【作者】 陈卓；

【导师】 黄志雄；

【作者基本信息】 武汉理工大学 ， 材料学， 2012， 博士

【摘要】 空心微球材料填充聚合物基体制备的复合泡沫塑料,因其低密度、高比强度、低雷达探测率、低吸水率及可设计性,被广泛应用于航天航空产品、水下载具结构件中。本文以空心玻璃微球填充环氧树脂基体制备了复合泡沫塑料,并对其进行了准静态单轴压缩测试；为分析复合泡沫塑料中的应力分布状态,建立了球颗粒在一定空间中的随机均匀分布模型；将球颗粒分布模型结合有限元软件分析了空心玻璃微球的球壁厚度及粒径变化对复合泡沫塑料应力分布的影响；使用工NV法测量了复合泡沫塑料悬臂梁的阻尼性能,并结合XPC Target实时控制环境对复合泡沫塑料悬臂梁进行了振动主动控制；通过以不同的方式将压电陶瓷／导电相／环氧树脂复合材料阻尼块布置在复合泡沫塑料悬臂梁上作为被动阻尼材料,并以不同强度Chirp信号激励悬臂梁结构,探讨了阻尼块的布置方式对减振效果的影响,为实现悬臂梁结构在变频率外载荷作用下于低频域内减小结构响应进行了可行性探索。本论文工作得到了如下重要结论：增大空心玻璃微球含量,复合泡沫塑料的密度下降。空心玻璃微球的种类与含量对复合泡沫塑料的力学性能有一定的影响,增大薄壁空心玻璃微球填充量会降低复合泡沫塑料的弹性模量和抗压强度；而增大厚壁空心玻璃微球填充量会增大复合泡沫塑料的弹性模量和抗压强度。使用粒径大球壁薄的空心微球与粒径小球壁厚的空心玻璃微球混合搭配的方式得到的新型空心玻璃微球制备复合泡沫塑料,其弹性模量和抗压强度高于同等密度的薄壁空心微球填制备的复合泡沫塑料。在随机均匀分散模型中,球颗粒的分布具有一定均匀性,不会出现局部颗粒数目陡增或陡降的现象。有限元分析结果表明,在复合泡沫塑料中,随空心玻璃微球球壁厚度的增大,复合泡沫塑料中最大应力减小。在一定的载荷下,空心玻璃微球球壁厚度较薄时,空心玻璃微球为主要的承载体；而当空心微球球壁厚度增大时,包覆空心玻璃微球的环氧树脂基体也参与吸收应变能。空心玻璃微球的球壁厚度越大,参与吸收应变能的树脂基体部分越多。通过INV阻尼计法测得了复合泡沫塑料悬臂梁结构的固有频率及阻尼比,增大空心玻璃微球含量,会增大悬臂梁结构的阻尼比；当空心玻璃微球含量增大到一定值时,悬臂梁结构的阻尼比降低。通过基于XPC Target的实时控制系统对复合泡沫塑料悬臂梁在瞬时激励下的振动进行了主动控制,主动控制可以有效减小悬臂梁的振动衰减时间及振幅,并提高结构阻尼比。但若悬臂梁自身结构阻尼较大,则主动控制对阻尼效能提升的效果会相对较差；对复合泡沫塑料悬臂梁在频率为一阶、二阶固有频率激励下的振动进行了主动控制,使振幅于一定程度减小,且一阶固有频率激励下的振动控制效果比二阶固有频率激励下的振动控制效果略差。在悬臂梁结构受到的强度较大的激励,且压电阻尼复合材料以某种特定的布置方式布置在悬臂梁上时,才能充分发挥压电阻尼复合材料的效能,使悬臂梁结构受到连续变频率外部激励时,于一定低频域内减小其频率响应。更多还原

【Abstract】 Syntactic foams are composite materials consisting hollow particles dispersed in a matrix material. Due to its low density, high specific strength, low radar detectivity and low moisture absorption, syntactic foams has been extensively used in aerospace, aviation applications and underwater, deep-sea buoyant material. In this paper, syntactic foam were prepared by mixing hollow glass microspheres (HGM) into epoxy resin, and their mechanical properties were tested by quasi-static uniaxial compression. In order to simulate the dispersion of hollow microsphere, a random spatial dispersing algorism was utilized. By using finite element analysis software,the stress, strain, displacement vector of syntactic foam were analyzed; the damping properties of syntactic foam cantilever are tested by INV damping calculation method; by using real-time system based on XPC Target, vibration active control of syntactic foam are tested; with different deploy strategy, PMN/CB/EP composite damper were deployed on the syntactic foam cantilever, and chirp simulation is applied to the cantilever in order to find an appropriate method to reduce the amplitude of the cantilever (time domain) and response (frequency domain) in low frequency width(0-500Hz).The following important conclusions might be drawn in this dissertation:To a certain degree, the density and wall thickness of HGM affects the mechanical and elastic properties of syntactic foam. Increasing the volume fraction of thin-walled HGM would leads to the decrease of compressive strength and modulus of syntactic foam whereas increasing the volume fraction of thick-walled HGM would increase the compressive strength and modulus of syntactic foam. With same density, Syntactic foam prepared with HGM consisting large-diameter but thin-walled HGM and small-diameter but thick-walled HGM owns higher compressive strength and modulus value then those prepared with thin-walled HGM.By analyzing the coordinates of spherical particles in the random spatial distribution models, it is found that particles are dispersed uniformly in the given space. Results of finite element analysis shows that when increasing the wall thickness of HGM, the von-Mises stress distribution changed in the syntactic foam. In syntactic foam prepared with thin-walled HGM, HGM is main energy absorber, and maximun stress is located on the inner surface of HGM, whereas in syntactic foam prepared with thick-walled HGM, maximum stress is located on the outer surface of HGM, which means matrix resin around HGM is also absorbing energy. More matrix get involved in energy absorping when increasing the wallthickness of HGM.The natural frequency and damping ratio tested with INV method shows that the damping ratio of syntactic foam cantilever increase when increase the volume fraction of HGM. But the damping ratio falls when the volume fraction of HGM increased to a certain value.The piezoelectric based active vibration control is carried out with XPC Target real time environment. The impulse harmer is used to generate an impulse to stimulus the cantilever, and the active control system could reduce the vibration to a certain extent. Active vibration control is also performed when the cantilevers are stimulated by excitation with first and second natural frequency. The result shows that the control system performance is better when controlling second mode vibration.By certain kind of deploy strategy and stimulus, PMN/CB/EP dampers could be used to reduce the vibration amplitude and structural response in a certain low frequency width.更多还原