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 %. 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. 1. Introduction Graphene is a single two-dimensional layer of carbon atoms bound in a hexagonal lattice structure. This material has been extensively studied since it was first isolated in 2004 [1]. In recent years, several works have been published on the topic of graphene, discussing its extraordinary mechanical, electronic, and thermal properties [2–5]. Cooper et al. [6] presented an extensive review of the most important experimental work on novel applications of graphene, and a section was dedicated to discuss its amazing mechanical properties. In other works, graphene has been mixed with carbon nanotubes in order to enhance the performance of the reinforced matrix. Song et al. [7] found multiple synergies in a polypropylene matrix using reduced graphene oxide and carbon nanotubes polymer latex coated. Chatterjee et al. [8] studied the reinforcement of an epoxy matrix with the addition of various mixture ratios of carbon nanotubes with graphene nanoplatelets and founding synergistic effects especially for the flexural modulus. However, it is possible to achieve synergy effects employing the same nanomaterial with different surface polarity, as this research proposes, in this case, graphene oxide and reduced graphene oxide. Young et al. [9] published a review concerning graphene and graphene oxide nanocomposites evaluating these materials’ properties. They comment that graphene oxide has some advantages over graphene, such as facility to obtain it in large quantities, presence of functional groups for bonding with a polymer matrix, easy to exfoliate and disperse it, in water or a polar solvent, and hence, can be readily mixed with water-soluble polymers [10]. Graphene oxide increases the mechanical properties of nanocomposites. Bortz et
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