How cracks are hot and cool: a burning issue for paper

Material failure is accompanied by important heat exchange, with extremely high temperature - thousands of degrees - reached at crack tips. Such a temperature may subsequently alter the mechanical properties of stressed solids, and finally facilitate their rupture. Thermal runaway weakening processes could indeed explain stick-slip motions and even be responsible for deep earthquakes.
Therefore, to better understand catastrophic rupture events, it appears crucial to establish an accurate energy budget of fracture propagation from a clear measure of various energy dissipation sources. In this work, combining analytical calculations and numerical simulations, we directly relate the temperature field around a moving crack tip to the part - of mechanical energy converted into heat.
By monitoring the slow crack growth in paper sheets using an infrared camera, we measure a significant fraction ? = 12% ± 4%. Besides, we show that (self-generated) heat accumulation could weaken our samples by microfiber combustion, and lead to a fast crack/dynamic failure/regime.
References: How cracks are hot and cool: a burning issue for paper. Renaud Toussaint, Olivier Lengliné, Stéphane Santucci, Tom Vincent-Dospital, Muriel Naert-Guillot et Knut Jørgen Måløy.

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