Process analysis of PMI foam sandwich structure
PMI structural foam have outstanding resistance to compression creep. The specific strength and specific stiffness of the PMI foam make the material have good performance. The PMI foam has compression and creep resistance, which makes the material also have good process performance. Generally, for foam sandwich structures, the processes that can be used are:
1. Molding process: The molding process is characterized by relatively high mold cost, the advantage is that the thickness and size of the composite material can be accurately ensured, and the components with two smooth surfaces are simultaneously provided. Components that typically use the molding process include flight control components, helicopter rotors, sports equipment, and medical bed plates. In the molding process, by imparting a certain amount of interference to the foam core material, the interference provides a counter pressure to the curing of the panel during the mold clamping curing process. The compression creep resistance of PMI foam is the premise and guarantee for the conversion of interference into back pressure. It can be adjusted according to the resin content of the laminate, the curing system, the thickness of the panel, and the back pressure. Meet the requirements of curing pressure.
2. Autoclave process: The autoclave process is characterized by a hard mold and a soft mold (vacuum bag). The composite laminate in the solidification is pressurized by vacuuming and pressurization in the autoclave. If a co-curing process is used, that is, the curing of the carbon fiber composite panel, the bonding of the sandwich structure core material and the panel is completed at one time. PMI foams have smaller voids than honeycombs and provide adequate support for panel curing without the telegraph effect of honeycomb panels.
3, RTM process: liquid resin injection is a relatively new optimized manufacturing process, with the help of RTM (resin transfer mold) technology, the production of high-performance sandwich structural members. The purpose is to simplify the production process, reduce manufacturing costs, and save the price of raw materials. The use of a relatively low-priced cloth with good lay-up properties enables mass production and the use of high-quality prepregs. If the pores of the honeycomb are sealed so that the low-viscosity injection resin does not flow into the honeycomb pores, the honeycomb can also be selected as the sandwich material in the RTM manufacturing process. However, if a sandwich structure composite is produced using the RTM process, a foam core is generally used. The PMI foam is the same as the autoclave process. The core material also needs to have good compression creep resistance, which meets the requirements of resin injection pressure and injection temperature.
1. Molding process: The molding process is characterized by relatively high mold cost, the advantage is that the thickness and size of the composite material can be accurately ensured, and the components with two smooth surfaces are simultaneously provided. Components that typically use the molding process include flight control components, helicopter rotors, sports equipment, and medical bed plates. In the molding process, by imparting a certain amount of interference to the foam core material, the interference provides a counter pressure to the curing of the panel during the mold clamping curing process. The compression creep resistance of PMI foam is the premise and guarantee for the conversion of interference into back pressure. It can be adjusted according to the resin content of the laminate, the curing system, the thickness of the panel, and the back pressure. Meet the requirements of curing pressure.
2. Autoclave process: The autoclave process is characterized by a hard mold and a soft mold (vacuum bag). The composite laminate in the solidification is pressurized by vacuuming and pressurization in the autoclave. If a co-curing process is used, that is, the curing of the carbon fiber composite panel, the bonding of the sandwich structure core material and the panel is completed at one time. PMI foams have smaller voids than honeycombs and provide adequate support for panel curing without the telegraph effect of honeycomb panels.
3, RTM process: liquid resin injection is a relatively new optimized manufacturing process, with the help of RTM (resin transfer mold) technology, the production of high-performance sandwich structural members. The purpose is to simplify the production process, reduce manufacturing costs, and save the price of raw materials. The use of a relatively low-priced cloth with good lay-up properties enables mass production and the use of high-quality prepregs. If the pores of the honeycomb are sealed so that the low-viscosity injection resin does not flow into the honeycomb pores, the honeycomb can also be selected as the sandwich material in the RTM manufacturing process. However, if a sandwich structure composite is produced using the RTM process, a foam core is generally used. The PMI foam is the same as the autoclave process. The core material also needs to have good compression creep resistance, which meets the requirements of resin injection pressure and injection temperature.
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