Composites include a base material or matrix and additives to improve the properties of the matrix. Nowadays, composite materials have attracted much attention in many industries such as aerospace, automotive and marine, due to their low weight, high strength-to-weight ratio and high stiffness-to-weight ratio [1]. Among all types of composites, polymer composites are one of the largest and most commonly used types of composites, with advantages such as specific strength and specific stiffness, easy production of complex components, good corrosion resistance and economic advantage [2]. Thermosetting resins are one of the most used matrices in the production of polymer composites. Thermosetting resins are perfect for the production of composites due to their excellent mechanical properties, good adhesion and resistance to chemicals. Therefore, it is important to study the properties of different compounds based on this group of polymers that many researchers have undertaken in recent decades. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get Original Essay Composite materials are made according to their application in various ways, such as hand lamination, pultrusion, resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM), sheet molding compound (SMC), bulk molding compound (BMC) and so on. Bulk molding compound is widely used in the transportation, electrical and electronics industries, especially for mass production of components with small and complex geometry, due to its ease of production, high strength-to-weight ratio, light weight, resistance to environmental conditions, excellent physical properties, good mechanical properties, temperature resistance, dimensional stability, low cost and rapid production process are of great use in the industry. Composites made by combining bulk molding compounds of chopped artificial fibers to improve mechanical properties, mineral fillers for economic benefits, and thermosetting resins [3, 4]. Thermosetting resins used in these composites include polyester, phenolic, vinyl ester and epoxy and fillers used in this type of composites includes clay, talc, carbon black, marble, glass, wood flour, metals and the most important and most used calcium carbonate [ 5]; fibers used in this type of composites include glass, carbon, Kevlar, boron and basalt; natural fibers (bamboo, hemp, linen, wood, banana and coconut) have also been studied as a reinforcement of polymeric materials to replace synthetic fibers [6-8]. Fiberglass today is an advanced and economical industrial material in many applications. Glass fiber reinforced thermoset materials have been important for many industrial applications due to their mechanical performance and cost. Among thermosetting resins, unsaturated polyester has been used for a wide range of applications [9, 10]. Unsaturated polyester resin has the highest application rate among existing resins in the industry, so it is inevitable to improve the properties of compounds based on unsaturated polyester resins. The widespread use of these polymers is due to their relatively low cost, easy processing and good compatibility with a variety of fillers, but, unlike other engineering plastics, unsaturated polyester has fewer mechanical and thermal properties that limit its applications . These defects can be eliminated by adding various fillers [11-14]. Unsaturated polyester resin has a wide range of applications in the plastics industrytransportation, in the production of water pipelines, in chemical tanks, in marine applications, in construction and in the paint industry [15, 16]. 85% of fiber-reinforced polymer products, such as boats, vehicle parts, and aircraft, were made using polyester [17]. Therefore, glass composites with unsaturated polyester matrices are of considerable commercial importance. Research shows that by adding fibers to the resin, the tensile strength and elastic modulus can be improved in the direction of the fiber, while the toughness and impact resistance remain weak. In recent years, many researchers have carried out the addition of nanoparticles as a second enhancer in the structure of polymer composite fibers. This group of composites with two types of micron- and nanoscale amplifiers are called multiscale composites, which have better mechanical properties than fiber composites without filler [3, 4]. In industry, adding mineral fill materials to the polymer is a common method; these materials not only improve multiple properties but also reduce the cost of composite processes [18]. Today, silica nanoparticles are of great interest for minerals. The advantage of nanosilica, small particle size, high specific surface area, commercial availability, convenience of industrial synthesis, its competitive cost compared to other nanoparticles and its chemical, thermal and mechanical properties [19, 22]. Silica from the gas phase (fumed silica), the most common type of nanosilica is known on the market. Fumed silica with large specific surface area and variable surface properties can easily disperse in liquid, and is able to penetrate many organic liquids, forming a silica network in the liquid structure, which will simultaneously improve the electrical, thermal, optical and mechanical properties [23 -28].The primary particles of silicon dioxide contain siloxane and silanol groups on their surface, and due to the hydrogen bonding interaction between neighboring silanol groups, the primary particles are interconnected and form an aggregate, the size of which are between 100 and 500 nm. These aggregates mainly result from agglomerations of nanoparticles, due to intrinsic van der Waals forces. Formulations typically require little taste to achieve improved properties due to its high surface-to-weight ratio [29, 30]. The effect of fumed silica on the unsaturated polyester resin matrix has been studied in many articles. For example, Marinković et al. [31] studied the mechanical properties of polyester matrix composites reinforced with four types of hydrophobic fumed silica having different specific surface areas. The addition of hydrophobic fumed silica nanoparticles was shown to decrease the tensile strength and tensile modulus, which indicates poor interaction between the hydrophobic filler particles and the polymer matrix. The mechanical properties of fumed silica reinforced polyester composites studied by Shokry showed that compressive strength increased steadily with increasing fumed silica content, tensile strength decreased with increasing fumed silica, tensile strength bending and elastic modulus, there was an ascending and descending trend with increasing fumed silica. Mirabedini et al. [33] The mechanical properties of polyester matrix composites reinforced with two types of fumed silica from two companies and two specific surface areas and two different surface modifications were investigated. The tensile strength and elastic modulus for both fumed silica had the same trend, they increased first, then.