剪切增稠液及其在抗冲击缓冲方面研究进展

剪切增稠液作为一种非牛顿流体,其独特的"流-固"转化流变性能引起了科学界广泛关注。近年来,将其应用到抗冲击缓冲领域更是成为了研究热点。但是,剪切增稠的机理和流变性能的控制仍有待于进一步探索。剪切增稠装备的工业化生产与相关器件的有效开发成为当前研究难点和挑战。重点对剪切增稠机理和性能进行综述分析,并综述了目前应用到防护、缓冲领域的最新研究进展,为开发新型抗冲击缓冲材料提供启示。     

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。     

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...     

剪切增稠液在阻尼减振技术中的应用研究

阻尼减振技术是振动噪声最有效的控制手段,既有被动控制的简单性又有主动控制的可调控性的半主动控制方法是该领域的研究热点,利用剪切增稠液剪切增稠过程中的能量耗散及刚度变化并将其应用于阻尼减振中,使复合结构有响应速度快、不需消耗外界能量、自适应性强的优点.本文主要介绍了剪切增稠液的基本性能、剪切增稠液阻尼器、剪切增稠液夹层梁,对它们的研究进展和阻尼机理进行了阐述,并展望了其减振应用的发展.     

纺织结构/STF柔性复合材料的机械防护性能

以纺织结构为增强体和剪切增稠液(STF)为基体制备的柔性复合材料为研究对象,综述了纺织结构/STF柔性复合材料在机械受力下的防护机理,分别介绍了织物结构、STF的流变性能及复合工艺等因素对机械防护性能的影响,对STF在柔性复合材料应用中目前存在的问题及应用前景进行了展望。为开发轻便、性能良好及舒适的柔性复合材料提供依据。     

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。     

剪切增稠胶/超高分子量聚乙烯复合材料低速冲击性能研究

剪切增稠胶(STG)是一种新型功能材料,通过流变测试研究了STG的稳态流变性能及其剪切增稠的作用方式。将STG与超高分子量聚乙烯(UHMWPE)织物复合制备了STG/UHMWPE复合材料,利用扫描电子显微镜对复合前后材料的形貌进行分析,并研究了复合材料的低速冲击性能。结果表明:加入STG后,STG/UHMWPE复合材料的剩余冲击载荷可减少50%;在不同冲击速度条件下,复合材料能量吸收系数均超过80%。STG具有优异的力学性能,通过与UHMWPE织物复合可显著提高复合材料的抗冲击性能。     

剪切增稠液体的缓冲机理和力学性能

剪切增稠液体(STF)是一种将纳米或微米级的颗粒分散到牛顿流体中而形成的非均质颗粒悬浮液。当冲击发生时,其表观黏度发生大幅度增大而变黏稠。冲击结束后,体系表观黏度降低,重新转变为液体。通过颗粒拥堵模型,解释了剪切增稠液体在冲击过程中的耗能机理,同时计算了冲击杆在冲击过程中的加速度响应。采用低速冲击试验,测试了其抗冲击特性,与传统吸能材料AV-200进行了吸能对比;结果表明:颗粒拥堵模型合理解释了低速冲击试验中出现的局部硬化现象,规避了传统方法中边界对剪切增稠液体的影响问题。剪切增稠液体具有优异的缓冲特性。理论分析结果与试验结果的良好吻合验证了理论方法的有效性。该研究为剪切增稠液体在缓冲领域的应用提供了参考。     

剪切增稠液阻尼器抗冲特性研究

剪切增稠液的黏度随剪切速率变大会迅速增大,以剪切增稠液为介质的阻尼器在抗冲设备中具有重要的应用潜力。采用分段幂律流模型描述剪切增稠液本构模型,首先通过建立基于FLUENT的阻尼器计算模型,分析剪切增稠液阻尼器的阻尼力输出特性,获得剪切增稠液流变参数对阻尼力的影响规律;其次建立基于剪切增稠液阻尼器的单自由度非线性系统抗冲计算模型,得到阻尼力特征参数对系统冲击响应的影响规律。研究结果可用于指导剪切增稠液的材料设计。     

SiO2粉体粒径对STF/Kevlar复合材料防刺性能的影响

采用自制的不同粒径的SiO₂粉体, 利用球磨分散技术配制具有剪切增稠特性的SiO₂/PEG200悬浮液流体(STF), 并利用静态浸渍方法制备STF/Kevlar复合材料, 研究了粉体粒径对流体体系流变性能和复合材料防刺性能的影响。结果表明, 不同粒径SiO₂粉体配制的悬浮液均具有明显的剪切增稠性能, 当SiO₂粉体质量分数相同时, 流体体系的起始黏度、 临界剪切速率、 最大黏度均随着粒径的增大而减小。16层STF/Kevlar试样能承受24.0 J锥体冲击, 远远优于相同面密度的纯Kevlar试样, 随着粒径的增加, 试样的防锥刺性能提高。刀体冲击能量为13.0 J时, STF/Kevlar试样的防刀刺性能优于相同面密度的纯Kevlar试样, 随着粒径的增大, 试样的被刺穿深度减小, 主要表现为剪切断裂破坏。      

CorkSTFμfluidics – A novel concept for the development of eco-friendly light-weight energy absorbing composites

CorkSTFμfluidics are environmentally friendly composites consisting of a laminar sheet of compacted micro-agglomerated cork engraved with a network of microchannels by laser and filled with a concentrated aqueous solution of cornstarch (shear thickening fluid). Thus the mechanical properties of these composites will result from the combination of the mechanical properties of the micro-agglomerated of cork and the enhanced shear thickening response of the STF flowing through the network of microchannels. In this work we have performed low velocity impact tests using a drop weight testing machine in order to asses the improvement of these composites with regards to the micro-agglomerated of cork alone. A numerical analysis was also performed and allowed to understand how shear thickening behavior is triggered by the appropriate combination microchannels’ size and the inlet velocity. Thus, for the 60P/40S/M sample, the peak force was larger than the one given by the cork sheets without engraved microchannel nor STF.     

SiO2粉体粒径对Kevlar/STF复合材料防刺性能的影响

采用自制的不同粒径的SiO2粉体,利用球磨分散技术配制具有剪切增稠特性的SiO2/PEG200悬浮液流体(STF),并利用静态浸渍方法制备Kevlar/STF复合材料,研究了粉体粒径对流体体系流变性能和复合材料防刺性能的影响。结果表明,不同粒径SiO2粉体配制的悬浮液均具有明显的剪切增稠性能,当SiO2粉体质量分数相同时,流体体系的起始黏度、临界剪切速率、最大黏度均随着粒径的增大而减小。16层Kevlar/STF试样能防住24.0J锥体冲击,远远优于相同面密度的纯Kevlar试样,随着粒径的增加试样防锥刺性能提高。刀体冲击能量为13.0J时,Kevlar/STF试样的防刀刺性能优于相同面密度的纯Kevlar试样,随着粒径的增大试样被刺穿深度减小,主要表现为剪切断裂破坏。     

经编间隔织物增强柔性复合材料冲击性能

针对传统个体防护材料刚硬、限制人体活动的缺点,设计了2种柔性复合材料: 剪切增稠液(STF)和硅橡胶填充经编间隔织物(WKSF)柔性复合材料,并对其冲击性能进行研究。WKSF具有上、下两个表层和间隔丝构成的间隔层,在其间隔层中加入STF和硅橡胶2种柔性材料。STF采用将纳米SiO₂分散于聚乙二醇(PEG)中制成,硅橡胶采用硅胶和固化剂混合而成。采用流变仪对STF的流变性能进行测试,采用Instron落锤冲击仪对WKSF及其复合材料的冲击性能进行测试。实验表明: STF在达到临界剪切速率后出现剪切增稠现象,纯织物的冲击过程可分为弹性、平台和压实3个阶段,且具有明显的平台阶段;经填充后所制成的2种复合材料的冲击过程与纯织物明显不同,其载荷-位移曲线呈线性;加入硅橡胶的复合材料刚度较大,没有应变率效应;加入STF的复合材料具有较好的能量吸收性能和明显的应变率效应。     

Numerical simulation of the impact behaviors of shear thickening fluid impregnated warp-knitted spacer fabric

The impact behavior of warp-knitted spacer fabrics (WKSFs) impregnated with shear thickening fluid (STF) under low-velocity impact loadings have been investigated from experimental and finite element analyses (FEA) approaches. From the experimental approach, the impact load–displacement curves have been obtained. It was observed that the WKSF impregnated with the STF composite material (the WKSF/STF composite) shows a higher stiffness and lower peak force than those of the WKSF under the same impact loadings. In FEA approach, the geometrical models of the WKSF and the WKSF/STF composite material were established based on the WKSF fabric architectures. The dynamic responses including the impact load–displacement curves and impact deformation of the samples were predicted based on finite element analyses at the microstructure level. It was found that the STF and the coupling effect between the STF fluid and fiber tows are the key factors which influence the cushioning behaviors of the composite. The energy absorption mechanisms include the buckling of the spacer finer tows and the thickening effect of the STF under impact loading. The WKSF/STF composite could be expected as a damping or energy-absorptive materials under impact loading.     

纳米材料在防弹衣上的应用

简单介绍防弹衣的重要性以及防弹衣材料的发展历程;阐述了剪切增稠液体（STF）特点以及STF—Kevlar织物的制备方法、防护机理;并指出其应用发展方向。     

浸轧压力对STF-Kevlar织物高速冲击性能影响研究

为研究浸轧压力对剪切增稠液体(STF)增强Kevlar织物高速冲击性能的影响,分别采用50 kPa, 100kPa, 200kPa的压力浸轧STF-Kevlar织物,并使用钛合金模拟叶片弹体开展打靶试验。研究结果表明:STF表现出明显的剪切增稠现象,增稠范围为169~1 500 s^-1,增稠比为56.4;Kevlar织物浸渍STF后,二氧化硅(SiO₂)纳米粒子均匀附着在纤维表面;浸轧压力的增加使STF-Kevlar织物的质量增加率降低;STF-Kevlar织物的能量吸收较纯Kevlar织物高29.4%,但其弹道性能指数(BPI)低于纯Kevlar;浸轧后STF-Kevlar织物的能量吸收高于纯Kevlar织物,但低于未浸轧STF-Kevlar织物;在100 kPa的浸轧压力下,STF-Kevlar织物的单位面密度吸收的能量最高;STF-Kevlar织物能量吸收的变化趋势与织物极限变形高度的变化一致。     

Micromechanics and damping properties of composites integrating shear thickening fluids

Damping is an important parameter for vibration control, noise reduction, fatigue endurance or impact resistance of composite materials. In this study, a micromechanical model was used to predict the damping of a composite material containing shear thickening fluids (STFs) at the fibre–matrix interfaces. Predictions of the model and dynamical mechanical analysis results are in concert. The damping of the composites was improved significantly. The dynamic properties exhibited a strong dependence on both frequency and applied external load amplitude. Damping peaks appeared which coincided with the thickening of the STF at the fibre–matrix interface. The location of the peaks depends on the onset of thickening and post-thickening rheological behaviour of the STF. This work shows that a micromechanics approach can be useful for an appropriate choice of microstructural design and properties of STFs in order to control the stiffness and damping behaviour of composites. STFs can be integrated at the microscale of polymer composites to create new materials with load-controlled adaptive dynamic stiffness-damping properties.     

Impact compressibility of a poly(ethylene glycol)-based nanocomposite fluid

The behavior of a poly(ethylene glycol)-based nanocomposite shear thickening fluid (STF) under impact loading conditions has been experimentally studied using the Kolsky method and related techniques. The dependence of the pressure in the STF on the volume strain magnitude has been determined. It is established that the radial and axial components of the stress tensor almost coincide, which shows that the material behaves like an incompressible liquid. The character of the stress-strain curves (hysteresis) indicates that the STF is characterized by some energy dissipation in the load-unload cycle.     

Optimal designing of soft body armour materials using shear thickening fluid

This paper deals with the optimal design of soft body armour materials by treating Kevlar (para-aramid) fabrics with silica nano-particle based shear thickening fluid (STF). Box and Behnken design of experiment (DOE) plan in conjunction with contour analysis has been used to study the effect of silica concentration, padding pressure and diluent: STF ratio (solvent ratio) on STF add-on% and impact energy absorption. Silica concentration, solvent ratio and square of solvent ratio were found to be statistically significant terms influencing the STF add-on% on Kevlar fabrics. On the other hand, silica concentration, padding pressure and the square of solvent ratio were the statistically significant terms influencing the impact energy absorption. Higher padding pressure enhances the impact energy absorption by the STF treated Kevlar fabrics although it does not influence the STF add-on% significantly. Higher STF add-on% is a necessary but not the sufficient condition for improving the impact resistance performance of Kevlar fabrics.