In RTM forming process, the fiber reinforced material must first be made into the same shape of the processed products.
The process of preforming the fiber and its fabric is called preforming, and the preformed fiber and fabric preform are called fillers.
There are three kinds of preforming process: stitching, spraying and stamping.
Stitching
The processing cost of preformed material mainly depends on the application field of processing products.
In the case of aerospace and aviation, the RTM molding products used in this field are usually made by cutting a seam, and other RTM products are also used.
But only for the production of small products.
Spraying
The preparation of larger preforming materials requires faster process, such as cutting fiber beam spraying technology.
Spraying technology makes large preforming materials fast, i.e. a preform per minute.
However, the mechanical properties of composites are affected by cutting fiber bundles.
In order to solve this problem, a new technique for spraying continuous circular shape fiber bundles or continuous oriented fiber bundles is developed.
Stamping
In the stamping process, the reinforced materials used are continuous and random glass fiber bundle felt, and the fiber is in a centrifugal configuration.
It can be coated with thermosetting resin and set it together after stamping.
Preforming process design
According to preforming process design, the second and third steps can be changed. Because of the use of fiberglass reinforced epoxy composite materials, this mold is less conductive than the metal mold, so the cooling rate is slow.
If the hole is used, the cooling speed will be accelerated.
Blank preforming
There are two kinds of preforming methods for the blank of bag pressure forming, as described below.
1. Hand Lay up forming method use Yin molding.
2. Mechanized forming.
The preforming machine is used to make blank, as shown below.
This method is suitable for making products with complex shapes and sizes.
Production preforming billet, the first to use glass fiber roving cutter, 2, 3, cut the growth of around 50 mm long fiberglass. In order to guarantee the billet has enough strength which not spread out in the process of handling, spray forming process to a certain number of water soluble resin adhesive glue agent, commonly used adhesive amount is 5% of the resin matrix, the production of pervious to light composite light shade and must choose the light transmittance does not affect of adhesive products.
