Atomistic aspects of load transfer and fracture in CNT-reinforced aluminium

TL;DR

This study uses atomistic simulations to analyze how carbon nanotubes interact with aluminum during deformation and fracture, revealing weak load transfer but potential for crack blunting and plastic dissipation depending on CNT placement.

Contribution

It provides detailed atomistic insights into the load transfer mechanisms and fracture behavior of CNT-reinforced aluminum, highlighting the effects of CNT positioning and fixation.

Findings

Weak load transfer between CNTs and Al under tensile load.

Embedded CNTs can increase fracture stress when fixed inside Al.

CNTs can blunt cracks and promote plastic deformation depending on orientation.

Abstract

This paper describes atomistic simulations of deformation and fracture of Al reinforced with carbon nanotubes (CNTs). We use density functional theory (DFT) to understand the energetics of Al-graphene interfaces and gain reference data for the parameterization of Al-C empirical potentials. We then investigate the load transfer between CNTs and Al and its effect on composite strengthening. To this end, we perform uniaxial tensile simulations of an Al crystal reinforced with CNTs of various volume fractions. We also study the interaction of the embedded CNTs with a crack. We show that the interaction between CNTs and Al is weak such that, under tensile loading, CNTs can easily slide inside the Al matrix and get pulled out from the cracked surface. This effect is almost independent of CNT length and volume fraction. Little load transfer and consequently no crack bridging are observed during the simulation of pristine CNTs threading the crack surfaces. CNTs that are geometrically fixated inside Al, on the other hand, can increase the fracture stress and enhance plastic dissipation in the matrix. CNTs located in front of a growing crack blunt the crack and induce plastic deformation of the Al matrix. Depending on the CNT orientation, these processes can either increase or decrease the failure stress of the composite.