AN ANALYTICAL EVALUATION OF INTERFACIALBONDING PROPERTIES OF SINGLE/MULTI-WALLEDNANOTUBE/POLYMER COMPOSITES

摘要

Since the discovery of carbon nanotubes, extensive research in the use of the nanotubes as nanoreinforcementsfor advanced composite materials has been dramatically emerged. The nanotubes havebeen appreciated as revolutionary high strength materials with possessing many unique electrical,mechanical and thermal properties in the World. The high aspect ratio property of the nanotubesenable them to be used as nano-fibres and nano-conductors for improving the electrical and thermalconductivity, and delamination resistance and fracture properties of polymer-based compositestructures. To adopt these nano-materials in real structural applications, understanding their stresstransfer properties between the nanotubes and surrounding matrices is a prior and important issue. Inthis paper, the stress transfer properties between single-/multi-walled nanotubes and polymer matrixare theoretically studied through the uses of local density approximation, elastic shells andconventional fibre pullout models. Several parameters such as the wall thickness, Young’s modulus,volume fraction and chiral vectors of the nanotubes were considered in the study. According to theanalytical results, it was found that the maximum shear stress decreases with increasing the size of thenanotubes. Increasing the number of wall layers of the nanotubes will cause (1) the decrease of theYoung’s modulus and (2) the increase of the effective cross section area of the nanotubes and thus theincrease of the total surface contact area at the bond interface. Although the author has previouslyaddressed that multi-walled nanotubes (MWNTs) could not be effectively used as nanoreinforcementsfor nanotube/polymer composites due to the axial stress could not be continuouslytransferred from the surface layer to the inner shells, the use of the MWNTs may have an advantageof avoiding debonding at the bond interface between the nanotubes and matrix of the composites.Besides, the stress transfer length of zigzag (n,0) nanotube is comparatively shorter than that of thearmchair (n,n) and chiral (n,m) nanotubes where m ≠ 0. In some cases, the Young’s modulus of theMWNTs is high enough for the design of advanced nanotube/polymer composites even theirsmodulus is comparatively smaller than that of the single-walled nanotubes (SWNTs).