This paper studies a penny-shaped crack at the middle of a symmetric sandwich structure and is under a sudden temperature gradient on the crack faces. The temperature field of the structure and the stress intensity factor (SIF) at the crack tip are derived based on the dual-phase-lag non-Fourier heat conduction theory. Two specific factors are identified to predict the coupling effects of the thermal property differences between the skin and the core (including the differences in thermal conductivity, thermal diffusivity, heat flux lag and temperature gradient lag) on the thermoelastic behavior. If the coefficient of thermal expansion (COTE) of the skins is greater than that of the core, the peak value of transient SIF increases. If the CoTE of the skins is smaller than that of the core, the transient SIF is scarcely influenced. The results are useful for the designs and applications of sandwich structures work under thermal shock. (C) 2019 Elsevier Ltd. All rights reserved.