Comparison of thermal and fire properties of carbon/epoxy laminate composites manufactured using two forming processes

Abstract Carbon/epoxy composites have been widely used in the aviation industry. However, the flammability of epoxy resins is of great concern within the industry. Currently, vacuum bag and autoclave forming processes are the most commonly used processes for composites. To compare the thermal and fire properties of carbon/epoxy laminate composites manufactured using these two forming processes, a comprehensive experimental investigation and theoretical analysis was carried out in this work. The glass transition temperatures and epoxy resin matrix content in composites were determined. Several thermal and fire properties were quantitatively evaluated, including onset decomposition temperature, time to ignition, mass loss rate (MLR), and heat release rate (HR). The morphologies of specimens before combustion were also observed. For vacuum bag (VB)‐C/ELC and A‐C/ELC, the critical heat flux (14.48 and 20.56 kW m⁻²), thermal response parameter (165.56 and 204.49 kW s^1/2 m⁻²), heat of gasification (9.13 and 20.10 MJ kg⁻¹), and theoretical heat of combustion (33.27 and 43.82 MJ kg⁻¹) were calculated and compared using the thermal behavior model, MLR model, and heat release rate model, respectively. It has been found that the forming process can significantly affect the fire properties of carbon/epoxy laminate composites. More specifically, the carbon/epoxy laminate composites formed using autoclave forming processes have more combustion resistance and thus have improved fire properties.