Glass fibers are materials commonly employed for the reinforcement of several polymers. Aircraft parts, rocket motor cases and automobiles, are examples of several structural composites where glass fibers have been used. It is well known that increasing the efficiency of stress transfer from the polymeric material to the fiber may lead to enhanced mechanical performance and, as with any composite materials, the interface between both materials play a critical role in the final mechanical properties. The presence of carbon nanotubes on the fibers surface may improve the adhesion between fibres and matrix since they may interlock with the polymer chains and thus creating a physically strong adhesion between the two phases.
In this work, carbon nanotubes were synthesized on the surface of carbon and glass fibers, by chemical vapour deposition of ethylene, under different experimental conditions. The resulting fibers-carbon nanotubes hybrids were further characterized by energy dispersive X-ray analyses, scanning electron microscopy, Raman spectroscopy and thermogravimetric analyses. The selected glass fibers-carbon nanotubes synthesized were embedded in polyethylene terephtalate glycol (PETG) and epoxy resin and the effect of the quality and amount of carbon nanotubes within the different samples on the fiber/matrix interfacial strength of PETG and epoxy fiber composites was evaluated by single fiber fragmentation tests (SFFT), microscopy and photoelasticity analyses. The results were compared with the sized treated fibers.
In relation to the PETG fiber composites, the results show that the sized treated fibers have a better fiber/matrix adhesion, when compared to fibers with CNTs grown on their surfaces. No significant difference in the fiber/matrix interfacial strength was found between the PETG composites using glass fibers containing carbon nanotubes on their surfaces.
On the other hand, the presence of carbon nanotubes on the fibers surface seems to enhance the interfacial bonding between fiber and epoxy. These observations are however only based on microscopy and photoelasticity analyses.