Fatigue Hysteresis Behavior of Unidirectional SiC/Si 3 N 4 Composite at Elevated Temperature under Tension-Tension Loadi
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Fatigue Hysteresis Behavior of Unidirectional SiC/Si3N4 Composite at Elevated Temperature under Tension-Tension Loading Longbiao Li 1
Received: 20 December 2016 / Accepted: 13 January 2017 # Springer Science+Business Media Dordrecht 2017
Abstract In this paper, the fatigue hysteresis behavior of unidirectional SiC/Si3N4 ceramic-matrix composite at elevated temperature has been investigated. The hysteresis loops models considering interface friction between fibers and the matrix have been developed to establish the relationships between the fatigue hysteresis loops, fatigue hysteresis dissipated energy and the interface frictional coefficient. Using the experimental fatigue hysteresis dissipated energy, the interface frictional coefficient of SiC/Si3N4 composite at 1000 °C were obtained for different cycle numbers and fatigue peak stresses. The effects of fatigue peak stress, test temperature and cycle number on the evolution of fatigue hysteresis dissipated energy and interface frictional coefficient have been analyzed. It was found that the fatigue hysteresis dissipated energy can be used to monitor the interface debonding and damage evolution inside of the composite. Keywords Ceramic-matrix composites (CMCs) . Fatigue . Hysteresis loops . Interface frictional coefficient
1 Introduction Ceramics have excellent stiffness-to-weight and strength-to-weight ratios compared with traditional metals, especially at elevated temperature. However, their use as structural components is severely limited due to brittleness. The inherent brittleness
* Longbiao Li [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
of ceramics can be overcome by using fiber reinforcements, which can debond and slide through matrix to dissipate energy. At the same time, the fiber-reinforced ceramic-matrix composites (CMCs) retain the attractive high temperature properties of ceramics [1]. In order to use CMCs with confidence, designers and engineers must be able to predict the mechanical response under cyclic fatigue loading [2, 3]. Ruggles-Wrenn et al. [4] investigated the tension − tension fatigue behavior of 2D woven SiC/SiC composite at 1200 °C in air and in steam environment. The fatigue limit and fatigue lifetime decreases with increasing loading frequency from 0.1 to 10 Hz in both test environments, and the presence of steam significantly degraded the fatigue performance. Ruggles-Wrenn and Lanser [5] investigated the tension − compression fatigue behavior of 2D woven Nextel™ 720/alumina composite at 1200 °C in air and in steam. The fatigue limit stress was achieved at 40% and 35% tensile strength in air and steam environment, respectively, when the maximum cycle number is defined to be 100,000 applied cycles. The presence of steam noticeably degrades the tension − compression fatigue performance of the oxide/oxide composite. RugglesWrenn and Lee [6] investigated the tension − tension fatigue behavior of 2D
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