Lateral–Torsional Instability of Soft-Core Sandwich Beams with Intermediate Supports

Abstract The lateral–torsional instability of soft-core sandwich beams with intermediate supports and the impact of the sandwich configuration on the evolution of instability are investigated. A nonlinear, high-order, sandwich model that accounts for the nature of the soft-core sandwich construction, its response to flexure and twist, and their interaction with the intermediate supports is adopted for this purpose. The research novelty lies in exploring, for the first time, the combined impact of the sandwich configuration and the supporting scheme on lateral–torsional instability and the roles these features play in the global nonlinear behavior. The numerical part of the investigation validates the model, explores two case studies, quantifies the parametric sensitivity, and reveals the unique physical features of the sandwich structure. In particular, the coupled evolution of global, wrinkling, and lateral instabilities, the distortion of the sandwich cross-sections, and the localization of stresses and deformations are observed and quantified. The paper presents new findings on the complex nonlinear response of sandwich beams to flexure, and the role of the core layer in this response. It shows that the combined effect of the core deformability and the presence of intermediate support can alter the sequence of instabilities. With relatively stiff cores, the lateral instability governs the nonlinear behavior. With more compliant cores, the localized distortion of the cross-section with the intermediate support triggers wrinkling and interactive local–global instability. These observations reveal, for the first time, the combined impact of the sandwich construction on its lateral instability and provide new insight into the nonlinear behavior of soft-core sandwich beams.