Bulletproof helmet molding process

           The vacuum assisted resin infusion (VARI) process is to evacuate the vacuum bag containing the bulletproof helmet prefabricated mold, and use the fluidity of the resin to extract the resin under vacuum and negative pressure, so that the resin is impregnated with the fiber reinforcement. The process of preparing composite materials is then cured at a certain temperature. The VARI process diagram is shown in Figure 5.

            Experimenters used the vacuum-assisted resin transfer molding (VARTM) process to prepare a three-dimensional corner interlocking aramid helmet.

          The research results show that the obtained helmet has no obvious wrinkles and has good performance. Based on the VARTM process, the testers first used vacuum-assisted drape technology (VADT) to lay the aramid fabric flatly on the mold, and then used the VARTM process to prepare the helmet shell. This method of combining the two processes does not require cutting and the helmet produced is wrinkle-free. Further test results show that the top curvature of this helmet is larger than the sides and rear, and the impact protection performance is good.

          The compression molding mechanism is to put the preform and resin into the mold, pressurize and heat the raw materials through equipment, and utilize the fluidity of the resin under heat and pressure to fully infiltrate the preform, and then solidify and form. The compression molding process has the characteristics of low raw material loss and high degree of completion.

        In this process, parameters such as pressure, temperature and time affect the performance of the ballistic helmet pressed parts. Testers found that the curing pressure affects the resin content, which in turn affects the mechanical properties of the pressed parts, while the curing temperature and curing time mainly affect the melting degree and wettability of the pressed parts.

        After determining the molding temperature and molding time, the testers changed the molding pressure to prepare carbon fiber fabric/polyamide 6 (CFF/PA6) composite materials.

        The results show that by increasing the pressure within a certain range, the wettability and interface strength of the composite material increase, and the mechanical properties are improved. Due to the high efficiency and low energy consumption of the compression molding process, and the stable and reliable performance of the prepared composite materials, this process has developed rapidly and has good application prospects. The schematic diagram of the molding process is shown in Figure 6.