Investigation of three preceramic polymer formulations for potential use in additive manufacturing technologies.

A novel route to fabricating hybrid ceramic matrix composites has been developed. The fabrication is based on the unique combination of additive manufacturing (AM), a preceramic polymer, and a chopped carbon fiber precursor. After introducing the photoinitiator to the preceramic polymer formulation, a photosensitive resin was introduced. The resulting resin was loaded with distinct weight percentages of stabilized polyacrylonitrile nanofiber-the carbon fiber precursor. These formulations were 3D printed, cured, and converted to ceramic phases using a pyrolysis cycle. The end objective of the pyrolysis cycle is the conversion of the polycarbosilane resin into a silicon carbide matrix and the transformation of the PAN polymer into reinforcing carbon nanofibers within one cycle. The results of this work showed that ceramic matrix composite components can be successfully fabricated using a suitable combination of 3D printing, resin formulation, and processing cycle. The pyrolyzed ceramic hybrid composite was fully dense with nearly linear shrinkage and a shiny, smooth surface.Approximately 60% retained weight after pyrolysis to 1350 • C was confirmed by thermogravimetric analysis. In terms of crystallography, the ceramic matrix composite displayed three coexisting phases including silicon carbide, silicon oxycarbide, and turbostratic carbon. The results showed this combination of material and processes has a high potential for fabricating hybrid composites with hightemperature performance and improved mechanical properties combined with complex geometries.

Modern aerospace applications demand the development of high‐performance components with advanced materials. The development of nanomaterial‐reinforced metal matrix composites is a practical approach to improve properties. Laser powder bed fusion (LPBF) is one of the popular additive manufacturing approaches to fabricating metal parts with complex geometric structures. This research investigates multiwalled carbon nanotube (CNT)‐reinforced nickel‐based alloy (Haynes 230) nanocomposite for property improvement. Three volumetric concentrations (0%, 2.5%, and 5%) of CNTs in the metal matrix are investigated with different printing parameters. Different characterizations are conducted on the test specimens. Results show that LPBF‐printed Haynes 230 with 2.5 vol% CNTs has higher relative density (99.36%) and less porosity compared to those printed with 5 vol% CNTs. Mechanical test results show that LPBF‐printed Haynes 230 with 2.5 vol% CNTs has the highest hardness, modulus of elasticity, yield strength, and ultimate strength than those printed with as‐received Haynes 230 powder (with 0 vol% CNTs), Haynes 230 with 5 vol% CNTs, and commercial Haynes 230 plates. The strengthening behavior of the CNTs in the metal matrix composites is discussed in this paper. The potential of CNT‐reinforced nickel‐based nanocomposites for applications requiring materials with outstanding mechanical properties, such as aerospace and defense, is demonstrated.