Description: Based on the knowledge and expertise gained in partnership with the University of Tennessee at Knoxville (UTK) during the NASA/STTR Phase I work, re:3D proposes the development of a pilot system for the deposition of a phenolic foam TPS surface onto a scaled demonstration article in parallel with refinements and improvements to the foam’s material characteristics.The Phase II research activities at UTK will focus on understanding the processing requirements to scale up production of the foam feedstock to 3D print large-scale test articles, refine the foam to further lower density and increase temperature stability, explore novel printing approaches to tailor effective density and elastic modulus and/or incorporate graded composition to raise temperature stability at the outer surface, and continued plasma arc jet torch testing of the developed materials and architectures.During Phase II, re:3D will be responsible for designing, developing and building the systems and mechanisms required for a pilot material extrusion system of the phenolic foam onto a scaled demonstration article consisting of an aluminum dome with a radius of curvature of approximately 1 meter and a 1-meter base diameter. The system would be comprised of the following elements: Mixing of the foam components, either outsourced or performed in-house as determined by a feasibility study during the course of the Phase II investigation at UTK Transport of the foam from the mixing containers to the deposition nozzle through the use of an appropriate metering pump Conformal deposition of the foam onto the aluminum dome with in-situ defect monitoring and advanced motion planning using a gantry printer based on re:3D’s existing Terabot platform and a custom-designed extruder with added degrees of motion Curing of the foam in an appropriate industrial oven Post-process machining to achieve the final desired finish of the TPS surface

Benefits: This process has applicability mission requiring an EDL phase dependent on parasitic surfaces for spacecraft survival. Current methods are expensive, labor intensive and result in non-optimum layering. In addition to cost benefits through material savings and automation, AM application of TPS surfaces offers real-time component certification, integration of sensors into the TPS during fabrication, & implementation of digital thread paradigms where TPS surfaces are generatively designed around engineering requirements.

Outside of research institutions, to our knowledge there are no commercially available large-scale printers capable of applying thermoset foams to conformal, non-planar surfaces. With the resources of a Phase II grant, our collaboration with UTK, and partnerships with industry, we believe this project is achievable and will result in a process to industries beyond space and DoD customers.