Strength Design of SMC Products

SMC products, namely Sheet Molding Compound products, are high-performance thermosetting composite products. In numerous application fields, strength design is extremely crucial for SMC products. Taking the automotive industry as an example, with the continuous development of the automotive lightweight trend, SMC products—thanks to their lightweight and high-strength characteristics—are widely used in the manufacturing of automotive body parts, structural components, and functional parts, such as engine covers, front and rear bumpers, fenders, and radiator brackets. These parts need to withstand various complex mechanical loads during vehicle operation, including vibration, impact, bending, and tension.

If the strength design is unreasonable, it may lead to premature damage of the parts, affecting the safety and reliability of the vehicle. In the construction field, SMC products are often used to manufacture exterior wall panels, curtain walls, roofs, pipelines, and storage tanks. These building components need to have sufficient strength to bear their own weight, wind loads, snow loads, and potential seismic forces; strength design is directly related to the structural stability and service life of buildings. In the electronic and electrical field, SMC products are used to produce electrical equipment enclosures, safety switches, and cable brackets—they not only need to meet electrical performance requirements but also possess a certain level of strength to protect internal electronic components from external damage.

Analysis of the Strength Design Principle of SMC Products The formation of the strength of SMC products is a complex process, involving the interaction between various internal components of the material and changes in the material structure during the molding process. From the perspective of material composition, the interfacial bonding force between the resin matrix and the reinforcing fibers is one of the key factors affecting strength. As the main reinforcing material, glass fibers, with their high-strength and high-modulus properties, provide the basic load-bearing capacity for SMC products. When the product is subjected to external forces, the glass fibers can bear most of the load and prevent the propagation of cracks. The unsaturated polyester resin matrix, on the other hand, bonds the glass fibers together, enabling them to work synergistically to withstand external forces.

During the molding process, SMC material undergoes a transformation from a flowable premix state to a cured and molded state—this process has a significant impact on the final strength of the product. During compression molding, under the action of high temperature and high pressure, the resin matrix undergoes a cross-linking and curing reaction to form a three-dimensional network structure. During this process, the molecular chains are connected to each other, gradually increasing the hardness, rigidity, and strength of the material. At the same time, high temperature and high pressure also promote a tighter combination between the various components, reducing internal defects and voids, and improving the compactness of the material.