Compression strength of titanium matrix composites depending on fibre volume content, fibre orientation and temperature

Abstract

SiC-fibre reinforced titanium matrix composites are marked by exceptional high specific strength and stiffness at temperatures up to 550°C. That is why these materials are considered as promising materials for components of future aeronautic gas turbines. Tensile and fatigue properties have been investigated precisely in the past. Although the compression strength of titanium matrix composites is expected to be very high there is a lack of knowledge and test results. However, some intended applications require compression strength. These are e.g. torque loaded components like shafts having tensile and compressive mean stresses. To support the design of low pressure shafts for aeronautic gas turbines within the European Project VITAL (enVIronmenTALly friendly aero engine) a test matrix has been set up to investigate the tension and compression properties of SiC-fibre reinforced titanium matrix composites with different fibre volume contents at room temperature and at 550°C. The tests were conducted in fibre direction and transverse to the fibres. Here, the results of the compression tests are presented and discussed. In fibre direction the compression strength increases with increasing fibre volume content. At room temperature maximum compression stress values over 5000 MPa at room temperature and of about 3700 MPa at 550°C were reached. Thus the compression strength is more than twice as high as the tensile strength. Transverse to the fibre direction the strength is limited by matrix flow. The influence of the fibre volume content is smaller and the strength level is influenced more by temperature than by fibre volume content. The results show that compression strength especially in fibre direction is an exceptional property offering new opportunities for special applications.