Constituent based analysis of composite materials subjected to fire conditions

Multicontinuum theory (MCT) is based on the two-constituent decomposition developed by Hill [Hill R. Elastic properties of reinforced solids: some theoretical principles. J Mech Phys Sol 1963;11:357-72] to calculate the constituent level stress/strain fields of a composite material from the 'smeared' composite stress/strain fields. The work presented in this paper expands previous isothermal MCT work to include thermal effects related to large temperature gradients caused by fires. Analytical fire conditions are simulated using a 1-D heat diffusion equation, which provides time-dependent temperature gradients through the thickness of the composite. Results illustrate that when the composite materials are subjected to extreme thermal conditions, the thermal residual stresses resulting from the fiber and matrix coefficient of thermal expansion mismatch are significant. Progressive failure simulations are performed using the thermal-mechanical MCT algorithm, in which an increased rate of failure is observed for a composite material when it is subjected to large external temperature gradients similar to those experienced in fire environments.