Response of a glass/phenolic composite to high temperatures

Determining the response of composite phenolic materials to fire remains a major unsolved problem that is important for high consequence safety analysis. Difficulties arise when thermophysical property measurements are obscured by decomposition reactions. This article presents several decomposition experiments and models for a phenolic resin impregnated into chopped 1.27-by-1.27 cm glass fabric. The thermal response of the material was measured using thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and laser flash diffusivity (LFD). The TG data was used to develop a 5-step decomposition mechanism describing mass loss due to reaction; the DSC data was used to describe the energy changes associated with these reactions; and the LFD data was used to describe energy flow into the decomposing material. An effective thermal conductivity model was used to partition energy transport by gas conduction, solid conduction, and diffusive radiation. The dynamic gas volume fraction is treated as a field variable to extrapolate thermal transport properties at high temperatures where decomposition is prevalent. These various models have been implemented into a finite element response model with an example calculation that includes uncertainty.