COMBINED STEADY-STATE NONLINEAR HEAT-TRANSFER THERMAL POSTBUCKLING COMPUTATIONS IN UNSTIFFENED AND STIFFENED LAMINATED COMPOSITE PLATES ANDSHELLS

A computational scheme for the solution of the decoupled (i.e. applied stepwise sequentially) nonlinear steady-state heat transfer and geome trically nonlinear thermoelastic problem is presented for unstiffened and stiffened multilayered composite plates and shells. More specifica lly, a two-step formulation is conceived; first, the nonuniform temper ature held resulting from applied heat fluxes is estimated by consider ing the three modes of heat transfer, namely nonlinear conduction, con vection and radiation; second, the resulting temperatures are used as input to a stress analysis code which performs geometrically nonlinear analysis of composite panels with emphasis on thermal postbuckling co mputations. Two triangular elements are used for the computational exp eriments. For the solution of the heat transfer problem a 3-node trian gular shell element is adopted which estimates the temperatures based on a first-order thermal lamination theory by employing primarily Cart esian notation. The element uses exact integrations for all nonlinear conduction, convection and radiation matrices [1,2] and accomplishes t his by using extensive symbolic algebra techniques. The nonlinear stre ss analysis problem is solved using a shallow shell multilayered trian gular element of varying and adaptable curvature which can accomodate the dependence of the material properties on temperature and also util izes only exact integrations [5] made possible by employing once again symbolic computation; the latter element is developed using the princ iples of the natural mode method. The algorithms used for the solution of the two-stage problem are discussed. Numerical examples are presen ted which show the efficiency of the formulation and the interest of t he thermophysical problem in hand.