Axially-Loaded Sandwich

Edge-loaded sandwiches such as columns and walls are subject to failure by overstressing the facings or core, or by buckling of the member as a whole. Direct stresses in facings and core can be calculated by assuming that their strains are equal, so that 

P = total load Of = facing stress Oc = core stress 

Af = cross-sectional area of facings /If = cross-sectional area of core 

Usually the elastic modulus of the core is so small that the core carries litde of the total load, and the equation can be simplified by 

The column buckling load of a sandwich L long simply supported at the ends is given by 

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Bonded inserts are also commonly used in sandwich structures, most typically in panels. The insert is bonded into the core and to one or both skins of the sandwich. Loads are then directed to the joint through the mechanical fasteners (i.e. the insert) in their axial direction, causing out-of-plane loading of the sandwich component. Sandwich structures typically have thin skins and therefore the loads from the insert are mainly transferred to the core. If the insert is loaded in the in-plane direction of the sandwich member, the connection is categorised as an embedded insert and it should be designed as a mechanical connection. 

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