Main defects and countermeasures of RTM products
The quality of the composite depends mainly on the following characteristic porosity: the content of bubbles or voids in the composite must be lower than the value allowed by the structural design. Compaction level: resin content, fiber volume content and related distribution gradients. Curing degree: Formation of polymer resins and their structures. Fiber Direction: Meet the design requirements. Interface bonding: degree of bonding between resin and fiber. Improper die design, low manufacturing quality of preform and unreasonable selection of process parameters will lead to various defects of RTM parts.
The defects reduce the quality of the composites, which is reflected in the mechanical properties, the apparent quality and the resistance to environmental humidity and heat. Bubble, dry spot and rich resin area are the main defects of RTM products. It is necessary to understand the formation mechanism of these typical defects so as to take appropriate measures during the implementation of RM process, restrain or eliminate these defects to improve the quality of RTM parts.
Theoretically, there are 5 reasons for void or dry spot:
1. Too much air is brought into the cavity when resin is injected, and there is no effective discharge during the injection.
2, the resin viscosity is too big, the bubble flow slowly, in the injection time is very difficult to emerge from the end of the product to form a gap.
3, resin injection pressure is too high, so that the bubble is wrapped in the resin can not be expelled.
4. The gate of the mould is not set up reasonably, and the gate switch is not set properly in the process of process implementation, which leads to the formation of weld mark on the resin flow front.
5, resin curing reaction exothermic too high, so that curing time is too short, so that the gas in the cavity is difficult to discharge.
