The shear buckling behaviour of thin composite plates with particular reference to the effects of bend-twist coupling

The effect of bend-twist coupling on the shear buckling behaviour of lamina ted composite plates is examined in this paper using a finite strip procedu re. The complex buckled shapes which are associated with shear loading are duly accounted for in the analysis approach through the multi-term facility of the strip formulation employed and, of course, through the appropriate level of structural modelling. The degree of bend-twist coupling in the lam inated composite plates is varied by changing the level of anisotropy in th e plies and by altering the lay-up configuration of the plies in the lamina ted stack. Symmetric laminates of a balanced and unbalanced nature are give n consideration. It is shown that, for a given degree of anisotropy in the plies of a laminate and for a given laminate thickness, the stacking sequen ce of the plies significantly alters the degree of bend-twist coupling. The shear buckling performance of composite plates having the same dimensions and being made from the same material are therefore shown in the paper to b e quite different. The preclusion of the bend-twist coupling coefficients i n the solution procedure of the finite strip method allows the shear buckli ng orthotropic solution to be determined. Comparisons between the coupled a nd orthotropic solutions are shown in the paper to be markedly different wi th respect to critical shear performance level and also buckled mode shape. For square plates or plates with a moderate aspect ratio the influence of bend-twist coupling on buckled mode shape is shown in the paper to be notic eable through increased distortion. For the larger aspect ratio plates it i s shown that the presence of bend-twist coupling can cause a complete chang e in the mode shape from a symmetric to an antisymmetric nature or vice ver sa. Amplitude modulation is shown in the paper to be clearly evident in the shear buckling mode shapes of long plates. (C) 2000 Elsevier Science Ltd. All rights reserved.