From prepreg to final parts, carbon fiber composite materials need to be processed by molding process. There are five main production processes for carbon fiber tubes. They are:
1.Rolling Process
Rolling processes often use prepreg products to ensure consistency. Prepreg is a composite product consisting of fabric or fibers that have been impregnated with the epoxy resin necessary to bond everything together.
The prepreg material is cut into layers with different fiber orientations. The layers are then rolled onto cylindrical rods called mandrels. The mandrel and prepreg are then wrapped in plastic film to contain the epoxy and compress the layers during curing. After curing is complete, the mandrel is removed from the center of the finished tube.
2.Winding Process
The tow is loaded onto multiple spools behind the winder. The front is a long mandrel, in the form of tubing. To make the tubing, a carriage travels up and down the length of the machine while the mandrel rotates. The tow is applied to the mandrel in a spiral pattern, like the stripes on a candy cane. The texture of the spirals and the number of spirals required to make a layer can be adjusted. Once fully formed, the tube is cured before being separated from the mandrel.
3.Pultrusion Process
The pultrusion process is so named because it combines the principles of pultrusion and extrusion. Extrusion is formed by pushing, forcing material through a die; pultrusion is formed by pulling material through a die. Pultruded tubes are made by pulling carbon or glass fiber strands through a heated die while dipping in epoxy. The material is pulled through a mandrel to ensure it retains its shape during curing.
4.Compression Molding
The carbon fiber prepreg is placed between the upper and lower molds, and the mold is placed on the hydroforming table. After a certain period of high temperature and high pressure to solidify the resin, the carbon fiber product is removed. This molding technology has the advantages of high efficiency, good product quality, high dimensional accuracy, and less environmental impact, and is suitable for the molding of mass and high-strength composite parts.
5. Vacuum autoclave
The composite material blank formed by laying up a single layer of prepreg in a predetermined direction is placed in an autoclave, and the curing process is completed under a certain temperature and pressure. An autoclave is a special pressure vessel that can withstand and regulate a certain temperature and pressure range. The blank is laid on the surface of the mold with release agent, and then covered with porous release cloth (film), absorbent felt, and air felt in sequence, sealed in a vacuum bag, and then placed in an autoclave. Before heating and curing, vacuum the bag to remove air and volatiles, and then heat up, pressurize and cure according to the curing system of different resins. The formulation and implementation of the curing system is the key to ensuring the quality of autoclaved parts.