Pyrolysis and combustion characteristics and reaction kinetics of carbon fiber/epoxy composites

The pyrolysis and combustion characteristics and reaction kinetics of epoxy resin matrix and carbon fiber/epoxy composites based on epoxy resin were studied by cone calorimetry and thermogravimetry. The results show that with the increase in thermal radiation intensity (increase from 25 kW m−2 to 55 kW m−2), the average ignition time of the experimental samples decreases, the peak heat release rate increases, and the peak appears earlier. Carbon fiber can inhibit the pyrolysis and combustion of epoxy resin. It can effectively inhibit the droplet and splash phenomenon during the combustion process. The time of ignition, heat release, and the peak value of the heat release rate are delayed. The ignition temperature of foam core materials in carbon fiber/epoxy foam laminates is low, which makes the average ignition time and peak heat release rate appear earlier. The theoretical critical heat fluxes of four experimental samples (epoxy resin matrix, carbon fiber/epoxy bidirectional woven fabric, carbon fiber/epoxy prepreg, and carbon fiber/epoxy foam laminate) were obtained by calculation. The theoretical critical heat fluxes are 12.12 kW m−2, 13.21 kW m−2, 11.12 kW m−2, and 0.93 kW m−2, respectively. The pyrolysis of carbon fiber/epoxy bidirectional woven fabric can be divided into three stages: two stages of epoxy resin matrix decomposition and carbon fiber decomposition. The heating rate has a significant influence on the pyrolysis process. With the increase in heating rate, the maximum weight loss rate temperature moves toward high temperature. The Kissinger method and Flynn-Wall-Ozawa method were used to analyze the pyrolysis kinetics. The apparent activation energy and pre-exponential factors were obtained at different heating rates. The results obtained by the two methods are basically the same. When the pyrolysis temperature of the three composites reached 450 °C, the mass loss was 20%, 17%, and 28%, respectively. This shows that the thermal stability of carbon fiber/epoxy prepreg is the best, the thermal stability of the two-way woven fabric of carbon fiber is better, and the thermal stability of the carbon fiber sandwich board is the weakest. It is consistent with this rule at any temperature.