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 oxidising 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 fibres such as alumina fibres. The increase of the mechanical stability of the composites in comparison to the non-fibre reinforced material is of outstanding importance. Possible stresses or cracks can be derived along the fibre under mechanical stress or deformation. Components made of fibre-reinforced ceramic composites with oxide ceramic matrix (OCMC) are currently produced in manual and price-intensive processes for small series. Therefore, the manufacturing should be improved. The ceramic injection moulding (CIM) process is established in the production of monolithic oxide ceramics. This process is characterised by its excellent automation capability. In order to realise large scale production, the CIM-process should be transferred to the production of fibre-reinforced oxide ceramics. The CIM-process enables the production of complicated component shapes and contours without the need for complex mechanical post-treatment. This means that components with complex geometries can be manufactured in large quantities.To investigate the suitability of the injection moulding process for the production of OCMCs, two different feedstocks and alumina fibres (Nextel 610) were compounded in a laboratory-scale compounder. The fibre volume fractions were varied. In a laboratory-scale injection moulding device, microbending specimens were produced from the compounds obtained in this way. To characterise the test specimens, microstructure examinations and mechanical-static tests were done. It is shown that the injection moulding process is suitable for the production of fibre-reinforced oxide ceramics. The investigations show that the feedstocks used have potential for further research work and for future applications as material components for high-temperature applications in oxidising atmospheres.

Ceramic-matrix composites (CMC) made of carbon and silicon carbide dual matrix reinforced with carbon fibres (C/C-SiC) have exceptional heat, thermal shock, creep, and wear resistance, while also having little density and high strength. In comparison to monolithic ceramics, CMC possess ductility and damage tolerance, which opens this material for severe applications. Starting in space applications, this material is today well established in friction applications, where lightweight high-performance brakes securely decelerate e.g. luxury cars or elevators. The high production costs still limit the broad application like as brake discs in standard passenger cars, although less weight, better performance and longer lifetime. The industrial used production process is the liquid silicon infiltration (LSI) with it three steps: green body shaping, pyrolysis and silicon infiltration. In this work, the shaping process of the carbon fibre reinforced plastic (CFRP) green body, is done by thermoset injection moulding. The application of plastic production processes like compounding and injection moulding in the liquid silicon infiltration process route, enables large-scale manufacturing. However, the screws and high shear forces inside the plastic processing machines significantly shorten the fibres. This paper describes the pros and cons of thermoset injection moulding in the LSI route, as well as the development and effect of different reinforcement types in dependence of their fibre length, since several energy dissipation mechanisms bases on a minimum length of reinforcement fibres in CMC. Various raw materials like short and chopped fibres with different length, rovings, and different approaches to receive longer fibres and their outcomes are presented. The mechanical properties show promising values and the micrographs display the infiltration status and crack development inside the specimen.

This work investigates the material extrusion‐based additive manufacturing (AM) process chain of a pure alumina‐based oxide ceramic matrix composite, starting from material selection, large‐scale compounding to pellets, the AM process itself, debinding and sintering as well as microstructural and mechanical characterization. The compounded pellets have a volume share of 50% binder (polyvinyl butyral [PVB], polyethylene glycol [PEG], and stearic acid) and 50% alumina (Al ₂ O ₃ , alumina powder, and Nextel 610 alumina fibers) with an aimed fiber volume share of 40% after sintering. The material is compounded on an industrial scale with approximately 10 kg/h and the material extrusion‐based AM process reaches speeds of up to 1000 mm/s. A variation of the feed rate leads to a significant increase in surface roughness and an increase in mass of 30%, in thickness of 12% and in width of 25%. The flexural behavior in the four‐point‐bending test can be described by a fast first peak and reaching higher flexural strength after the first crack subsequent with averages of 23.8 ± 3.6 MPa below .1% elongation. The fracture surfaces show the expected failure mechanisms like pull‐out and crack deflection. The resulting fiber length in the printed samples is 140 µm in average.

The production of C/C-SiC composites comprises a three-stage process: forming (CFRP-composite), pyrolysis (C/C-composite) and liquid silicon infiltration (C/C-SiC). A new promising approach for the manufacturing of CFRP intermediate composites is the injection moulding of customised granulates (novolac resin, hardener, processing additives and short carbon fibre) produced by compounding technique. To date, a direct dosing of short carbon fibre into the compounder was technically not realisable due to fibre separation and electrostatic charging in the hopper. A possible substitute solution has been the direct feeding of a carbon fibre bundle from a roving into the compounder. However, this is associated with a severe damage of the fibres and an inaccurate adjustment of the fibres content. In the present article, new chopped carbon fibres provided with an adapted sizing to be directly dosed into the compounder are used. The fibres possess a predefined length of 3 and 6 mm and their content amounts to 50 and 58 wt.%. The influence of the initial fibre length and fibre content on the physical and mechanical properties of the resulting CFRP-, C/C-and C/C-SiC-composites is presented and discussed. In addition, the impact of fibre feeding procedure at the compounding stage on the microstructure is considered