Preforms made by the Overbraiding Technique
• Overbraiding is the technique used to produce net shape cost-effective structural preforms.
• During overbraiding the braid is placed directly onto a core, which has the inner geometry of the desired preform.
• By reciprocating the core through the braiding point a pre-selected number of layers can be braided to obtain the desired wall thickness/aerial weight.
• The lightweight core can remain in the product or a lost core technique can be used for production of a hollow product.
Benefits of Overbraiding
• Cost effective method and low waste rates (5-10%).
• Reproducible due to computer control and automated processes.
• Time saving compared to building your own preforms manually.
• Braiding angles are programmable from 15° to 80°.
• 0° (UD) yarns can be integrated to form a tri-axial braid.
• The ratio between bias and UD can vary from 100/0 up to 15/85.
• Hybrids are possible in the bias and in the UD direction.
• Excellent energy absorption in crash structures. Braided structures act as crack stoppers.
• Braided structures have a good resin permeability.
• Eccentric products are possible, even banana shaped preforms.
• Preforms injected with the RTM process can have a fiber volume fraction of 55%.