A critical review on the factors affecting the impact resistance behaviour of soft body armour is presented here. The effect of several material and structural parameters of fibrous assemblies used ...in soft armour is dealt with in depth. The standards of performance evaluation of soft body armour and modes of energy absorption are elucidated. The paper also reviews different approaches resorted to by the researchers to enhance the ballistic or stab resistance performance of these soft body armour materials. These approaches include surface treatments and modifications of the base material to increase yarn to yarn friction as well as implementation of 3D woven fabrics to enhance structural integrity. Among these, the effect of shear thickening fluid (STF) is discussed extensively. The review concludes with the future directions of research in the area of soft body armour.
A critical review on the factors affecting the impact resistance and various approaches adopted to enhance the performance of soft body armour materials is presented here.
Simulations are used to study the steady shear rheology of dense suspensions of frictional particles exhibiting discontinuous shear thickening and shear jamming, in which finite-range cohesive ...interactions result in a yield stress. We develop a constitutive model that combines yielding behavior and shear thinning at low stress with the frictional shear thickening at high stresses, in good agreement with the simulation results. This work shows that there is a distinct difference between solids below the yield stress and in the shear-jammed state, as the two occur at widely separated stress levels, with an intermediate region of stress in which the material is flowable.
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To improve the performance of shear thickening fluids (STFs), we propose the addition of fibrous sepiolite. Through macroscopic rheological tests and microscopic characterization, the effects of ...different sepiolite mass fractions (0 wt%, 1 wt%, 2 wt% and 3 wt%) on the shear thickening of a SiO2-STF system (with a PEG200 dispersion medium) at different ambient temperatures (20 °C, 30 °C, 40 °C and 50 °C) were investigated. Rheological experiments revealed a significant improvement in the shear thickening of SiO2-STF with the addition of sepiolite (Sep/SiO2-STF), with 7.11- and 1.94-fold increases in absolute and relative shear thickening, respectively. As the sepiolite mass fraction increased from 0 wt% to 3 wt%, the temperature sensitivity coefficient decreased from 13.493 to 4.839, indicating that the Sep/SiO2-STF system still exhibited favourable shear thickening at 50 °C. Dynamic oscillatory shear testing revealed that with an increase in sepiolite mass fraction from 0 wt% to 3 wt%, the maximum energy storage modulus, maximum energy dissipation modulus and shear stress increased by 5196.25 %, 1676.16 % and 377.54 %, respectively. Microscopic characterization revealed that sepiolite induced the formation of more clusters in the STF system primarily through the physical adsorption of silica particles and Si–OH on its surface, leading to a significant increase in the shear thickening effect.
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•This study represents the first investigation into the enhancement of STF rheology by sepiolite.•The temperature sensitivity of STF system was reduced by adding sepiolite.•The mechanism by which sepiolite enhances the rheology of STF is proposed.
This study examines the rheological properties of shear thickening fluid (STF) enhanced by additives such as multi-walled carbon nanotubes (MWCNTs), polyvinylpyrrolidone (PVP), and nano-silica (SiO
) ...at different mass fraction ratios. The rheological properties of the liquid (MWCNTs–PVP/SiO
–STF) and the effect of the rheological properties of the STF under different plate spacing of the rheometer were investigated. The optimal mass fraction mixing ratio was also studied. The MWCNTs–PVP/SiO
–STF system with different PVP mass fractions was fabricated using ultrasonic technology and the mechanical stirring method. Then, the steady-state rheological test of the MWCNTs–PVP/SiO
–STF system was carried out with the aid of the rheometer facility. Dynamic rheological and temperature sensitivity tests on the MWCNTs–PVP/SiO
–STF system with 0.1 and 0.15% PVP mass fractions were performed. The rheological test results show that the MWCNTs–PVP/SiO
–STF system has a significant shear thickening effect when the PVP mass fraction is increased from 0 to 0.15%. When the PVP mass fraction is 0.1% and the plate spacing is 1 mm, the system exhibits the best shear thickening performance. This is based on the following facts: the viscosity can be achieved as 216.75 Pa s; the maximum energy storage and energy consumption capabilities can be observed. As a result, PVP can significantly enhance the shear thickening performance of the MWCNTs/SiO
–STF system.
Shear thickening polishing (STP), an emerging polishing method, is used to polish the cemented carbide insert with complex shape in this study. The principle and performance of STP were introduced. ...Four parameters having significant influence on the STP process, including polishing speed, abrasive concentration, abrasive size, and inclination angle of fixture, were experimentally investigated. The influence of the four parameters on the surface quality of cemented carbide insert was analyzed by orthogonal experiment method, and the optimal processing parameter combination for the STP of cemented carbide insert was determined. Although the influence degree of the processing parameter on the left cutting edge
P
A
, the top cutting edge
P
B
, the root cutting edge
P
D
, and the right cutting edge
P
K
was different, the optimal processing parameter combination for each position was the same: polishing speed of 90 rpm, abrasive concentration of 9 wt%, abrasive size of #8000, and inclination angle of 4°. Under the optimal processing parameter combination, the surface roughness of cemented carbide insert at the left cutting edge
P
A
was reduced from 121.8 to 7.1 nm after 15 min polishing. The scanning electron microscopy (SEM) and the white light interferometer confirmed the effectiveness of the STP process in the polishing of cemented carbide insert. The experimental results show that STP was a promising and feasible processing method in the polishing of cemented carbide insert with complex shape.
•Bio-Inspired Energy-Absorbing Device using shear thickening fluid (STF) is studied.•Shear thickening behaviour of STF is used as the main energy absorption mechanism.•Proposed device can absorb the ...impact energy and slowly recover.•Effects of loading rate, viscosity and contact area on energy absorption of BIEAD.
In this study, a novel type of Bio-Inspired Energy-Absorbing Device (BIEAD) utilising shear thickening characteristics of shear thickening fluid (STF) is proposed. The viscoelastic material between the suture interfaces found in skulls of headbutting animals and beaks of woodpeckers is mimicked to propose a recoverable energy-absorbing device. The viscoelastic material and tooth of the suture are mimicked by shear thickening fluid and a rectangular tube, respectively. The thickening behaviour of the STF is utilised as the main mechanism of the energy absorption of the proposed device. In this study, the proposed BIEAD is investigated by using finite element software LS-DYNA. Fluid-Structure Interaction (FSI) approach is used to model the interaction between the fluid and the solid parts, and the apparent viscosity as a function of shear rate is considered to model the shear thickening behaviour of STF. Unlike conventional energy-absorbing structures which dissipate the impact energy through plastic deformation, the proposed device dissipates the impact energy through viscous dissipation and internal friction of the STF. The proposed BIEAD also shows good energy absorption capacity and can slowly recover after the impact due to the shear thickening behaviour, sticky characteristic of the STF, and the elastic springs in the prototype design. By conducting parametric studies, it is found that the energy absorption capacity of the BIEAD is sensitive to the apparent viscosity of STF, which is influenced by the applied shear rate, shear gap and rheological property of the STF.
Percec-type substituted benzyl alcohol mini-dendrons as new hydrophobic end-cappers can effectively improve the thickening performance of hydrophobically modified ethoxylated urethanes (HEURs) in ...aqueous solution. To demonstrate the effects of substituted structure of Percec-type mini-dendritic end groups on aggregation and rheological properties of HEURs in aqueous solution and latex, three model HEURs end-functionalized by mono-, di- and tri-substituted benzyl alcohol mini-dendrons were synthesized, respectively. For a reasonable comparison, the total carbon number of substituted alkyl tails is set to be 24 for the three mini-dendritic end groups: HOCH2-Ph-C24H49 (C24), HOCH2-Ph-(C12H25)2 (2C12) and HOCH2-Ph-(C8H17)3 (3C8), which respectively correspond to single-, two- and three-tail according to their substituted degrees. Interestingly, rheological properties of these HEURs in aqueous solution and latex significantly depend on the substituted degree of mini-dendritic hydrophobes. The high-substituted mini-dendritic hydrophobes help HEURs to form a strong physical network with high thickening performance and fast relaxation in both aqueous solution and latex, because shorter alkyl tails in high-substituted dendritic hydrophobes will lead to a smaller aggregation number and a lower rheological activation energy. This work not only provides new insights into the connection of networks in solutions of mini-dendron functionalized HEURs but also offers a new approach to preparation of high performance thickeners used in water-borne systems.
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•Three HEUR model polymers with different dendritic end groups were synthesized.•The solution aggregation and rheology of these HEURs depend on the substituted degree of dendrons.•High-substituted dendrons lead to strong hydrophobic networks and rapid solution relaxation.•This work opens a new approach to highly efficient thickeners in waterborne systems.
The present work explores the magnetohydrodynamic (MHD) flow of Carreau nanoliquid by exponentially convected stretchable surface. Formulation and computations are presented for Brownian motion and ...thermophoresis. Concentration by zero mass condition is reported. Consideration of thermal radiation characterizes the heat transfer process. Transformation procedure is utilized for reduction of PDEs into ODEs. Highly nonlinear complex problems are computed numerically through Runge–Kutta Fehlberg technique. Salient characteristics of local Weissenberg number, Hartman number, Biot number, thermophoresis parameter, Prandtl number, thermal radiation parameter and Schmidt number on the velocity, temperature, nanoparticles concentration, surface drag force and Nusselt number are reported through graphs and Tables. The results demonstrated here reveal that the velocity distribution for local Weissenberg number in case of shear thinning liquid reduces whereas it increments for shear thickening liquid. Temperature and thermal layer thickness are increasing functions of thermal radiation. Besides this the results of presented analysis are compared with the available works in particular situations and reasonable agreement is noted.
•Flow of Carreau nanoliquid subject to magnetohydrodynamics is modeled.•Formulation and computations are presented for Brownian motion and thermophoresis.•Consideration of thermal radiation and convective heating characterizes the heat transfer process.•Concentration by zero mass condition is reported.•Numeric solutions are obtained through Runge–Kutta Fehlberg technique.
Flocculation occurring in a feedwell plays a critical role in tailings slurry thickening process, which is complicated and significantly influenced by flow characteristics. This work presents a ...numerical approach to explore the effect of flow characteristics on flocculation performance. It combines an aggregation kernel and a breakage kernel, used to describe the polymer-bridging flocculation kinetics, with a conventional Computational Fluid Dynamics-Population Balance Model (CFD-PBM) coupling to model the complex flocculation-thickening behavior in a lab-scale gravity thickener. The solid-liquid phase interaction is described by an Euler-Euler approach with a modified Schiller-Naumann drag model. The turbulence of liquid phase is resolved by the RNG k-ε turbulence model, while the solid kinematic eddy viscosity is described by a dispersed phase zero equation model. The capability of this proposed model is validated by a good agreement between experimental and predicted results in terms of single-liquid velocity and floc size distribution. The momentum and turbulence dissipation rates are investigated in and around the feedwell over a wide range of feed velocities, showing that the momentum and turbulence dissipation rates have a positive correlation with feed velocity. The momentum and turbulence dissipation rates decrease with the increase in scaled depth in the feedwell. The formation of large vortexes in the feedwell may cause a locally low turbulence dissipation rate. A reasonable increase of feed velocity favours the flocculation, however, an excessive feed velocity can cause a decrease in mean floc size. Modelling tailings flocculation is of great significance for understanding the flocculation behavior and revealing the effect of flow characteristics on flocculation performance.
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•A population balance model (PBM) was used to describe the polymer-bridging flocculation kinetics.•The Tailings flocculation process in a thickener was modelled by a coupled CFD-PBM approach.•The capability of the proposed model was validated both in liquid velocity and floc size distribution.•The effects of feed velocity on flow characteristics and flocculation performance were explored.
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