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Thermal Fracture of an Interpenetrating Phase Composite: Effects of Local Thermal Nonequilibrium

When subjected to thermal shocks, an interpenetrating phase composite may undergo significant, long range temperature difference between the constituent phases due to the interconnected microstructural networks, which facilitate faster heat transfer in the phase of higher thermal diffusivity. This temperature differential may alter the macroscopic temperature field thereby inducing additional thermal stresses in the composite. This work presents a local thermal nonequilibrium (LTNE) thermoelasticity theory for interpenetrating phase composites. In the LTNE thermoelasticity theory, the temperatures of the constituent phases are governed by the LTNE heat conduction equations based on the continuum theory of mixtures. A weighted average of temperatures for the constituents is employed in the thermoelastic constitutive equations of the homogenized composite. The model is subsequently applied to an infinite composite strip with an edge crack subjected to a thermal shock. Asymptotic solutions of temperature, thermal stress, and thermal stress intensity factor are obtained using the Laplace transform technique. The numerical results for an interpenetrating Al2O3/Al composite show that the temperature and thermal stress fields of the LTNE theory deviate from those of the classical theory. More importantly, the thermal stress intensity factor is reduced by considering the LTNE effect, which indicates that interpenetrating networks enhance the thermal fracture resistance of ceramic-metal composites.