Preparation And Sound Absorption Properties Of Multilayer Foam Composites Based On Piezoelectric Effect

With the promotion of industrialization,noise and vibration pollution is aggravating day by day,a new type of highly efficient sound absorption and vibration damping material has become a research focus.The piezoelectric effect of piezoelectric rubber material and the damping effect of polymer matrix can convert mechanical vibration into electric energy and thermal energy,which is an ideal vibration-damping material.Because of its easy forming and processing,low-quality polymer foam Good is also widely used in various types of shock absorption devices.According to the literature and experimental studies,in the case of small thickness,the two sound absorption effect is poor at low frequency,and many low frequency noise and vibration situations can't be fully adapted.Phononic crystal structure because of its special bandgap shielding effect to make it in the use of small-size low-frequency noise control has broad application prospects.Phononic crystals are composite media or structures composed of periodically arranged units of two or more components or configurations.In some specific frequency ranges,the propagation of elastic waves in such materials is suppressed to form sonic band gaps.If the use of piezoelectric materials and polymer foam materials made of phononic crystal structure will make it in the application of the hair to get more promotion.?1?Ba?CH₃COO?₂ and Ti?C₄H₉O?₄ were used as raw materials to prepare barium titanate?BaTiO₃?prepolymer by sol-gel method andcalcined at high temperature to obtain ceramic powder.BaTiO₃ powder with tetragonal phase structure was prepared by FT-IR,XRD,SEM and particle size analysis.The particle size distribution ranged from 0.1 to 0.5?m.The synthesis conditions were as follows:barium acetate:tetra-n-butyl titanate=1:1?molar ratio?were mixed and heated in a water bath to 40°C for 2h at constant temperature,then aged for 4h,next dried in an oven at 100°C for 4h,lastly calcination at 900°C for 4h.?2?BaTiO₃ was used as piezoelectric phase and conductive carbon black was used as the conductive phase.NBR and CR were used as matrix respectively to prepare piezoelectric rubber materials.At the same time,CaCO₃,SiO₂,Yttrium?Y₂O₃?,lanthanum oxide?La₂O₃?and gadolinium oxide?Gd₂O₃?were as fillers?Use stearic acid and silane coupling agent respectively to modify them?,and NBR and CR respectively was as a matrix to prepare ordinary rubber composites.SEM,FT-IR,damping and sound absorption performance tests were performed?piezoelectric constants were also tested for piezoelectric materials?.The effects of different fillers and dosage on the damping sound absorption performance were investigated.The results were as follows:From the perspective of the modification effect,stearic acid-modified BaTiO₃ was the best.In the piezoelectric constant test,the piezoelectric constant of stearic acid-modified-BaTiO₃/NBR piezoelectric rubber is the largest?d33/pC/N=0.3?.In damping performance research,Gd₂O₃ filled CR has maximum temperature damping value of 1.3,the average frequency damping value of NBR piezoelectric rubber material is the largest?tan=0.2?,CR piezoelectric rubber temperature damping peak value decreases only 0.7,but the damping temperature range of the two is about 10°C higher than that of other filler materials,and the corresponding peak damping temperature is-10°C.The maximum storage elastic modulus of NBR piezoelectric rubber is 10000MPa,the storage modulus of CR piezoelectric rubber is the smallest,which is 2000MPa.In sound absorption performance research,during the low to medium frequency range,piezoelectric material has certain sound absorption performance within 1400²000Hz.The average sound absorption effects of electro-rubber material are better than all the control groups,and the average sound absorption coefficient is 0.24.In the high-frequency range?2000⁶300Hz?,the sound absorption effect is significant,and the sound absorption coefficient at 6300Hz reaches 0.8.?3?Foam rubber materials were prepared with BaTiO₃,CaCO₃,SiO₂,Y₂O₃,La₂O₃ and Gd₂O₃ which are as fillers,stearic acid,zinc oxide?ZnO?and urea are auxiliary foaming agents,and azodicarbonamide?AC?which is as foaming agent respectively.The research is about the effects of foam system,filler type and dosage,material thickness on sound absorption performance.The results were as follows:Foaming system research shows that ZnO:Urea:AC=5:1:25 is the optimum ratio,the opening rate can reach up to 80%.In damping performance research,type of filler has little effect on frequency conversion damping,the average damping coefficient of foamed rubber filled with various filler is about 0.15,and has little effect on temperature change damping.Among them,La₂O₃-filled NBR foam has a maximum temperature change damping peak value of 1.18,the minimum of damping peak value of SiO₂ filled CR is 0.8,the maximum value of storage modulus of Gd₂O₃ filled NBRfoam is 3300MPa,the minimum of storage modulus of Y₂O₃ filled with CRfoam is 450MPa.In sound absorption performance research,foamed rubber has good sound absorption effect within 1200-2000Hz,stearic acid+ZnO+urea foaming system has the best sound absorption effect,the average sound absorption coefficient is 0.4,with the increase of filler content,the sound absorption coefficient of the foaming material first increased and then decreased,and the sound absorption effect of SiO₂ filled CR foam was the best,with the maximum sound absorption coefficient of 0.44.The filler type had little effect on the sound absorption effect,and the unfilled foam rubber Best absorption effect,the average sound absorption coefficient is 0.38;subsequently increases,significant improvement in sound absorption,sound absorption nitrile foam rubber best at 6cm,a maximum sound absorption coefficient of 0.75.?4?A composite sound absorbing structure was prepared by using ordinary rubber composite material?unfoamed?with nitrile foam rubber,chloroprene rubber foam,butyl rubber foam,natural rubber foam and polyurethane foam.All kinds of composite structures have the extreme value between 200⁶00Hz.Among them,the composite structure made of no foam rubber rubber and polyurethane foam had the best effect,the sound absorption coefficient at 500Hz was0.95,and the other frequencies had no sound absorption effect.It was in accordance with the characteristics of the finite element one-dimensional phononic crystal structure and had a shielding effect on sound waves at a specific frequency?bandgap?.The effects of filler amount and type,cell structure of foam layer,thickness of foamed layer and the number of unit structure?foamed rubber/polyurethane foam?on the structure were further investigated.Under the same dosage,the filler type has no influence on the band gap of the structure.The shielding effect of the open cell structure of foam was better than that of the closed cell structure.The same open cell structure,the cell size of the foam layer decreased and the band gap moved to low frequency.The layer thickness increased,the band gap moved to the low frequency and the band gap width didn't change.However,as the cell structure increased,the peak value of the structure decreased and peaks appeared,and the average sound absorption coefficient increased and gradually departed from the characteristics of the phononic crystal structure.