Strain rate sensitivity of SiC-fibre reinforced titanium matrix composites under tensile loading

Efficiency and thrust to weight ratio of aeronautic gas-turbines shall be increased by new material and design concepts. Titanium matrix composites continuously reinforced by silicon carbide fibres are considered as key technology for a new generation of aero-engines. High specific strength and stiffness promise significant weight savings and performance improvements. However, impact loading may be one critical aspect in the design of rotating compressor components reinforced with titanium matrix composites. On the other hand the strength increases at high strain rates. Considering this additional loading capability enables a design closer to the edge. Therefore, the strength to strain rate relation needs to be examined. This contribution presents results of high strain rate tests at the rotating wheel device. Round specimens of Ti-6Al-2Sn-4Zr-2Mo reinforced by 33 vol.-% SCS-6-fibres were produced by the matrix coated fibre route. Loadings resulting in strain rates from quasistatic loading up to 740 1/s were applied. An increase of ultimate tensile strength as well as yield strength of about 25% has been found for the highest strain rate compared to quasistatic loading. The results are discussed and the mechanism of energy consumption was investigated by determination of the plastic deformed length by scanning electron microscopy. The experiments are described and the relevance of the results for engine designers is pointed out