Localized effects near non-vertical core junctions in sandwich panels - A high-order approach

The article investigates the role of localized effects in the vicinity of junctions between core materials of different stiffness when these joints are non-vertical and may take any shape. The mathematical formulation uses a variational approach, and the proposed analysis incorporates the effects of the vertical flexibility of the core following the high-order sandwich panel theory (HSAPT) approach. The proposed analysis is geometrically non-linear. The presented study examines various joint types in the vicinity of the boundaries between cores of different stiffness in the load introduction zone, including: straight vertical (traditional 'butt' junction), straight non-vertical with different inclination angles, a double line joint, and finally a double line joint with extremely large difference between the stiffness properties of the joined cores. The response is described in terms of deflections and stress resultants in the face sheets, as well as in terms of the interfacial stresses at the upper and lower face-core interfaces near the edges of the stiffened core. The concept of equivalent modulii for the modulus of elasticity and the shear modulus of the core is presented and validated through numerical examples. It is shown that the stress concentrations induced near junctions between core materials of different stiffness can be reduced significantly, if non-vertical junctions are used instead of the traditional vertical ('butt') junctions.