Fabrication Of Carbon Nanotubes/Carbon Fiber Multi-Scale Reinforcemancet And Study On Performances Of Composites

Carbon fiber reinforced polymer based composites have earned widespread attention due to their outstanding high strength-to-weight ratio, mechanical and thermal performances. However, insufficient implementation of mechanical property of carbon fiber could be ascribed to the poor interfacial bonding to resin matrix. The exceptional physical properties combined with high aspect ratios and quasi-one dimension of carbon nanotubes(CNTs) render it an attractive candidate for the modification of polyme r composites. The introduction of CNTs into continuous fiber reinforced composites offers an opportunity for creating hybrid multiscale composites to further enhance the properties of composites.In this study, a multi- scale fibrous reinforcement consisting of CNTs grafted carbon fiber was engineered with diisocyanate as coupling agent. The interfacial bonding strength and mechanical properties of resulting hybrid composites were also examined. Carbon fiber was initially activated by oxygen plasma treatment and then grafted to carboxylic acid functionalized multiwalled carbon nanotubes via coupling agent to prepare CNTs/CF hybrid multi-scale reinforcement. The chemistry and functionalities of CF before and after surface treatment were quantitively characterized by X-ray photoelectron spectroscopy(XPS) and wettability test. The carbon fabric/epxoy composite laminates were manufactured by compression molding technique and evaluated with universal testing machine, dynamic mechanical analysis(DMA) and scanning electron microscopy(SEM) with respect to flexural properties, interlaminar shear strength(ILSS), glass transition temperatures(Tg) and microstructure, respectively. It is demonstrated that the grafting of CNTs onto CF significantly improved the flexural strength and interlaminar strength(ILSS) of the composites containing varying scale reinforcements by 65.1% and 63.4%, respectively, as compared to the control carbon/epoxy composites. Scanning electron microscopy(SEM) was used to examine the fracture surface of the failed specimens. The microscopy pictures of the fracture surfaces confirm that there is more resin adhering to CF surface with chemically grafted CNTs, which is beneficial to improve the mechanical properties of the resulting hybrid multi-scale composites.