剪切增稠胶力学性能及非线性弹簧研究

发布时间：2018-07-28 12:44

【摘要】：剪切增稠胶(Shear Thickening Gel,STG)是一种类似橡皮泥的非晶线性聚合物。在低应变速率下,表现出流体特性;受到冲击时,迅速变硬,表现出固体特性;并且冲击过后可恢复到初始状态。由于STG在液-固转换过程中吸收大量的能量,因此被广泛用于减震、防护领域。目前针对STG力学性能表征和性能改善的研究尚处于初级阶段,特别的对其能量吸收能力与其力学性能对应关系的认识还不够透彻。本论文首先采用流变仪探究STG在剪切模式下的力学参数随剪切应变幅值、激励频率变化关系,分析粘弹性与能量吸收能力的相关性。其次通过无机粒子掺杂,分析不同粒子改性后STG力学性能,得到性能优异的STG。最后,运用力学性能改善后的STG,设计得到阻尼、刚度自我协调的非线性弹簧。本文针对剪切模式STG流变性能和非线性弹簧关键问题展开研究,对于评价STG、理解STG微观结构变化以及STG的应用研究具有十分重要意义。本论文主要研究成果如下:1)纯STG采用大振幅振荡剪切(LAOS)实验,界定其材料线性、非线性区域,分析粘弹性能与能量吸收能力的相关性。由应变扫描及其相应的应力-应变曲线分析表明剪切应变幅值2%为STG线性到非线性转变临界应变点。STG由类液态变为类固态,临界转换频率为7Hz,在液固转换区域STG具有优异的能量吸收能力。2)采用无机粒子(CaCO_3、SiC、ZrO2)对STG力学性能改性。测试相同粒子不同质量分数、相同质量分数不同粒子剪切模式下力学性能,对模量变化、损耗因数、复合粘度变化及其相应的应力-应变曲线分析,表明CaCO_3在力学性能改善方面具有显著优势。3)基于STG设计出非线弹簧具有自适应变刚度、变阻尼特性,在单轴压缩测试条件下STG非线性弹簧最大刚度为7N/mm。在频率为10Hz动态测试条件下STG非线性弹簧最大刚度达到98N/mm是单轴压缩下测试时14倍。随着频率增加,迟滞回线形状也越来越饱满,具有很强自我协调特性。为了将STG更好用于减震防护领域,对STG线性、非线性界定,在非线性区域时STG内部组织结构破坏,在工程应用中需避免。设计STG非线性弹簧在轻微振动条件下有很好的柔性性能,剧烈振动条件下有很好的变刚度特性,进一步推动STG实用化发展。
[Abstract]:Shear thickening adhesive (Shear Thickening) is a kind of amorphous linear polymer similar to puree. At low strain rate, it exhibits fluid characteristics; when it is impacted, it harms quickly and exhibits solid properties; and it can be restored to its initial state after impact. Because STG absorbs a lot of energy in the process of liquid-solid conversion, it is widely used in the field of shock absorption and protection. At present, the study on the characterization and improvement of mechanical properties of STG is still in the primary stage, especially the understanding of the relationship between its energy absorption capacity and its mechanical properties is not enough. In this paper, the rheometer is used to study the relationship between the mechanical parameters of STG under shear mode and the amplitude of shear strain and the excitation frequency, and to analyze the correlation between viscoelasticity and energy absorption capacity. Secondly, the mechanical properties of STG modified by different particles were analyzed by doping inorganic particles. Finally, the nonlinear spring with damping and stiffness coordination is designed by using the improved STG. In this paper, the rheological properties of shear mode STG and the key problems of nonlinear spring are studied. It is of great significance to evaluate STG, understand the microstructure changes of STG and the application of STG. The main results of this paper are as follows: 1) the pure STG uses the large amplitude oscillatory shear (LAOS) experiment to define the linear and nonlinear regions of the material and to analyze the correlation between the viscoelastic energy and the energy absorption capacity. The analysis of strain scanning and its corresponding stress-strain curve shows that the shear strain amplitude of 2% is STG linear to nonlinear transition critical strain point. The critical conversion frequency is 7 Hz, and STG has excellent energy absorption in the liquid-solid transition region (2). The mechanical properties of STG are modified by inorganic particles (CaCO3 / SiCZO 2). The mechanical properties of the same particle with different mass fraction, the same mass fraction and different particle shear mode were tested, and the variation of modulus, loss factor, composite viscosity and the corresponding stress-strain curve were analyzed. The results show that CaCO_3 has a remarkable advantage in improving mechanical properties. 3) based on STG, the nonlinear spring with adaptive variable stiffness and variable damping is designed. The maximum stiffness of STG nonlinear spring under uniaxial compression test is 7 N / mmm. When the frequency is 10Hz, the maximum stiffness of STG nonlinear spring is 14 times higher than that under uniaxial compression. With the increase of frequency, the hysteresis loop becomes more and more full and has strong self-coordination. In order to better use STG in the field of shock absorption and protection, the linear and nonlinear definition of STG, the destruction of internal structure of STG in nonlinear region, should be avoided in engineering application. The design of STG nonlinear spring has good flexibility under the condition of slight vibration and good variable stiffness under the condition of violent vibration, which further promotes the practical development of STG.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O631.21

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