The effect of process variation on pristine carbon nanotube particle dispersion within glass-fibre reinforced epoxy polymer composites and its resultant mechanical characteristics

Abstract

The present work focused specifically on two fabrication processing methods, namely, vacuum-assisted resin transfer moulding (VARTM) and double vacuum-assisted resin transfer moulding (DVARTM) processing methods. DVARTM was essentially a modified VARTM process. The research focused on the effect of nanoparticle dispersion within the composite and the effect of process variation on its mechanical properties. The resultant composites consisted of E-glass fibre (GF) infused with an epoxy matrix doped with 0, 0.1, 0.3 and 0.5 wt% of pristine multi-walled carbon nanotubes (MWCNT). Dynamic mechanical analysis (DMA), tensile testing and a quantitative “burn-out” test analysis were conducted to show the effect of MWCNT dispersion due to the process variation. The overall graphical DMA analysis for the DVARTM method revealed trends consistent to specimens containing homogeneously dispersed nanoparticle content. At 30°C, the 0.5 wt% composite from the DVARTM method displayed a 34% stiffness increase compared to VARTM with the similar wt%. Glass transition temperatures (Tg), displayed a steady incremental increase in DVARTM from 0.1 to 0.5 wt% content. The VARTM method showed a steady increase in Tg for 0.1 and 0.5 wt% content with a decline in 0.3 wt% content. In the DVARTM method, the damping for 0.1 wt% decreased by 14.5% and 10%, compared to the 0.5 wt% and the control, respectively. The decreased damping indicated an enhancement to the fillermatrix interfacial bonding. The ultimate tensile strength (UTS) had a uniform increase with increasing weight percentages of MWCNT content for the VARTM method. Both methods experienced optimum UTS with 0.3 wt% MWCNT content. A “burn-out” test on various layers of the composite along the lengths and thickness directions was conducted for both methods. The resultant quantitative analysis of the residue on the GF after combustion suggested improved dispersion of MWCNTS for the DVARTM method in comparison to VARTM. The important finding in this study highlighted that enhancements to mechanical properties were achievable when using pristine MWCNTs along with process variation, as opposed to past studies which stated that pristine MWCNTs were non-effective unless functionalized.