纳米SiO2/聚乙二醇复合体系剪切增稠特性与机制

为分析纳米固体颗粒在剪切增稠液体(STF)稠化过程中的影响及其在中低速稳态剪切和高速动态冲击环境下发挥的作用,以纳米SiO2和聚乙二醇(PEG 200)作为分散相和连续相,以不同含量的纳米石墨和纳米金刚石颗粒为添加剂,制备STF.研究样品的摩擦系数曲线和不同温度下的流变特性,以临界剪切速率、稠化区间长度和增稠比为指标依...     

剪切增稠液及其复合材料

剪切增稠液以其独有的剪切增稠效应引起了研究者的关注,以其为增强体开发的复合材料显著增强了基体材料的抗冲击性能。首先综述了剪切增稠液的基本性质、影响剪切增稠行为的因素、新型剪切增稠液体系和不同剪切增稠体系的增稠机理,然后概述了基于剪切增稠液制备的复合材料在防弹防割刺、抗冲击和夹层结构等领域的应用,并对其作用机理进行了阐述,最后展望了剪切增稠液及其复合材料的发展。     

剪切增稠液及阻尼器性能研究

以聚苯乙烯-丙烯酸乙酯纳米粒子为分散介质,制备剪切增稠液（Shear Thickening Fluid, STF）,研究以STF为工作介质的双出杆式阻尼器动态性能,利用流变仪测量STF流变特性。实验结果显示,STF粘度特性曲线呈现明显非线性：低剪切速率时轻微剪切变稀（shear thinning）;达临界剪切速率后剪切增稠（shear thickening）。利用MTS对阻尼器进行不同频率、不同振幅加载条件下的动态测试,结果表明,阻尼器工作在STF剪切增稠区间时,STF粘度急剧增加,储能模量、耗能模量迅速增大,阻尼器输出力跃升,表现出巨大的吸收及耗能能力。采用以有效刚度、有效粘滞阻尼建立线性模型,定性评价STF阻尼器的弹性特性、阻尼特性。     

硅微粉对剪切增稠液流变性能的影响

以聚乙二醇为分散介质,二氧化硅作为第一分散相粒子,硅微粉作为第二分散相粒子制备增稠效果显著的新型复合剪切增稠液(STF)。基于PEG—SiO2基础体系,研究不同比例第二分散相粒子对新型体系的流变性能的影响并探讨其作用机理。结果表明:随着添加硅微粉含量的增加,剪切增稠效果大幅提升,临界剪切速率变小,最大黏度上升。但当第二分散相粒子比例达到3%后,临界剪切速率和最大黏度受其影响变小,其相应数值始终保持在0.21/s和2000Pa·s左右,外观由接近透明变得偏向灰色。     

不同分子量PEG对剪切增稠液体流变性能的影响

将两种不同分子量的聚乙二醇(PEG200,PEG600)作为剪切增稠液体的分散介质,按不同比例进行复配,制备剪切增稠液并在透射电镜中进行观察,同时对几种不同的剪切增稠液进行流变性能测试。比较了不同分子量的分散介质对剪切增稠液流变性能的影响,包括稳态流变性能以及动态流变性能。研究得出,分散相粒子质量分数相同的情况下,适当提高分散介质的分子量对剪切增稠液体的流变性能有积极的影响,在较小的冲击力下,STF体系便能发生剪切增稠效应。     

剪切增稠凝胶/环氧树脂复合材料的制备及性能研究

剪切增稠凝胶(STG)是近年来引起人们极大研究兴趣的一种剪切增稠材料,表现出冲击硬化效应。将STG与环氧树脂材料进行复合,获得一种强度更高的STG增强环氧树脂材料,一方面解决剪切增稠材料在实际过程中的冷流问题,另一方面通过高分子聚合物与剪切增稠凝胶材料的耦合作用,进一步改善环氧树脂的脆性以抗冲击防护性能。采用热分析表征样品的热稳定性;采用电子万能材料试验机对复合材料进行了多重拉伸速率的拉伸力学性能测试;采用扫描电子显微镜对材料进行微观结构观察。     

剪切增稠胶/碳酸钙复合材料的制备及其抗冲击性能研究

为了提升人体防护装备的轻便性和灵活性,以剪切增稠胶(STG)为基体,并用纳米CaCO₃对其进行补强,制备了缓冲吸能性能优异的剪切增稠STG/CaCO₃复合材料,研究了CaCO₃含量和粒径对STG剪切增稠性能的影响。结果表明:添加CaCO₃后复合材料的最大储能模量比未添加时增加455%;添加的CaCO₃粒径越小,复合材料的剪切增稠性能越优异。通过落锤冲击实验表征了复合材料的抗冲击性能,CaCO₃的填充可使复合材料在具有最小变形量的情况下吸收更多的冲击力。探究了STG剪切增稠和CaCO₃补强的作用机理,指出剪切增稠现象是由交联键的形成和分子链的缠结作用产生的,CaCO₃通过吸能阻裂,分散冲击力产生补强作用。     

剪切增稠液体对织物防刺性能的影响

制备了剪切增稠液体(STF)并对其稳态和动态流变性能进行了研究,发现体系具有明显的剪切增稠现象,用粒子簇生成机理能较好地解释这种现象。为降低成本,暂选用普通玻纤织物作为载体,制备出STF-玻纤织物,并将其和纯玻纤织物进行准静态防刺试验。结果表明在面密度相同的情况下,剪切增稠液体的使用能有效提高玻纤织物的防刺性能,使其顶破强力比未处理时高28.14%。     

Low-velocity penetration damage of Kevlar woven fabrics impregnated with shear thickening fluid penetrated with different tups

Abstract

Low-velocity penetration damage behaviors of Kevlar woven fabrics impregnated with shear thickening fluid (STF) were investigated. Cone-shaped tup (CST) and hemispheric tup (HST) were employed to penetrate fabric/STF composites with the velocities of 1.5 m/s and 3.0 m/s under drop-weight tests. The fabric impregnated with 3:1 diluted volume ratio has the highest energy absorption and the lowest deformation. The peak load and energy absorption under HST penetration at 3.0 m/s are 2.0?kN and 36.7 J, which are higher than the CST penetration. Energy absorption increment under HST penetration at 3.0 m/s is 61.76% while 117.88% for CST penetration.     

石墨烯对剪切增稠液挤压流动力学性能的影响

含有剪切增稠液的振动控制装置在服役阶段涉及挤压过程,研究剪切增稠液的挤压力学性能有着重要的意义.采用石墨烯增强纯二氧化硅纳米颗粒剪切增稠液,并利用旋转流变仪开展了挤压流动实验,测试了不同剪切增稠液的流变性能和挤压流动力学性能,得到了黏度曲线以及不同挤压速度下法向应力和临界间隙的变化规律,分析了石墨烯对剪切增稠液流变性能...     

The effect of silicon carbide additives on the stab resistance of shear thickening fluid treated fabrics

Applications of shear thickening fluids (STFs) with ballistic fabrics improve the protection performance of body protective systems. This article presents an innovative view of STF-impregnated ballistic fabrics by integrating silicon carbide (SiC) particles into targets. In this study, SiC particles were added into silica-based STFs, and Twaron fabrics were impregnated with this novel suspension. The effect of the SiC particles in the STFs was investigated with rheological testing. The results show that SiC particles are able to increase the viscosity profile of the suspension. In the stab testing, two types of impactors, such as spikes and knives, were dropped on the composite targets. According to the results, SiC particles enhance the protection performance of the STF-treated ballistic fabrics while keeping the flexibility.     

Continuous shear thickening and discontinuous shear thickening of concentrated monodispersed silica slurry

Concentrated slurry is known to exhibit shear thickening behavior, in which viscosity increases as the shear rate ascends. However, to identify the differences between this shear thickening behavior and rapid increases in viscosity (such as the dilatancy behavior of starch, sand, and other concentrated slurries) and the smooth increases in viscosity exhibited by concentrated slurries, this research investigated the rheological behavior of a polyethylene glycol suspension containing monodispersed silica particles with a size of 2.5 μm. The results found that the increases in viscosity as the shear rate ascends or the increases in elasticity as the strain ascends change consecutively from smooth and reversible behavior (i.e., continuous shear thickening (CST)) to rapid and irreversible behavior (i.e., discontinuous shear thickening (DST)) simply by increasing the concentration of the slurry, even in the case of concentrated slurries comprising of the same particles. DST is a manifestation of dilatancy in which a jamming transition occurs due to collisions between particles. Because CST transitions successively to DST, and the on-set shear stress of shear thickening of CST is almost the same with that of DST, shear thickening in the CST region may, therefore, also be regarded as the result of friction due to collisions between particles. This supports the research by Seto, Mari, Poon et al., which stated that shear thickening occurs due to friction from particle collisions.     

亚微米级SiO_2微球对抗撞击材料剪切增稠液的影响

采用改进的溶胶-凝胶法制备出平均粒径为150,180,200和250 nm的SiO2微球,反应温度为20~50℃,正硅酸乙酯浓度为0.2~0.3 mol/L,反应后添加0.02%~0.04%(体积分数)的硅烷偶联剂KH-570,再通过球磨将亚微米级SiO2均匀分散到PEG(聚乙二醇)中,获得相应的抗撞击体系。利用TEM、XRD、Physica MCR301型流变仪分别对不同粒径的SiO2微球的粒度分布、结构以及流变性能进行测试,结果表明,粒径为200 nm的SiO2微球制备的抗撞击体系粒度分布均匀,为非晶结构,并且表现出很好的剪切增稠现象。     

复配型剪切增稠液体对非织造织物防刺性能的影响

引入"复配"的概念,制备出不同复配方式的剪切增稠液体(STF),并将该复配型STF对超高分子量无纺布进行处理,通过对STF无纺布的复合材料进行扫描电镜形貌分析以及静态防刺实验,来对复合织物的防刺性能进行研究。主要阐述了不同分子量分散介质(PEG200、PEG600)复配后的剪切增稠液与无纺布织物复合后对复合材料防刺性能的影响,发现采用不同分子量分散介质较单一分子量分散介质的STF无纺布复合织物的防刺性能好,采用复配分散介质的方式对剪切增稠液体在防刺效果上有一定程度的改善作用,在同等单位质量的情况下,此复配方式可将复合材料的防刺性能提高7.13%。     

低收缩块状PMMA/SiO_2杂化材料制备及性能表征

以甲基丙烯酸甲酯(MMA)、正硅酸乙酯(TEOS)和硅烷偶联剂(MPMS)为原料,采用溶胶-凝胶法制备出低收缩、具有良好光学性能的PMMA/SiO2杂化材料。通过透射电子显微镜、差热分析、红外吸收光谱和紫外光-可见分光光度计表征了杂化材料的微观形貌、热性能和透明性。结果表明材料的网络结构相对比较均匀,在可见光波长范围内材料均一性好;有机相和无机相之间是通过共价键相互连接的,没有出现有机相、无机相分离现象;杂化材料的透光率约90%。     

剪切增稠流体增强尼龙纤维织物的防刺性能

研究了SiO2/PEG剪切增稠流体对尼龙纤维织物防刺性能的影响.研究结果表明,固相体积分数为10％的SiO2/PEG 400分散体系,具有典型的剪切增稠特性.经过SiO2/PEG 400剪切增稠流体处理的复合防刺纤维织物的防刺性能优于普通尼龙纤维织物.对纤维织物的显微损伤机制的研究表明,剪切增稠流体使尼龙纤维实现强化粘...     

The influence of graphene on the dynamic mechanical behaviour of shear thickening fluids

The viscosity and shear thickening efficiency of the nanoparticle-based shear thickening fluids (STFs) were influenced by hydrodynamic lubrication force between nanoparticles. To enhance such an influence and improve the performance of STF, graphene was adopted to reinforce SiO₂ nanoparticle-based STF in this paper. The viscosity of the reinforced STF was improved obviously by graphene, which makes an increase of 30% compared to the pure STF. In order to characterize the influence of graphene on the flow stress of STF at high strain rates, a split Hopkinson pressure bar was implemented to test the dynamic compressive mechanical properties at strain rates in the range from 3 × 10³ to 10⁴/s. The results showed that graphene has a significant influence on the flow stress of reinforced STF at different strain rates compared to the pure STF, and the effects of the strain rate and graphene volume fraction on the flow stress were analyzed. Based on the hydrodynamic lubrication force theory, the attribution done by grahpene to the hydrodynamic lubrication force in STF was discussed. The results of the paper provide an efficient way to develop a novel STF with high shear thickening efficiency.