Narrow Results

Based on the Eringen nonlocal elasticity theory and multiple time scale method, an asymptotic nonlocal elasticity theory is developed for cylindrical bending vibration analysis of simply-supported, $N_l$-layered, and uniformly or nonuniformly-spaced, graphene sheet (GS) systems embedded in an elastic medium. Both the interactions between the top and bottom GSs and their surrounding medium and the interactions between each pair of adjacent GSs are modeled as one-parameter Winkler models with different stiffness coefficients. In the formulation, the small length scale effect is introduced to the nonlocal constitutive equations by using a nonlocal parameter. The nondimensionalization, asymptotic expansion, and successive integration mathematical processes are performed for a typical GS. After assembling the motion equations for each individual GS to form those of the multiple GS system, recurrent sets of motion equations can be obtained for various order problems. Nonlocal multiple classical plate theory (CPT) is derived as a first-order approximation of the current nonlocal plane strain problem, and the motion equations for higher-order problems retain the same differential operators as those of nonlocal multiple CPT, although with different nonhomogeneous terms. Some nonlocal plane strain solutions for the natural frequency parameters of the multiple GS system with and without being embedded in the elastic medium and their corresponding mode shapes are presented to demonstrate the performance of the asymptotic nonlocal elasticity theory.

Molecular dynamics (MD) simulations are performed to study the fracture behavior of armchair and zigzag graphene sheets with V-shaped notches subjected to tensile loading. The effects of temperature and notches depth on the fracture characteristics of the graphene sheets are examined. The results show that the cracks propagate from the notch tip along the direction perpendicular to the loading axis for armchair sheets. This is different from the zigzag graphene propagating along the direction of 45° from the loading axis. In addition, the fracture energy of zigzag graphene sheets is larger than armchair one at the same temperature condition.

An effective electromagnetic interference (EMI) shielding cyanate ester (CE) composite has been fabricated with a combination of graphene nanosheets (GNSs) and nickel ferrite (NiFe₂O${}_4)$ particles. NiFe₂O₄ particles were loaded on the reduced graphene oxide (RGO) to improve the dispersibility while the composites were synthesized via solution blending method. Scanning electron micrographs (SEM) showed good dispersion of GNSs and RGO–NiFe₂O₄ in CE. Electromagnetic properties and EMI shielding effectiveness (SE) of the nanocomposites were determined over X-bands (8.2–12.4GHz). It was observed that the EMI shielding performance of composites was improved by increasing the filler loading of composites and absorption was found to be the dominant shielding mechanism. The total EMI SE is almost reaching 50dB for samples with thicknesses of $\sim$2.7mm, which suggests that the GNSs/RGO–NiFe₂O₄/CE could be good candidates for highly efficient EMI shielding materials in the whole X-band.