Objective Submarines are symbolic to a country's sea power.The long acoustic wave transmission distance,low cost of underwater acoustic communication,high flexibility and stable transmission are the only effective and mature means of underwater wireless communication.In order to ensure the operational advantages of submarines,reduce the threat of sonar detection on submarines,this research aims to improve the submarine underwater acoustic materials in terms of low thickness,strong and low-frequency acoustic performance by employing the filled microperforated plate(F-MPPL)structure into the conventional hollow bead-filled underwater acoustic material Method We have designed a new three-phase composite underwater acoustic material(F-MPPL composite)based on 3-D spacer fabrics by introducing the filled-microperforated plate-like(F-MPPL)structure,which is both porous and resonance acoustic absorption,into the conventional hollow bead-filled underwater acoustic materials(HBF composites).In view of the influence of the complex environment in the sea on the acoustic performance of underwater acoustic materials,artificial seawater immersion was used for seawater ageing of F-MPPL composites.Meanwhile,the lifetime prediction of the F-MPPL composites was explored based on the effect of porosity and perforation rate under seawater ageing on the final macroscopic model simulation results.Results The introduction of the F-MPPL structure significantly improved the underwater acoustic absorption performance of the F-MPPL composites with low thicknesses.The average sound absorption of the F-MPPL composites was higher than that of the HBF composites,and the peak values of the absorption coefficients were shifted to lower frequencies compared to that of HBF composites.The peak sound absorption coefficients of both the F-MPPL and HBF composites decreased gradually with the increase of immersion time and moved towards high frequencies,which were attributed to the increase of porosity and perforation rate,respectively.After 12 months of immersion,the average decrease in sound absorption coefficient of F-MPPL composites was 7.35%smaller than that of HBF composites,attributing to the fact that the structural damage of the F-MPPL composites was smaller than that of the HBF composites after aging.The F-MPPL structure was still retained inside the material after the 12 months of aging.The macroscopic composite acoustic absorption model established in this research well predicted the acoustic absorption of F-MPPL composites after 12 months of aging and the main absorption frequency bands.The comparison between the finite element simulation and the results of pulsed acoustic tube hydroacoustic test showed that the macroscopic composite acoustic absorption model accurately predict the acoustic absorption performance of F-MPPL composites in the underwater band of more than 1 000 Hz and accurately predict the peak location 1 900 Hz.However,the peak of the absorption of F-MPPL composites in the frequency band of 500 Hz or so was over predicted and the peak prediction of the absorption coefficient was low.Conclusion The underwater acoustic absorption performance of F-MPPL composites is better than that of HBF composites before and after aging due to the introduction of three-dimensional spacer fabrics.The prediction results of the macroscopic composite acoustic absorption model for F-MPPL composites are in general agreement with the experimental measurements,it accurately predicted the acoustic absorption performance of F-MPPL composites in the underwater band of more than 1 000 Hz and accurately predict the peak location 1 900 Hz.Therefore,it can be concluded that the macro-composite acoustic absorption model for F-MPPL composites established in this study is valid and can predict the aqueous acoustic response of F-MPPL composites in the frequency range of 500-4 000 Hz.This study provides practical experience for the aging study of the acoustic performance of various types of underwater acoustic materials,and provides theoretical support for the durability prediction and performance optimization of F-MPPL structures under seawater aging.
维普
万方数据