IMPROVED HIGH ORDER FREE¬ VIBRATION ANALYSIS OF THICK DOUBLE CURVED SANDWICH PANELS WITH TRANSVERSELY FLEXIBLE CORES

Abstract

THIS PAPER DEALT WITH FREE VIBRATION ANALYSIS OF THICK DOUBLE CURVED COMPOSITE SANDWICH PANELS WITH SIMPLY SUPPORTED OR FULLY CLAMPED BOUNDARY CONDITIONS BASED ON A NEW IMPROVED HIGHER ORDER SANDWICH PANEL THEORY. THE FORMULATION USED THE FIRST ORDER SHEAR DEFORMATION THEORY FOR COMPOSITE FACE SHEETS AND POLYNOMIAL DESCRIPTION FOR THE DISPLACEMENT FIELD IN THE CORE LAYER WHICH WAS BASED ON THE DISPLACEMENT FIELD OF FROSTIG'S SECOND MODEL. IN THIS CASE, THE UNKNOWNS WERE COEFFICIENTS OF THE POLYNOMIALS IN ADDITION TO DISPLACEMENTS OF THE TOP AND BOTTOM FACE SHEETS. THE FULLY DYNAMIC EFFECTS OF THE CORE LAYER AND FACE SHEETS WERE ALSO CONSIDERED IN THIS STUDY. USING HAMILTON'S PRINCIPLE, THE GOVERNING EQUATIONS WERE DERIVED. MOREOVER, EFFECT OF SOME IMPORTANT PARAMETERS LIKE THAT OF BOUNDARY CONDITIONS, THICKNESS RATIO OF THE CORE TO PANEL, RADII CURVATURES AND COMPOSITE LAY-UP SEQUENCES WERE INVESTIGATED ON FREE VIBRATION RESPONSE OF THE PANEL. THE RESULTS WERE VALIDATED BY THOSE PUBLISHED IN THE LITERATURE AND WITH THE FE RESULTS OBTAINED BY ABAQUS SOFTWARE. IT WAS SHOWN THAT THICKER PANELS WITH A THICKER CORE PROVIDED GREATER RESISTANCE TO RESONANT VIBRATIONS. ALSO, EFFECT OF INCREASING THE CORE THICKNESS IN GENERAL WAS SIGNIFICANT DECREASE IN FUNDAMENTAL NATURAL FREQUENCY VALUES.