On application of catenary principles to sandwich structure design—Sandwich/ catenary hybrid beams under uniformly distributed load

Abstract

Application of catenary principles to sandwich structure design, whereby one face sheet follows the equilibrium shape of a catenary according to the applied load, is investigated. The difference between load transfer through a sandwich beam and through a catenary is outlined. An initial comparison between an inclined elastic string and a sandwich core under shear deformation provides an indication of the potential stiffness advantages of catenary design. A stiffness comparison is made between an ordinary sandwich beam with thin, parallel face sheets, a catenary suspended by the end-points, and a sandwich/catenary hybrid. It is demonstrated that, for mass parity and a uniformly distributed load, and depending on the constituent materials moduli, the sandwich/catenary hybrid may be designed for superior stiffness. A numerical modeling method is outlined for evaluating the deflection of a catenary, and subsequently expanded to predict deflection of a sandwich/catenary hybrid beam. The method is verified through comparison with experimentally measured deflection. It is demonstrated that first-order shear deformable theory, commonly applied to sandwich structures, is inherently unsuited for describing the elastic response of sandwich/catenary hybrids. For a typical range of face-sheet/core moduli, comparisons of relative stiffness for parallel-face sandwich beams and sandwich/catenary hybrid beams are calculated over a range of core heights, for equivalent core height and equivalent core volume.