Stress-localization induced toughening in CNT–silica nanocomposites

Abstract

Applying a combination of atomistic and continuum scale simulations, we show that stress-localization forms the fundamental basis for toughening in “carbon nanotube reinforced amorphous silica” (CNT−aSiO2). Depending on the cohesive strength of the interface, a propagating crack renders three distinct types of failure conditions: (i) with stronger cohesive interactions both silica and nanotube undergo catastrophic failure, (ii) with moderate cohesive interactions the nanotube debonds from the matrix and undergoes severe mechanical deformation but fracture remains in the matrix, and (iii) with lower cohesive strengths the nanotube debonds from the matrix easily and allows quicker failure of the matrix, compared to the previous two failure conditions. For either of the cases, continued propagation of the crack requires renucleation at the opposite side of the nanotube. However, the renucleation criteria are mostly unaffected by the strength of interfacial interactions. Also, the effective toughness of the nanocomposite increases nonlinearly with increasing interfacial strength and the maximum possible toughness enhancement is strictly controlled by the strength of elastic interactions between the nanotube and the matrix. The overall toughening behavior of the nanocomposite is governed primarily by stress-localization at the nanotube–silica intersections along the projected crack path direction in the composite. The observations highlight the dramatic role of site-selective interatomic interactions that can affect the macroscopic mechanical behavior of the nanocomposite substantially.

Application of FE method in predicting the properties of nanocomposites

“…Finite element model of copper matrix/carbon nanotube nanocomposite was done for a RVE sample (Figure 1). 2 Carbon nanotubes nanocomposites Hardening mechanisms strength Cui et al 3 Silver nanowire polyamide composites Tensile-resistant Alam 4 Nanocomposite materials Micro-mechanical modeling Sadeghpour et al 5 Graphene-based nanocomposites Stress and strain surface slip Rahimi Mehr et al 6 Mg SiC nanocomposite Density distribution flexibility Hao and Hossain 7 Porous polypropylene nanocomposites Tensile load test mechanical properties Ghasemi et al 9 Aluminum/nano-silica nanocomposites Uniaxial tensile test Motamedi et al 10 Straight and curved CNTs in nonlinear elastic nanocomposites…”

“…Hao and Hossain 7 studied the strength of silica nanocomposites using the FE method. They proposed a new method to investigate the effect of surface interaction on the mechanical properties of silica nanocomposites.…”