Face Wrinkling Instability in Circular Sandwich Frames with Composite Laminated Faces and Isotropic Foam Cores

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Mohammed Ali Hjaji A. K. El-Senussi Ezedine Allaboudi Hasan Nagiar


The theoretical solution of the face wrinkling instability of circular sandwich frames with isotropic cores and composite laminated faces when subjected to in-plane compressive stress is investigated. The equilibrium buckling equations for the orthotropic laminated faces and isotropic foam cores are derived. The problem is governed by four simultaneous differential equations for displacement functions of the faces. A solution is determined by using a suitable Airy stress function combined with appropriate displacement continuity conditions at the face-core interfaces. For non-trivial solution of these equations, the second order algebraic equation in the in-plane constant compressive stress is obtained. Numerical results are then carried out to predict the critical wrinkling in-plane compressive loads in the sandwich faces. Two types of laminations are considered; symmetrical three-layer cross-ply (0o, 90o, 0o) and angle-ply (+45o, -45o, +45o) laminates. The results obtained based on the present formulation are compared with aluminum alloy isotropic. The effects of sandwich face thickness, sandwich ring middle surface radius, Poisson’s ratio, core thickness on the critical wrinkling constant compressive loads are investigated.

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