Write a short note on sandwich panel of structural composite write its applications.

Sandwich panel (a structural composite)

A sandwich panel has two thin, strong and stiff outer face sheets (skins) bonded to a thick, lightweight core.

   ===========================  <- face sheet (Al alloy / FRP / steel / plywood)
   |/\/\/\/\/\/\/\/\/\/\/\/\/|  <- lightweight core (honeycomb / foam / balsa)
   ===========================  <- face sheet
        (adhesive bonds core to faces)

• Faces: aluminium alloys, fibre-reinforced plastics, titanium, steel or plywood. They carry the in-plane loads and the bending stresses (tension on one face, compression on the other).
• Core: low-density material such as honeycomb (aluminium or aramid paper), rigid polymer foams (PU, PVC) or balsa wood. It keeps the faces apart, resists shear and stops the faces buckling. It also gives thermal and sound insulation.
• The result is a panel with high bending stiffness and strength for very low weight.

Applications: aircraft floors, wings, rotor blades and fuselage panels; walls and roofs of buildings; ship hulls and decks; truck and railway-coach bodies; refrigerated containers; skis and surfboards; satellite panels.