A flow through porous media model for pore pressure during heating of polymer–matrix composites

During heating of moisture saturated polymer composites that are damaged and has an interconnected pore network, the water from the damaged composite evaporates into the interconnected pore network and induces pore vapor pressure as it escapes out of the material. The model proposed by Sullivan and Stokes [A model for the effusion of water in carbon phenolic composites. Mech Mater 1997;26:197–207] is adopted to study the evolution of pore pressure in such a composite and is applied to study the pore pressure generated in a moisture saturated plate exposed to dry air and subjected to various heating rates. It is shown that the maximum pore vapor pressure, which occurs at the center of the plate for isothermal heating conditions, depends only on two dimensionless parameters; the porosity ϕ   and the normalized heating rate τ=T˙L2μ(T0)/(T0kp0), where T˙ is the heating rate, L is the plate thickness, T0 is the initial temperature, k is the material permeability, μ(T0) and p0 are the vapor viscosity and saturated vapor pressure at the initial temperature, respectively. An exact self-similar solution of the non-linear equation is obtained for the special case of rapid heating of a thick plate. This solution is useful in understanding the short time behavior of pore pressure evolution and is used to check our numerical results.