Aramid fibres are human-made fibres having molecules that are characterized by relativelyrigid polymer chains. These molecules are linked by strong hydrogen bonds that transfermechanical load very efficiently, making it possible to use chains of relatively low molecularweight with much higher tenacity and elastic modulus. The aramid fibres have a high degreeof orientation, similar to the UHMWPE fibres.The fibres are known for high strength, good impact and ballistic properties, low flammability,no melting point, and good resistance to chemicals and abrasion. The density of aramid fibresvaries from 1.44 to 1.46 g/cm3.Aramid is one of the most important fabrics used in armour applications. The aramid fibrereinforced composites provide the highest strength-to-weight ratio compared to otherreinforcing fibres. Aramid fibres belong to the polyamide fibres family, which have aromaticring structures constructed by their amide links. The chemical structure of para-aramid fibreis a long-chain structure of high molecular weight, high-temperature resistance, and hightensile strength. Typical properties and an image of one kind of specific aramid fabric aregiven in Table and Fig
.Aramid fibre composites are made of aramid reinforcing fibres and matrix materials. Thematrix has a greater elongation than reinforcement and a lower modulus than reinforcement,but the fibres carry the maximum load. Generally, two types of aramid fabric are used inarmour application, namely, woven and nonwoven fabrics.
Ballistic application of aramid fibres:Threats to military and law enforcement have multiplied in recent years, creating the need forprotection against armour-piercing bullets and improvised explosive devices.
Today, both woven aramid fabrics and UD cross-plied materials provide greater protection,more comfort, and advantageous performance/weight ratios for military, police, and other lawenforcement people than older aramid materials. A number of civilians who face ballisticthreats such as prison guards, cash carriers and private people benefit from aramid fibrebased composites. The table provides some typical properties of aramid yarns.Aramid-coated fabrics are extensively used for manufacturing military helmets and providingspall liners inside military vehicles.Aramid fibres are used in the armouring of police and civilian vehicles while keeping in mindtheir maneuverability. Even tanks and other military vehicles can be made lighter and saferwith aramid fibre composites. The aramid fibre composites can reduce the weight of armouredvehicles by 30 – 60% compared to steel. Aramid fibre ballistic solutions exist for a number ofthreat levels, ranging from direct fire and shell fragments to high explosives.
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