Influence of Trapezoidal Shapes and Cutout Sizes on the Buckling Behaviour of Composite Laminates Under Thermally Induced Loads

TRAPEZOIDAL LAMINATED PLATES WITH CUTOUTS ARE COMMONLY FOUND IN MANY ENGINEERING FIELD, ESPECIALLY IN AEROSPACE STRUCTURES. IN MANY CASES THESE PLATES ARE SUBJECTED TO VARIOUS HARSH ENVIRONMENTAL CONDITIONS DURING ITS SERVICE LIFE. THERMALLY INDUCED LOAD IS THE ONE WHICH SERIOUSLY AFFECT THE BUCKLING CHARACTERISTICS OF THE STRUCTURAL COMPONENTS. THE STUDY PRESENTS THE EFFECT OF RISE IN TEMPERATURE ON THE THERMAL BUCKLING CHARACTERISTICS OF TRAPEZOIDAL LAMINATED COMPOSITE PLATES WITH AND WITHOUT CUTOUTS BY USING FINITE ELEMENT TECHNIQUE. IN ORDER TO MODEL THE PLATE, A 9-NODED HETEROSIS PLATE ELEMENT HAS BEEN USED BY INCORPORATING THE EFFECT OF SHEAR DEFORMATION. BY CORRELATING PRESENT FINDINGS WITH THE AVAILABLE LITERATURE, THE EFFECTIVENESS OF THE PRESENT FORMULATION IS VERIFIED. FOR A GIVEN TRAPEZOIDAL SHAPE AND CUTOUT SIZE, THE THERMAL STRESS DISTRIBUTION WITHIN THE PLATE IS HIGHLY NON-UNIFORM IN NATURE, THUS TWO TYPES OF BOUNDARY CONDITIONS HAVE BEEN USED. ONE IS FOR INITIAL STRESS CALCULATIONS AND OTHER ONE FOR THERMAL BUCKLING CALCULATIONS. THE PRESENT STUDY MAINLY DEALS WITH THE EFFECT OF THE VARIOUS CUTOUT SIZES AND THE TRAPEZOIDAL SHAPES UNDER THERMALLY INDUCED LOADS. THE COMPUTER PROGRAM BY USING FORTRAN LANGUAGE HAS BEEN DEVELOPED TO INVESTIGATE THE EFFECT OF DIFFERENT PARAMETERS SUCH AS TRAPEZOIDAL SHAPES, CUTOUT OFFSETS, PLATE ASPECT RATIO, PLY-ORIENTATIONS, DIFFERENT THICKNESS AND PLATE EDGECONDITIONS. THE INFLUENCE OF EACH PARAMETER ON THE THERMAL BUCKLING BEHAVIOR IS WELL INVESTIGATED THROUGH THIS WORK.