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We present an easy and effective way to improve the mechanical properties of an epoxy matrix by reinforcing it with a combination of graphene oxide (GO) and reduced graphene oxide (RGO). These nanocomposites were prepared with different load of nanofillers: 0.1, 0.4, 0.7, 1.0 wt% and a neat epoxy. Ratios of graphene oxide and reduced graphene (GO : RGO) employed were: 0 : 1, 0.25 : 0.75, 0.5 : 0.5, 0.75 : 0.25, and 1 : 0. Results show that with only 0.4 wt% and a ratio 0.2 : 0.75 of GO : RGO, tensile strength and tensile toughness are 52% and 152% higher than neat epoxy while modulus of elasticity was improved~20%. The obtained results suggest that it is possible achieve advantageous properties by combining graphene in oxidized and reduced conditions as it shows a synergic effect by the presence of both nanofillers.

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This work reports the influence of seawater ageing on the mode I and mode II interlaminar fracture toughness ([Formula: see text] and [Formula: see text]) of prepreg-based unidirectional carbon fiber/epoxy laminates containing carbon nanofillers. Double cantilever beam and end notched flexure specimens were fabricated from composite laminates containing multiwalled carbon nanotubes and/or reduced graphene oxide at their middle plane interface. Experimental results showed that the addition of carbon nanofillers moderately increased the [Formula: see text] and [Formula: see text] propagation of composite laminates before and after their immersion in seawater with respect to the reference laminate under dry condition. For double cantilever beam and end notched flexure specimens aged in seawater, it was observed that [Formula: see text] and [Formula: see text] increased by 57% and 13% for specimens with multiwalled carbon nanotube/reduced graphene oxide hybrid combination, 39% and 4% for specimens with multiwalled carbon nanotubes and 53% and 8% for specimens with reduced graphene oxide respectively, as a consequence of the plasticization effect of seawater immersion on the matrix. Fracture surface examination by scanning electron microscopy revealed interlaminar failure associated to mode I and mode II delamination and toughening mechanisms produced by the multiwalled carbon nanotubes and reduced graphene oxide at delaminated regions of composite laminates.

A hybrid based on graphene nanoplatelets and carbon nanotubes (G‐CNT) is obtained through direct exfoliation of graphite in a liquid medium, and tested as reinforcement material in epoxy resin. CNT act as exfoliation material in contact with graphite under ultrasound irradiation, and the thickness of graphite decreases to produce graphene nanoplatelets in an easy one‐step method. The morphology of the hybrid, is observed through transmission electron microscopy micrographs exhibiting delamination of graphite. XRD, UV–vis, and atomic force microscopy (AFM) results provide evidence of the exfoliation of graphite by interaction with CNT. Ultrasonic process does not generate additional oxygenated groups on carbon structures, as it is supported by XPS spectra; and the disorder in the carbon structures detected in Raman spectra is attributed to defects originated by some fragmentations. Epoxy nanocomposites incorporating 0.3 wt% of G‐CNT display the highest enhancement in storage modulus (~2706 MPa), glass transition region increases meaning higher thermal stability, and glass transition temperature increases until 119°C. Impact resistance also enhances with 0.3 wt% of G‐CNT, obtaining ~95% of increment. The hybrid obtained by exfoliating graphite with CNT in one‐step improves the performance of nanocomposites, and it offer an easy and viable alternative to obtain hybrid systems.

The mechanical, electrical, thermomechanical, and thermal properties of a thermoset matrix reinforced with pristine carbon nanotubes (1-D) and reduced graphene oxide (2-D) have been evaluated. Epoxy resin was reinforced with 1-D and 2-D nanomaterials in a wide range of load for a detailed study: 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0 wt. %. It is observed that carbon nanomaterials’ dimensionality influences its ability to transfer their unique properties to the nanocomposites. In this work, carbon nanotubes are more suitable than reduced graphene oxide to improve some properties, even though graphene-related materials have outperformed 1-D nanomaterials in other research. Tensile tests of nanocomposites show the best increment, with loads of 0.7 and 0.1 wt. % carbon nanotubes and reduced graphene oxide, respectively. Tensile strength at these loads is ∼120 % higher than epoxy resin, but the load for obtaining the best mechanical performance is different for each nanomaterial. Electrical conductivity measurements show that 1-D nanostructures are able to form conductive paths better than nanosheets. In this work, carbon nanotubes yield up to three magnitude orders higher than reduced graphene oxide. The highest initial storage modulus is achieved by employing 1-D nanomaterials and contributes to improving the thermomechanical stability. Therefore, the dimensionality of carbon nanomaterials impacts the properties of nanocomposites, and each nanostructure is able to improve the matrix at different regions of the load.

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