Effect of Spring-in Deviation on Fatigue Life of Composite Elevator Assembly
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Effect of Spring-in Deviation on Fatigue Life of Composite Elevator Assembly Hua Wang 1,2
Received: 5 December 2017 / Accepted: 11 December 2017 # Springer Science+Business Media B.V., part of Springer Nature 2017
Abstract The spring-in deviation results in the extra stresses around the joints of the composite C-beam and metallic parts when they are assembled together. These extra stresses affect the composite elevator’s fatigue life, which should be explored with the fatigue experimentation. The paper presents the experimental investigation on the effect of spring-in deviation on the fatigue life of the composite elevator assembly. The investigation seeks to build the relationship between the spring-in and the fatigue life in order to determine the spring-in threshold during the course of assembling. The phenomenological model of the composite Cbeam is constructed to predict the stresses around the joints. Based on the predicted spring-in induced stresses around the joints, pre-stresses are precisely added to the fatigue specimen when conducting the fatigue experiment. At last, the relationship curve of the spring-in on the composite C-beam’s fatigue life is obtained from the experimental data. Giving the fatigue life accepting limits, the maximum accepting spring-in deviation during the course of assembling could be obtained from the relationship curve. The reported work will enhance the understanding of assembling the composites with spring-in deviation in the civil aircraft industry. Keywords Composite C-beam . Fatigue life . Spring-in . Pre-stress
1 Introduction Composite elevator is one important assembly in the aircraft. It is mainly composed with the metallic and composite components: the nose ribs, the forward spar, the metallic joints, ribs and the skin panels. The forward spar, a kind of Carbon Fiber Reinforced Plastic/Polymer
* Hua Wang [email protected]
1
Shanghai Key Laboratory of Digital Manufacture for Thin-walled Structures, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China
2
Present address: School of Mechanical Engineering, Shanghai Jiao Tong University, No.800 Dongchuan Rd, Shanghai 200240, China
Appl Compos Mater
(CFRP) C-beam, forms the front structures of the elevator. The forward spar is cured hot. There are residual stresses in laminates because of the mismatch of thermal expansion along and across the fibers, cure shrinkage of the thermoset resin and the change from cure to room temperature. When the forward spar comes out of the mould, there are spring-in deviations (Fig. 1) in it which should be properly handled in the following assembling process [1–3]. The spring-in results in the interference in the structure when the spar and metallic parts are being assembled together (Fig. 1). The assembling with the interferences will introduce the extra stresses around the joints and the structure. These extra stresses affect the composite elevator’s fatigue behavior, which could be explored with the fatigue experimentation. The test specimens are subjected t
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