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Residual Strength Evolution of 2D C/C-SiC Composites Subjected to Tensile Fatigue Stresses

B.-G. Zhang^,1, Y. Li^,1,2, P. Xiao^,1, W. Zhou^,1,3, H. Luo^,1, Z. Li^,1

¹ State Key Laboratory of Powder Metallurgy, Central South University, Changsha, 410083, PR China
² Ceramic Materials Engineering, University of Bayreuth, Bayreuth, 95447, Germany
³ College of Metallurgical Engineering, Hunan University of Technology, Zhuzhou, 412008, PR China

received October 20, 2016, received in revised form November 7, 2016, accepted November 15, 2016

Vol. 8, No. 1, Pages 53-58   DOI: 10.4416/JCST2016-00087

Abstract

An experimental investigation was performed to study the residual tensile strength (RTS) of liquid silicon infiltration (LSI)-based plain-weave reinforced C_f/C-SiC composites (2D C/C-SiC) after different loading cycles. The specimens were previously subjected to the cyclic stress of 57 MPa for the preselected numbers of cycles (10², 10⁴ and 10⁶, respectively) before the final quasi-static tensile test. The microstructures, fractured surfaces and coefficient of thermal expansion (CTE) after the quasi-static tensile test were characterized by means of Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and a classical mechanical push-rod dilatometer, respectively. The results showed that the RTS of the specimens after the preselected fatigue cycles numbers of 10², 10⁴ and 10⁶ increase to 90.9, 94.1 and 84.5 MPa, respectively, which are somewhat higher than that of virgin samples (79.7 MPa). Additionally, the tensile stress-strain curves of the post-fatigue specimens present cycle-independence within the region of linear response. Finally, the CTE in the range of 200 – 1000 °C gradually decreased with the increasing cycles owing to higher damage induced by fatigue stress along the loading direction.

Keywords

C/C-SiC, fatigue, cracking, residual strength

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