High‐Order Behavior of Sandwich Beams with Flexible Core and Transverse Diaphragms

Abstract

The bending behavior of a sandwich beam with transversely “soft” core and transverse diaphragms is analytically investigated using variational principles. The beam consists of one or two skins, upper and lower, interconnected at discrete locations through transverse diaphragms, metallic or composite laminated, with a symmetric lay‐up and a fully or partially bonded (delaminated) transverse flexible core made of foam or low‐strength honeycomb type. The diaphragm is rigidly connected to the skins but may be bonded or unbonded with the adjacent core through its entire height. The analysis considers the discrete diaphragm as a concentrated interference that affects the beam's behavior through particular boundary and continuity conditions. The behavior of the beam is determined with the aid of a high‐order theory that uses a two‐dimensional elasticity formulation for the core, in the longitudinal and the transverse directions, combined with a beam theory for the skins and the diaphragms. The core‐diaphragm interaction is determined explicitly for the bonded and the unbonded cases and the equivalent conditions in terms of the solution unknowns are derived. The presence of a discrete diaphragm yields concentrated effects that affect the beam's behavior globally and locally. These localized effects are significantly important for the safety of the structure and are explicitly determined by the analysis for the entire structure as well as in the vicinity of the diaphragm. A study that investigates the effects of the existence of a reinforcing diaphragm and its interaction with the adjacent core in a vertical cut‐off end connection between a sandwich panel and its supporting members is presented, including the level of stress concentration involved.