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A damage investigation of a lightweight composite sandwich beam under concentrated loading

Abstract Sandwich beam damages are different from thick laminates because of thick and low modulus core. Faces and core fracture and core compressive yielding are three major damages of a lightweight sandwich beam under concentrated loading. The sandwich panel classical theory (SPCT) measures core compression using the Winkler foundation theory. The sandwich panel higher-order theory (SPHOT) assumes sandwich beams in three sections (top face, core, and bottom face). SPHOT models deformation of faces with the classical laminate deformation theory and for core with the elasticity theory. This is a closed-form solution resulting in seven ordinary differential equations (ODEs). The compression of the core is also considered. In the present research, the behaviour of faces is modified according to the first-order shear deformation theory in SPHOT. The modified sandwich panel higher-order theory (MSPHOT) models behaviour of sandwich beam with nine ODEs. The present article shows that core compressive yielding damage is the first damage mode in a fully backed (sandwich on the rigid ground boundary condition) state. Faces fracture, core fracture, and core compressive yielding (indentation) are examined in three point bending by mentioned theories, and the results (SPHOT, MSPHOT) are compared with those obtained from finite element-analysis using ANSYS software and the available experimental data. SPCT predicts core fracture critical load well but results show good agreement between MSPHOT and the experimental data for face fracture and core compressive yielding.