Designer viscoelastic nano - Composite and sandwich materials

The paper presents an analytical study of viscoelastic composite-sandwich plates consisting of calculus of variation and inverse approaches to determine optimum designer materials, which will specify optimum ply orientation, stacking sequences, number of fibers, number of plies, viscoelastic properties, weight, etc., for pre-determined service conditions. This is the opposite of selecting "off the shelf" composites with available fiber orientation to satisfy the identical task. The ultimate aim is to analytically engineer composites that lead to low weight, high strength and long life aerospace structures. The governing constraint for the designer material considerations is delamination onset probability and creep survival / life time. In particular, an analysis is presented for the theory of designer nano-viscoelastic composite and sandwich materials as an extension of the general theory developed in [1 - 5]. Designer materials are defined by inverse determinations through calculus of variation protocols of optimum tailored/engineered material property parameters that achieve the best prescribed conditions, such as maximum stress, defection, survival time, and least weight, cost, failure probability, etc. These protocols determine optimum designer materials, which will specify ply orientation and number of plies for pre-determined service conditions. This is the opposite of selecting off the shelf composite/ sandwich materials with predeter-mined fiber orientation, plies, etc. to satisfy identical tasks. While the analysis is given in general terms, such optimum solutions must be applied on a case-bycase basis for each combination of governing and con-straint relations. It is noted that the analysis is identical for nano- and macro- composite and sandwich materials, although optimized parameters will differ. An illustrative example of a composite/sandwich plate subjected to aerodynamic noise is presented. These protocols are applicable to a variety of problems in-volving static or dynamic aero/hydro elastic or viscoelastic problems, including responses to variety of loads, aerodynamic lift and vibrations. Such designer materials are in particular pertinent to the analysis of standard aircraft, UAVs and MAVs with fixed or movable lifting surfaces, composite submarine hulls, automo-bile bodies and electronic circuit boards.