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In this work, metal-ceramic composite parts based on aluminum and alumina were manufactured in a two-stage process. First, silica was printed using a vat photopolymerization technique, followed by a curing and sintering stage, which resulted in ceramic precursors. Subsequently, these samples were subjected to a metal infiltration process to form interpenetrating metal-ceramic composites (IPCs). These composites have attracted considerable attention in the aerospace and defense sector due to the ductility associated to the metal phase and the strength offered by the ceramics. A novel application with utility includes composite tooling which requires a low coefficient of thermal expansion (CTE) for high temperatures. The investigated specimens were tested for surface quality and shrinkage, followed by a mechanical characterization. It was recorded that the samples presented a 12%-18% of shrinkage after the sintering process. The mechanical testing showed that the hardness, compression, and flexural strength of the composites were superior to the printed and sintered ceramics. A thermal analysis on the composite showed that its CTE is more than two times lower than the common composite tooling materials. It is expected that the present work can provide the foundations for further studies on these systems in the refractory, automotive, and armor-based fields. K E Y W O R D Sceramic-metal systems, fracture, mechanical properties 414 | MUMMAREDDY Et Al.

The use of additive manufacturing (AM) provides an opportunity to fabricate composite tooling rapidly and cost effectively. This project appears to have demonstrated the use of an additive technology for the production of composite processing tools. In particular, this work has addressed tooling that is functional in the range of autoclave temperatures around 300–350°F. This has led to the use of Invar and ceramic materials for use in composite molding tools because of their relatively low coefficient of thermal expansion (CTE) performance, which is in range to that commonly displayed by carbon fiber reinforced composites during their solidifying-curing process. In this project, two main approaches have been considered. The first approach consisted on using binder jetting for 3D printing sand molds to cast molten Invar to produce the composite tooling. Indeed, 3D sand printing offers the ability to cast complex geometries without the geometric limitations associated with conventional pattern making. The second innovative approach was based on printing a mold based on silica sand and infiltrating it with a polymer to yield a robust ceramic composite tooling. An additional technology using a Hybrid Direct Energy Deposition (DED) System for cladding Invar upon a steel molding structure has also been considered for producing potential composite tooling. Indeed, this unique approach could represent a promising technology for producing low cost composite tooling since only a small layer of Invar would be printed upon a non-expensive substrate. The results have shown that the aforementioned processes have successfully resulted on low CTE composite tooling molds. This work presents innovative AM processes by initially investigating 3D ceramic systems for composite tooling.

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