The Basic Study On Water Acoustic Absorption Polymer Materials

Campaign platforms underwater such as submarine are very important underwater force for every military country. Along with the development of the underwater detection technology, the threat to them is much larger when facing the enemy active sonar and the underwater weapons. To meet the development of new type submarine and the campaign platform underwater, the purpose of this work is to synthesize acoustic absorption polymer materials. This thesis consists of three parts.The intrinsic acoustic absorption performance of polymer materials was investigated in PartⅠ. The intrinsic acoustic absorption performance was due to the molecule structure of polymer and the acoustic filler. The excellent acoustic absorption capability was gained by studying of polymer and filler in this work.Various polymers can be made into acoustic absorption polymer material. Polysiloxane and polyurethane were selected because of solidification at room temperature and enduring capability underwater. The synthesized polymer were redesigned and modified on molecule structure. The result indicated that the damping peak of polyurethane embedded polysiloxane segment was widened; and the interpenetrating polymer networks shew more excellent acoustic performance at high frequency.On the investigation of acoustic absorption filler, the matching of filler and polymer was filtered by experimental design firstly. Then, effects of diameter, content and thermal conductivity of filler on the acoustic absorption capability of material were investigated. The result indicated that kind of polymer was the most important factor of the acoustic absorption capability, the capability of acoustic absorption decreased with diameter of sphericityα-Al2O3, but increased with coefficient of thermal conductivity, also heightened with content of graphite. The flake graphite because of excellent thermal conductivity contributed to acoustic absorption performance most.After optimized of molecule structure and filler, PSO-G and PU8-G were synthesized. The average acoustic absorption coefficient of PSO-G was 0.93 under 0 MPa, but declined rapidly along with hydraulic pressure increasing. When frequency ranged from 3 to 30 kHz the acoustic absorption coefficient of PU8-G rised along with hydraulic pressure under 0~3.0 MPa, and reached 0.88 under 3.0 MPa. When thickness of sample was decreased to 30.0 mm, the acoustic absorption performance remained invariable.Effect of acoustic structures on the acoustic absorption capability of materials was discussed in PartⅡ. New acoustic structures were designed to improve the absorption coefficient of PU8 series acoustic absorption materials. Effects of foam, interphase, gradual changing acoustic cavity and phononic crystals on the acoustic absorption capability were researched. The result indicated that absorption coefficient in a certain frequency range was improved by chemical foamer. Efficiency of sound absorption at low frequency enhanced along with increasing of interphase number. After imported the modified gradual changing acoustic cavity, the average absorption coefficient of 50.0 mm sample was improved obviously, the speciality that absorption coefficient rised along with hydraulic pressure remained. The sound absorption taper of 132.0 mm total length was devised, the average acoustic absorption coefficient of the single taper reached 0.92~0.98 in 0~3.0 MPa hydraulic pressure. Frequency range was extended about 800 Hz by adding phononic crystals into sample.The coating, new type folium tile and taper that made from PU8-G in our work showed excellent acoustic absorption performance. The polymer material of PU8-G was potential acoustic absorption material used to new type deep diving submarine.PartⅢinvestigated absorption theory.In this work, PSO-G and PU8-G showed the distinct performances of acoustic absorption. To explain this acoustic phenomenon, effects of macromolecule structure on acoustic absorption capability were investigated by methods of ATR under pressure, simulation, volume test and epoxy upderprop. The acoustic absorption mechanism of free volume was brought forward and was validated by experiment. The outline of this mechanism includes that the movement of free volume of polymer is the basic factors for acoustic absorption. Free volume move more easily, the capability of acoustic absorption of material is better. The movement of free volum is related to the chain structure of polymer. The chain is more flexible, and the function between chains is weaker, free volume moves more easily, and then the capability of acoustic absorption is better.