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Electrospun Poly(vinylbutyral)/silica composite fibres for impregnation of aramid fabrics
... The fabrics could be impregnated with adhesives or shear thickening fluids, reinforcement particles [11][12][13][14], the number of layers being 2-20. ...
This paper presents preliminary results and discussion on two aramid fabrics in order to establish their stab resistance when used as panels with different numbers of layers. Twaron fabrics SRM509 and CT736CMP, were arranged in 16 and 20 layers and in a combination of them (10 layers SRM509 and 10 layers CT736CMP). Samples of 130 mm x 130 mm were cut from the fabrics, weighed and measured for thickness. All tests were done for an impact energy of 24 J (the resulting impact velocity being 3 m/s). The blade had the geometry recommended in the standard Stab Resistance of Personal Body Armor NIJ Standard-0115.00 as P1. The conclusion of this analysis is that the better behavior to stab is obtained for panels that have higher gradients in time, for all four characteristics here discussed: force, displacement, absorbed energy and velocity. When using hybrid panels, the results could intermediate those of the components, this solution could be recommended for reasons as price, weight.
... The glass transition temperature of PVB nanofibers in Figure 4 was detected at 73℃ as in the literature e.g. [74]. No melting transition was noticed for PVB nanofibers. ...
Electrospun nanofibers are proven to be effective toughening agents in polymer matrix composites. They are typically incorporated into laminated composites as interlayers such that resistance against delamination and progression of matrix cracking through the thickness are enhanced in comparison to the neat resin dominated interlaminar characteristics. The nanofibrous interlayers are indeed nanofiber reinforced nanocomposites. This thesis work presents an approach for manufacturing nanocomposites which are representative of the in-situ interlayer formation during the cure and consolidation of the prepreg based laminated composites. Several nanofibrous veils of different base polymers are studied. Mechanical and thermal characterization of the nanofibers and their epoxy matrix nanocomposites are reported along with the reference results on neat epoxy. Scalability of the nanocomposites is also demonstrated by processing novel nanofiber/epoxy laminated nanocomposites much like forming structural laminates. The proposed manufacturing approach enables to collect
representative and consistent nanocomposite mechanical test data. The material model and the elastic modulus of single nanofibers are back-calculated in reference to the experimental tensile behavior of the neat epoxy and representative nanofiber/epoxy nanocomposites. The results are compared with the elastic moduli of single nanofibers extracted with an Atomic Force Microscope (AFM) reported in the literature.
... The development of bulletproof materials using novel nanotechnologies is of high interest to the military, police, and other groups. Impregnating nanofibers with nanoparticles with higher strength, made from materials like silica, can yield such fabrics [127]. Other approaches incorporate carbon nanotubes into such electrospun scaffolds to reinforce their mechanical properties [128]. ...
This study reports the ballistic penetration performance of a composite material composed of woven Kevlar fabric impregnated with a colloidal shear thickening fluid (silica particles (450 nm) dispersed in ethylene glycol). The impregnated Kevlar fabric yields a flexible, yet penetration resistant composite material. Fragment simulation projectile (FSP) ballistic penetration measurements at 244 m/s have been performed to demonstrate the efficacy of the novel composite material. The results demonstrate a significant enhancement in ballistic penetration resistance due to the addition of shear thickening fluid to the fabric, without any loss in material flexibility. Furthermore, under these ballistic test conditions, the impregnated fabric targets perform equivalently to neat fabric targets of equal areal density, while offering significantly less thickness and more material flexibility. The enhancement in ballistic performance is shown to be associated with the shear thickening response, and possible mechanisms of fabric-fluid interaction during ballistic impact are identified.
The primary function of military body armour is to provide protection from fragmenting munitions and improvised explosive devices (IEDs). This is usually achieved by the use of multiple layers of woven para-aramid fabric. The resulting body armour is heavy and contributes to the burden on the dismounted soldier. Reduction in body armour mass and hence thermophysiological loading without reducing the level of protection is therefore of interest worldwide. Many manufacturers quilt the fabric component of body armour which reportedly improves fragment protective performance, however, the topic does not appear to have been explored thoroughly. In this work a preliminary study on the effect of quilting on the fragment protective performance of a commercially available woven para-aramid fabric is reported. The fragment protective performance of specimens varying in construction (1, 2, 3 and 5 layers) with three quilting regimes (no quilting, diamond quilting, square quilting) is presented and analysed.
The stab resistance of shear thickening fluid (STF)-treated Kevlar® and Nylon fabrics is investigated and found to exhibit significant improvements over neat fabric targets of equivalent areal density. Specifically, dramatic improvements in puncture resistance (spike threat) are observed under high and low speed loading conditions, while slight increases in cut protection (knife threat) are also observed. Studies on the effect of fabric architecture indicate that STF addition provides benefits analogous to the effect of increasing fabric yarn count, with STF addition primarily reducing the mobility of filaments and yarns in the impact zone. Microscopy shows significant energy dissipation in the damage zone that includes plastic flow of the polymeric filaments, as well as deformation of the filaments due to mechanical interaction with the colloidal particles of the STF. These results indicate that these novel materials could be used to fabricate flexible body armors that provide improved protection against stab threats.
Electrospinning uses electrical forces to produce polymer fibres with nanometre-scale diameters. Electrospinning occurs when the electrical forces at the surface of a polymer solution or melt overcome the surface tension and cause an electrically charged jet to be ejected. When the jet dries or solidifies, an electrically charged fibre remains. This charged fibre can be directed or accelerated by electrical forces and then collected in sheets or other useful geometrical forms.
More than 20 polymers, including polyethylene oxide, nylon, polyimide, DNA, polyaramid, and polyaniline, have been electrospun in our laboratory. Most were spun from solution, although spinning from the melt in vacuum and air was also demonstrated. Electrospinning from polymer melts in a vacuum is advantageous because higher fields and higher temperatures can be used than in air.
Multiwalled carbon nanotube (MWNT)/poly(vinyl butyral) (PVB) composite nanofibers were prepared by electrospinning, successive twisting and heat treatment. The MWNTs were highly oriented in an electrified thin jet during electrospinning. The heat treatment of the twisted electrospun nanofiber yarns produced the characteristics of the CNT in the composite nanofiber yarns and enhanced their electrical properties, mechanical properties, and thermal properties. The electrical conductivity of the heated yarn was significantly enhanced and showed the maximum value of 154 S cm(-1) for the yarn heated at 400 °C. It is an order of magnitude higher than other electrospun CNT composite materials. These results demonstrated that the novel top-down process based on electrospinning, twisting, and heat treatment provide a promising option for simple and large-scale manufacture of CNT assemblies.
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