Hybrid Material Systems

Metal Matrix Composites



Metal Matrix Composites
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Metal matrix composites (MMCs) link the properties of metals e.g. toughness, thermal conductivity, and machineability with the properties of ceramic fibres e.g. stiffness, strength and low thermal expansion.

For extreme demands the strength and stiffness of titanium alloys can be enhanced by the reinforcement with ceramic fibres. These titanium matrix composites (TMCs) are used for highly loaded components to reduce stress peaks locally. By the matrix coated fibre technique reinforcing elements are produced at the Institute of Materials Research, which are implemented by diffusion bonding or brazing into the component. Stress reductions in the base component are obtained as shown in the image.

A unique processing route has been developed by the institute which uses matrix coated fibres leading to metal matrix composites with exceptional good properties. Due to the longstanding experience a huge data base exists especially for titanium matrix composites. Current research work concentrates on the development of affordable processing routes.

Basically the integration of siliconcarbide fibres increases strength and stiffness of unreinforced titanium alloys by about 100%. Particulary, Young’s modulus’ of 210 GPa and tensile strengths of 2200 MPa at room temperature can be obtained with a fibre volume content of 45%. Depending on the matrix material used service temperatures up to 550°C are possible.

Components with exceptional high thermal and electrical conductivities along with high strengths and moderate thermal expansion can be made by SiC-fibre reinforced copper alloys. To produce copper matrix composites the process of the matrix coated fibres developed for TMCs is transferred for the reinforced copper alloys. As a result high strength components can be produced marked by high thermal conductivity e.g. for heat sinks in fusion reactors or rocket engines. Advantages compared to unreinforced copper alloys are extended life times and a thermal expansion more compatible to neighbour components.


Contact
Dr.-Ing. Joachim Hausmann
German Aerospace Center

Institute of Materials Research
, Mechanics of materials and joining technology
Tel: +49 2203 601-2054

Fax: +49 2203 696480

E-Mail: Joachim.Hausmann@dlr.de
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