Back in the air with safety, style and KEVLAR

Citation

(2002), "Back in the air with safety, style and KEVLAR", Aircraft Engineering and Aerospace Technology, Vol. 74 No. 2. https://doi.org/10.1108/aeat.2002.12774baf.003

Back in the air with safety, style and KEVLAR

Keywords: Aircraft, Safety, Technology

An innovative use of high performance KEVLAR from DuPont is one of the high tech safety solutions that has been instrumental in putting Concorde back into commercial service. KEVLAR performance technology from DuPont is playing a key role in making possible the relaunch of the world's only commercial supersonic aircraft.

A special hybrid fabric system comprising KEVLAR in conjunction with a high-grade elastomer is being used to line the fuel tanks and offer the protection needed for both the plane and its passengers.

Developed and manufactured by Paris- based Groupe Zodiac's Aerazur subsidiary, the liners use advanced fabric and moulding technology to meet a demanding technical specification. They are being produced for the European Aeronautic Defence & Space Company (EADS) which supplies them to British Airways and Air France.

The reinforcement of the fuel tanks has been one of the most significant modifications to Concorde. The upgrade involves the introduction of a new concept in liners, incorporating high strength KEVLAR encapsulated within a matrix of high durability fluoro-elastomeric. In this advanced compound material, the elastomeric provides resilience and sealing properties while KEVLAR provides the strength and impact resistance.

More than 100 individually shaped sections of KEVLAR composite material have been precisely engineered then fitted by hand into the extremely constricted fuel tanks within Concorde's delta wings. These ''cardboard thin'' liner pieces range from 1.2 m to 1.8 m in length and are 30–45 cm wide.

Extensive tests on this fuel tank reinforcement system are reported to indicate that despite their thin profile, the liners provide a high degree of protection against the puncture and cut effects of the type of impact suffered by the downed French Concorde. Complimenting the enhanced impact protection delivered by KEVLAR, the fluoroelastomer element of the system are said to offer vital fuel leakage containment and flow restriction. It is believed that in the unlikely event that the liner were to be breached, the liner system significantly stems fuel leakage; down from 100 litres per second from a 30 sq.cm hole to just 1 litre per second. The result claimed is that leakage is contained to a level where ignition would be virtually impossible.

While safety and protection are paramount, any solution also needs to be evaluated in terms of load capacity implications. The exceptional strength to weight ratio of this KEVLAR composite material system means that an entire set of these liners adds less than 400 kg to the aircraft's overall weight. Further weight-saving improvements to the tyres plus interior refurbishment to Concorde mean that the relaunched aircraft is likely to weigh even less than its previous generation.

The integration of high strength KEVLAR within a high performance elastomeric substrate is said to result in a coated fabric system with flexibility, extraordinary strength, chemical resistance, resistance to impact and temperature stability. Most importantly, it claims to exhibit excellent self-sealing properties, meaning that in a fuel tank puncture situation it will tend to close up over the rupture thus stemming the outflow of fuel.

Famous for its bullet-resistant qualities in police and military vests, the energy absorbing nature of KEVLAR along with its inherent strength and ultra low mass make it thought ideal for demanding commercial and military aerospace applications. Since its first use in Concorde as a solution for reducing interior weight, KEVLAR has been continuously refined and developed to meet the ever- increasing demands of modern aviation and travel. Its applications in aircraft include spot fuselage reinforcement, radomes, and containment rings for jet engines.

Bright yellow in colour, KEVLAR is a para- aramid (poly-paraphenylene terephthalamide) fibre, which, because of its chemical nature and linearly oriented polymer structure, claims an excellent combination of physical properties. High tensile strength, high stiffness and damage tolerance, and high thermal stability with self-extinguishing properties (KEVLAR fibre does not melt), make KEVLAR fibres ideal for a huge range of demanding applications.

These exceptional properties, particularly its high strength to weight ratio, temperature resistance and versatility, are thought responsible for KEVLAR being used in a huge range of demanding applications ranging from deep sea umbilical lines and premium sports goods to high performance structural composites in boat hulls, aircraft components and high-performance cars.

Dupont considers that, its excellent energy absorption and non-sparking characteristics make it the material of choice for a host of critical protective applications including the strengthening of bridge columns against vehicle impact, bullet-resistant apparel and vehicle armouring.

Technical properties claimed of KEVLAR;

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  High Tensile Strength at Low Weight

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  Low Elongation to Break

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  High Modulus (Structural Rigidity)

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  Low Electrical Conductivity

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  High Chemical Resistance

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  Low Thermal Shrinkage

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  High Toughness (Work-To-Break)

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  Excellent Dimensional Stability

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  High Cut Resistance

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  Flame Retardant, Self-Extinguishing

DuPont Advanced Fibre Systems. Tel: +41 22 717 58 20; Fax: +41 22 717 61 31; E-mail: Simone.Huguet@che.dupont.com