NATURAL FREQUENCY-CHARACTERISTICS OF COMPOSITE PLATES WITH RANDOM PROPERTIES

Exercise of complete control on all aspects of any manufacturing / fab rication process is very difficult, leading to uncertainties in the ma terial properties and geometric dimensions of structural components. T his is especially true for laminated composites because of the large n umber of parameters associated with its fabrication. When the basic pa rameters like elastic modulus, density and Poisson's ratio are random, the derived response characteristics such as deflections, natural fre quencies, buckling loads, stresses and strains are also random, being functions of the basic random system parameters. In this study the bas ic elastic properties of a composite lamina are assumed to be independ ent random variables. Perturbation formulation is used to model the ra ndom parameters assuming the dispersions small compared to the mean va lues. The system equations are analyzed to obtain the mean and the var iance of the plate natural frequencies. Several application problems o f free vibration analysis of composite plates, employing the proposed method are discussed. The analysis indicates that, at times it may be important to include the effect of randomness in material properties o f composite laminates.