Spalling fracture has been engineered to controllably and intentionally exfoliate thin film electronic devices from single crystal semiconductors for the purposes of creating flexible devices or enabling substrate use to mitigate costs. The process uses a sub-critical stressor layer, combined with an externally applied mechanical force, to initiate and propagate a lateral fracture parallel to the substrate surface. Devices have been successfully removed from silicon, gallium arsenide, germanium, and gallium nitride substrates using this method. The spontaneous spalling model of Suo & Hutchinson has been used to model behavior in these systems, approximating spall depth and critical spalling conditions reasonably well. This talk will discuss the areas where the LEFM model succeeds in approximating spall depth and critical spalling conditions as well as its limitations with respect to edge effects, elastic and plastic anisotropy, and dynamic behavior during crack propagation that are inherent to this application space.