Mechanistic Approach to Structural Fire Modeling of Composites

In this paper, a framework is presented for the modeling of the response of structural composites subjected to combined mechanical loading and fire. An emphasis is placed on the response of composites at temperatures below the decomposition temperature, where the viscoelastic response of the composite material becomes important. Material property characterization results are presented for an E-glass reinforced vinyl ester composite typical of that used for naval ship applications. Time-temperature equivalence is used in a compression strength model to predict the time to failure of composites subjected to isothermal compression loading (compression creep rupture failure). These predictions are compared with experimentally determined times to failure with good agreement. In particular, shift factors obtained from shear compliance testing are able to collapse the compression creep rupture data at different temperatures, indicating that viscolelasticity is the dominant mechanism driving the failure. This model is combined with a standard diffusion model for heat transfer in the composite to predict the time-dependent failure of composites subjected to simultaneous one-sided heat flux and compression loading. Predicted times to failure are compared with experimental results with good agreement.