Ballistic fibres

Structure of the fibre. It is reported that its tensile strength and energy-absorbing capabilities have been increased by the development of a new spinning process. 

in which the fibres of each layer are oriented in a 0°/90° fashion and are bonded by thermoplastic matrices. The system is found to be far more ballistically protective than conventional woven fabrics with the same area density.  

The most commonly used polyamide fibre in ballistic application prior to the development of aramid fibres was Nylon 6.6. Technically, the basic built-ups of Nylon 6.6 are the methylene and amide groups. 

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A ballistic panel can be made from a single ballistic material or from two or more materials in combination. Where more than one ballistic fibre is used, the vest is often referred to as a hybrid . The location and number of layers of each material within the multiple-layer protective panel ate critical to the overall performance of the panel. If a manufacturer uses insufficient ballistic material, the body armour will offer insufficient protection. It is thus indispensable that sufficient material and a suitable margin of safety be incorporated into well-designed, properly manufactured body armour (McConnell, 2006). 

Composites for military and aerospace uses The preparation and properties of composites using aromatic polyamide-hydrazide fibres have been described/ and one area in which the X-500 fibres have clearly been tested as composite reinforcements outside Monsanto is that of personnel armour for ballistic protection. Type 3 seems to have given the most promising results, the stiffer types tending to fail by longitudinal splitting. ... 

Zhou Y, Chen X, Wells G. Influence of yam gripping on the ballistic performance of woven fabrics from ultra-high molecular weight polyethylene fibre. Compos B Eng 2014 62 198-204. 

Lee BL, Song JW, Ward JE. Failure of Spectra polyethylene fibre-reinforced composites under ballistic impact loading. J Compos Mater 1994 28 1202-25. 

Dyneema UD is a unidirectional laminate made of two layers of extended chain polyethylene filament tows, cross plied and sandwiched in a thermoplastic film. It is one of the strongesf " and most exclusive fibre laminates designed for ballistic protection. It is very thin and one of the lightest ballistic protection materials available, with a relative density lower than that of water. - It offers good protection from cuts and slashes and will also help to protect against stabs. It will withstand temperatures of up to 140 °C and maintains its protective properties down to -150 °C (Fig. 7.15). 

Aramid and ultra-high molecular weight polyethylene are used extensively as base materials for ballistic protection. As discussed earlier (section 7.3.1), these high performance fibres are characterised by high strength, high eneigy absorption, and low density. However, to meet the protection requirements for typical ballistic threats, approximately 13-50 layers of fabric are required, which results in a bulky and stiff armour. The bulk-iness limits its comfort and has resfiicted its appUcation primarily to torso protection. 

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