Composites include a base material or matrix and additives to improve the properties of the matrix. Today, 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 stiffness-to-weight ratio. high weight [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 an economic advantage [2]. Thermoset resins are one of the most widely used matrices in the manufacturing of polymer composites. Thermoset resins are perfectly used in the manufacture of composites due to their excellent mechanical properties, good adhesion and resistance to chemical agents. It is therefore important to study the properties of different compounds based on this group of polymers, which has been undertaken by many researchers over the past decades. Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”? Get an original essay Composite materials are manufactured depending on their application in various ways, such as hand layup, pultrusion, transfer molding of resin (RTM), vacuum assisted resin transfer molding (VARTM), sheet molding compound (SMC), bulk molding compound (BMC), etc. Bulk casting compound is widely used in transportation, electrical and electronics industries, especially for mass production of components with small and complex geometry, due to its easy production, high ratio high strength/weight, light weight, resistance to environmental conditions, excellent physical properties, good mechanical properties, temperature resistance, dimensional stability, low cost and fast production process are of 'great utility in industry. Composites made from a combination of chopped artificial fibers to improve mechanical properties, mineral fillers for economic benefits, and thermosetting resins [3, 4]. Thermoset resins used in these composites include polyester, phenolic, vinyl ester and epoxy and fillers used in this type of composites include clay, talc, carbon black, marble, glass, the most important and most used wood flour, metals and calcium carbonate [5]; fibers used in this type of composite include glass, carbon, Kevlar, boron and basalt; also natural fibers (bamboo, hemp, linen, wood, banana and coconut) as reinforcement of polymer materials replacing synthetic fibers have been studied [6-8]. Fiberglass is today an advanced and cost-effective industrial material in many applications. Glass fiber reinforced thermoset has played an important role in many industrial applications due to its 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 unsaturated polyester resin compounds. The widespread use of these polymers is due to their relatively low cost, ease of processing andtheir good compatibility. with a variety of fillers, but unlike other engineering polymers, unsaturated polyester has fewer mechanical and thermal properties that limit their applications. These defects can be eliminated by adding various fillers [11-14]. Unsaturated polyester resin is used in a wide range of applications in the transportation sector, water pipe production, chemical tanks, marine applications, construction and the color industry [ 15 , 16 ]. 85% of fiber-reinforced polymer products, such as boats, vehicle parts, and airplanes, were made from polyester [17]. Therefore, unsaturated polyester matrix glass composites 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 low. In recent years, the addition of nanoparticles as a second enhancer in the structure of polymer composite fibers has been carried out by many researchers. This group of composites with two types of amplifiers at micron and nanoscales are called multi-scale composites, which have better mechanical properties than filler-free fibrous composites [3, 4]. In industry, adding mineral filler materials to 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 nano silica, its small particle size, high specific surface area, commercial availability, convenience of industrial synthesis, competitive cost compared to other nanoparticles and its chemical, thermal and mechanical properties [ 19 , 22 ]. Silica from the gas phase (fumed silica), the most commonly known type of nano-silica 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 by forming a silica network in the liquid structure, which will simultaneously improve the electrical properties , thermal, optical and mechanical [23 -28].Primary silicon dioxide particles contain siloxane and silanol groups on their surface and due to the interaction of hydrogen bonding between neighboring silanol groups, the primary particles are interconnected and form an aggregate whose dimensions are between 100 and 500. nm These aggregates mainly result from agglomerations of nanoparticles, due to the intrinsic forces of van der waals. Formulations generally require little flavor to enhance their properties due to their high surface-to-weight ratio [29, 30]. The effect of fumed silica on unsaturated polyester resin matrix has been studied in many papers. 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 has been shown to decrease the tensile strength and tensile modulus, indicating poor interaction between the hydrophobic filler particles and the polymer matrix. 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 , bending strength and.