Mechanical and Thermal Properties of Multi-scale Carbon Nanotubes–Carbon Fiber–Epoxy Composite

Abstract

Multi-scale composite material was developed by combining carbon fabric and multi-wall carbon nanotubes (MWCNTs) in epoxy matrix. Varying concentrations of MWCNTs were ultrasonically dispersed in epoxy resin and applied on carbon fabric followed by curing. Tensile and flexural tests were conducted to observe the influence of MWCNTs on the mechanical properties of carbon fiber-reinforced plastic (CFRP). Coefficient of thermal expansion (CTE), thermal stability and glass transition temperature were determined through dilatometry, thermo-gravimetric analysis and differential scanning calorimetry, respectively. The MWCNTs dispersion in the epoxy was characterized through optical microscopy and scanning electron microscopy. Fractured surfaces of tensile samples were examined through high-resolution scanning electron microscope to investigate the failure mechanism. Tensile and flexural strengths were improved by 60 and 54%, respectively, on addition of 0.25 wt% MWCNTs in CFRP composite. This enhancement was attributed to the micro-crack bridging effect of the MWCNTs. Nanotubes acted as nano-stitches by holding the matrix together, thereby increasing the load bearing capability. Glass transition temperature and CTE of the CFRP was reduced by addition of MWCNTs whereas MWCNT–CFRP was found thermally stable up to 350 $${^{\circ }}$$ C. Microscopy results showed that the nanotubes were well dispersed in the epoxy matrix. However, higher weight fraction of MWCNTs in the epoxy had promoted agglomeration.