13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Study on Delamination Behavior and Crack Opening Contour of Advanced Hybrid Laminates during Fatigue Crack Propagation Process Xiao Huang1, Jianzhong Liu1,* 1 Beijing Institute of Aeronautical Materials, Beijing 100095, China * Corresponding author: jianzhongliu09@sina.com Abstract To study crack opening contour and delamination behavior of one kind of advanced hybrid laminates during fatigue crack propagation process, this research accomplished fatigue crack propagation test under R=0.1 for two kinds of saw-cut length and two kinds of stress level, acquired the basic appearance of crack opening contour and delamination, obtained the effect of saw-cut length and stress level on crack opening contour and delamination size. The results indicate that crack opening contour becomes larger as the stress level or saw-cut length rises. Delamination size increases when the stress level becomes larger. The saw-cut length is almost not able to affect delamination size. Keywords Fiber metal laminates; Advanced hybrid laminates; Delamination; Fatigue crack propagation; Saw-cut 1. Introduction Fiber metal laminates (FML) have been developed in recent years[1]. Advanced hybrid laminates (AHL) applied to wing load-carrying structures have been developed from ARALL, GLARE and the concept of Selective Reinforcement[2]. One of the AHL, named CentrAl, developed by GTM-advanced structures and Alcoa Technical Center, will be applied in the wing box structure for airliner and cargo plane[3]. Significant research on fatigue crack propagation behavior has been adequately conducted for ARALL and GLARE. And various prediction models have been developed by researchers[4-15]. As Alderliesten said[13], bridging stress, crack opening contour and delamination shape are in balance. As a result of it, in order to calculate bridging stress and then predict fatigue crack propagation behavior effectively, there is significance for studying crack opening contour and delamination behavior deeply. Existing a few papers[2, 16] present that it is very different from the fatigue crack propagation behavior of AHL and traditional FML. ARALL and GLARE is thin enough to show a nearly same fatigue crack propagation rate in each aluminum alloy sheet layers and a similar delamination shape and size between each layer. But there is a remarkable difference for crack length and delamination size between each layer because of a thickness effect. As the same time, research on the crack opening contour of AHL has not yet been published. To understand the fatigue crack propagation behavior of AHL, this research accomplished fatigue crack propagation test under different saw-cut lengths and stress levels, recorded crack opening contour, obtained delamination shape and size by etching, got the initial results from the influence of saw-cut length and stress level on crack opening contour and delamination behavior, laid the foundation of validating theoretical analysis results. 2. Experiment 2.1. Materials and Specimen The lay-up of AHL in this research is shown in Fig. 1. There is a 3/2 lay-up laminate bonded between two 2mm-thick 2A12-T4 aluminium alloy sheets by adhesive film. Central 3/2 lay-up was laid by three 0.5mm-thick LY12-M aluminium sheets and two prepregs. Prepregs are prepared by
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