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The growth in practical applications of sandwich constructions in high performance vehicles, aerospace, marine, automobile, and electronic packaging industries needs a thorough investigation of all vibration modes of the structure. This is to ensure that debonding between facings and core in the through-thickness vibration mode does not occur during service. In the present work, experimental modal analysis on sandwich panels of different densities and core thicknesses have been carried out under three different boundary conditions. The influence of rigid inserts of different volume fractions on the dynamic behavior has also been examined. A non-dimensional parameter representing the ratio of core density and core thickness to face density and face thickness has been established, which correlates excellently with measured fundamental natural frequency. The corresponding mode shapes and modal damping have also been evaluated.

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Sandwich panels with strong and stiff face sheets separated by light weight core are increasingly being used in aero-space, marine, automobile, and electronic packaging industries due to their low mass coupled with other attractive properties like corrosion resistance, thermal insulation, and acoustic damping. Most of the design methodology for the sandwich constructions is based on stiffness and core shear stress and the methodologies do not bring out clearly the loading situations under which sandwich panels would work. In this work, a holistic approach has been made to identify the applicability of sandwich construction based on a step-by-step procedure combining the stiffness requirement, allowable core shear stress, interface bond strength, allowable face compressive strength derived from failure modes. Further, weight optimization exercise is also included as a part of design procedure. A computer algorithm is developed and is illustrated with an example on sandwich beam with epoxy-resin impregnated bi-woven glass cloth as face sheets and polyurethane foam as core material with densities varying from 100 to 400 kg/m3.

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