Improvement of Curing Uniformity and Efficiency in the Electrothermal In-Situ Curing of Carbon Fiber Composites

Electrothermal in situ curing with carbon nanotube (CNT) film is an advanced preparation process for carbon fiber composites. However, the complex curing mechanisms during the electric heating process pose great challenges to improving their curing uniformity and molding efficiency. To this end, a coupled electro-thermal-chemical finite element model was established for the molding of composites by CNT film electrothermal in situ curing. Based on this model, it is found that decreasing the number of prepreg layers or increasing the relative size of CNT film is conducive to improving uniformity in temperature and curing degree distribution in the composites. On these bases, the lay-up parameters for uniform electric heating curing were determined as 20 layers of prepreg + a CNT film with sizes 1.9 times those of the prepreg. In addition, considering the rapid internal inside-heating characteristics of the CNT film, a new efficient two-stage holding temperature curing regime was proposed instead of the conventional four-stage. By combining the optimized process parameters and curing regime, electrically heated composite plates were prepared. Compared to conventional oven-heating cured composite, the electrically heated cured composite exhibits an increase of 8.0% in tensile strength and 5.9% in flexural strength; meanwhile, the total curing time was reduced by 54.7%.