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Frequency Effect on Fatigue Tensile Behaviour of Carbon/Epoxy Plain Weave Laminates under Different Hygrothermal Conditions

Mohamed Khay, Anh Dung Ngo and Rajamohan Ganesan

Abstract


The purpose of this paper is to study the load frequency effect on the fatigue behaviour at different environmental conditions of a quasi-isotropic carbon/epoxy plain weave laminate containing artificial flaw under tensile loading. Dry and wet specimens were exposed to tensile load-controlled cyclic loading with a stress ratio R = 0.1 at room temperature (RT) and at 82°C for load frequencies of 7 and 15Hz under different stress levels. Allowable stiffness reduction as a failure onset criterion was used to determine the delamination propagation threshold under cyclic tensile loading at each frequency and environmental condition. The propagation of delamination was verified using the ultrasonic imaging (C-Scan) technique. The experimental results show that load frequency played a positive effect by increasing the fatigue life of specimens for two conditions (RT, 85%RH) and (82°C, Dry). However, for the condition (RT, Dry) higher load frequency tended to reduce the fatigue life of tested specimen at high stress levels while starting from certain lower stress level it tended to increase their fatigue lives. On the contrary at the condition of (82°C, 85%RH) the effect was reversed compared to that of (82°C, Dry).

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