Acoustic Vibration Characteristics Of Low-Noise Composite Materials For Sonar Dome

Acoustic stealth performance and sonar long-range detection capability is an important factor affecting the survivability and combat effectiveness of submarines and other underwater vehicles,while the self noise of the bow sonar platform area is not conducive to the efficient work of the sonar system,these self noise sources include sonar deflector flow noise,propeller noise,hull mechanical noise,etc..At present,China’s large number of deflector structures,whether metal deflectors or non-metal deflectors,most of them are single-layer structures,whose acoustic performance and mechanical strength are difficult to take into account at the same time.In order to ensure the normal operation of the bow sonar,it is urgent to provide a design solution for the structure of the deflector with low noise and excellent sound transmission performance.This paper takes the negative Poisson’s ratio sandwich structure as the research object,and focuses on the acoustic characteristics of the sonar dome,with "the band gap characteristics of the negative Poisson’s ratio sandwich structure","the acoustic transmission performance of the negative Poisson’s ratio sandwich structure",and "the acoustic properties of the composite negative Poisson’s ratio sandwich structure"."The research focuses on the band gap characteristics of negative Poisson’s ratio sandwich structures,the acoustic transmission properties of negative Poisson’s ratio sandwich structures,the vibration and acoustic radiation characteristics of negative Poisson’s ratio sandwich structures,and the acoustic vibration characteristics of negative Poisson’s ratio structures.(1)Four types of negative Poisson’s ratio structures,namely,four-ligament chiral structure,six-ligament chiral structure,concave hexagonal structure and star structure,are studied.Several structural forms and their structural parameters were obtained to meet the performance requirements of the sonar dome.(2)As the sonar dome needs good sound transmission performance,COMSOL Multiphysics is used to analyse the sound transmission performance of the negative Poisson’s ratio structure based on the acoustic-solid coupled finite element method.Firstly,the sound transmission coefficients of steel plates and composite laminates were calculated,and the reliability of the numerical calculation method was verified by comparing with literature and experiments.Simulation studies on the sound transmission performance of negative Poisson’s ratio structures of composite materials such as four-ligament chiral structures,six-ligament chiral structures,inner concave hexagonal structures and star structures were also carried out.(3)The four-ligament chiral structure and the inner concave hexagonal structure were selected as research objects,and the finite element software(ABAQUS)and the acoustic calculation software(Virtual Lab)were used to analyse their acoustic vibration characteristics,and the sandwich panel of carbon/glass fibre composite negative Poisson’s ratio sandwich structure was compared with the commonly used material for sonar deflectors,and its good The sandwich panel with negative Poisson’s ratio of carbon/glass fibre composite material is compared with the current commonly used material of the sonobuoy.Finally,the sound vibration characteristics of the composite reinforced sandwich panel were calculated,which proved that it has good vibration damping characteristics and good sound transmission performance.(4)Modal tests,forced vibration tests,underwater vibration and sound radiation tests and free-field sound transmission tests were carried out on the composite inner concave hexagonal sandwich panel.Firstly,modal tests were carried out on the top and bottom panels,i.e.the carbon/glass fibre hybrid laminate,to obtain its inherent frequency,vibration pattern and damping loss factor,and to obtain its material parameters by multi-level parameter correction.The Mooney-Rivilin model was selected as the intrinsic model and the intrinsic model parameters were calculated.Forced vibration tests in air and water and underwater acoustic radiation tests were carried out on the composite inner-concave hexagonal sandwich panel and the results were compared with the numerical simulation data to further verify the accuracy of the numerical simulation method.Finally,a free-field acoustic transmission test in an anechoic pool was carried out on the composite inner concave hexagonal sandwich panel to verify the accuracy of the numerical simulation method and the good acoustic transmission performance of the model structure respectively.