High-order bending of sandwich beams with a transversely flexible core and unsymmetrical laminated composite skins

The bending behavior of a sandwich beam with a “soft” core and unsymmetrical laminated composite skins has been analytically investigated. The effects of the extension-bending coupling caused by the unsymmetrical layups on the bending behavior, are presented. The skins may be made of different materials, different layups, i.e. symmetrical or unsymmetrical, different geometries and may have different boundary conditions (even at the same section). The “soft” core is considered compressible and a change in its height is allowed. The analysis uses variational principles and models the core as a two-dimensional elastic medium, and the skins as one-dimensional composite laminated beams, or a composite panel with cylindrical bending. The analysis is general, rigorous, includes high-order effects and uses closed-form solutions for any type of sandwich construction, for any type of loading and for any combination of boundary conditions. The solutions include the stress and displacement fields along the beam and through the height of the core. Local effects in the vicinity of concentrated loads that consist of dimples and high bending moments in the skins and abrupt changes in the peeling stresses, are studied.