Session: 11-09-01: Thermal Transport Across Interfaces I

Paper Number: 70556

Start Time: Wednesday, 10:25 AM

70556 - Thermal Transport in Carbon Nanocomposites Under Mechanical Strain 

Flexible electronics are repeatedly subjected to a constant mechanical strain during daily use. Plastic deformation and micro-cracks generated by this fatigue loading will degrade the heat dissipation capacity of the materials used in flexible electronics. In this regard, carbon nanocomposites that are comprised of polymer matrix and carbon nanostructures such as carbon nanotubes (CNTs) and graphene are exciting new 3D print inks for the fabrication of flexible electronics because of the excellent transport properties of their base carbon nanostructures, i.e., CNTs and graphene. To better utilize carbon nanocomposite inks for the fabrication of flexible electronics, a detailed understanding on the effect of mechanical deformation on their thermal transport properties is necessary. In this research study, we employ molecular dynamics simulations using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) with PCFF interatomic potential to investigate the strain effect on the thermal transport properties of various carbon nanocomposites. More specifically, the thermal conductivity of the various composite structures such as PE/graphene, PE/CNT, and PE/3D carbon network with different carbon nanostructure filler ratio is investigated during mechanical strain. Initial results showed the thermal conductivity of graphene to be 334.17 W/m-k while the thermal conductivity of graphene in the composite is 124.78 W/m-k. The unusually low thermal conductivity values are explained by the size effect at nano scale solids and the suppression of out-of-plane phonon mode in graphene. The thermal conductivity of carbon nanocomposite is increased with an increase in the loading level of carbon nanostructure fillers because of the increased filler-to-filler connections. Also, at a low loading level of fillers, the thermal conductivity of carbon nanocomposite is improved with an increase in strain because of straightened polymer chains. However, at a high loading level of fillers, the thermal conductivity of carbon nanocomposite is dominated by filler-to-filler connections and the thermal conductivity is decreased with an increase in strain because of broken filler-to-filler connections by strain. Fillers with higher aspect-ratio such as CNT and graphene are shown to allow for larger amounts of filler-to-filler connections, and thus improve the thermal conductivity of carbon nanocomposite inks better than fillers with lower aspect-ratio (3D carbon network). At a low loading level of fillers, lower strain rate improves the thermal conductivity better because it straightens polymer chains more effectively. However, at a high loading level of fillers, the thermal conductivity is dominated by filler-to-filler connections and is not affected much by strain rate. The results obtained in the present study will be used to accelerate the development of novel nanocomposites for futuristic flexible electronics.

Presenting Author: Nick Kinports Kennesaw State University

Authors:

Jungkyu Park Kennesaw State University
Nick Kinports Kennesaw State University
Jihad Kudsy Kennesaw State University