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Doctoral thesis accepted to be open access on May 2015, and available online via RMIT University website to download click here
Topic
Comfort and Stab-Resistant Performance of Body Armour Fabrics and Female Vests
Abstract
This research reports the design and engineering of Kevlar-based stab resistant body armour fabrics and female vests, and evaluates their performance for protection and comfort especially for female police officers. Kevlar-wool woven fabric has been employed as a potential material for body armour vests. This current study investigates the thermal comfort properties of woven Kevlar-wool ballistic fabrics and commercial woven 100% Kevlar ballistic fabrics. The effects of fabric physical properties on laboratory-measured thermal comfort were analysed. In this context, their thermal comfort performance was compared, and fabric friction and surface roughness were evaluated. A water repellent treatment was applied to the woven Kevlar-wool fabric to ensure comparable thermal comfort results with the commercial 100% Kevlar. Since the commercial Kevlar fabric showed a water repellent result in the moisture management test, the effects of the water repellent treatment on the Kevlar-wool fabric were examined as well. This study also presents the fabric bursting strength and tear strength for comparison. Experimental results show a clear difference in thermal comfort properties: the Kevlar-wool fabric possesses better moisture management properties and mechanical properties than the Kevlar fabric.
Protection and comfort are significant aspects for body armour. A questionnaire survey was conducted in order to determine the risk assessment and comfort performance provided in current body armour used by prison officers. There were 102 prison officers surveyed in Saudi Arabia on the current body armour they may use in terms of protection and comfort. This was to understand the need for protection with body armour and to improve protective fabric and vest designs with enhanced comfort performance for future soft body armour. The survey results revealed that 12% of male and 29% of female prison officers had been attacked and protective measures against this violence could not be ignored.
Seams and stitching in body armour could affect their protective and comfort performance. Seamless technology is a method used to minimise cutting and sewing processes in making knitted garments. Seamless technology was adopted to accommodate the bust contour for female body armour designs. The 3D-knitting technology Shima Seiki SES–S.WG® and its whole-garment program were used to develop seamless female body armour vests for fit and comfort. The Kevlar-wool and 100% Kevlar fabrics were produced as weft-knit single jersey using the whole-garment knitting machine and their physical properties were measured. These properties were used to design and engineer two different styles of 3D seamless female body armour vest, the loose-vest and the bra-vest.
The knitted 100% Kevlar fabric was coated with abrasive particles to enhance stab protection performance. The stab-resistance of personal body armour standard (NIJ 0115.00) was used to determine the protection level. Single– and double-blade knives were used in this stab test. The knitted fabric mechanical properties were also investigated using bursting strength tests and stab resistance drop tests with a range of impactors. The results show that one layer of knitted Kevlar-wool, plus eight layers of knitted 100% Kevlar, and one coated layer with abrasive sand particles (a total of ten layers), passed the tests with less than 7 mm perforation at 8 J using a single-blade knife. Moreover, a combination of the knitted fabrics (Kevlar-wool, 100% Kevlar and coated Kevlar) could improve their stab-resistance. Multi-layered flexible stab-resistant vests were assembled and evaluated for comfort using a thermal manikin and sweating guarded hot-plate. The moisture management properties of the knitted fabrics were investigated. The results of this research provide a good reference for designing and engineering female body armour capable of resisting stab penetration, as well as possessing improved comfort performance.
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