Effect Of Stone-wales Defects On The Mechanical Properties Of Carbon Nanotube/polypropylene Composites By Molecular Simulation

The excellent mechanical,electrical and thermal properties of carbon nanotubes make it a preferred reinforcement for composites,and the carbon nanotube/polymer composites have broad application prospects in the fields of aerospace,machinery manufacturing and industrial production.However,defects on the surface of carbon nanotubes,e.g.,the typical Stone-Wales defects,will be introduced during the preparation of carbon nanotubes and their composites.The presence of Stone-Wales defects will affect the mechanical properties of composites.Due to the limitation of experimental techniques,it is difficult to characterize the defects on the surface of carbon nanotubes.In this study,we performed molecular dynamics simulation to study the effect of Stone-Wales defects on the mechanical properties of carbon nanotube/polypropylene composites.We studied the influence of Stone-Wales defects on the interfacial bonding characteristics of carbon nanotube/polypropylene composites through simulating the extraction process of carbon nanotubes from the polypropylene matrix.Results indicated that Stone-Wales defects can enhance the interfacial interaction between the carbon nanotubes and polypropylene matrix,and the interfacial bonding characteristics of carbon nanotube/polypropylene composites will be increased by increasing the number of defects.Using a “Constant Strain Energy Minimization Method”,we investigated the effect of Stone-Wales defects on the mechanical properties of carbon nanotubes and carbon nanotube/polypropylene composites through simulating uniaxial tensile process of composites.Results reveal that,for the pure carbon nanotubes,the axial mechanical properties of carbon nanotubes will be reduced by decreasing the number of Stone-Wales defects,while the radial mechanical properties of carbon nanotubes remain essentially unchanged.For the carbon nanotube/polypropylene composites,the longitudinal mechanical properties of carbon nanotubes can be reduced by increasing the number of Stone-Wales defects,while the transverse mechanical properties can be increased gradually.We also studied the temperature on the interfacial bonding characteristics and mechanical properties of carbon nanotube/polypropylene composites.Results show that,with increasing the temperature,the interfacial bonding characteristics and mechanical properties of composites were decreased.The increased temperature leads to thermal expansion of the composites,and weakens the interactions between carbon nanotubes and polypropylene matrix.Therefore the interfacial bonding characteristics and mechanical properties were decreased.