Effects of simultaneous compression and one-sided heat flux on the time to failure of carbon fiber-reinforced polymer composites

The time to failure of carbon fiber-reinforced polymer composites is investigated during simultaneous compression and one-sided thermal degradation from a constant heat flux. The purpose of this investigation is to determine the rate of thermal degradation and mechanical property loss from fire exposure by observing the time to failure during simultaneous compression loading. A custom compression test fixture is designed and validated for use under thermomechanical loading. Testing is conducted on CFRP samples of varying thicknesses and quasi-isotropic layups. Test conditions are adjusted for a range of heat fluxes and compressive loads. Test parameters are isolated to observe individual impacts on time to failure. In each case, decreasing exponential trends are observed. High heat fluxes and high compressive loads result in shorter failure times. Temperature profiles are created based on heat flux exposure time and the position through the material thickness in order to determine failure criteria for thermomechanical loading. An empirical model is created to extrapolate and predict failure times using a stretched exponential function, based on mechanical preload, heat flux, and material thickness.