The BULCANATU project wanted to develop feasible techniques for advanced and cost-effective composite manufacturing of aviation parts. The development of new epoxy resin Carbon Nanotube doping techniques compatible with Liquid Resin Infusion will open a new era on fabrication of aerospace parts with improved mechanical properties, thanks to nanoparticles. Future aircraft manufactured with doped CNT epoxy resins, would be the increase on electrical conductivity that could lead to the removal of copper lightning protection mesh of advanced composite fuselage.
The main issues to overcome were the dispersion and stability of the CNT over the epoxy resin, filtration phenomena within the infusion process, and the manufacture of high-performance composite parts under “out of autoclave” conditions at greater viscosities than expected. Thanks to the joint venture between TR Composites and the Universidad Rey Juan Carlos, all aspects of the call were covered with wide experience to achieve good results.
This project had been performed between Technical & Racing Composites S.L. (project leader, TR from now on) and Universidad Rey Juan Carlos (project partner, URJC from now on).
The project objective was to investigate and develop a method to manufacture a composite bulkhead (D=2250mm) with the Liquid Resin Infusion system using a Carbon Nanotube doped Resin System. For this purpose a number of research activities were developed. Those can be summarised as follows:
- Research on Doped Resins (leaded by URJC).
- Research on Process Development (leaded by TR).
Current State of Art of aerospace composite structures show two main electrical conductivity requirements as a result of the isolation behaviour of composite materials (due to the resin):
- Lightning Strike Protection: the industry uses external layers (whose thickness depends on a zonation of the aircraft) to allow a proper dissemination across the structure of the energy of lightning strikes.
- Electrical Bonding: electrical and electronic equipment, as well as metallic systems such as high pressure hydraulic lines (normally manufactured with titanium) or other systems like actuators, etc. need an electrical bonding network (a global network on the inner side of all composite aerostructures) made of aluminium strips riveted or bonded to the structure and metallic cables that perform the static current discharge from the systems to the strips.
The objective of doping a resin with carbon nanotubes was to increase the electrical conductivity of the composite material, in order to explore applications that could comply with the mentioned electrical requirements. However, one of the technical issues of doped resin was achieving a proper distribution of the nanotubes and keeping a low viscosity to allow infusion of a dry preform. This, of course, limited the concentration of nanotubes and thus the resulting electrical conductivity.
The Bulcanatu project investigated a resin system doped with nanotubes that was suitable for production at large scale and able to be infused, and also to apply such resin on the development of a full-scale demonstrator of an aircraft structure. Rear Pressure Bulckhead of an A320 size aircraft with integrated omega stringers was the part selected.