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With the exception of high-technology industries such as space and aeronautics, producing composite materials has developed from production of low-technology products manufactured by hand, for example, to automated manufacturing of more advanced products.
Pultrusion is a process for continual production of composite profiles with constant cross sections and material properties which are manufactured for specific purposes. The method ensures consistent quality that can be reproduced. In principle, the process is simple and has been used since the 50s in its basic form.
At Fiberline Composites A/S, pultrusion is done by continual reinforced material being pulled through a guide where the fibres are placed precisely in relation to the profile cross section. The fibres are then led through processing equipment where the fibres are impregnated with the matrix material. The combined mixture of fibres and matrix is pulled on through the heated equipment where the profile is cured in its final geometry. The fully cured profile is then pulled forward to a floating suspended saw which cuts the profiles into defined lengths.
The actual combination of reinforcement in a profile, in other words, the type and number of continual fibres, as well as the type and dimensions of complex weaves and mats are arranged in a way that facilitates visual checking when the fibres and mats are positioned in a profile. Precise positioning of fibres and mats in relation to the cross section of a profile is very important to the properties and qualities of the finished product.
When the reinforcement is pulled into the processing equipment, the matrix is added by injection. Pultrusion by injection is advantageous in controlling and checking the reinforcement, it speeds changing from one profile to another, and eases matrix changes during a process. The degree of impregnation of the fibres is another decisive factor for the properties of the finished product, and the injection method used by Fiberline Composites A/S always ensures the best possible impregnation. The injection method is a fully enclosed process which keeps evaporation of solvents at a minimum. This ensures a good work environment in comparison with traditional pultrusion, in which reinforcement is led through an open vat containing the matrix.
After the fibres are impregnated with the injected matrix, the entire product moves forward to the next zone in the process where heating takes place and where curing of the profile is accelerated. The final curing takes place in the last section of the processing equipment. A profile is thus fully cured and stable in form when it leaves the processing equipment. The pulling power that overcomes friction in the processing equipment
– and thus the driving force in the process – is provided by pullers placed outside the processing equipment. Pulling can be done by either belts or reciprocal pullers. During the last phase of the process, the profiles are shortened by a saw mounted to move at the same speed as the profile being pulled out of the equipment. This ensures a continual process.
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