| With the development of the modern military technology, the acoustic stealth capabilities of the ships have become increasingly important. On the subject of acoustic stealth, it is an important research direction to develop and employ multifunctional composite materials, such as good damping and sound absorption performances. Composites have excellent mechanical properties, light weight, good corrosion resistance to seawater, good dielectric performance and nonmagnetic property. They have been widely used and play an important role in the field of ship. Furthermore, composites have viscoelasticity and sound absorption ability. Therefore, it is great significant to study underwater acoustic properties of composites. The purpose of the paper is to study the underwater sound absorption property and structural acoustic radiation of the carbon fiber reinforced composites, to discuss the feasibility of using carbon fiber reinforced composites as underwater acoustic materials.Firstly,the underwater sound absorption property of carbon fiber reinforced composites is studied using the pulse tube test method. The sound absorption coefficients at high frequencies (from 27kHz to 30kHz) of carbon fiber reinforced composites specimen are measured for different dimensions in thickness (5.7mm and 11.4mm) and different surface properties. The results indicate that the thicker specimen has better sound absorption property. In addition, the pitted surface can greatly improve the sound absorption property obviously.Secondly, a half-space fluid-structure finite element coupling model and acoustic boundary element model are established based on the finite element method and the boundary element method. The underwater acoustic radiation properties of carbon fiber reinforced composites are analyzed. The underwater acoustic radiation of the unidirectional composites with the fiber orientation angle of 0°and 90°is studied to show the relationship between acoustic radiation and fiber orientation. The results show that acoustic radiation properties are closely related to the vibration characteristic. The directions of acoustic radiation are not only dependent on the fiber orientation, but also are affected by frequencies. At low frequencies, acoustic radiation is mainly determined by the first mode, and the sound pressure is almost the same on space. As the frequency increases, the direction of acoustic radiation becomes clear, and the sound pressure distributes along the fiber. At high frequencies, the direction of the acoustic radiation becomes more complicated, but the sound pressure distribution is still related to the fiber orientation.Underwater acoustic radiation properties of carbon fiber reinforced composites are studied in the paper. Damping, load and ply parameters are discussed to evaluate the influences on the acoustic radiation properties of composite plates. The results indicate that the vibration and noise level are reduced effectively by using cross-ply laminates and increasing the layers. Different load positions will excite different modes and take different effects to the vibration and acoustic radiation characteristic of the composite plates. In addition, the damping property of composite materials makes it good performance on reducing vibration and noise.Finally, the experiments on the structural underwater vibration and acoustic radiation are studied to verify the simulation results. The results show that the acoustic radiation properties are coincident between the experiment results and the simulation results. The numerical simulation method is reasonable in this paper. In addition, comparing with the experiments of steel, carbon fiber reinforced composites show good performance of reducing vibration and noise. |
