A Review on Vibration Damping in Sandwich Composite Structures

A sandwich structure consists of three elements: the face sheets, the core, and the adhesive interface layers. The great advantage of sandwich structures is that optimal designs can be obtained for different applications by choosing different materials and geometric configurations of the face sheets and cores. By inserting a lightweight core between the two face sheets, the bending stiffness and strength are substantially increased compared to a single layer homogenous structure, without the addition of much weight. The viscoelastic core has a high inherent damping capacity. When the beam or plate undergoes flexural vibration, the damped core is constrained to shear. This shearing causes the flexural motion to be damped and the vibrational energy to be dissipated. Additionally, the normal-to-shear coupling between the core and face sheets reduces the sound transmission. So in recent years, such structures have become used increasingly in transportation vehicles and other applications. Rao has described the applications of viscoelastic damping in automotive and aircraft structures. Besides damping treatments used in structures, sandwich glass has been used in automotive side and rear windows to reduce noise. Composite materials are also used in pipes and ducts. Nakra has published a series of reviews on vibration control with viscoelastic materials. Trovik has summarised the major uses of constrained layer damping treatments up to 1980. A thorough review of work in fibre-reinforced composite material damping research has been given by Chandra et al. Some classical books and book chapters give more details on viscoelastic damping and sandwich structures. 2. ANALYTICAL THEORIES