Fluid-Structure Simulations of Composite Material Response for Fire Environments

Abstract

The focus of this effort is to develop models and numerical methods for coupled simulations of composite material response in fire environments. This research has comprised of two main activities. The first is the development of a thermo-mechanical damage model for composite materials subject to high temperature environments. 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 volume fractions of the composite fiber, resin, char and gas. Results are presented for a clamped beam case with comparison to experimental data for a glass-phenolic composite. Overall good agreement is observed between model predictions and measurements of temperature and pressure. The clamped beam is observed to undergo an interesting bifurcation for which the beam bows away from the applied heating load due to thermal expansion, but then later in time, bows towards the applied heat load after sufficient char is formed. The second research activity is on the development of fluid-structure coupling algorithms for simulating the coupled response of 2D composite structures and the local flow environment. Results show that the spatial distribution of material decomposition is sensitive to the local flow environment from the fire that, in turn, is defined by the structure geometry. Near the material surface enhanced heat transfer to the material surface is observed from the near-wall flame that is established by the resin off-gases. These observations highlight the importance in considering the coupled response of both the material response and the flow field for assessing the performance of composite structures for fire environments.