similar fashion. Subsequently, the same material preparation and evaluation was conducted using a medium format pellet-fed 3D printer. An observable change in mechanical and rheological properties can be observed when subjecting glass fiber-reinforced polycarbonate to recycling processes.