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FROM:
Ali Talezadehlari and Gholam Hossein Rahimi (Mechanical Engineering, Tarbiat Modares University, Tehran, Iran),
“Investigating the effect of circular opening on axial buckling of unstiffened and stiffened composite shell”, International Academic Journal of Science and Engineering, Vol. 3, No. 5, pp 116-125, 2016
ABSTRACT: Due to high strength and stiffness-to-weight ratio of composite materials, they are increasingly being used in different industries in the last decades. Cylindrical composite shells are one the most common structures and depending on their usage they may face several loading condition. One of the most popular failures of these structures is buckling under axial compression. Different types of stiffeners can be added to improve the buckling resistance of these structures. Moreover, these cylinders may have some opening because of several reasons such as weight reduction, make access to inner part, and attach other equipment. Existence of an opening affects the buckling behavior of composite shells, and they should be considered in designing these structures. Circular cutout is one the most common opening. In this paper, by employing commercial finite element package ABAQUS, a numerical study is carried out to investigate the effect of cutout size on the axial buckling response of unstiffened and stiffened composite shell. The presented model is verified in comparison with the experimental and numerical results available in the literatures. The results show that the perfect unstiffened shell always fails in global mode but the failure mode of the stiffened one depends on the skin thickness. The results also indicate that for the perfect shell, the maximum improvement in buckling load according to adding stiffening ribs befalls in the case that the combination of global buckling and local skin buckling occurs. Although the influence of existence of an opening on the buckling behavior of composite shells is generally similar but there are some differences. For example, increasing the cutout size in simple shell always decreases the critical load; however, in the stiffened cylinder the buckling load may increase. The results also illustrate that the stiffened shell always have higher critical load than the unstiffened ones. Even thought, for some sizes of the cutout the difference between the buckling load of the stiffened and unstiffened shell tends to zero.
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