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This work analyzes the morphology and behavior of hybrid composites reinforced with carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). In order to avoid the weak interface of laminar nanofillers, GNPs were functionalized with amine groups. Different tendencies were observed as a function of the measured property. Storage modulus showed a synergic trend, being the stiffness of hybrid CNT/GNP/epoxy composites higher than the corresponding ones measured in neat epoxy composites reinforced with CNTs or GNPs. In contrast, the thermal and electrical conductivity increased with the nanofiller addition, the final value of the mentioned properties in the hybrid composites was strongly influenced by specific graphitic nanofiller. Neat GNP/epoxy composites showed the highest thermal conductivity, while neat CNT/epoxy composites presented the highest electrical conductivity. This behavior is explained by the observed morphology. All composites exhibited a suitable nanofiller dispersion. However, on hybrid GNP/CNT/epoxy composites, CNTs tend to be placed between nanoplatelets, forming bridges between nanoplatelets. This morphology implies a less effective electrical network, limiting the synergic effect in the properties, which requires percolation. In spite of this, the hybrid GNP/CNT/epoxy composites showed a better combination of properties than the neat composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46475.

A melt-mixing procedure has been used to disperse multi-walled carbon nanotubes (MWCNT) in an epoxy matrix. According to dynamic viscoelastic results, a physical network is formed for carbon nanotube concentrations of 0.3 weight per cent (wt%) and above. The temperature activated curing process is followed analyzing the evolution of the dynamic viscoelastic functions and the dielectric loss with time. Curing process from a physical to a chemical network is monitored. The presence of MWCNT accelerates curing, even when the rheological percolation is not reached (absence of physical network). Several hypotheses are considered to explain this result. Electrical conductivity decreases during cure, so lower electrical conductivities are found for cured MWCNT/epoxy samples than for dispersions: this is explained by a distortion of nanotubes physical network and a reduction of the ionic conductivity contribution of the liquid phase.

PurposeBonded composite patches are ideal for aircraft structural repair as they offer enhanced specific properties, case‐tailored performance and excellent corrosion resistance. Bonding minimizes induced stress concentrations unlike mechanical fastening, whilst it seals the interface between the substrate and the patch and reduces the risk of fretting fatigue that could occur in the contact zone. The purpose of this paper is to assess the electrochemical corrosion performance and the environmentally induced mechanical degradation of aerospace epoxy adhesives when carbon nanotubes (CNTs) are used as an additive to the neat epoxy adhesive.Design/methodology/approachThe galvanic effect between aluminium substrates and either plain or CNT enhanced carbon fibre composites, was measured using a standard galvanic cell. Also, rest potential measurements and cyclic polarizations were carried out for each of the studied systems. The effect of the CNT introduction to a carbon fiber reinforced plastic (CFRP) on the adhesion efficiency, before and after salt‐spraying for 10, 20 and 30 days, was studied. The adhesion efficiency was evaluated by the single lap joint test.FindingsThe corrosion behaviour of the system is polymer matrix type dependent. CNT introduction to a CFRP may induce small scale localized degradation.Originality/valueThis paper fulfills an identified need to study how the shear strength and the response to galvanic corrosion are affected by epoxy resins modified by carbon nanotubes.

This study describes two approaches for the incorporation of carbon nanotubes (CNTs) in carbon fibre reinforced polymer (CFRP) composites, through the addition of the CNTs in the bulk resin and by the addition of CNT-based buckypaper (BP) in the CFRP structure. Several laminates were successfully manufactured integrating these two approaches, where a significant improvement of the electrical conductivity (EC) values was found. Additionally, in order to compare different surface preparations and testing methods, a cross check of EC test was carried out among different laboratories. This characterization was complemented with scanning electron microscopy (SEM) analyses, results of which were used to rule out a complete filtering effect of the CNTs. Furthermore, interlaminar shear strength (ILSS) tests were also performed, with the aim of assessing the mechanical behavior of the different configurations.