# Mechanical Properties of Green Synthesized Graphene Nano-Composite Samples
## 1 Introduction  
Graphene is a one-atom-thick 2D honeycomb structure of carbon atoms with extra high in-plane elastic stiffness and electrical and thermal conductivities. Graphene's density equals 2.1 g/cm\({}^{3}\), and it has been investigated widely by researchers since 2004. Graphene-based nanocomposites can be used in different industries. Graphene is one of the more exciting materials in the composite sectors. The graphene material shows considerably high mechanical strength (Young's modulus: -1000 GPa), high thermal conductivity (3000-5000 W/(m\(\cdot\)K)) and good optical transparency (-97.7%) [1]. Because of the good mechanical, electrical and physical properties of graphene, it can be used in various industrial applications, such as solar cells, energy storage devices, sensors, photocatalysis, electrocatalysis, electronic panels, lightweight composites, lubrication, LEDs and so on [1, 2]. Graphene oxide and polystyrene composites can decrease the friction in microelectromechanical systems (MEMS) by a self-lubricating thin film over the silicon substrate [2]. The lamellar structure results in admirable mechanical strength, a large surface area, low shear strength and high thermal conductivity [3]. Adding the proper weight percent of graphene can improve the corrosion behavior of fabricated composites, and a self-healing capacity can be observed in many cases [4; 5; 6; 7]. The graphene enhances the durability of the polymer composites exposed to sunlight, and a 3% mass fraction of graphene increases the service life of the polymers in products [8]. [PERSON] et al. [9] studied the effect of graphene nanoplates on the electrical properties of SnSe/GNPs composites (metal matrix composite (MMC)). The results showed that the graphene was able to keep its crystallinity at short milling times, but it exhibited agglomeration and poor dispersion within the matrix. However, a long milling time increased the disorders on the graphene structure. Simultaneously, it provided good dispersion of the graphene particles, and the homogeneous distribution of graphene particles led to a considerable increase in electrical conductivity. Other investigations showed that the microstructure was another parameter affecting the properties of the fabricated nanocomposites [10]. [PERSON] et al. [11; 12; 13; 14; 15; 16] published several research works about graphene nanoparticles and their effect on mechanical behavior. [PERSON] et al. [15] studied the effects of graphene nanoplatelets and graphene nanosheets on the fracture toughness and tensile epoxy resin properties. The graphene nanoplatelets were prepared from graphite powder by changing the magnetic field to achieve strong shear forces and obtain low thickness graphene particles. The results showed that a higher fracture toughness and tensile strength would be obtained using the graphene nanoplatelets compared with the graphene nanosheets. The stiffness of graphene nanoplatelet and epoxy nanocomposites can be evaluated by theoretical approaches [11; 14]. An investigation showed that the embedded graphene's longitudinal stiffness is different from that of the isolated graphene and is a function of its length. Therefore, a relationship was developed to consider the nanosize effect in macroscale [11]. A similar study was conducted by [PERSON] et al. [17]. In addition, the stiffness of the graphene nanocomposites was predicted by combining the finite element method and micromechanics formulations. The matrix was considered a continuum phase, and each covalent bond of the graphene sheet was simulated by an equivalent structural beam. Nonlinear springs were used as Van der Waals bonds in the interphase region of the graphene and polymer. The random distribution of graphene sheets in a polymer was reached using the moduli of different graphene sheets with different sizes. The flexural fatigue behavior is another critical parameter in mechanical properties assessment.