China
Africa
Explore chapters and articles related to this topic
Woven Fabrics and Composite Laminates for Armour Applications
Published in Paul J. Hazell, Armour, 2023
Kevlar was first developed by DuPont in the 1960s from aromatic polyamides. This and similar fibres such as Twaron, manufactured by Teijin Aramid, are known as aramids and are derived from polymer molecules containing benzene rings. These molecules readily align parallel to each other to form highly ordered structures and consequently demonstrate excellent properties along the direction of the fibres. The fibres, however, are highly anisotropic due to the weak inter-chain bonding between each of the molecules and therefore are susceptible to splitting. This is illustrated by the experiments of Cheng et al. (2004, 2005) who measured the longitudinal and transverse properties of a single Kevlar KM2 fibre. The longitudinal modulus is significantly higher. See Table 9.3.
Fibre reinforcements
Published in A.R. Bunsell, S. Joannès, A. Thionnet, Fundamentals of Fibre Reinforced Composite Materials, 2021
R. Bunsell, S. Joannes, A. Thionnet
Although the bonds are not completely straight in these fibres they are nearly so and this results in a high-tensile stiffness as well as thermal stability. The glass transition temperature of PPTA is over 375°C and the polymer is thermally stable up to about 550°C. The same type of fibre has been commercially produced under the name Twaron®. It was developed by Akzo in Holland and is now produced there by the Japanese company Teijin Aramid. These aramid fibres were truly remarkable as they took organic fibres from a range of stiffness of less than 20GPa to 135GPa.
Reinforcements and Matrices for Polymer Matrix Composites
Published in Manoj Kumar Buragohain, Composite Structures, 2017
Aramid fibers are extensively used in both composites and noncomposites applications, in diverse industrial sectors including aerospace, sports, automotive, and marine. Use of aramid fibers depends upon the specific type and fiber form. Meta-aramid fibers such as Nomex, owing to their excellent thermal resistance, good textile characteristics but poor mechanical properties, are used in protective clothing, reinforced belts and hoses, industrial coated fabrics, etc. Para-aramid fibers such as Kevlar and its various subtypes, Twaron, etc. possess excellent mechanical properties. Continuous filament yarns and rovings of para-aramids are used in composite pressure vessels, rocket motor casings, sporting goods, rope, and cable, etc. Fabrics are used in facings of sandwich constructions in aircrafts and helicopters, boat hulls, etc. Staple fibers are used in automotive applications such as brake and clutch linings, gaskets, etc.
UHMWPE textiles and composites
Published in Textile Progress, 2022
Ashraf Nawaz Khan, Mohit Gupta, Puneet Mahajan, Apurba Das, R. Alagirusamy
Glass fibre was the first non-metallic fibre having a strength exceeding 2 GPa used in structural applications, but later, carbon fibre was developed which had the advantage of higher strength and stiffness than the glass and a lower density. Both of these fibres are still widely-used to produce composite material having very high specific strength in different applications. High-performance polymer fibres now present alternative options for the replacement of glass and carbon fibre with other low-density materials, whereas, initially, the commonly-available polymer fibres could not match their mechanical strength and modulus. Solvent-based spinning technologies now make it possible to develop ultra-strong polymer fibres. There are two classes of polymer fibres, one with rigid-rod molecules such as Kevlar® (DuPont, Wilmington, DE, USA), Twaron® (Teijin Aramid, Arnhem, The Netherlands), or Zylon® (Toyobo, Osaka, Japan). These fibres reveal high bending stiffness. Another class of polymer fibres has a very flexible nature such as UHMWPE as used in Dyneema® (Royal DSM, Heerlen, The Netherlands) Spectra (Honeywell International Inc. Charlotte, NC, USA) and Tensylon™ (DuPont, Wilmington, DE, USA). With no charged polar or ionic groups along its polymer chains, PE possesses very low intermolecular forces of attraction therefore it is necessary to have polymer chains of considerable length size to generate a high level of interaction, such as is the case with the polymer chains in UHMWPE fibres (Marissen, 2011; Polk, Vigo, & Turbak, 2002).
Technical textiles for military applications
Published in The Journal of The Textile Institute, 2020
R. G Revaiah, T. M. Kotresh, Balasubramanian Kandasubramanian
Prior to 1960, non-FR cotton flight suits were used in flying clothing, which were replaced by FR cotton in the subsequent years. Aramid fibres were introduced by Du Pont and found extensive usage in flying clothing due to their exceptional FR properties. The transition from flame-resist fabrics to inherently FR fabrics is primarily due to wash durability and enhanced fire protection. Meta aramid fabric (commercially known as Nomex, Conex etc.,) is known to shrink, break open and expose underlying skin when exposed to high temperature (DuPont, 1999). This shortcoming was overcome by adding 5% para aramid (known as Kevlar, Twaron, etc., commercially) which holds fabric in place and acts like scaffold. Further, to discourage the static charge nuisance, 2% P140 antistatic fibre was also added. The blend known as (93/5/2) is known as Nomex IIIA and Conex IIIA. To completely evaluate FR properties, the protective clothing has to undergo standard FR tests such as thermal protective performance (TPP) test, flame resistances tests and thermal manikin test. The other bench scale tests are; 45° flammability test, vertical flammability test, Lateral ignition flammability test etc. (Horrocks, 2013).
Evaluation of a new ballistic vest design for compliance with Standard No. PN-V-87000:2011 using physiological tests
Published in International Journal of Occupational Safety and Ergonomics, 2019
Anna Marszałek, Grażyna Grabowska, Krzysztof Łężak
The bulletproof vest is a special vest-like garment, and its task is to protect the chest from firearm-fired projectiles. Such items are used by police and military services, but also by personal protection services and private individuals in situations where their health and life may be at risk [1]. Soft ballistic panels, also known as basic inserts, are the main elements of ballistic protection and are the main protective layer against firearms and shrapnel [2]. Szołucha [2] states that ballistic soft insert manufacturers use essentially two types of materials – aramid fibres and high-molecular-weight ballistic polyethylene. Aramid fibres, or polyamide fibres, such as DuPont Kevlar and Teijin Twaron, have five times the tensile strength of steel with the same weight, and this difference is six times greater in water. Aramid fibres are thermally stable and do not melt. They also have self-extinguishing properties – when the fire source is stopped, they cease to burn. Low temperatures (approximately −50 °C), do not affect their resistance. Szołucha [2] indicates also that resistance of a vest to puncture with knives or similar close-quarter weapons is a separate issue. A projectile fired from a firearm does not penetrate the ballistic fibre of the protection panel, as opposed to a blade that penetrates the vest, just between the fibres, and is therefore more difficult to stop. There are special knife-resistant and/or needle-resistant vests; however, they seem to be a compromise between the level of resistance and user comfort, as they are usually much stiffer than classic protective vests [3–5].