Experimental Characterization of the Effect of Charring on the Residual Load Carrying Capacity of a Structural Fibre Reinforced Composite

An experimental study conducted to investigate the residual load carrying capacity of a commonly used structural composite plastic, isophthalic polyester, reinforced with S-glass fibreglass when exposed to heat-fluxes representative of a fire is presented. The purpose of this study is to explore the relationship between fire insult and the remaining flexural strength of a thermally damaged commonly used composite plastic. The samples were subjected to 20 kW/m2 through 40 kW/m2 heat fluxes for varying amounts of time. Selected samples were allowed to ignite to ensure that both radiant and fire exposures were considered. Resulting sample temperatures and mass loss quantities were recorded as a function of time through the use of implanted thermocouples and a load cell. All samples were allowed to cool in a zero moisture environment prior to being structurally loaded to failure using a 3-point bending machine. The results obtained tend to demonstrate a clear linear relationship between the depth of un-charred material (on a Non-Ignition sample) and its residual load carrying capacity. Furthermore, a linear correlation between the total amount of energy imposed on a sample and its residual strength is evident. The type of correlation depends on whether the sample ignited or not.