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Science and technology never cease to amaze with ever more sophisticated solutions on offer. But should it really come as a surprise that Mother Nature can come up with something every bit as effective?
(Published on August-September 2005 – JEC Magazine #19)
It is an accepted fact that natural fibres such as flax and hemp are being increasingly incorporated in composite solutions, notably in the automobile sector. The latest recruit is the fibre from the abaca tree (musa textilis), native to the Philippines and a member of the banana family. The fibres are now being used in a PP thermoplastic application for an exterior panel for the Mercedes A-Class.
The process used is an adaptation of the LFT-ILC process to accommodate the abaca fibres. The natural fibre has been used as a replacement for glass fibre, as it offers similar or even higher performance characteristics. The challenge has been therefore to adapt the LFT process for natural fibres while maintaining fibre length and the correct distribution of fibres in the matrix.
The project brought together three partners: Rieter Automotive Systems of Switzerland played the main role in the processing (including the adapatation of current LFT technology for the new application). DaimlerChrysler AG were responsible for the concept and the product and carried out the first tests on the raw materials; they also took charge of the time-schedule for the common project.
“We discussed with Rieter the idea for an innovation using natural fibres instead of glass fibres. We thought that Rieter was a competent partner to start up a project with, and be able to enlarge our support with its own capacity for development. Also Rieter had the right components in the material equation, so it was a good opportunity for us. We started up the common project with financing including partners and suppliers.
And then there was also another dimension to the whole project – what was happening in the Philippines, because it’s not simply economic, it’s part of a reforestation project there. It’s more than just growing banana plants; it’s part of the reforestation of the rain forest there. The abaca trees grow between the bigger trees and they are cut down after about ten years and so they have got a lot of growth. Now, young trees have got to be planted again in the shade of the bigger trees – so you’ve got this environmental effect which is beneficial for everyone. You’ve got work for the local people there and that’s sustainable too.”
The Manila Cordage Company in the Philippines supplied the natural fibres, working in close cooperation with Rieter concerning the adaptation of the abaca fibres which were necessary for the project’s aims to be reached.
These were basically to achieve savings in terms both of cost and of weight, but the project started out on a purely theoretical basis. No-one could know how well the natural fibres could be incorporated, nor was it possible to know how well the final part was going to behave. The challenge of the project could be seen in two ways: this would be the first exterior application in serial application for the car sector and then it would be the first single-step process with several fibres.
A sustainable project
The sustainable side of the project was also of prime importance. In the Philippines, the fibres are produced in the most ecological way possible; farmers are supported to grow and cultivate the abaca fibres and at the same time, the supply chain is set up from the farmer to the use of the finished part. The farmers are shown how to cultivate; measures are taken to avoid soil erosion and to combat the recurrent landslides provoked by massive deforestation in the Philippines; the local population are guaranteed an income.
The right kind of fibre had to be found and then the process was developed using the chosen fibres. From the fibres, a semi-finished product was created, a roving which had to be transported to Europe. This raised, for instance, the problem of humidity levels during shipping. And in Europe, a great amount of development had to be carried out on the process level and also on the material level from the point of view of the coupling between fibres and plastics and so forth. Thought had to be given to things like additives and the paramaters had to be changed and adapted.
There is no doubt that this has proved to be a highly competitive solution; the abaca fibres have ensured a high-quality product which offers, for instance, greater impact-resistance than glass fibre. Production started last September with a small volume for the Mercedes A-Class model, but now that the process has become an established one, it will no longer be limited to specific applications. At the moment, application is exclusively focused on the automotive sector in Europe, but the technology could quite easily be used elsewhere in the world – in other parts and in other sectors.
“The abaca fibre presents no problems whatsoever. Besides, DaimlerChrysler would never use a fibre if it presented any health hazard, for instance. We checked all that out and we also did a life-cycle analysis of the whole thing and compared it with glass fibres and the abaca fibres showed us a great advantage over glass fibres – about 60% greater impact-resistance.
Work is still being done on improving the process and there are many small details which have to be taken into consideration. You have to be aware that natural fibres have variations in quality and that the rovings are not the same as glass-fibre rovings, for example. There are different weights per metre. At the start we were maybe 10% above the pure matrix regarding properties. We had to go a long way towards optimization in order to meet our standards – and it turned out to be an incredibly long way. We had so many parameters to encroach upon us – humidity control and the like, and the quality of the fibres. There are the same requirements as with glass fibres – and that’s why we have an aluminium heat-shield.”
The innovative process caught the eye of the judges at this year’s JEC Composite Show and the partners were the recipients of a JEC Award in the Ground Transportation category. In their appraisal, the judges underlined the fact that the process gave both sustainable development and technical demands their due.