Characterizing the mechanical and thermal properties of multilayer graphene nanocomposites using molecular dynamics simulation

• Main Authors: Tseng, Po-Ying, 曾柏穎
• Other Authors: 蔡佳霖
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/9332xn

碩士 === 國立交通大學 === 機械工程系所 === 106 === The study aims to characterize the mechanical and thermal properties of multilayer graphene nanocomposites using molecular dynamics (MD) simulation. The effects of surface functionalized and wavy graphene on nanocomposites were also investigated. The results indicated that the increase in the number of graphene layers will reduce the Young's modulus of the nanocomposite, which is mainly derived from the low load transfer efficiency of the graphene inner layer. The pullout simulation also shows that the interfacial shear stress of the multilayer graphene is lower than that of the monolayer graphene. Graphene surface functionalization can effectively improve the load transfer efficiency between graphene and epoxy matrix, thereby improving the Young's modulus of the nanocomposites, wherein the enhancement of the outermost layer is more significant than the inner layer. The wavy effect will significantly reduce the Young's modulus of the graphene nanocomposite, and minimize the difference between multilayer and monolayer graphene In terms of thermal properties, due to the specific area of graphene, low interfacial thermal conductivity and the thermal conductivity of surrounding epoxy matrix, the increase of the number of layers will reduce the in-plane thermal conductivity of nanocomposites, but the out-of-plane thermal conductivity is improved. In the in-plane direction, the surface functionalization can enhance the thermal conductivity of the surrounding epoxy matrix more significantly, and thus increase the thermal conductivity of nanocomposites. In the out-of-plane direction, the surface functionalization will improve the thermal conductivity of the graphene/epoxy interface, but at the same time, the thermal conductivity of the multilayer graphene itself will decrease, and the out-of-plane thermal conductivity of the nanocomposite will still improve. From the vibrational density of state (VDOS), it can be found that the VDOS mismatch between graphene outermost layer and epoxy can be reduced by the functional groups, but the VDOS mismatch between graphene outermost layer and inner layer increase, accordingly. Compare of Effective medium approximations (EMA) and Modified Mori-Tanaka model (MMT) with experimental data. The results show that when graphene with small lateral size or thickness, the EMA model will underestimate the thermal conductivity of nanocomposite. This is because of the EMA model ignore the interaction between graphene inclusions.