This paper investigates the mechanical properties of graphene/PMMA nanocomposite system by using the molecular dynamics simulations. The graphene nanoplates are assumed to be fully exfoliated in the ...PMMA matrix and are all planar orientated, which are similar to the ones assembled using layer-by-layer technique. The Young's modulus and shear modulus of the composites with different graphene volume fractions under different temperatures are simulated and discussed. The results show that the Young's and shear moduli increase with the increase of graphene volume fraction and decrease as the temperature rises from 300 K to 500 K, while the efficiency of the reinforcement is reduced as the graphene content becomes higher. Simulations of single layer graphene under uniaxial tension, in-plane pure shear and uniformly distributed transverse load are performed and the effective thickness and the elastic moduli of graphene are subsequently determined uniquely. The obtained stiffnesses of graphene are then substituted into the simple rule of mixture to predict the overall mechanical properties of the composite. Large discrepancies between the results from the MD simulations and the rule of mixture are observed.
•The mechanical properties of graphene reinforced nanocomposites are obtained by MDS.•The material properties of graphene reinforced nanocomposites are temperature dependent.•The conventional rule of mixture cannot be used directly for the graphene reinforced nanocomposites.
A postbuckling analysis is presented for nanocomposite cylindrical shells reinforced by single-walled carbon nanotubes (SWCNTs) subjected to axial compression in thermal environments. Two kinds of ...carbon nanotube-reinforced composite (CNTRC) shells, namely, uniformly distributed (UD) and functionally graded (FG) reinforcements, are considered. The material properties of FG-CNTRCs are assumed to be graded in the thickness direction, and are estimated through a micromechanical model. The governing equations are based on a higher order shear deformation theory with a von Kármán-type of kinematic nonlinearity. The thermal effects are also included and the material properties of CNTRCs are assumed to be temperature-dependent. A singular perturbation technique is employed to determine the buckling loads and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling behavior of axially-loaded, perfect and imperfect, FG-CNTRC cylindrical shells under different sets of thermal environmental conditions. The results for UD-CNTRC shell, which is a special case in the present study, are compared with those of the FG-CNTRC shell. The results show that the linear functionally graded reinforcements can increase the buckling load as well as postbuckling strength of the shell under axial compression. The results reveal that the CNT volume fraction has a significant effect on the buckling load and postbuckling behavior of CNTRC shells.
Thermal postbuckling analysis is presented for nanocomposite cylindrical shells reinforced by single-walled carbon nanotubes (SWCNTs) subjected to a uniform temperature rise. The SWCNTs are assumed ...to be aligned and straight with a uniform layout. Two kinds of carbon nanotube-reinforced composite (CNTRC) shells, namely, uniformly distributed (UD) and functionally graded (FG) reinforcements, are considered. The material properties of FG-CNTRCs are assumed to be graded in the thickness direction, and are estimated through a micromechanical model. The governing equations are based on a higher order shear deformation theory with a von Kármán-type of kinematic nonlinearity. The thermal effects are also included and the material properties of CNTRCs are assumed to be temperature-dependent. Based on the multi-scale approach, numerical illustrations are carried out for perfect and imperfect, FG- and UD-CNTRC shells under different values of the nanotube volume fractions. The results show that the buckling temperature as well as thermal postbuckling strength of the shell can be increased as a result of a functionally graded reinforcement. It is found that in most cases the CNTRC shell with intermediate nanotube volume fraction does not have intermediate buckling temperature and initial thermal postbuckling strength.
This paper presents an investigation on the nonlinear bending of functionally graded graphene-reinforced composite (FG-GRC) laminated plates resting on an elastic foundation and in a thermal ...environment. The plate is subjected to a transverse uniform or sinusoidal load combined with initial compressive edge in-plane loads. The plate is made of graphene-reinforced composites which are functionally graded in the thickness direction with a piece-wise type. The material properties of GRCs are estimated through a refined micromechanical model. Governing differential equations for the bending of the FG-GRC plates are based on a higher order shear deformation plate theory and the general von Kármán-type equation and the effects of plate-foundation interaction and temperature variation are taken into consideration. A two-step perturbation technique is employed to determine the load-deflection and load-bending moment curves. The nonlinear bending responses of FG-GRC laminated plates under different sets of loading and thermal environmental conditions are presented and discussed in details.
This paper presents an investigation on the nonlinear vibration behavior of graphene-reinforced composite (GRC) laminated cylindrical shells in thermal environments. The material properties of the ...GRCs are temperature-dependent and the functionally graded (FG) materials concept is adopted which allows a piece-wise variation of the volume fraction of graphene reinforcement in the thickness direction of the shell. An extended Halpin-Tsaia micromechanical model is employed to estimate the GRC material properties. The motion equations for the nonlinear vibration of FG-GRC laminated cylindrical shells are based on the Reddy’s third order shear deformation theory and the von Kármán-type kinematic nonlinearity, and the effects of thermal conditions are included. The nonlinear vibration solutions for the FG-GRC laminated cylindrical shells can be obtained by applying a two-step perturbation technique. The results reveal that the nonlinear vibration characteristics of the shells are significantly influenced by the GRC material property gradient, the stacking sequence of the plies, the temperature variation, the shell geometric parameter and the shell end conditions.
This paper presents an investigation on the nonlinear bending of simply supported, functionally graded nanocomposite plates reinforced by single-walled carbon nanotubes (SWCNTs) subjected to a ...transverse uniform or sinusoidal load in thermal environments. The material properties of SWCNTs are assumed to be temperature-dependent and are obtained from molecular dynamics simulations. The material properties of functionally graded carbon nanotube-reinforced composites (FG-CNTCRs) are assumed to be graded in the thickness direction, and are estimated through a micromechanical model. The governing equations are based on a higher order shear deformation plate theory with a von Kármán-type of kinematic nonlinearity and include thermal effects. A two step perturbation technique is employed to determine the load-deflection and load-bending moment curves. The numerical illustrations concern the nonlinear bending response of FG-CNTRC plates under different sets of thermal environmental conditions, from which results for uniformly distributed CNTRC plates are obtained as comparators. The results show that the load-bending moment curves of the plate can be significantly increased as a result of a functionally graded reinforcement. They also confirm that the characteristics of nonlinear bending are significantly influenced by temperature rise, the character of in-plane boundary conditions, the transverse shear deformation, the plate aspect ratio as well as the nanotube volume fraction.
Modeling and nonlinear vibration analysis of graphene-reinforced composite (GRC) laminated beams resting on elastic foundations in thermal environments are presented. The graphene reinforcements are ...assumed to be aligned and are distributed either uniformly or functionally graded of piece-wise type along the thickness of the beam. The motion equations of the beams are based on a higher-order shear deformation beam theory and von Kármán strain displacement relationships. The beam–foundation interaction and thermal effects are also included. The temperature-dependent material properties of GRCs are estimated through a micromechanical model. A two-step perturbation approach is employed to determine the nonlinear-to-linear frequency ratios of GRC laminated beams. Detailed parametric studies are carried out to investigate the effects of material property gradient, temperature variation, stacking sequence as well as the foundation stiffness on the linear and nonlinear vibration characteristics of the GRC laminated beams.
The current research deals with the postbuckling behavior of axially-loaded graphene-reinforced composite (GRC) laminated cylindrical shells under thermal environmental conditions. The piece-wise GRC ...layers are arranged in a functionally graded (FG) pattern along the thickness direction of the shells. The material properties of GRCs are assumed to be temperature-dependent and are estimated by the extended Halpin–Tsai micromechanical model. The governing equations for the GRC laminated cylindrical shells are based on the Reddy’s third order shear deformation shell theory and include the effects of the temperature variation. The nonlinearity effects are taken into account in the sense of von Kármán nonlinear kinematic assumptions. The buckling loads and the postbuckling equilibrium paths for the perfect and geometrically imperfect GRC laminated cylindrical shells can be obtained by solving the governing equations with a singular perturbation technique in conjunction with a two-step perturbation approach. The results show that the buckling loads and the postbuckling strengths of the GRC laminated cylindrical shells may be enhanced through piece-wise functionally graded distribution of graphene reinforcement.
This paper presents full-scale modeling and nonlinear dynamic analysis of sandwich plates with auxetic 3D lattice core, which is further designed to possess three functionally graded (FG) ...configurations through the plate thickness direction for the first time. The effective Poisson’s ratio (EPR) and fundamental frequencies of auxetic 3D lattice metamaterials are analyzed and verified by static and vibration tests using specimens fabricated by 3D printing. Considering the large deflection nonlinearity of sandwich plates and the accompanying changes in effective properties of lattice microstructures, full-scale FE modeling and nonlinear dynamic thermal–mechanical analysis are performed, with material properties assumed to be temperature dependent. Numerical results revealed that the auxetic core can significantly reduce the dynamic deflections, in comparison with its counterpart with positive EPR. Furthermore, FG configurations have distinct effects on the natural frequencies and dynamic deflection–time curves of sandwich plates, along with EPR–deflection curves in the large deflection region.
•We propose a multi-scale approach for nonlinear analysis of FG-CNTRC beams.•Beam with intermediate material properties does not necessarily have intermediate frequencies.•Beam with intermediate ...material properties does not necessarily have intermediate temperatures.•Thermal postbuckling path of unsymmetric FG-CNTRC beams is no longer of the bifurcation type.
This paper studies the behaviors of large amplitude vibration, nonlinear bending and thermal postbuckling of nanocomposite beams reinforced by single-walled carbon nanotubes (SWCNTs) resting on an elastic foundation in thermal environments. Two types of carbon nanotube-reinforced composite (CNTRC) beams, namely, uniformly distributed (UD) and functionally graded (FG) reinforcements, are considered. The material properties of FG-CNTRCs are assumed to be graded in the beam thickness direction, and are estimated through a micromechanical model. The motion equations of a CNTRC beam on an elastic foundation are derived based on a higher order shear deformation beam theory. The thermal effects are also included in the motion equations and the material properties of CNTRCs are assumed to be temperature-dependent. Numerical studies are carried out for the nonlinear vibration, nonlinear bending and thermal postbuckling of CNTRC beams resting on Pasternak elastic foundations under different thermal environmental conditions. It is found that a CNTRC beam with intermediate CNT volume fraction does not necessarily have intermediate nonlinear frequencies, buckling temperatures and thermal postbuckling strengths. Thermal postbuckling path of unsymmetric FG-CNTRC beams is no longer the bifurcation type.
