海水老化下类填充微穿孔板结构水下吸声材料的性能及其寿命预测

Effect of seawater aging on performance of filled-microperforated plate-like underwater sound absorption materials and durability prediction

针对现阶段潜艇用水下吸声材料的低厚度强低频吸声的性能诉求,基于三维间隔织物,将兼具多孔和共振吸声特性的类填充微穿孔板(F-MPPL)结构引入常规空心微珠填充水下吸声材料(HBF复合材料)中,设计出新型三相复合水下吸声材料(F-MPPL复合材料)。鉴于海中复杂环境对水下吸声材料声学性能的影响,采用人工海水浸泡的方法对F-MPPL复合材料进行海水老化,结果发现老化12个月后的F-MPPL复合材料平均吸声系数下降了13.6%。同时,基于海水老化下孔隙率和穿孔率的变化对最终宏观模型仿真结果的影响,对F-MPPL复合材料的水下吸声性能寿命进行预测发现,模型可准确预测材料吸声峰值的位置,但对材料吸声系数峰值的大小预测稍有偏差。研究结果可为各类水下吸声材料的吸声性能老化研究提供实践经验,并为F-MPPL结构在海水老化下的长期寿命预测及性能优化提供理论参考。

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(HBF composite).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 1000 Hz and accurately predict the peak location 1900 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 1000 Hz and accurately predict the peak location 1900 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 500-4000 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.