Minimum material cost design of five-layer sandwich beams

Welded aluminium box beams have very low vibration damping capacity. Regarding damping it is better to use a three-layer beam constructed from two rectangular hollow sections and a rubber layer glued between them. These three-layer beams have good damping capacity, but the dynamic deflection is large due to shear deformation of the rubber layer. To decrease this deflection two fiber-reinforced plastic layers are used. The minimum material cost design is worked out for such five-layer sandwich beams using the Rosenbrock Hillclimb mathematical programming method. Constraints on stress and local buckling are considered. A comparison is made between the optimized versions of a simple welded aluminium beam, three-layer and five-layer beams. It is shown that the deflection of the five-layer beams is smaller than that of the three-layer ones, but the cost of the five-layer beams is greater.