Fused Deposition Molding And Acoustic Properties Of TPU/ZnO Underwater Sound Absorption Structure

With the application of Low frequency active sonar(LFAS),due to improve the safety and concealment performance of the underwater vehicle,developing the surface sound-absorbing coating with excellent performance have great significance;and 3D printing technology as a non-mold molding process has great use of space in the verification and actual manufacturing of underwater sound absorption structure in the future.In this paper,a thermoplastic urethanes(TPU)and zinc oxide composite wire will be prepared as the base material of sound absorption structure,in order to improve the sound absorption performance,designing a local resonance underwater sound-absorption structure with double cone metal vibrator,using an algorithm to optimize the sound-absorption structure and obtain the best structure.Finally,the underwater sound-absorption test sample with above-mentioned structure will formed by fused deposition molding(FDM)printing.Through the basic theory of wave acoustics,research and discussion the influence of characteristic impedance and loss factor on the sound absorption performance of materials,obtaining the calculation method of sound absorption coefficient based on sound energy,which lay a foundation for the modeling calculation in the following paper.From Bloch theory provide a theoretical basis for setting model boundary conditions and calculation method of band structure.Through calculating and analyzing the band structure of the local resonance structure with simple spherical vibrator and combining with the local resonance mechanism to discuss the cause and the influence in the sound-absorption of band gap,lay a theoretical foundation for the subsequent research.From the above discussion,the simulation model of underwater sound absorption structure is established in Comsol Mutiphysics software,by the way,its rationality and correctness were verified.Through curves of the absorption coefficient and elastic strain,finding there has a close relationship between the band gap which caused by vibration response in the local resonance structure and sound absorption performance of this structure,combined with the local resonance mechanism to further explore the influence of material performance and the geometric structure on the sound absorption performance,providing direction for material selection and structure design.Based on the above research,a double cone local resonance underwater sound absorption structure is proposed,which can improve the sound absorption performance by optimizing the geometric structure without changing the mass of the vibration.Genetic algorithm is adopted and fitness function is designed to achieve directional optimize that structure.Geometric optimization of the local resonance structure whit the double cone is carried out to obtain a sound absorption structure with two broadband peaks absorption which coefficients higher than 0.8 within 6000 Hz and an average absorption coefficient is 0.6092.The surface coating modification technology of nano-ZnO was investigated,and TPU/ZnO composite wires with different filling rates were prepared by ball milling and single screw extrusion.The elastic modulus,density and loss factor which have significant influence on the sound absorption performance are tested.The wire was used in a fused deposition molding(FDM)printer to form the underwater acoustic absorption test sample.Based on the above studies,FDM process is adopted to prepare underwater acoustic absorption test samples,which can well combine the advantages of geometric structure design and convenient molding,and will have high application value in future related studies.