Dissertation Proposal Defense – Emily R. Fitzharris
Prof. Meisha L. Shofner, Advisor, MSE
Prof. David Rosen, Advisor, ME
Prof. Donggang Yao, MSE
Prof. Seung Soon Jang, MSE
Prof. H. Jerry Qi, ME
"Fused Deposition Modeling of High Performance Thermoplastics"
Additive Manufacturing (AM) describes a class of manufacturing processes in which parts are fabricated in a layer-by-layer fashion. Fused deposition modeling (FDM) is an AM process involving thermoplastic polymers. While FDM offers many advantages over traditional manufacturing methods, it has been limited by the number of materials that have been developed to work with the process. However, not all materials work well with the FDM process and experience part warpage and residual stresses during fabrication that lead to low quality FDM parts. This proposal seeks to extend the use of FDM to additional materials, improve FDM part quality, and offer enhanced design freedom to various industries and applications. The first research objective in this dissertation proposal develops finite element process simulation models to examine the effect of material properties on the FDM process. Process simulation models were developed for polyphenylene sulfide (PPS) and initial results suggest that the coefficient of thermal expansion greatly determines the amount of part warpage experienced during FDM. Additional process simulation models will be developed for polyether ether ketone (PEEK), polyether imide (ULTEM), and a polyphenylene oxide and polystyrene blend (NORYL). The development of these simulations provides a fundamental understanding of the thermal and mechanical processes experienced during FDM. In addition, these process simulation models could be used as valuable tools in order to reduce the time and cost associated with material development for FDM. The second research objective performs a process optimization design of experiments technique known as the Taguchi method in order to examine how different process parameters affect FDM part quality. The process parameters examined in this objective include deposition temperature, heat treatment time, and heat treatment temperature. Process optimizations will be performed on PPS, PEEK, ULTEM and NORYL. While there are studies that suggest heat-treating FDM parts could improve their material properties and decrease their anisotropy, heat treatments have not been widely examined. This objective could provide a framework for heat-treating both amorphous and semicrystalline FDM parts in order to increase FDM part quality. The third research objective examines the use of multiple materials in FDM. Recent advancements in FDM machines now allow a single part to be fabricated with multiple materials. In these FDM parts, the interfaces between the different materials affect the overall material properties and quality of the produced part. This objective seeks to characterize the interfaces in multiple material FDM parts using PPS, PEEK, ULTEM and NORYL. By understanding the interfaces experienced during multi-material FDM, this processing method could be used to fabricate complex multi-material parts that are unrealizable with traditional manufacturing methods. Overall, the proposed research seeks to extend the use of FDM to additional materials, improve the quality of FDM parts, and increase the design freedom available to various industries and applications.