Honeycomb and Other Structural Sandwich Panels

Structural sandwich panels represent what is probably one of the most common applications for structural adhesives. Facing materials can be made to adhere to core materials, such as aluminum or paper honeycomb, to give a high composite strength-to-weight ratio. 

Adhesives with filleting properties are required for honeycomb cores. A modified phenolic is often used with aluminum honeycomb for high strength, while a neoprene- or nitrile-based organic solvent type of adhesive is often used with impregnated paper honeycomb. Epoxy adhesives are also commonly used in the fabrication of honeycomb sandwich panels. 

Facings of metal, paper, or plastic may be combined with a variety of solid-core materials. The adhesive must transmit shear stress from the facing to the core. It must also be able to resist the tendency of the thinner facing to buckle under design loads or under thermal stresses caused by variations in the panel components coefficients of thermal 

Common adhesives for sandwich construction include nitrile phenolic films, modified epoxy pastes and films, epoxy-nylon films, polyimide films, and modified urethane liquid 

Concrete provides a substrate surface that changes during its cure and also during environmental exposure. The main difficulty with bonding concrete is due to the presence of moisture. This moisture can be retained in fresh concrete and may be present in old concrete due to the environment. 

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