كليدواژه :
Molecular dynamics simulation , Shear behavior , Nanocomposite , Carbon nanotube
چكيده فارسي :
Carbon nanotube (CNT) is a highly effective reinforcement material for metal matrices like aluminum, enhancing their performance and toughness. It is suitable for applications in aerospace, automotive, and electronics. Understanding the shear behavior of Al-CNT nanocomposites is crucial for structural integrity and reliability. Molecular dynamics (MD) simulations are a powerful tool for studying nanocomposites at the atomic scale. MD simulations can investigate interactions between individual atoms and predict mechanical responses under different loading conditions. Analyzing the shear behavior of Al-CNT nanocomposites provides valuable insights into deformation mechanisms, such as dislocation generation, CNT-matrix interaction, and load transfer. This research aims to investigate the effect of loading direction on the shear behavior of Al-CNT nanocomposites using MD simulations. The study used the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) to conduct a virtual shear test on a single crystal Al matrix with CNT. The model had a size of 96 × 96 × 96 Å3 and was modeled using the EAM, AIREBO, and LJ interatomic potentials. Structural relaxation was performed under the NPT ensemble at 300 K to minimize energy, and mechanical testing was conducted on relaxed structures along the z and x axes with a strain rate of 2.5 × 10-4 /ps. The total mechanical stresses on the samples were calculated, and atomistic results were visualized utilizing the OVITO packages. The investigation revealed a significant dependence of the loading direction on overall shear strength of the composite. According to stress-strain curve of Al-CNT nanocomposite model, when shear loading was applied parallel to the CNT axis, the shear strength of the nanocomposite demonstrates a higher shear strength of 3.2 GPa, while the perpendicular loading condition exhibits a lower shear strength of 2.5 GPa. This disparity in shear strength highlights the importance of CNT alignment and interfacial bonding in enhancing the mechanical properties of the nanocomposite. According to atomic configurations, in the parallel loading mode, the CNT effectively resisted and transferred the applied shear forces along their highly oriented and aligned structure, which was evident in the stress distribution of the composite. Also the difference in aluminum and CNT characteristics gave rise to the generation of geometrically necessary and statistically stored dislocations at CNT/Al interface. The CNT then hindered the movement of dislocations and slipping planes until reaching its ultimate strength. At this point, the CNT broke from its upper point due to the localized stress concentration. However, the interfacial bonding between the CNT and the aluminum matrix remained intact, allowing load transfer to occur primarily through the CNT. All of this resulted in a significant increase in shear strength compared to the perpendicular loading condition. In contrast, in perpendicular mode, the CNT experienced limited interaction with the applied shear forces, resulting in reduced load-bearing capacity. The primary failure mechanism observed in the perpendicular loading condition is the debonding CNT. The shear stress induces interfacial separation, leading to the detachment of CNTs from the aluminum matrix. This debonding phenomenon weakens the strengthening mechanisms, importantly the load transfer and diminishes the overall shear strength of the nanocomposite. Overall, studying the shear behavior of Al-CNT nanocomposites is essential for harnessing their full potential and expanding their applications in industries where shear loading is a critical factor. The insights gained from this research can guide the development of advanced materials with improved mechanical properties, leading to enhanced performance and durability in various engineering applications.
