NATURAL FREQUENCIES OF THICK, LAYERED COMPOSITE PLATES

We develop analyses and numerical calculations for the free vibration of simply supported, thick, layered composite plate strips composed of off-axis lamina. It is assumed that each layer of the composite plate is of arbitrary thickness and possesses up to monoclinic symmetry. Fo rmal solutions are obtained for the individual layers which relate the field variables at the upper and lower layer surfaces. Here, linear t ransformations are used to refer the anisotropy of each layer to a glo bal coordinate system. The solution of the characteristics for the tot al system proceeds by utilizing the matrix transfer method, which reli es on satisfying appropriate interfacial conditions across the constit uents, and results in a third-order eigenproblem. The order of the fre e vibration eigenproblem of the layered plate strip is thereby rendere d independent of the number of layers in the composite plate. Numerica l illustrations are given in the form of normalized natural frequency vs nondimensionalized mode number. The effect of the plate's microstru cture on its vibration characteristics is investigated by examining ch anges in natural frequencies for various laminate lay-ups and material combinations.