To achieve this goal, the project consortium has conducted an extensive experimental characterization of different natural fibres, resins and eco-composites, and analysed possible enhancements (mechanical, electro-magnetic, flammability, etc.) of these eco-composites with different techniques. Besides improving the existing knowledge about eco-composites, in order for these to be a real alternative to synthetic composites, it was also necessary to have analysis and simulation tools capable of representing accurately their performance, in order to ensure that the structures designed with them comply with the required security and functionality standards.
Natural fibres flax and ramie were used for different types of reinforcements like fabric and nonwoven. Honeycomb sandwich cores with wood fibres substituting a part of the aramid fibres were successfully tested. Substitution of bisphenol-A based epoxy resins in secondary structures by partly bio-based epoxy resins was investigated with promising results. Material protection technologies were studied to reduce environmental influence and improve fire resistance. Modelling and simulation of chosen eco-composites optimised the use of materials while the Life Cycle Assessment aimed to investigate the ecological advantages compared to synthetic state-of-the-art materials.
Based on the current results with the materials considered in ECO-COMPASS, partly bio-based epoxy resin systems have the highest potential for a successful application in aviation. Their properties approach the performance of the fully petrol-based epoxy resins used today. Another promising group of thermoset bio-based resin, furan, has not been considered in ECO-COMPASS, but needs to be mentioned here for the very good fire properties comparable to classic phenolic resins. As a conclusion, thermoset bio-based resins show high potential to be applicable in aircraft secondary structure (epoxy) and interior (furan).
Natural fibres such as ramie, flax and sisal have a high potential for weight reduction due to their low density and good damping properties. However, their long-term behaviour (ageing) and mechanical properties need to be further improved. Potential technologies are under development, e.g. CNC coating, plasma treatment and hybridization with rCF. Fire properties are still an obstacle for the use of natural fibres in the interior. While flammability and toxicity are already under control, the heat release and smoke density properties need further improvement. On the other hand, the Green Honeycomb (GHC) with small amount of natural fibre mixed with classic aramid fibre can be another technology with high potential for the introduction of bio-based materials in aviation composite structures. Its long-term stability (humidity, etc.) needs to be validated in further tests. Nevertheless, the GHC may be used for secondary and interior structures because of its good fire and mechanical properties.
