Effects of different silica particles on quasi-static stab resistant properties of fabrics impregnated with shear thickening fluids

The effects of fumed silica in shear thickening fluids at a weight fraction of 20% and submicron silica particles in shear thickening fluids at a weight fraction of 65% on quasi-static stab resistance properties of fabrics impregnated with shear thickening fluids were investigated on a basis of a similar shear thickening behavior. For better understanding of the effects of these two different silica particles on resistance mechanism of fabric during quasi-static stab, the single yarn tensile test was carried out to obtain tensile properties of single yarn and yarn pullout test was performed to examine interface friction among yarns. The results show that aramid fabrics treated with shear thickening fluid exhibit a significant enhancement in quasi-static stab resistance. Further, quasi-static stab resistant properties of treated fabrics containing submicron silica particles are better than that of treated fabrics containing fumed silica particles. Possible mechanism responsible for the enhancement is discussed in detail.     

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%。     

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.     

剪切增稠液体的制备及其性能表征

研制了一种新型功能材料——剪切增稠液体（Shear thickening fluid，即STF）。采用溶胶凝胶方法制备纳米二氧化硅作为分散相，极性溶剂作为分散介质。用流变仪测量了二氧化硅质量分数分别为30％、40％、50％、60％和70％的体系稳态和动态粘度曲线，结果表明，在低剪切速率下，出现剪切变稀现象，在高剪切速率下，出现剪切增稠现象。从实验角度证明了剪切增稠的可逆性。并对不同固相含量的剪切增稠液体的性能进行了分析比较。     

Effect of Si02 particle size on stab resistant properties of STF/Kevlar composites

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Si2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24．0J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,试样的防锥刺性能提高。刀体冲击能量为13．0J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。     

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.     

剪切增稠液复合三维织物抗高速冲击性能的研究

制备剪切增稠液,通过透射电镜图观察分散相粒子在STF系中的形貌结构和分散状况,利用稳态流变测试来分析STF的流变性能和剪切增稠机理。将STF与UHMWPE三维织物在一定工艺条件下复合,得到STF复合三维织物,分析纯UD布靶样、UD布结合三维织物靶样、UD布结合STF复合三维织物靶样的高速冲击性能。实验结果表明,STF能够有效地增强三维织物的高速冲击性能。     

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。      

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,100 kPa,200 kPa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...     

High performance zeolitic imidazolate framework-8 (ZIF-8) based suspension: Improving the shear thickening effect by controlling the morphological particle-particle interaction

A novel shear thickening fluid (Z-STF) was developed via dispersing zeolitic imidazolate framework-8 (ZIF-8) nanoparticles into ethylene glycol (EG). By varying the morphologies of the ZIF-8 nanoparticles, the rheological properties of the Z-STF were controlled. In comparison to the traditional SiO₂ based STF (S-STF), the Z-STF showed a superior shear thickening behavior because of the porous nature and polyhedron morphology of the ZIF-8 nanoparticles. Firstly, the EG molecule could be incorporated into the micropores of ZIF-8, which increased the volume fraction of the dispersing phases and enhanced the hydrodynamic forces between the particles. Secondly, the poor relative sliding of truncated cubic particles led to easily form a more robust structure of frictional contact network in truncated cube ZIF-8 based STF (TCZ-STF) than in truncated rhombic dodecahedron ZIF-8 based STF (TRDZ-STF) and S-STF, thus the TCZ-STF showed smaller critical shear rates and higher maximum viscosities. This work provides a morphology turning method to design high performance STF and supplies a good understanding of the relationship between ST behavior and particles' structure. In view of the easy preparation and wonderful mechanical properties, the Z-STF possessed broad application in damping, body armor, and safe energy.     

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...     

电场处理对碳化硅/聚合物复合材料电导特性的影响

通过在碳化硅(SiC)/低密度聚乙烯(LDPE)的热压成型和SiC/硅橡胶的硫化过程中施加不同形式的直流电场,研究了电场处理对SiC/聚合物复合非线性绝缘材料电导特性的影响.研究结果表明,在SiC/LDPE的热成型过程中待到模具中的物料流动结束后施加均匀电场仅使复合材料的电导率发生微弱变化,而在SiC/LDPE的热压流动过程中施加均匀电场导致复合材料的电导率明显增加;SiC/硅橡胶共混物的粘度较SiC/LDPE的粘度低,故均匀电场处理导致前者电导率增加的趋势较后者明显;非均匀电场处理导致复合材料的电导率明显增大,电导非线性特性明显得到改善,其作用效果明显好于均匀电场.     

Ab initio DFT study of ideal shear strength of polytypes of silicon carbide

Ab initio density functional calculations are performed to investigate the ideal shear deformation of SiC polytypes (3C, 2H, 4H, and 6H). The deformation of the cubic and the hexagonal polytypes in small strain region can be well represented by the elastic properties of component Si₄C-tetrahedrons. The stacking pattern in the polytypes affects strain localization, which is correlated with the generalized stacking fault energy profile of each shuffle-set plane, and the ideal shear strength. Compressive hydrostatic stress decreases the ideal shear strength, which is in contrast with the behavior of metals. __________ Translated from Problemy Prochnosti, No. 1, pp. 8–13, January–February, 2008.     

Effect of infiltrants on the electrical resistivity of reaction-sintered silicon carbide

The effect of infiltrants on the electrical resistivity of reaction-sintered silicon carbide, at temperatures ranging from RT to 1000°C, has been studied. Electrical resistivity decreases with increase in temperature up to 1000°C in VC and MoSi₂, whereas minimum electrical resistivity is observed at ∼600°C in B₄C infiltrant.     

温度对化学气相沉积碳化硅涂层的影响

以三氯甲基硅烷和氢气为气源,研究了化学气相沉积碳化硅过程中,温度(850-1350℃)对沉积速率、反应物消耗效应、涂层形貌和相结构的影响.用磁悬浮天平在线实时称量基体质量变化进行动力学研究;采用扫描电镜和X射线衍射对样品做了表征.结果表明,沉积过程存在四个控制机理:a区(<1000℃)为表面反应动力学控制;b区(1000-1050℃)主要是HCl对沉积的抑制作用;c区(1050-1300℃)是表面化学反应和传质共同控制;d(>1300℃)为传质为限速步骤.由于不同的控制机制,导致所得涂层的形貌存在差异.含碳含硅中间物质浓度的减小、HCl增多和MTS的分解共同导致反应物消耗效应.涂层由热解碳和碳化硅两相组成,温度的升高使热解碳相减少,碳硅比接近1.     

The effect of aluminum on the microstructure and phase composition of boron carbide infiltrated with silicon

Reaction-bonded boron carbide is prepared by pressureless infiltration of boron carbide preforms with molten silicon in a graphite furnace under vacuum. The presence of Al₂O₃ parts in the heated zone, even though not in contact with the boron carbide preform, causes aluminum to appear in the liquid silicon. The formation of aluminum sub-oxide (Al₂O) stands behind the transport of aluminum into the composite. The presence of aluminum in the boron carbide–silicon system accelerates the transformation of the initial boron carbide particles into B_x(C,Si,Al)_y and Al_1.36B₂₄C₄, newly formed carbide phases_. It also leads during cooling to the formation of some Si–Al solid solution particles. The effect of Al on the microstructural evolution is well accounted for by the calculated isothermal section of the quaternary Al–B–C–Si phase diagram, according to which the solubility of boron in liquid silicon increases with increasing aluminum content. This feature is a key factor in the evolution of the microstructure of the infiltrated composites.     

聚碳硅烷先驱体转化法制备SiC涂层研究

以自合成的聚二甲基硅烷(PDMS)为原料,常压裂解合成聚碳硅烷(PCS),通过FT-IR分析PCS的结构,用GPC测定其分子量及分布,用熔点分析仪测定其熔点.在此基础上,采用聚碳硅烷先驱体转化法在石墨基体上制备SiC涂层,通过X射线衍射对涂层进行晶相分析,用扫描电镜分析涂层表面和横断面的形貌.结果表明,在石墨基体上形成了明显的β-SiC晶相,可以获得均匀、致密的SiC涂层,其厚度可通过涂层次数的改变进行调节,单次涂层最大厚度大约为2μm.     

Effect of microstructure on the high temperature strength of nitride bonded silicon carbide composite

Four compositions of nitride bonded SiC were fabricated with varying particle size of SiC of ∼ 9.67, ∼ 13.79, ∼ 60 μ and their mixture with Si of ∼ 4.83 μ particle size. The green density and hence the open porosity of the shapes were varied between 1.83 to 2.09 g/cc and 33.3 to 26.8 vol.%, respectively. The effect of these parameters on room temperature and high temperature strength of the composite up to 1300°C in ambient condition were studied. The high temperature flexural strength of the composite of all compositions increased at 1200 and 1300°C because of oxidation of Si₃N₄ phase and blunting crack front. Formation of Si₃N₄ whisker was also observed. The strength of the mixture composition was maximum.     

固/液态聚碳硅烷共混制备碳化硅纤维的研究

以超支化液态聚碳硅烷(LPCS)与固态聚碳硅烷(纯PCS)的共混物作先驱体,熔融纺丝;所得原丝再在热空气气氛中氧化交联,在高温氮气气氛中热裂解,得到碳化硅纤维。研究表明,15%(质量分数)LPCS的加入,可使纯PCS先驱体的纺丝温度,从285℃降低到225℃;纺丝性能和纤维表面质量明显提高;还可以提高氧化交联的效率,降低交联温度,从而减少纤维部分融并、粘结的弊端;虽然纤维的室温力学强度有所降低,但抗氧化性能提高,1400℃氧化交联后,力学性能几乎不变;而纯PCS的力学性能却降为原来的50%。