Design and development of an additive friction stir deposition test bed for functional polymer surfacing

Abstract

Additive friction stir deposition (AFSD) is an emerging solid state additive manufacturing technique capable of producing alloy deposits with minimal porosity. In AFSD, the material does not melt; instead, frictional heat generated between the rotating feedstock and the substrate softens the material, which then undergoes plastic deformation. The deformed material is consolidated into a dense billet-like structure with refined grain characteristics. Manufacturers use AFSD to produce large near-net-shaped parts with less material than traditional billet stock, reducing production costs and shortening lead times. Although AFSD is well-established for metal processing, its application to polymers remains limited due to a lack of understanding of process, structure, and property relationships during deposition. The objective of this thesis is to investigate AFSD processing parameters and to generate a predictive model for polymer deposition. In this regard, a programmable filament-fed AFSD system was developed to produce continuous polymer-to-polymer deposits. The developed AFSD system mechanically mixes the successive layers creating enhanced interlayer bonding that surpasses that of fused filament fabrication. A predictive model was developed to guide the scaling of AFSD for larger applications and enable bonding across similar and dissimilar polymers. Notably, the AFSD process was hybridized with subsequent subtractive machining and electroless copper plating to achieve electrically conductive polymer surfaces, enabling application in electronics, sensors, and multifunctional polymer components. Collectively, this convergent manufacturing approach converts arbitrary polymers into multifunctional materials with enhanced electrical and thermal properties.