CORDIS - Forschungsergebnisse der EU

Multifunctional Fibre Nano Composites

Final Report Summary - MUFIN (Multifunctional Fibre Nano Composites)

The general objective of MUFIN was the integration of macroscopic fibres made of Carbon NanoTubes (CNT) in polymer composites, in a way that their mechanical, electrical, electronic and piezoelectric properties are exploited on a macroscopic length-scale. As such, the project has spanned from the synthesis of molecularly-controlled fibres, up to their integration in 100 x 100 cm2 structural laminate composites. The results obtained provide a comprehensive route for the industrial implementation of these new high-performance fibres in selected formats and applications. A guiding objective throughout the project has been to reduce weight and fabrication costs/time of materials used in transport, with the associated benefits for the competitiveness of the European composite sector and the potential reduction in greenhouse gas emissions.

The initial stages of the project involved setting up a reactor to produce continuous macroscopic fibres of CNTs. After chemical engineering optimisation this facility can reducibility produce uniform fibres at rates above 50m/min and in comparatively large amounts > 10km/day. Such development has been critical to produce large samples consisting of arrays of fibres, e.g. unidirectional sheets, integrate them into polymer matrices using semi-industrial composite fabrication techniques and carry out a meaningful assessment of their performance.

A further output of MUFIN has been the discovery that various group 16 elements can be used as promotors for the growth of CNT fibres, and an understanding of their role in controlling the number of layers and general morphology of the constituent CNTs. The research group has provided tools to produce continuous fibres of predominantly singlewalled or multiwalled nanotubes and the corresponding theoretical framework to extend this knowledge for further control of the chemical vapour deposition reaction. This molecular control has been instrumental in exploiting the low-dimensional properties of CNT on a macroscopic scale, for example for energy storage.

The research in MUFIN has also explored the piezoresistive and chemoresistive properties of CNT fibres. Our results show that chemoresistance is driven mainly by molecular adsorption and its effects on the transport properties of the individual CNTs. An analytical model to describe electrical resistance changes upon liquid and polymer infiltration has been developed. As a demonstration of the sensing capabilities of the fibres and the predictive capability of the models, we have integrated CNT fibre sensors in a fibre lay-up and monitored the fabrication of a laminate composite by vacuum infusion. The sensor could accurately predict the flow of the polymer front. The detection of matrix gelation and other piezoresistve effects were also demonstrated. As a further implementation of this technology, CNT fibre sensors were integrated into the UC3M SAE Formula racing car. These results pave the way for the development of CNT fibre-based sensors to control composites at the point of manufacturing and for structural health monitoring and damage detection in service.

With the view that composites containing CNT fibres will soon be produced on a large scale and used for initial niche applications, we have carried out a study on the reinforcement mechanisms in these fibres. In particular, their large porosity (>20%) implies that the polymer phase infiltrates the fibres and changes their mechanical properties compared to the dry polymer-free material. MUFIN has provided a first model to describe the mechanics of this system and its implications for polymer matrix selection.

Either as sensors or thin sheets, materials of CNT fibres have been integrated in hybrid composites containing CF-lamina. As part of MUFIN we have explored different processing routes and the corresponding interfacial microstructure and interlaminar properties. These hybrid composites are seen as an attractive first embodiment to exploit the properties of CNT fibres in structural composites.

The multifunctional nanocomposites group is working in continuing this research, extending it to new areas and is actively involved in collaborating with partners to pave the way for the industrial implementation of CNT fibres. For more details contact