During omni-directional freezing of a material, a frozen solid shell forms at the surface, and the volume changes associated with freezing of the interior causes stresses on the outer shell. The objectives of this study are to quantify such thermal stresses developed in a biomaterial during phase change in the context of food freezing. Mechanical properties of frozen materials will be measured in a temperature controlled Instron machine using samples specially prepared to minimize residual stresses, by freezing from one side. Stress cracks during typical freezing processes will be observed under a cryomicroscope. Observed cracking pattern will be correlated to fracture patterns predicted by a suitable failure theory. This will be the first quantitative analysis of thermal stresses in a biomaterial due to large volumetric changes from phase transformation. Important applications include not only freezing of biomaterials as in food processing but also in cryosurgery and cryopreservation of organs.
