13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Study on damage tolerance properties of fiber metal laminates Yu E Ma1,* Zhongchun Xia1 Shuang Yun1 XiaoFeng Xiong2 QingMao Zhang2 1 BOX 118, School of Aeronautics, Northwestern Polytechnical University, 710072, P.R. China, 2 AVIC ChengDu Aircraft Design & Research Institute, ChengDu, P.R. China, 610041 * Corresponding author: ma.yu.e@nwpu.edu.cn Abstract Fatigue crack growth rates in different notched fiber metal laminates under constant amplitude fatigue loading were studied experimentally and numerically. An modified numerically approach was used for predicting the crack growth rate with delamination growth, where the effective stress intensity factor in the metal layer is modulated by a bridging stress intensity factor. Then, fatigue lives of different notched fiber metal laminates were calculated. Good agreement was achieved between the predictions and experimental results. Keywords Fiber metal laminates, crack growth , delamination growth, bridge stress, fatigue lives 1.Introduction In modern aircraft fuselage design, advanced composite materials are increasingly utilized. A special family of such materials are the hybrid composites, also known as fiber metal laminates (FMLs), consisting of alternating layers of Al alloy and glass fiber reinforced epoxy. This material provides improved fatigue characteristics, considerable fire resistance and provides improved damage behaviour[1]. This paper deals with a numerical approach of this material, focusing on the fatigue crack growth rates in different notched FMLs. The numerical approach developed by Alderliesten[2] for predicting the fatigue crack propagation of FMLs is modified, and good agreement is achieved between the predictions and experimental results. 2.Experiments The FMLs studied in this paper were consists of three layers of Al alloy 2024-T3 with the thickness of 0.254mm per layer and two layers of [0/90/0] glass/epoxy prepreg with the thickness of 0.15 mm per glass fiber layer. The dimensions of the specimens are 700 mm in length (L) and 140 mm in width (W). FMLs specimens were designed with 3 different notch sizes(2as): 5mm, 10mm and 20mm. Constant amplitude fatigue testing was conducted using an MTS testing machine, as is shown in Fig 1. Fatigue tests were performed according to ASTM E 468-2004 at room temperature with a frequency of 10 Hz and a stress ratio of R = 0.1. The maximum applied stress was 160 MPa. Crack lengths and the cycles correspondingly were recorded. Crack growth rates were plotted in Fig 2. Fig 1 Delamination shape in FML during testing Fig 2 Crack growth rates
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