Structured Filaments for High Performance 3D Printed Plastic Objects

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This grant will support research that will contribute new fundamental knowledge related to the design of the feedstock for one common method of 3D printing to provide guidance for improved plastic parts to enable the translation from rapid prototyping to manufacture. Additive manufacturing generates near net shape object of virtually any shape from a digital computer model and is critical to the development of new manufacturing approach essential for the national productivity. Additive manufacturing is commonly called 3D printing and offers revolutionary possibilities in terms of massive customization for the individual consumer, so the fit is ergonomically perfect. However, almost all additive manufacturing processes for plastic parts lead to inherent weaknesses in the parts that make them inferior to traditionally manufactured plastics. This grant supports fundamental research to provide needed knowledge for the development of improved performance of additive manufactured plastic parts through scalable changes in the feedstock for one type of 3D printing called fused filament fabrication. The new materials will be compatible with existing printers, including consumer printers that are available to the general public, but will enable significant improvements in obtaining parts that better match the desired dimensions and with improved toughness. Additive manufacture of plastic parts is growing with applications from healthcare to assist doctors with planning surgery and custom implants for craniofacial restoration to aerospace parts to decrease the weight of non-critical components. Through improving the performance of plastic parts, this research will benefit the U.S. economy and society by extending the potential applications for additively manufactured plastic parts. This research involves several disciplines including manufacturing, materials science, and mechanical engineering, which will provide a unique educational experience for the students involved in this research. Additionally, the materials produced will be compatible with many commercial 3D printers, including those found in some K-12 schools, so outreach to these schools will provide the students with an opportunity to learn about additive manufacturing and design of materials with a hands-on approach. The design of structured filaments is hypothesized to overcome the intrinsic trade-off between mechanical properties and dimensional accuracy associated with extrusion-based polymer additive manufacturing. Generally, there is poor interlayer strength during the print as the interdiffusion of polymer chains is limited by the temperature and increasing the printing temperature leads to flow and deformation of the printed part. This research seeks to overcome this trade-off with a core-shell structure to the feedstock filament, where the core provides mechanical reinforcement to inhibit flow, while the shell solidifies at lower temperature to provide interlayer strength. However, the fundamental requirements associated with the materials selection and the print processing are poorly understood for the core-shell materials in additive manufacturing. This research will fill the knowledge gap on the relationships between solidification temperature, mechanical properties and miscibility of the core and shell polymers through systematic experimental investigation. The research team will establish relationships between process parameters, intrinsic material properties of the polymers, the dimensional accuracy of the printed part, and mechanical properties to provide insights into the limitations of extrusion-based additive manufacturing for plastic objects.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.