Experimental Measurement of Residual Stress-Induced In-Plane Displacements of As-Machined Polymer Structures Resultant from Fused Filament Fabrication Additive Manufacturing

This dissertation documents the research work accomplished to experimentally determine the surface displacements resultant from the manifestation of the internal stresses caused by the thermal flows within the body of a structure created during the act of Fused Filament Fabrication (FFF) manufacturing processes. One of the most critical technical issues plaguing additive manufacturing (AM) technologies are the effects of warping and dimensional variations found print-to-print in manufactured structures. These issues arise as a result of the creation of manufacturing-induced residual stresses within the body of the structure being created. To overcome these issues, it is necessary to first understand how these stresses manifest and effect the structure of interest during the build process. To establish this level of understanding one needs to utilize a method to locate, quantify, and measure surface displacements over the entire build process in order to develop a means to mitigate the residual stresses causing these problems. This dissertation documents the experimental and analytical processes created to perform these essential measurements. Application of this novel experimental and analysis framework allows for the understanding to be generated as to the behavior of the residual stress induced displacements as well as determining the most significant manufacturing parameters leading to the creation of these displacement events. Through the execution of the experimental and analysis work presented within the following dissertation, an in situ displacement measurement capability was developed for small scale AM FFF manufacturing systems. As part of the design of this overall measurement capability, it was first required to determine the best modalities available to accurately sense and record the surface displacements developed within the AM structure being assembled during manufacturing. Through a thorough literature review and targeted preliminary experimentation, it was determined that a “no touch” and “no ...