Characterization of shape memory polymer composites for the fabrication of resilient aircraft ducting via fused deposition modeling

In recent years, the use of additive manufacturing techniques has gained interest for its possible uses in a multitude of different industries. Additive manufacturing methods allow for the fabrication of geometrically complex parts without the need for tooling and with reduced need for post-fabrication machining; this makes additive manufacturing a desirable method of fabrication from both a design and economic standpoint. In particular, the aerospace industry has expressed interest in additive manufacturing techniques for applications in rapid prototyping and production of tooling and non-structural aerospace components such as ducts, brackets, and enclosures. The Air Force Research Laboratory's Composites Branch (AFRL/RXCC), the Propulsion, Structures & Manufacturing Enterprise Branch (AFRL/RXMS) and Raytheon Missile Systems have teamed to fabricate and determine the physical, mechanical and shape memory properties of an additively manufactured polymer. The examined shape memory polymer is being considered for the fabrication of resilient aircraft ducting via fused deposition modeling (FDM). The subject material was delivered by Raytheon Missile Systems in loaded and neat varieties of injection molded and 3D-printed thermoplastic polyurethane (TPU). The loaded specimens were doped with milled carbon fiber and milled glass in a ratio that allowed for the materials to be electro static discharge (ESD) compliant, while still being suitable for application in the FDM process. The 3D-printed tensile bar specimens were fabricated using two different orientations: horizontal orientation (XY-plane; flat on build plate) and vertical orientation (Z-plane; standing on build plate). In this study, we will characterize the thermo-mechanical properties and shape memory response of this new class of FDM material with an emphasis on characterizing the pore micro-structure and processing-dependent mechanical anisotropy of FDM printed parts.