Modeling of charring and burning carbon-epoxy composites in fire environments

This study concerns the development of a numerical methodology to conduct conjugate heat and mass transfer simulations of burning composite materials leading to ultimate material failure. The flow is described using an Eulerian LES description and the solid described using a Lagrangian finite element (FE) method. The damaged composite is expressed as two regions of non-charred and charred materials. Homogenization methods are used to formulate the damaged material in terms of the volume fractions associated with composite fiber, resin and char. The gas transport within the structure is described using Darcy's law. Model validation studies are first conducted against the data from Quintiere et al. Verification is conducted at both coupon and intermediate scales using one-sided heating tests. Comparisons of the heat release rate (HRR) and time-to-ignition as well as the final products (mass fractions, volume percentages, porosity, etc.) are conducted. Fully coupled simulations of flame spread are performed using a newly developed ghost-fluid methodology. Predictions of the critical heat flux required for flame spread are in good agreement to the data.