Comparison of Fatigue Life Between C/SiC and SiC/SiC Ceramic-Matrix Composites at Room and Elevated Temperatures
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Comparison of Fatigue Life Between C/SiC and SiC/SiC Ceramic-Matrix Composites at Room and Elevated Temperatures Li Longbiao 1
Received: 31 March 2016 / Accepted: 11 April 2016 # Springer Science+Business Media Dordrecht 2016
Abstract In this paper, the comparison of fatigue life between C/SiC and SiC/SiC ceramic-matrix composites (CMCs) at room and elevated temperatures has been investigated. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface wear model and fibers statistical failure model at room temperature, and interface/fibers oxidation model, interface wear model and fibers statistical failure model at elevated temperatures in the oxidative environments. When the broken fibers fraction approaches to the critical value, the composites fatigue fracture. The fatigue life S–N curves and fatigue limits of cross-ply, 2D and 3D C/SiC and SiC/SiC composites at room temperature, 550 °C in air, 750 °C in dry and humid condition, 800 °C in air, 1000 °C in argon and air, 1100 °C, 1300 °C and 1500 °C in vacuum, have been predicted. At room temperature, the fatigue limit of 2D C/SiC composite with ECFL of 20 % lies between 0.78 and 0.8 tensile strength; and the fatigue limit of 2D SiC/SiC composite with ECFL of 20 % lies between 0.75 and 0.85 tensile strength. The fatigue limit of 2D C/SiC composite increases to 0.83 tensile strength with ECFL increasing from 20 to 22.5 %, and the fatigue limit of 3D C/SiC composite is 0.85 tensile strength with ECFL of 37 %. The fatigue performance of 2D SiC/SiC composite is better than that of 2D C/SiC composite at elevated temperatures in oxidative environment. Keywords Ceramic-matrix composites (CMCs) . Fatigue . S−N curve . Life prediction
* Li Longbiao [email protected]
1
College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, No.29, Yudao St., Nanjing 210016, People’s Republic of China
Appl Compos Mater
1 Introduction The need for better efficiency and higher thrust-to-weight ratio in military and civil gas turbine engines is pushing the development of advanced materials, especially new materials tested and validated at very high temperatures which surpass 1300 °C. Ceramic-matrix composites (CMCs) are lighter than superalloys and maintaining the structural integrity even at higher temperatures, desirable qualities for improving aero engine efficiency, and have already been implemented on some aero engines’ components [1]. Among CMCs, carbon fibers reinforced silicon carbide (SiC) matrix composites (C/SiC CMCs) and silicon carbide fibers reinforced SiC matrix composites (SiC/SiC CMCs) have capability to withstand higher temperature. The C/SiC tail nozzles were designed and fabricated by SNECMA (SAFRAN, Paris, France) and completed the first commercial flight on CFM56–5B aero engine (CFM International, Cincinnati, OH, USA) on 2015. The SiC/SiC combustion ch
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