CMC with a Graded Lay-up Manufactured via LSI-Process

Kurzfassung

Ceramic matrix composites (CMC) armed by long fibres are promising candidates for structural applications due to their damage tolerance even at very high temperatures. Since CMC based on SiC fibres are still very costly most cost-efficient CMC are based on carbon fibres. Among the processing routes for CMC most common for industrial applications is the liquid siliconization infiltration process (LSI) developed by DLR. In this three-step-process (CFRP manufacture, pyrolysis, siliconization) the fibre matrix bonding is determining the final microstructure, SiC content, mechanical properties and damage tolerance as well as oxidation and abrasion resistance. In general, higher SiC content enhances oxidation and abrasion resistance, however, lowers mechanical properties and damage tolerance significantly. For components applied in severe environments it is thus, desirable to have a SiC rich outer layer bearing a core being capable to carry high mechanical loads. Another possibility to obtain CMC with a graded lay-up concerning mechanical properties can be achieved by filament winding using a combination of selected winding angles, especially on tubes. In this paper several methods to manufacture CMC with a graded lay-up as well as properties and potential applications are presented.