Qingjie Zhang

Influence of matrix modulus on the mechanical and interfacial properties of carbon fiber filament wound composites

The effect of epoxy resin matrix modulus on the mechanical and interfacial properties of T700 carbon fiber and T800 carbon fiber filament wound composites was investigated. Different aromatic amine curing agents were selected to change the modulus of the same kind of resin matrix. The mechanical properties of carbon fiber filament wound composites were characterized through Naval Ordinance Laboratory-ring (NOL) burst tests, and interlaminar shear strength (ILSS) tests. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic mechanical thermal analysis (DMA) were used to characterize the failure surfaces and interfacial properties of the resulting composites. The results showed that, even if carbon fibers were fully impregnated with epoxy resin, the mechanical properties of composites and the mode of interfacial failure were closely related to the modulus of the resin matrix. The resin matrix with a high modulus was found to be an essential prerequisite to excellent mechanical and interfacial properties of the resulting composites.

Effect of epoxy monomer structure on the curing process and thermo-mechanical characteristics of tri-functional epoxy/amine systems: a methodology combining atomistic molecular simulation with experimental analyses

The curing kinetics and thermo-mechanical characteristics of two kinds of high-performance amine cured tri-functional epoxy resin compounds, including diglycidyl-4,5-epoxycyclohexane-1,2-dicarboxylate and N,N-diglycidyl-4-glycidyloxyaniline, were systematically studied herein. Different to the simple bi-functional epoxy resins studied before, the increase in epoxy functionality and resultant asymmetric monomer structure made the whole curing behaviour more difficult to analyse. Nevertheless, there is an urgent demand to provide a thorough understanding of the tri-functional epoxy resin/amine system in order to obtain the desired macro-performance. In this paper, a methodology, which combines atomistic molecular simulation with experimental research, was established to expound the effect of the asymmetric epoxy monomer structure on the reaction kinetics and ultimate performance of the tri-functional epoxy/amine system. It can be utilized to efficiently analyse the cross-linking procedure and the microstructure–property relationships of epoxy resin with poly-functionality and asymmetric monomer structures, thereby serving as guidance to design high-performance polymer matrices for advanced composites.

Influence of hollow carbon microspheres of micro and nano-scale on the physical and mechanical properties of epoxy syntactic foams

Epoxy syntactic foams were prepared by introducing hollow carbon microspheres (HCMs) of micro and nano-scale. Based on the surface structure analysis of the HCMs, the effects of HCM content and particle size on the mechanical properties, dimensional stability, thermal conductivity, thermal stability and dielectric properties of the epoxy foam were investigated. The density of the epoxy foam gradually declined with the increase of the micro-scale HCM (M-HCM) content up to 9 wt%, and the compression strength of the epoxy foam just decreased slightly, while the compression modulus and flexural modulus were enhanced continuously. When 0.5 wt% and 1 wt% of HCMs were involved, the reinforcing effect of nano-scale HCMs (N-HCMs) was superior to the M-HCMs. The compression strength of the N-HCM/epoxy foams was almost equivalent to the neat epoxy, while the flexural strength of the N-HCM samples exhibited an obvious superiority. The dimensional stability and thermal stability of the epoxy foams were also improved with the addition of HCMs. Besides, the introduction of the M-HCMs and N-HCMs gave rise to different effects on the thermal conductivity, electrical conductivity and dielectric constant of the resulting epoxy foams due to the diversity in the interfacial interactions and microstructure. These results indicate that the HCM/epoxy syntactic foams show potential for application in multifunctional materials that are lightweight and of high rigidity.

Surface Sizing Treated MWCNTs and Its Effect on the Wettability, Interfacial Interaction and Flexural Properties of MWCNT/Epoxy Nanocomposites

A surface-sizing technique was offered to take full advantage of multi-walled carbon nanotubes (MWCNTs) and epoxy resins. Two surface-sizing treated MWCNTs were obtained through a ball-milling treatment of amino-functionalized MWCNTs (MWCNT-NH2) with n-butyl glycidylether (BuGE) and benzyl glycidylether (BeGE). These were referred to as MWCNT-BuGE and MWCNT-BeGE. The results indicated that the surface sizing effectively enhanced wettability, dispersibility of MWCNTs in the epoxy resin. These ameliorating effects, along with improved interfacial interaction between MWCNT-BeGE containing benzene rings and the epoxy matrix, which can offer a more efficient local load-transfer from matrix to MWCNTs, as observed by a higher G-band shift in Raman spectrum under bending loads than that of MWCNT-BuGE reinforced ones. Correspondingly, MWCNT-BeGE/epoxy nanocomposites exhibited increasing flexural strength and modulus of 22.9% and 37.8% respectively compared with the neat epoxy, and 7.3% and 7.7% respectively compared with MWCNT-BuGE/epoxy nanocomposites with the same MWCNT content.