Influence of Graphene Platelet Aspect Ratio on the Mechanical Properties of HDPE Nanocomposites: Microscopic Observation and Micromechanical Modeling

Abstract

A series of high-density polyethylene nanocomposites filled with different diameter sizes (5, 15, and 25 μm) of graphene nanoplatelets at various amounts (0.5–5 wt.%) are prepared by the melt-mixing method. The effect of diameter size and filler content on the mechanical properties is reported, and the results are discussed in terms of morphology and the state of dispersion within the polymer matrix. The measured stiffness and strength of the nanocomposites were found to be mainly influenced by the filler aspect ratio and the filler-matrix adhesion. Fractography was utilized to study the embrittleness of the nanocomposites, and the observations revealed that a ductile to brittle transition is caused by a micro-deformation mechanism change in the nanocomposites. Several micromechanical models for the prediction of mechanical properties of nanocomposites, taking into consideration filler aspect ratio, percolation effect, and interphase regions, are considered. The three-phase model proposed by Ji accurately predicts the stiffness of graphene nanoplatelets with a higher diameter size, while Takayanagi modified model II was found to show good agreement with the experimental results of smaller ones at low filler content. This study demonstrates that the diameter size of the filler plays a central role in determining the mechanical properties.

On the Improved Mechanical Properties of Ball-Milled GNPs Reinforced Short Chain Branched-Polyethylene Nanocomposite: Micromechanical Modeling and Fractography Study

“…This results in stress concentration around the filler's particles and/or aggregates, where less energy is required to propagate a crack. Similar findings have been found by Tarani et al for high-density polyethylene (HDPE)/GNPs nanocomposites [23]. Additionally, it is observed that the elastic modulus and tensile strength at yield of the SCB-PE/GNPs w BM nanocomposites are larger in value than those of the SCB-PE/GNPs no BM samples.…”

“…More specifically, HDPE/GNPs nanocomposites prepared via melt-mixing containing 1wt. % filler content presented a 5% elastic modulus increase [23], while the corresponding augmentation for SCB-PE/1 GNPs w BM is 47.7%. Linear low-density polyethylene (LLDPE)/GNPs nanocomposites were also studied in terms of their physicomechanical properties.…”

“…The sample's plane view presents plastic tearing due to the share stresses applied parallel to the fracture plane and the chain stretching of the matrix. Some superficial voids are also observed, while no intense fibril formation occurs due to the homogenous polymer chain fracture during the macromolecular chains' alignment and orientation caused by the uniaxial tensile stress [23]. The fracture surface of SCB-PE/0.5 GNPs no BM is presented in Figure 4a.…”

“…Many efforts have been made to predict the nanocomposites' tensile behavior using micromechanical models [21][22][23][24][25][26][27]. This has become a difficult task due to the nanocomposites' peculiar behavior, depending on the matrix's structure, filler's dispersion, as already stated, the particles' aspect ratio, the filler-filler and filler-matrix interactions etc.…”

Multiscale Modeling of Epoxy-Based Nanocomposites Reinforced with Functionalized and Non-Functionalized Graphene Nanoplatelets

“…However, for the nanoscale fillers or particles, such as graphene nanoplatelets and carbon nanotubes, the situation is different as these nanofillers are produced with a wide range of aspect ratios [39][40][41][42]. The reported results from experiments that have been conducted to capture the influence for particular carbon nanofiller sizes (aspect ratio) mostly refer to an improvement in the engineering properties of nanocomposites as the aspect ratio increases [41][42][43][44]. Unfortunately, experimental techniques are infeasible and limited to investigating the role of aspect ratio in reinforcing polymer matrix with nanoscale fillers.…”