Structure factors of carbon nanotubes on the thermal conductivity of carbon nanotube/epoxy composites

Abstract

The structure factors of carbon nanotubes such as the dispersion, morphology and size have effects on the thermal conductivity of carbon nanotube/epoxy composites (kc). However, the behavior how these structure factors affect the kc has still not been fully understood. To seek the answer, three-dimensional computational models containing various dispersion of bending single wall carbon nanotubes (SWCNTs) are developed using the finite element method. A conjecture is proposed based on these models that the dispersion and the number of the overlapping heat-affected zones (OHAZs) of heat conduction networks play an important role on the kc. To prove the conjecture, a feature parameter–a dispersion coefficient is proposed to quantify the dispersion uniformity. The kc is calculated in models with different dispersion coefficients. The results show that the kc increases with the dispersion coefficient. The effects of the morphology and the size of SWCNTs on the kc could also be explained using this conjecture. SWCNTs with a larger length efficiency and diameter are found to be beneficial to a higher kc. Because a larger length efficiency increases the number of OHAZs and a larger diameter SWCNT has a wider heat-affected zone which also increases the number of OHAZs.

Effect of carbon nanotubes on thermoset curing and mechanical properties of carbon fiber reinforced epoxy resin laminates fabricated by self‐resistance electric heating

“…However, excessive CNTs may cause locally concentrated heat conduction networks due to the agglomeration of CNTs. These networks significantly diminished the efficiency of thermal conduction due to the lack of interconnected channels 40 . Consequently, the curing degree of CFRP laminates in different local regions became disparate, which led to inhomogeneous resistance distribution during the SRE heating process.…”

“…It indicates that the addition of CNTs can increase the curing degree of the CFRP laminates, because the CNTs have a catalytic effect on the curing reaction of epoxy resin, leading to a decrease in the active energy of epoxy matrix composites during the curing process, which is a favor to the enhancement of curing degree for epoxy matrix composites 43 . In addition, for SRE heating, the CNTs network in the resin matrix can provide additional electrical and thermal conduction for the preparation of CFRP composites, which is favored to improve the curing degree due to the in‐situ curing mechanism 40,44 . However, the CFRP laminate composites with 1.5 wt% CNTs had the lowest value of T g and curing degree, which indicated that excessive CNTs have a negative effect on the curing degree of CFRP composites fabricated by SRE heating due to nonuniform heating caused by agglomeration of CNTs.…”

“…These networks significantly diminished the efficiency of thermal conduction due to the lack of interconnected channels. 40 Consequently, the curing degree of CFRP laminates in different local regions became disparate, which led to inhomogeneous resistance distribution during the SRE heating process. Corresponding to the results of the infrared thermal image, it can be deduced that the difference in electrical resistivity at different local positions of the CFRP laminates led to the deviation of the maximum temperature position away from the center of CFRP laminates during the SRE heating process.…”

Effect of Thermal Dependency of Diameter on Density of States for Zigzag Carbon Nano-Tubes

“…7 shows that the DOSs related to higher temperatures were shifted to higher energies as the bands of energies were expanded with the CNTs. Knowing about the structural properties of CNTs can give us information about the thermal conductivity of these materials [32]. This opens the possibility of overcoming the challenges of interdependency between the structural, mechanical, and optical parameters of CNTs [33].…”

Study of the synergistic effect of boron nitride and carbon nanotubes in the improvement of thermal conductivity of epoxy composites

“…The other important issue is the high interfacial thermal resistance between nanofiller and polymeric matrix . Previous published studies showed that pristine CNTs at low concentration can enhance TC when a good dispersion is reached. Nonetheless, a beneficial method for improving the epoxy–CNT interactions and thus the dispersion of CNTs is their functionalization (usually by oxidizing the surface), which can preserve the CNT pristine structure, through delocalized π‐bond interactions .…”