Thermal behavior and kinetics study of carbon/epoxy resin composites

Carbon/epoxy laminates and foam-core sandwich composites are frequently used as engineering materials within the aerospace sector. However, epoxy resin matrix and foam-core materials are highly flammable. In this work, the thermal behaviors of carbon/epoxy laminates and foam-core sandwich composites were investigated using thermogravimetric analysis at different heating rates in atmospheric air. The morphological images of specimens and the residue after pyrolysis at different characteristic temperatures were further investigated using scanning electron microscopy. Additionally, thermogravimetric Fourier transform infrared spectroscopy was used to analyze the vapors and gases evolved during the thermal decomposition. It was determined that the pyrolysis reactions of carbon/epoxy laminates and foam-core sandwich composites consist of three decomposition steps. Furthermore, an increase in the heating rate of each material results in higher initial and final temperatures for each thermal decomposition step. Kinetic parameters for the decomposition for carbon/epoxy composites were estimated using Kissinger, Flynn-Wall-Ozawa, and Starink methods, and the corresponding thermodynamic parameters were obtained. Through analysis of the reaction kinetics, it was determined that the pyrolysis reactions of carbon/epoxy composites are not easily activated, requiring significant activation energy, but the series of reactions take place easily once this energy barrier is overcome.