Cutout reinforcements for shear loaded laminate and sandwich composite panels
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Cutout reinforcements for shear loaded laminate and sandwich composite panels Shijun Guo Æ L. Zhou Æ C. W. Cheung
Received: 16 January 2007 / Accepted: 26 November 2007 / Published online: 11 December 2007 Ó Springer Science+Business Media B.V. 2007
Abstract This paper presents the numerical and experimental studies of shear loaded laminated and sandwich carbon/epoxy composite panels with cutouts and reinforcements aiming at reducing the cutout stress concentration and increasing the buckling stability of the panels. The effect of different cutout sizes and the design and materials of cutout reinforcements on the stress and buckling behaviour of the panels are evaluated. For the sandwich panels with a range of cutout size and a constant weight, an optimal ratio of the core to the face thickness has been studied for the maximum buckling stability. The finite element method and an analytical method are employed to perform parametric studies. In both constant stress and constant displacement shear loading conditions, the results are in very good agreement with those obtained from experiment for selected cutout reinforcement cases. Conclusions are drawn on the cutout reinforcement design and S. Guo (&) Department of Aerospace Engineering, School of Engineering, Cranfield University, Bedfordshire MK43 0AL, UK e-mail: [email protected] L. Zhou C. W. Cheung School of Engineering and Mathematical Sciences, City University, London EC1V 0HB, UK e-mail: [email protected] C. W. Cheung e-mail: [email protected]
improvement of stress concentration and buckling behaviour of shear loaded laminated and sandwich composite panels with cutouts. Keywords Monolithic carbon/epoxy plate Composite sandwich panels Shear loaded Cutout reinforcements
1 Introduction It is well known that laminated composite materials are increasingly used in aircraft structures for their great potential to achieve structural design tailoring in specific stiffness and strength, weight saving and desirable mechanical behaviour against applied loads. However, cutouts are often necessary in the construction of aircraft structures for lightening holes, passages for wire bundles, hydraulic and fuel pipes, control linkages, accessibility for final assembly and maintenance inspections. In the construction, cutout usages are categorised (Niu 2001) and the most noticeable feature of cutout for metallic structure is the rounding of the corners to prevent excessively high stress concentrations. Aircraft engineers view cutouts in airframe structures with disfavour because they cause reduction in strength and stiffness and the necessary reinforcement increases cost and weight to the overall design. In addition, the design of reinforcement is a difficult task since it is a problem area for both static and
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fatigue strengths and there is insufficient design data especially with regard to composite structures. To ensure structural integrity around a cutout in composite structures, two approaches are currently used. Firstly, the thickness of the st
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