【作者】 张玮；

【导师】 龚兴龙；

【作者基本信息】 中国科学技术大学 ， 固体力学， 2011， 博士

【摘要】 磁流变弹性体(亦可称为磁敏弹性体)作为磁流变材料中的一个重要分支,其具有典型的流变学特征,即模量、阻尼等力学性能都可通过外加磁场进行控制。磁流变弹性体除具有上述磁控特性外,还具备磁致伸缩、磁致电阻、吸波性能等优异的电磁学特性。磁流变弹性体所具有这些独特的可控性使其在振动控制和电磁器械等领域有着广阔的应用前景。然而目前在磁流变弹性体材料研制方面还存在着一些问题,例如材料机械性能较差、磁流变效应较低以及耐久性能不好等。而且目前有关高性能磁流变弹性体研制方法的研究也较少。根据以上述存在问题,本文首先系统研究了基于天然橡胶和顺丁橡胶的混合橡胶基磁流变弹性体的制备方法。以设计高磁流变效应、高机械性能和低阻尼为优化目标,从材料设计的理念出发,对磁流变弹性体材料制备中的各相关条件进行深入研究和系统优化,并详细分析了制备过程中各条件对材料性能的影响。首先结合本课题组先前制备磁流变弹性体的经验和方法,同时天然橡胶和顺丁橡胶为基体,制备出了六种配比的混合基磁流变弹性体。为了更好地对混合基磁流变弹性体的各项性能进行评估,利用本课题组建立的粘弹性材料力磁耦合测试系统对磁流变弹性体的在外加磁场下的机械性能和动态力学性能进行了测量,并研究混合基磁流变弹性体的力学性能在不同疲劳和老化测试条件下的变化规律。这是首次研究不同的循环加载条件下(循环加载的幅值和加载次数)以及不同老化条件下(不同的老化温度和老化时间)对于混合基磁流变弹性体力学性能的影响。还结合橡胶材料的疲劳和老化理论推导出了有关磁流变弹性体疲劳性能和老化性能关系式。在实验中发现这些测试条件对材料的动态力学行为影响很大,特别是循环加载幅值和老化温度对材料动态力学性能的影响尤为显著,因此在实际测试和工程应用中需要特别注意以上条件对材料性能的影响。根据磁流变弹性体老化性能实验中得到的结果显示,温度对材料动态力学性能的影响非常显著,因此本文着重研究了环境温度对磁流变弹性体力学性能的影响。不同温度条件下对不同基体材料的力学性能进行了测试,其中包括顺丁橡胶基磁流变弹性体、天然橡胶基磁流变弹性体以及混合橡胶基磁流变弹性体。为了给出温度与磁流变弹性体力学性能之间的理论关系,给出了磁流变弹性体在不同温度条件下的应力应变本构关系。为了研制性能更高的磁流变弹性体,通过向磁流变弹性体中注入磁流变液和磁流变胶的方法,制备了两种新型夹杂磁流变弹性体(磁流变液弹性体和磁流变胶弹性体),目的主要是利用磁流变液和磁流变胶材料本身所固有的高磁流变效应来提高传统磁流变弹性体的性能。还对这种夹杂磁流变弹性体的各项性能(模量、磁流变效应、损耗因子及磁滞等)进行了测试,系统地研究了不同体积比含量注入物(磁流变液和磁流变胶)对新型混合磁流变弹性体力学性能的影响。最终通过一系列的实验找到最优的体积比含量。用复合材料力学的理论对这两种夹杂弹性体进行了力学解释,将注入的磁流变液和磁流变胶当做增强纤维考虑,将传统的磁流变弹性体当做基体,并结合磁流变液和磁流变胶本身的磁致模量计算方法,得出了夹杂磁流变弹性体的模量计算公式。更多还原

【Abstract】 Magnetorheological (MR) materials are kinds of smart materials and Magnetorheological elastomers (MREs) are a class of MR materials. The mechanical properties of the MREs can be controlled by an applied magnetic field. Besides the modulus and damping, other properties such as magnetostriction and piezoresistivity are also controllable. These unique characteristics enable the MREs be applied in many areas, such as adaptive tuned vibration absorbers (TVAs), stiffness tunable mounts and suspensions, and variable impedance surfaces. Unfortunately, the present MREs products can not fully meat the requirments of the practical application due to their low MR effect, weak mechnical properties and large dynamic damping. To this end, more research should be done to prepare high-performanced MREs with improved mechanical properties. This dissertation is focused on the preparation of high-performance MREs which exhibits high MR effect, good mechanical performance and small dynamic damping. The influences of the preparation condition on the properties of MREs are systematically studied.The preparation of high-performance MREs based on rubber natural rubber (NR) and cis-Polybutadiene rubber (BR) was studied at first. The synthetic parameters were optimized to produce MREs materials with high MR effect, good mechanical performance and small dynamic damping. MREs samples based on the mixed rubber were fabricated according to our previous reported method and the synthetic route was optimized. The hybrid MREs materials with different mass ratios (BR/NR) were prepared by using the high temperature vulcanization method and the mechanical property of the products was improved.To evaluate the performances of the as-prepared MREs under the applied magnetic field, a mechanical-magnetic coupled quasi-static shear mode load device was established. We first investigated the durability properties of the hybrid MREs under cyclic loading and high temperature conditions. The results revealed that the MR effect and modulus of all samples depended on the testing conditions, such as number of loading cycles, load amplitude, aging temperature and time. The relationship between the durability properties, cyclic loading and aging conditions were also analyzed.According to the results of the aging test,their mechanical properties, including modulus and damping capability, depend both on an external magnetic field and an environmental temperature. In order to systematically investigate their temperature-dependent mechanical properties, six different kinds of MREs samples which based on a mixed rubber matrices (cis-Polybutadiene rubber and natural rubber), were fabricated in this part. The steady-state and dynamic mechanical properties of the samples were measured under different conditions by using a rheometer. An improved constitutive equation was developed to model these properties under different magnetic fields and temperatures. The comparison between modeling predicting results with experimental data demonstrated that the model can well predict the modulus of MRE in different conditions.To further improve the mechanical performance of MREs, two novel hybrid MREs which were embed with MR fluids (MRFs) and MR gels (MRGs) were fabricated. In this work, MRF and MRG were injected into different numbers of holes, which were punched on MREs specimens regularly. The mechanical properties of MR fluid-elastomers (MRFEs) and MR gels-elastomers (MRGEs) investigated in the presence of externally applied magnetic fields. The modulus and loss factor have been evaluated by using a modified dynamic mechanical analyzer (DMA) and researched respectively. Dependence of the rheological response on volume fraction was also investigated. As a results, not only the foundation modulus of two novel hybrid MR materials were higher than both MRF’s and MRGs’s but also their MR effects were better than MREs’s. The loss factor of two new hybrids was different from traditional MREs’. Moreover, their dynamic properties changed according to the difference volume ratio of MRFs and MRGs injected in MREs specimens. These results suggest that the two novel hybrid MREs are an improved system with volume fraction dependent rheological response. The mechanical properties of MREs can be improved by embedding with MRFs and MRGs. All their mechanical properties, especially MR effect, exhibit significant improvement compared with traditional MREs. A new model based on theory of composite materials and MRFs were used to explain the nonlinear mechanical properties of the hybrids, and it fit the experimental data well.更多还原