THE NONLINEAR PREBUCKLING RESPONSE OF SHORT THIN-WALLED LAMINATED COMPOSITE CYLINDERS IN BENDING

The geometrically nonlinear Donnell shell theory is used to determine the prebuckling response of short thin-walled laminated circular cylin ders in bending. Bending is induced by a known rotation of the clamped cylinder ends. The equilibrium equations and strain-displacement equa tions are manipulated so the governing partial differential equations are in first-order form. Using the separation of variables technique, along with a harmonic expansion in the circumferential direction, thes e first-order partial differential equations are converted to first-or der ordinary differential equations. These equations are solved numeri cally using a finite-difference procedure and prebuckling responses ar e computed for cylinders with a radius:thickness ratio of 160 and leng th:radius ratios of 2 and 5. The range of validity of the prebuckling solution is limited by the critical, or buckling, end rotation, which is estimated by the simple classical method. The use of the classical estimate is justified by comparing it with more rigorous approaches. T hree laminated composite cylinders are considered: an axially stiff [- /+45/0(2)](s) layup, a circumferentially stiff [-/+45/90(2)](s) layup, and a quasi-isotropic [-/+45/0/90](s) layup. The displacement respons e is discussed for each cylinder as a function of axial and circumfere ntial location, with particular emphasis on the character of the radia l displacement and the boundary layer associated with the nonlinear re sponse. Comparisons with a geometrically linear. analysis are made. An analog with the axial compression problem is developed and valuable i nformation about boundary layer length as a function of laminate mater ial properties and applied end rotation is presented. In addition, the role of the laminate Poisson's ratio nu(x theta) on the displacement behavior is discussed. (C) 1996 Elsevier Science Ltd.