Sandwich structures are often used to capitalize on the benefits of the individual components. Thus, it is essential to compute the overall mechanical behavior and buckling characteristics of these structures. This study employs analytical methods to address the buckling issue of sandwich beams, including the flexoelectric effect and the combined effects of temperature and moisture for the first time. The formulae are derived from the new shear deformation theory and consider large strain following Von-Karman’s theory. The nonlocal theory also considers the small size impact simultaneously. The critical load is derived in an explicit analytical form to clearly demonstrate the influence of temperature, moisture content, size-dependent effects, geometric nonlinearity, and the flexoelectric effect. The establishment of such a comprehensive expression constitutes the key novelty of the present work and has not been reported in the existing literature. The calculation theory has been confirmed by comparing it with both analytical findings and numerical data. This study examines how material characteristics, geometry, and temperature affect the buckling response of sandwich beams. This research demonstrates that the flexoelectric effect has enhanced the rigidity of the structure, hence improving the operational efficiency of the sandwich beam.
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