Innovators at NASA Glenn Research Center, in collaboration with the University of Louisville and the U.S. Air Force, developed an additive manufacturing technique to produce composite parts with high-temperature capabilities using thermoset polyimide resins. The process uses selective laser sintering (SLS) to melt-process a powdered version of NASA’s novel RTM370 imide resin filled with finely milled carbon fibers.
The SLS-manufactured carbon-filled thermoset polyimide composite shown is not fully cured. The “green” part is subjected to a multi-step post-cure process that gradually heats the composite from room temperature to slightly below its softening temperature to complete the final curing.
The resulting composite part can be subsequently post-cured to prepare for high-temperature aerospace applications, offering a 3D-printed composite part that can withstand temperatures over 300 °C. This is a significant advancement in the state of the art in additive manufacturing polymers, offering an SLS process that requires relatively low melting temperatures and creates composites with high temperature capabilities.
SLS typically uses thermoplastic polymeric powders and the resultant parts have a useful temperature range of 150-185 °C, while often being weaker compared to traditionally processed materials. Recently, higher-temperature thermoplastics have been manufactured into 3D parts by high-temperature SLS that requires a melting temperature of 380 °C but the usable temperature range for these parts is still under 200 °C.
The thermoset polyimide composites are melt-processable between 150-240 °C, allowing the use of regular SLS machines. The resultant parts are subsequently post-cured using multi-step cycles that slowly heat the material to slightly below its glass transition temperature, while avoiding dimensional change during the process.
This invention could benefit aerospace companies in the production of parts with complex geometry for engine components requiring over 300 °C applications, while having other potential applications such as printing legacy parts for military aircraft and producing components for high-performance electric cars.