Design Of A Damping Evaluation System For Viscoelastic Mateials And Study On The Damping Property Of Composite Damping Structure

Vibration and noise exist in the fields of aviation, automobile, ship and construction, which can accelerate the fatigue damage of mechanical structure, shorten the service life of machinery equipment, damage the environment of working, even do harm to human health when met with long time. The viscoelastic damping materials have been widely used to reduce the vibration and noise, which are laid on the surface of metal to prepare composite structure.There are lots of methods to characterize the dampig properties. Forced resonance method and flexural resonance method can accurately characterize the damping properties of uniform meterials, but the design of the composite structure is also an important factor for the damping property besides the viscoelastic damping material. Therefore, the article designs a set of evaluation system for viscoelastic materials which incudes the testing of meterial, structure and model. The dynamic mechanical testing guides the design and optimization of damping material, cantilever beam test is for optimization of material structure design, vibration test can give a overall damping effect of the composite plate in a frequency range, and the modal testing charactizes the resonance frequency, damping ratio and vibration type. All of these tests are consistent, complement each other, and can completely evaluate damping material on the effect of vibration and noise.In the article, we designed a new constrained-layer damping composite structure specially used in seawater wet/dry cycling. The damping layer was prepared with NBR as base material, different shapes inorganic as damping filler, which was suitable as a damping layer in sea, because glass transition temperature is about 5 degree. The effects of shape, size and amount of the fillers on damping property were analyzised in detail. The results show that the mica powder which shows a layered structure can significantly improve the damping perfoemance of materials, and when particle size is 52 um, the dosage is 60 phr, NBR get a high damping performance.Constrained-layer damping composite structure was prepared with fiber reinforced plastics as constrained layer material, can range temperature with effective damping property from 25 degree to 55 degree or above, which can avoid the strong corrosive effect in the sea when with metal material as constrained layer. Therefore the effects of temperature, stiffness of constrained layer and structure of damping layer were studied in detail. The results show that:the free damping composite has high composite loss factor when the damping layer in glass transition region, it can be extended to high elastic state regional when pasted with fiber reinforced plastics as constrained layer, increasing the thickness and the porosity of damping layer can improve the damping property of constrained-layer composite plate, the effect of the aluminum plate which pasted as constrained layer is particularly significant, however, in seawater wet/dry cycling, aluminum plate cannot be used as constrained layer because of the serious corrosion, anti-corrosion fiber reinforced plastics is preferred.