The growing importance of hybrid pre-forms for lightweight construction
In the last blog we talked about the rising importance of fibre-based composite technologies. The important research establishments in the field of composite technologies along with the manufacturers of weaving, knitting and embroidery machines constantly research new lightweight technologies in the fields of automotive and wind turbine construction. In this regard, hybrid pre-forms are playing an ever bigger role. One of the innovations in terms of machine construction is an embroidery machine from Tajima with which it is possible to manufacture prepregs that are optimised for load force. The University of Bremen Fibre Institute has played a significant role in this development, focussing on the processing of high-grade carbon fibres. These fibres are embroidered onto an inexpensive substrate to create pre-forms close to the final shape required with hardly any production-related carbon fibre waste. What is more: the carbon, high tensile strength fibres, follow precisely the lines of load force flowing through the component, while a second, more cost-effective type of fibre reinforcement provides sufficient strength in areas that are subjected to a lesser mechanical load.
The technology of the hybrid pre-form may still be very young, yet its further development is now already in the offing: tow placement technology in which the carbon fibres act as ‘tow ropes’, while thermoplastic PEEK fibres with an iron-ore based nano-coating act as binder yarn and stabilise the 2D or 3D form without any need at all for tacking threads. In addition, the PEEK fibres are laid by a robotic arm in two or three dimensions and heated by an induction unit just before they are dispensed. So the nano-sized iron ore particles indirectly heat the PEEK rovings which can then be freely formed. This results in pre-forms that are close to the final shape required and which can be processed next by thermoforming or as a structural insert on injection moulding machines. This technology even enables localised thickening at points subjected to a high mechanical load force – without any limitation in terms of the number of layers.
Picture: Expensive fibres are optimally aligned with force flow lines and used sparingly – also in combination with other types of fibres, such as three-dimensional positionable and fixable hybrid fibres with a surface of ferrite nano-particles that can be inductively activated. Copyright: Tajima