剪切增稠液体及其纤维复合材料的制备与性能研究

发布时间：2018-05-01 06:37

本文选题：剪切增稠液体 + 流变性能　；参考：《北京理工大学》2015年硕士论文

【摘要】：剪切增稠液体(ShearThickeningFluid: STF)是一种非牛顿液体，在一定的外力作用粘度会急剧增大。STF是新型“液体装甲材料”的关键组分，在阻尼设备方面也有很多重要应用。对STF的性能及其影响因素的研究有利于制备高性能的防护材料和阻尼器件。本文以气相SiO2粒子和亚微米级SiO2粒子为分散相，，聚乙二醇（PEG）为分散介质，制备出了不同配比的剪切增稠液体，通过优化工艺参数提高了STF的流变性能。通过测试STF的稳态与动态流变性能，以及在霍普金森压杆高速加载下的动态响应规律，探讨了固含量、粒子种类和粒径等因素对STF性能的影响，并结合高速摄影分析了其相应的影响机理。采用STF浸渍Kevlar纤维织物制得了STF/Kevlar复合材料，对复合材料进行低速冲击实验，探讨了浸渍液的种类、STF固含量以及面密度等因素对STF/Kevlar复合材料防护性能的影响。得到主要结论如下：（1）固含量、粒子种类、粒径和粒径分布等因素均会影响STF的流变性能。固含量、粒径和粒径分布均会影响STF的有效体积分数，有效体积分数越高，其黏度越高，临界剪切速率越小，剪切增稠效应越显著。对SiO2/PEG分散体系，SiO2粒子和PEG之间的氢键作用以及粒子之间的静电作用是流变性能的内在影响因素。（2）流体同时具有粘性行为和弹性行为，分别以储能模量（G′）和耗能模量（G″）来表征。对于剪切增稠体系，G″与G′均会随着剪切应力提高而增大，而对于非剪切增稠体系，G″则只会发生小幅度变化，G′则随剪切应力先急剧减小，然后略微增大，整体表现为下降。（3）剪切增稠液体在高速加载下发生了剪切增稠，由液态转变为固态，具有应力波衰减效应。剪切增稠效应显著提高了STF的动态流变应力，剪切增稠效应越显著，流体的动态流变应力就越大。强约束条件的施加有利于STF发生剪切增稠，提高其动态流变应力。套筒孔径越大，约束效果越弱，流体动态流变应力则越小。（4）剪切增稠液体通过提高纤维摩擦力和纤维间的耦合作用提高Kevlar纤维织物的抗低速冲击性能，STF种类、SiO2粒径、固含量和面密度等因素对STF/Kevlar复合材料的抗低速冲击性能均有影响。固含量影响剪切增稠特性，粒径和STF种类则同时影响纤维摩擦力和剪切增稠特性。STF剪切增稠效应越显著，越有利于纤维之间的耦合和载荷传递，以及STF/Kevlar复合材料的抗低速冲击性能的提高。
[Abstract]:Shear thickening liquid Shearding fluid: STF is a kind of non-Newtonian liquid. The viscosity of shear thickening liquid increases sharply under a certain external force. STF is a key component of a new type of "liquid armored material" and has many important applications in damping equipment. The study of the properties of STF and its influencing factors is beneficial to the preparation of high performance protective materials and dampers. In this paper, SiO2 particles and submicron SiO2 particles were used as dispersed phase and polyethylene glycol (PEG) as dispersing medium to prepare shearing thickening liquid with different ratios. The rheological properties of STF were improved by optimizing the process parameters. By testing the steady and dynamic rheological properties of STF and the dynamic response of Hopkinson compression bar under high speed loading, the effects of solid content, particle type and particle size on the properties of STF were discussed. Combined with high-speed photography, the influence mechanism is analyzed. The STF/Kevlar composites were prepared by impregnating Kevlar fiber fabric with STF. The low speed impact tests were carried out on the composites. The effects of the type of impregnating solution and the surface density on the protective properties of STF/Kevlar composites were discussed. The main conclusions are as follows: (1) solid content, particle type, particle size and particle size distribution all affect the rheological properties of STF. Solid content, particle size and particle size distribution all affect the effective volume fraction of STF. The higher the effective volume fraction, the higher the viscosity, the smaller the critical shear rate and the more significant the shear thickening effect. The hydrogen bond interaction between SiO2 particles and PEG and the electrostatic interaction between PEG particles in SiO2/PEG dispersion system are the internal factors affecting the rheological properties. (2) the fluid has both viscous and elastic behaviors, which are characterized by the energy storage modulus (G) and the energy dissipation modulus (G "), respectively. For shear thickening system, both G "and G 'will increase with the increase of shear stress, while for non-shear thickening system G" will only change by a small margin. Overall performance is down. (3) Shear thickening of shear thickening liquid occurs under high speed loading, which changes from liquid state to solid state, and has the effect of stress wave attenuation. The effect of shear thickening significantly increases the dynamic rheological stress of STF, and the more obvious the effect of shear thickening, the greater the dynamic rheological stress of fluid. The application of strong constraint conditions is beneficial to the shear thickening of STF and to increasing its dynamic rheological stress. The larger the diameter of the sleeve is, the weaker the confinement effect is, and the smaller the dynamic flow stress of the fluid is. (4) Shear thickening liquid can improve the low speed impact resistance of Kevlar fiber fabric by increasing the friction force and the coupling effect between fibers. The particle size, solid content and surface density of Kevlar fiber fabric have effects on the low speed impact resistance of STF/Kevlar composites. Solid content affects shear thickening, particle size and STF type affect fiber friction and shear thickening at the same time .STF shear thickening effect is more significant, which is more favorable to fiber coupling and load transfer. And the improvement of low speed impact resistance of STF/Kevlar composites.
【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33;TQ340.1

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