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1 Applied Mechanics and Engineering

1 1999

1 Congalton D.

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Shape memory alloys for use in thermally activated clothing systems

100%

Congalton D.

Applied Mechanics and Engineering

1999

tom Vol. 4, no spec.

423-428

Shape memory alloys, SMAs, have been in use as actuators in many mechanical processes for some time. The alloys are "trained" to return to a given shape when an actuation temperature is reached. These alloys can be incorporated into clothing systems to give, on actuation, an increased air gap between the clothing layers and hence greater insulation. The air gap is one of the determining factors for insulation but to have this increased prior to exposure to intense heat, i.e. a bulky garment, would subject the wearer to heat stress. Currently, Nickel Titanium alloy has been investigated as an SMA. A flat spring shape with a transition temperature of ~45oC has shown good potential in this rôle. Initial testing on the Cone Calorimeter has demonstrated a significant increase of protection at a heat flux of 15 kW/m2, a level that the UK Fire Service regards as life threatening. The clothing layers separate when the SMA spring is actuated and this in turn greatly reduces the temperature experienced at skin level, resulting in an increase of 40 seconds before the onset of second-degree skin burn. The results obtained demonstrate the potential for utilising SMAs in clothing for protection against flame and heat. The springs can be incorporated in bellows-style pocket panels. The pleats allow for the expansion of the air gap while the attachment of the spring holds the fabric layers together prior to actuation. Potential applications are for the fire service, drivers in enclosed vehicles, e.g. tank crew, racing drivers, and any other personnel who may be accidentally exposed to intense heat.