Fire behaviour of pultruded composites

Abstract

This thesis describes the development of a model to predict the failure response of loaded pultruded composites in fire. The model takes an existing thermal model [1- 9] capable of describing temperature evolution and residual resin content as functions of time through a pultrusion for fires with heat-fluxes up to and including 125kWmý. Experiments were developed to determine how tensile and compressive strength (aT and ac), and longitudinal and transverse stiffhess (Ei and E2) of the composites varied with temperature. This required specialised equipment to be designed and fabricated. The mechanical property data were recorded as functions of temperature and combined with the thermal model and classical laminate theory. The resulting failure model, outputs tensile and compressive strength of the pultrusion as a function of time for fires with heat- fluxes up to and including 125kWm-2. A, B, D matrix evolution as a function of time is also produced. The modelling procedure was carried out for polyester and phenolic glass fibrereinforced pultrusions subjected to a 5OkWm-2 heat-flux and verified by a series of propane burner tests. The modelled tensile and compressive results match the data from the propane burner tests to a reasonable degree of accuracy. It was shown that the materials were more susceptible to compressive failure rather than tensile failure, when subjected to a fire. Work on the model was supplemented by a series of larger scale fire tests on box and T sections, including flexure tests in a pool fire and temperature controlled furnace. In both tests it was found that failure occurred on the compressive side of the section, with a failure time in the order of 100 seconds. Compression tests were also carried out on short box columns to investigate the effect various fire protections systems had on failure time of the columns, when surrounded by a heat-flux of 50k)V2. It was found that protecting the loaded section inside an insulating sleeve proved the most successful approach.