HEAT PROTECTION
AN ORIGAMI-INSPIRED FIRE SHELTER The combination of fire-resistant materials and the centuries-old practice of origami may protect people during a bushfire emergency. BY
RICKY W K CHAN
School of Engineering, RMIT University
T
he south-east of Australia is known to be one of the most hazardous bushfire regions in the world. The volatile mix of climate, geography and vegetation can easily lead to bushfires, and CSIRO research indicates that the increasingly warmer and drier climate caused by climate change will make them more prevalent. During a bushfire, heat transfer occurs by a combination of convection (movements of hot air mass),
FIGURE 1. Yoshimura crease pattern.
conduction (heat travelling through material), and radiation (a form of electromagnetic wave). Of the three, radiation, which is measured in heat flux (in kW/m2), does not require a medium to transfer. It is the most dangerous aspect of a bushfire— research indicates that an unprotected person may feel pain at 140 metres from flames after one minute of exposure. At 55 m, the heat flux is fatal after a few minutes. The best protection from radiant heat is distance. When that is not an option, a protective barrier will become the difference between life and death. When battling wildfires, US firefighters carry a lightweight fire shelter they can deploy when needed. It is designed to reflect radiant heat and trap breathable air, but cannot withstand sustained contact with flames. To overcome this, researchers at RMIT University have developed a protection system that can be used in an emergency. It is a fire-rated blanket that deploys like an origami-type structure that encloses a person on the ground. When it is not in use, it can be folded into a small bag that can be carried by hand. The research team at RMIT University is attempting to optimise the fire shelter to:
FIGURE 2. Lay-flat geometry of the origami fire shelter.
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FIRE AUSTRALIA ISSUE ONE 2021
1. facilitate deployment and enclosure of a person 2. increase stiffness of a fire-rated fabric to create creases 3. meet Australian Standards fire tests.
Origami structures
The word ‘origami’ comes from the Japanese ‘oru’ and ‘kami’, meaning ‘to fold’ and ‘paper’ respectively. It is a recreational art and involves folding a sheet of paper into shapes resembling objects and animals. Origami has become very complex, with some creations even involving kinetic movements. The fascinating shapes of origami have inspired artists, mathematicians, architects and engineers, and have often been applied in spatial design, robotics and medical devices. The fire shelter presented in this article is inspired by the Yoshimura crease pattern (Miura & Tachi, 2010). The geometry consists of repetitive pairs of triangles that form a diamond shape. By alternating ‘mountain’ and ‘valley’ folds, the Yoshimura crease pattern may collapse (‘buckle’, in engineering terms) when compressed (Hunt & Ario, 2005) and extend under tension. The basic pattern is illustrated in Figure 1. The geometry is characterised by the apex angle (b), deployment angle (q), length
