【作者】 滕素浩；

【导师】 赫晓东；

【作者基本信息】 哈尔滨工业大学 ， 工程力学， 2011， 硕士

【摘要】 随着现代军事技术的发展,对舰船的声隐身能力要求越来越高,开发和选用多功能复合材料(兼有阻尼减振和吸声降噪功能)成为声隐身课题的一个重要研究方向。树脂基复合材料具有优异的力学性能,重量轻,良好的耐海水腐蚀性、介电性,无磁性等特点,在舰船领域发挥越来越重要的作用。同时,树脂基复合材料具有较好的粘弹阻尼性和吸收声波的特点,因此,研究树脂基复合材料的水声性能具有重要的意义。本文的主要目的就是研究碳纤维/环氧树脂复合材料层合板的水声吸声性能及其水下振动声辐射特性,探讨碳纤维环氧树脂复合材料作为水声材料的可行性。本文首先利用脉冲管实验方法研究了碳纤维环氧树脂复合材料的水声吸声性能,测试两种不同厚度(5.7mm和11.4mm)和不同表面性质的碳纤维环氧树脂复合材料层合板在高频率段(27-30kHz)的水声吸声系数。实验结果表明:厚度为11.4mm的试件具有较好的吸声性能,麻面性质的表面可以大大提高材料的吸声系数。本文基于有限元/边界元计算方法,建立了半空间流固耦合有限元模型以及声学边界元模型,分析了碳纤维环氧树脂复合材料方板的水下振动声辐射特性。本文研究了0°和45°单层板的水下振动声辐射特性,揭示了声辐射规律与纤维方向的关系。研究结果表明:单层板的水下声辐射规律与振动响应密切相关,声辐射方向不仅取决于纤维方向,而且与载荷频率有关。在低频下,声辐射主要由第一阶模态影响,声压在空间中各个方向相同。随着频率的升高,声辐射表现出了明显的方向性,声压分布主要沿着纤维方向。在高频阶段,声压分布方向性变得复杂化,但仍然与纤维方向相关。本文研究了碳纤维增强树脂基复合材料层合板的水下振动声辐射特性,分析了铺层、阻尼以及载荷对树脂基复合材料层合板水下振动声辐射的影响。研究结果表明:采用正交铺层,增加铺层层数能够有效降低结构振动噪声;激励载荷位置不同,模态发生变化,结构的振动声辐射特性将发生明显的变化;复合材料的阻尼性能使其具有良好的减振降噪效果。为了验证模拟的可靠性,对碳纤维环氧树脂复合材料层合板的水下振动声辐射规律进行了实验研究。实验结果表明:实验结果与数值模拟结果的规律是一致的,验证了数值模拟计算方法的合理性,同时通过与钢板的对比验证了树脂基复合材料具有优良的减振降噪性能。更多还原

【Abstract】 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.更多还原