Study Of Mechanical Properties For Carbon Nanotubes/Polyethylene Composites

Since carbon nanotubes have many excellent properties, such as mechanical, chemical,optical, and electromagnetic properties, they are expected to be widely applied to reinforcingmaterials, sensors and nanoelectronics. Study on the mechanical properties of carbonnanotubes and composite materials reinforced by carbon nanotubes have become the researchfocus in the world.This paper mainly study mechanical properties of carbon nanotubes and carbonnanotubes/polyethylene composites reinforced by carbon nanotubes by means of thecontinuum mechanics and molecular dynamics method. Through the analysis and comparisonof the results, the scale effects of carbon nanotube and effect of physical field on axialbuckling, uniaxial tensile and compressive stress-strain curve of single-walled carbonnanotubes, evidence on the tensile properties enhancement of carbon nanotubes/polyethylenecomposites by carbon nanotbues, the effect of temperature on mechanical properties of carbonnanotubes/polyethylene composites, and finally the influence of van Edward force betweenpolyethylene and carbon nanotubes on axial buckling behavior of carbon nanotubes areshowed.First of all, this paper used elastic shell model of the continuum mechanics theory, thenonlocal theory and the thermo-electro-mechanical constitutive relations to study the axialbuckling behavior of carbon nanotubes in multi physical field. The linear axial bucklinggoverning equation of multi walled carbon nanotubes in multi physical field based onnonlocal theory is driven. Then taking double walled carbon nanotubes as an example, theaxial buckling governing equation of double walled carbon nanotubes is solved by numericalmethod, which found that for small size carbon nanotubes, the axial critical buckling load ofclassical theory is overestimated, change of temperature is a negative linear relationship athigh temperature and a positive linear relationship at low temperature, and change of voltageis a negative linear relationship between the axial critical buckling load of carbon nanotubes.Secondly, uniaxial tension and compression properties of single carbon nanotubes werestudied by molecular dynamics method. The uniaxial tensile and compressive stress-straincurve of (7,7) single wall carbon nanotubes is given, which shows that the elastic modulus of(7,7) single wall carbon nanotubes at uniaxial tension and compression are respectively1.13TPa and1.17TPa. The uniaxial compression of many different sizes of single wall carbonnanotube are simulate by molecular dynamics method, and the critical buckling load valuesare compared with the theoretical value, which better reflect the scale effects in the study above.Finally, the mechanical properties of carbon nanotubes/polyethylene composites(CNTs/PE) reinforced by carbon nanotubes was studied by molecular dynamics method.Comparing the tensile properties between carbon nanotubes/polyethylene composites andpure polyethylene polymer, it supports the enhancement of carbon nanotubes on the tensileproperties of polyethylene polymer. And effect of temperature on mechanical properties ofcarbon nanotubes/polyethylene composites is studied, which found that the rise in temperatureto decrease the mechanical properties of carbon nanotubes/polyethylene composites. The lastshow, between the polyethylene polymer and single wall carbon nanotube, van der waalsforces’s influence on axial buckling behavior of single wall carbon nanotube, it change theaxial buckling behavior of carbon nanotubes.