**4. Discussion**

In this work, the idea of adding high loadings of graphene derivative into the polymer matrix to increase both the elastic modulus and tensile strength of CFRP has been achieved with Fibre Glast fabrics and 2000/2060 resin. To further demonstrate the universality of this idea, we tested the tensile properties of CFRP made with another widely used resin system, MGS 285/287, and with different classes of CFs. To maintain consistency, all CF fabrics used were made with Toray CF. In these carbon fibers, T300 and T700 represent the standard modulus CF. T300 is primarily used for automotive parts and sports products, and T700 is used in gas tanks. The T800 represents the intermediate modulus carbon fiber used in aircraft applications. The M55 is a high modulus carbon fiber mainly used in spacecraft. MGS resin systems have been widely used in CFRP wet layup fabrication with applications in aircraft. By testing CFRP made using widely popular commercial resin with different grades of CFs, we demonstrated the universality of our idea.

**Table 3** summarizes the elastic modulus and tensile strength of CFRPs made with different CF using MGS 285/287 resin with 10 wt% ERFG. the elastic modulus


#### **Table 3.**

*Mechanical properties of CFRP made by different types of CF fabrics and 10 wt% ERFG MGS resin.*

of all the CFRP samples made with ERFG show a 15–20% increase in these mechanical properties, due to formation of highly uniform dispersion of ERFG in the polymer matrix and from stronger interfacial interaction between polymer and ERFG through epoxy monomer functionalization. However, the trend observed in tensile strength is more complex. With T700, T800, and M55 CFRPs, the tensile strength increased by ~15–20% when 10 wt% ERFG was added in the resin. When compared, the strength of CFRPs with T300 CF increased by only ~10%. The variation with use of different carbon fibers could be the result of different sizing used on the carbon fibers and structure of fabrics. The thickness, stiffness, and chemical structure of the sizing radically affects the interface between carbon fiber and the polymer matrix. The addition of ERFG amplifies the effect of sizing on interfacial interactions. Different CF weaving structure and fabric density (gsm) affect the resin penetration through the fabric, which together with the increased resin viscosity due to dispersed ERFG particles, resulted in a non-uniform distribution of the particles across CFRP thickness.
