Ceramic materials are suitable for use in the high temperature range. Oxide ceramics, in particular, have a high potential for long-term applications under thermal cycling and oxidizing atmosphere. However, monolithic oxide ceramics are unsuitable for use in high-temperature technical applications because of their brittleness. Thin-walled, oxidation resistant, and high-temperature resistant materials can be developed by reinforcing oxide ceramics with ceramic fibers such as alumina fibers. The increase of the mechanical stability of the composites in comparison to the non-fiber reinforced material is of outstanding importance. Possible stresses or cracks can be derived along the fiber under mechanical stress or deformation. Components made of fiber reinforced ceramic composites with oxide ceramic matrix (OCMC) are currently produced in manual and price-intensive processes for small series. The ceramic injection molding technology, which is commonly used for monolithic ceramics, is to be developed for the use of OCMC, but the freedom of design is still limited.
This work presents a novel additive manufacturing process (3D printing) of short fiber reinforced all-oxide ceramic matrix composite. Nextel 610 fibers are compounded with alumina powder and thermoplastic binder (PVB, PEG, stearic acid) to a feedstock. In the following additive manufacturing bases on the extruder principle, where the produced feedstock granulates melts in the extruder and is laid on a moving table. Using “cheap” granulate for 3D printing in an extruder instead of the fused deposition modeling, stereolithography or the binder jet method, enables high output volumes and short production times. Each added layer has a thickness of approx. 0.8 mm, width of approx. 3 mm and the feed rate is approx. 25 mm/s. For example, for a specimen with a width of 9 mm, three strands will be deposited in parallel. The 3D printed samples pass a two-step debinding process before sintering. Subsequently, the flexural strength and modulus are measured in the four-point-bending test and the microstructure and the fracture surfaces are examined via light and scanning electron microscopy. Furthermore, the utilization of continuous reinforcement fibers is shown and a complex demonstrator.