In situ curing of polymeric composites via resistive heaters comprised of aligned carbon nanotube networks

Abstract

The widespread application of polymer matrix composites (PMCs) has encouraged the use of nanofibers, especially carbon nanotubes (CNTs), to concurrently enhance the physical properties of such composites while adding multi-functionality. However, current-generation manufacturing routes of PMCs have drawbacks including geometrical limitations and high energy utilization. Improvements to manufacturing processes are needed, and in this thesis the in situ curing of a PMC using a resistive heating film comprised of an aligned CNT network is developed, and the underlying physics that govern the electron transport properties of the aligned CNT network as a function of temperature and orientation are explored. Aligned CNT film heaters have anisotropic electrical properties and show negative coefficient of resistance with temperature. A carbon fiber reinforced plastic (CFRP) system is effectively cured by a single (top layer) CNT network heater. Evaluation of the curing efficacy (via degree of cure) shows that the in-plane spatial variation of the degree of cure directly correlates to maximum temperature during cure as evaluated with a thermal camera. Through-thickness spatial variation in degree of cure is found to be < 8% for the one-sided curing heater. Future work will include characterization and modeling of the underlying physics that govern the performance of aligned CNT networks as resistive heaters, exploration of possible methods to scale-up the in situ curing process to laminates with sizes on the order of meters, and evaluation of the structure and properties of composites manufactured using the method reported here to elucidate any difference in composite performance when compared to materials synthesized using current-generation techniques.