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

Abstract

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.

On the Effectiveness of Temperature-Responsive Protective Fabric Incorporated With Shape Memory Alloy (SMA) Under Radiant Heat Exposure

“…It was observed that the clothing system with SMR prolonged the rescue time by approximately 30 s. Later, White (2012) found that the TPP was significantly improved when SMRs were stuck on the outer surface of the moisture barrier, and those with an actuation temperature of 45 °C also showed good performance when reducing heat transfer from the atmosphere to body skin. This is similar to Congalton’s (1999) findings. On the basis of Hendrickson’s (2011) study, Yates (2012) constructed a prototype gear with SMRs embedded in the pockets at the shoulder and upper arm.…”

On the Improvement of Thermal Protection for Temperature-Responsive Protective Clothing Incorporated with Shape Memory Alloy

“…The incorporation of any arrangement of SMA spring within the fabric assembly could improve the TPP to some extent, since the temperature at the end of exposure (T fa ) was found to be notably reduced due to the use of SMA springs under both thermal exposures. The positive effect of the SMA spring under exposures to the RHE and HSC conditions consisted with those of Congalton’s study [ 18 ], in which the effectiveness of SMA springs was reported as the fabric was exposed to a radiant heat produced by a cone calorimeter. Under both RHE and HSC conditions, it was found that incorporations of the One and the Three Diag were the most effective way in reducing the internal temperature of the thermal liner (shown in Figure 4 c and Figure 6 c), increasing the thermal protection times of t 44 /t 56, and decreasing the final temperature T fa .…”

“…Thus, the positive effect of the big spring size on reducing heat transfer was offset by the increasing heat conduction from the spring. The problem of heat conduction of the SMA spring was also motioned in a previous study, which have reported that the great conductive heat travelling through the spring is not benefit for the thermal protection [ 18 ]. It seemed to indicate that as compared to the RHE condition the HSC condition may add the risk of heat conduction from the metal-based SMA spring.…”

“…It seemed to indicate that as compared to the RHE condition the HSC condition may add the risk of heat conduction from the metal-based SMA spring. An insulative disc with low heat conductivity might be used to attach the springs in the fabric, and thus decrease the heat conduction to skin [ 18 ]. In addition, this heat conduction should be paid more attention under the HSC condition because in real-life situations protective clothing with multilayers of fabric is easily compressed as firefighters are blundering into a structural heating wall, crawling on a hot ground, or holding a heated stuff.…”

Investigation of the Thermal Protective Performance of Shape Memory Fabric System: Effect of Moisture and Position of Shape Memory Alloy

“…Subsequently, White (2012) validated Hendrickson's model and investigated the effects of the SMR position between the fabric layers and the T a of SMR (50 C and 90 C). White (2012) found the protective performance was improved when SMR was placed in the external surface of the moisture barrier, and the SMR's T a of 45 C showed a good potential to decrease heat transfer to human skin, which was consistent with Congalton's (1999) finding. Yates (2012) further performed human trial tests based on Hendrickson's study.…”