Ebalta introduces Fibretemp, a new innovative manufacturing technique

ebalta-fibretempEbalta presents a new innovative manufacturing technique, Fibretemp. Fibretemp is a process that involves electrically heating a composite mould, allowing the production of composite parts, either through the use of a resin infusion system, resin filled carbon fibre prepreg or standard wet layup procedures, without requiring heating or post-curing in a large scale oven or autoclave.

The process is ideal for big moulds with a large surface area, as the system offers a very productive, energy efficient and cost effective solution.

Specific arrangement Most processes for fabricating composite parts require heating. Different methods for heating moulds have been tried for many years, but have typically run the risk of short circuits and warpage of the moulds due to non uniform heating. With Fibretemp, these problems have been overcome by the specific arrangement of the carbon fibres and integrated construction of the area to be heated, which is positioned close to the surface of the tool.

The operating principle is very simple. It uses standard carbon fibres which are electrically conductive but when compared with a metal such as copper wire, the electrical resistance is many times higher, so if energized, the carbon fibres heat up due to this electrical resistance. Instead of using single fibre strands, complete fibre patterns are used as heating elements, providing a 2-dimensional structure.

Fibres positioned parallel to current flow act as conductors whereas transverse fibres distribute current over the entire surface, leading to uniform temperature distribution all over the mould surfaces. A flexible copper strip is fed into each side of the mould which is connected to the control module, a low voltage transformer, allowing the heating of the mould surfaces to be controlled.

The composite moulds can be produced from a number of different ebalta laminating resins including LH 26, LH 28-1 or LH 30 depending on the heat required in the mould, which is determined by the final composite part requirements. The carbon laminates, which form the surface structure as well as the heating element, are quite thin with wall thicknesses of 0.5 mm on small moulds and up to 5 mm on large moulds. Moulds are typically built as a sandwich structure, so the core increases the wall thickness and the flexural strength, which serves as insulation to keep the heat inside the mould. This way, the temperature remains where it is required, on the mould surface, to heat the mould and cure the resin infusion or prepreg material.

The key advantages of Fibretemp include shorter demoulding times for increased productivity, energy savings as no oven or autoclave is required and a safe working environment as only low voltages are applied to the tool. Moreover, the heating element matrix of carbon fibre ensures full heating functionality with virtually no heat loss even if some of the carbon fibres within the mould become damaged. No investment in ovens is required for the production of large moulds and big lightweight moulds can be built. Finally, as the tool surfaces are heated, the resin flow improves within the mould ensuring the production of accurate, high-quality composite parts.

Fibretemp is a joint development between ebalta and partners Prof. Dr. Funke of the Fachhochschule Dortmund and Dipl. -Ing. Jens Brandes of Fibretech Composites. It has already been trialled and proven for use in both wind turbine and aerospace applications.


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