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Four unidirectional fiber reinforced SiCN ceramic matrix composites were manufactured by means of polymer infiltration and pyrolysis. Two carbon fibers (T800H and Granoc XN90) as well as two silicon carbide fibers (Tyranno ZMI and SA3) without fiber coating were chosen. As matrix precursor, a poly(methylvinyl)silazane was investigated and utilized. The composites with the SA3 and the XN90 fiber had the highest tensile strengths of 478 and 288 MPa, respectively. It is considered that these high modulus fibers with the low modulus SiCN matrix create weak matrix composites. After exposure to air (T = 1200°C, 10 h), a significant decrease of the mechanical properties was found, caused by the burnout of carbon fibers and the oxidation through open pores stemming from the PIP process and SiCN/SiCN interfaces in case of the SiC fiber based composites.

Nozzle extensions made of ceramic matrix composites (CMCs) have shown the potential to replace heavy superalloy nozzles and improve the performance of future upper‐stage and orbital rocket engines. Gas permeability has been reported to be a critical issue during the manufacture for CMC nozzles. This work shows the manufacture of a dense radiation‐cooled C/C‐SiC nozzle demonstrator. A multi‐angle fiber architecture was applied using filament winding technique to reduce the incidence of delaminations during the manufacturing process under high temperatures. Additional efforts were made to improve the final gas tightness and reduce the amount of residual silicon by means of an adapted liquid silicon infiltration process. The manufacture, the material, and structural characterization as well as a finite element analysis of a performed internal pressure test are presented.

This study presents enhanced studies of inverse approach of the classical laminate theory for prediction of the elastic properties of a wound oxide ceramic matrix composites material (CMC). Based on mechanical tests and microstructure analysis, elastic properties of virtual equivalent unidirectional layers were calculated. To adapt the analytical model to CMCs from different batches which show various fiber volume contents, porosities, and different fiber orientations, a scaling factor Ω was introduced with the help of modified mixing considering these specific properties. A good correlation between experimental and analytically calculated results showed in this study.