Study On Underwater Vibration Characteristics Of High Damping Composite Materials

The ship will generate noise due to vibration in the course of water moving forward.The presence of noise will reduce the stealth effect of the ship,make it easy to be detected,positioned and tracked by the enemy,which greatly reduces the survival and combat effectiveness of the ship.The technology of vibration reduction and noise reduction can effectively reduce the self noise of ships.On the one hand,the detection distance of sonar(when attacking)is increased,on the other hand,the concealment of ships(when defending)is improved,and the attack and defense ability can be enhanced.At present,it is difficult to make breakthrough in the research on the technology of vibration reduction and noise reduction around traditional materials and structures.Therefore,this paper attempts to use the characteristics of light,high damping and strong designability of composite materials to seek high damping composite materials and design new composite structures to realize the vibration reduction and noise reduction of underwater ship structures.Firstly,two kinds of high damping composites,carbon fiber / vinyl and aramid fiber / vinyl,were prepared.The experiments of high and low temperature circulation,salt mist box aging and high pressure seawater medium are carried out around various complex environment conditions of ship operation.The mechanical and damping properties of high damping composite materials under different environmental conditions are analyzed,and the underwater mechanical / acoustic performance parameters of composite materials are improved.Secondly,based on the method of fluid solid coupling and modal strain energy,the numerical simulation method of underwater composite vibration characteristics is established.The finite element model of composite laminate is constructed by ACP technology;The modal and modal acoustic modules of workbench are used to calculate and analyze the dry / wet modal performance;The damping performance parameters are extracted by APDL parametric finite element method.Based on this method,the natural frequency,mode mode and damping ratio of carbon fiber / vinyl composites under air / underwater environment are studied;The underwater vibration characteristics of high damping composites with different reinforcements(carbon fiber and aramid fiber)were analyzed;The influence of different fiber placement angles on the mode mode,natural frequency and damping ratio of composite materials is studied,which provides the basis for further design of high damping composite materials and structures.Finally,the structure of high damping sandwich composite is designed by using finite element numerical simulation technology.The vibration characteristics of the composite materials such as the mode,natural frequency and damping ratio of the wet and dry modes are analyzed,and the performance of the composite is compared with that of the composite with high damping;At the same time,the sandwich composite structure was prepared by 3D printing technology,and the technological realizability of different sandwich structures was analyzed,and its damping performance was tested and analyzed.The results show that the damping performance of sandwich structure composites is significantly improved compared with that of ordinary carbon fiber / vinyl resin composites.