PARAMETRIC STUDY ON LAMINATED STIFFENED PANELS SUBJECTED TO TRANSVERSE LOADING

Abstract

Stiffened panels are general structural elements in weight sensitive structural systems such as long span girders, aerospace structures, ship decks hulls and superstructure of offshore oil platforms. These panels are becoming increasingly used in structural applications because of their high specific stiffness (stiffness per unit weight) and high specific strength ( strength per unit weight).The stiffened elements representing a relatively small part of the total weight of the structure substantially influence their strength, stiffness and stability. In the present work parametric study is carried out on unstiffened and stiffened laminated composite orthotropic panels and the behavior of the panel is studied. Parameters used in this work include aspect ratio, orthotropic ratio and patch load size. FEM software ANSYS 10 version is used for this patch loading analySis and the models are validated from the literature. An attempt has been made to make use of pigeaud's curve which was developed for isotropic panels to be used for laminated composite orthotropic panels. Multiplying factors are produced which can be used along with pigeaud's curve to obtain moment co-efficients for laminated composite orthotropic panels. The dummy load procedure given by pigeaud for obtaining moment co-efficients for un-symmetrically placed load is validated for orthotropic laminated composite panel for different orthotropy ratios. An orthotropy ratio of 10, 1 and 0.1 are used for unstiffened panel where the ratio is varied by changing the fiber orientation. Stiffened panels are used in order to obtain higher orthotropy. In the present work transversely stiffened panels are used in order to obtain higher orthotropy in the transverse direction. From the literature review it is observed that the behavior of stiffened panel under patch loading has not been studied yet which is also carried out in this thesis work. Numerical studies by changing the aspect ratio, orthotropy ratio and patch load size are presented to get an understanding of the bending behavior of stiffened panels.