Process of PMI foam sandwich structure:
1. Molding process: The characteristic of the molding process is that the cost of the mold is relatively high. The advantage is that it can accurately ensure the thickness and size of the composite material; at the same time, it has two components with smooth surfaces. Components commonly used in the molding process include flight control components, helicopter rotors, sports equipment and medical bed plates. In the molding process, by giving the foam core a certain amount of interference, during the mold clamping and curing process, the interference provides a back pressure to the curing of the panel. The compression creep resistance of PMI foam is the premise and guarantee for the change of interference into back pressure. You can adjust the amount of back pressure by setting the appropriate interference, according to the resin content of the layer, curing system, panel thickness, Meet the requirements of curing pressure.
2. Hot-pressing process: The hot-pressing process is characterized by one side hard mold and one side soft mold (vacuum bag). By evacuating and pressurizing in the autoclave, the composite laminate under pressure is pressurized. If a co-curing process is used, the curing of the carbon fiber composite panel and the bonding of the core material of the sandwich structure and the panel are completed at once. The pores of PMI foam are smaller than those of honeycomb, which can provide sufficient support for the curing of the panel, and there will be no telegraph effect like honeycomb structure panel.
3. RTM process: Liquid resin injection is a relatively new optimized manufacturing process. With the help of RTM (resin transfer injection molding) technology, high-performance sandwich structural members are produced. The purpose is to simplify the production process, reduce manufacturing costs, and save the price of raw materials. The use of relatively low-cost fabrics with good draping performance can achieve mass production, and the components can achieve the effect of using high-quality prepregs. If the pores of the honeycomb are sealed to prevent low-viscosity injection resin from flowing into the pores of the honeycomb, in the RTM manufacturing process, the honeycomb can also be selected as the sandwich material. However, if the RTM process is usually used to produce the sandwich structure composite material, the foam core material is generally used. The process of PMI foam and autoclave is the same, and the core material also needs to have good compression creep resistance to meet the requirements of resin injection pressure and injection temperature.