Shape memory alloys for use in thermally activated clothing, protection against flame and heat

Shape memory alloys (SMA) 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. Once actuated the clothing layers will separate resulting in an increased air gap. The air gap is one of the major determining factors for insulation. To have this increase prior to exposure to intense heat, i.e. a bulky garment, would subject the wearer to heat stress. Presently nickel titanium alloy has been investigated. A flat spring shape with a transition temperature of ∼45°C has shown good potential. Initial testing on the cone calorimeter has demonstrated a significant increase of protection at heat flux of 15 kW/m2, giving an extra 40 s before the onset of second degree skin burn. The springs can be incorporated in bellows 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. © Crown copyright 1999.