The use of composite materials in aeronautics has brought a step change to the way aircraft are designed and built, mainly with a drive for light-weighting. However, the use of thermoplastic composites, until now has come at a price in terms of manufacturing recurring and non-recurring costs, as well as long lead times and relatively modest production output. Notwithstanding these issues, the use of thermoplastics offers considerable advantages over the more established thermosets. These include avoiding the need for long curing cycles at high temperature and pressure (in autoclaves), and utilising the ability of the thermoplastic to be reheated, which opens the door to alternative manufacturing processes such as induction welding. Thermoplastics also have the benefit that at end of life they can be recycled to produce new polymer materials for other applications.
In order to progress this technology, the Clean Sky 2 programme is developing a large-scale regional aircraft fuselage demonstrator. The TOD project is contributing to this programme by producing a full-scale thermoplastic door, together with its surround and fittings, manufactured using a number of advanced techniques.
The specific objectives of the project were:
• Advance the industrial know-how on the above mentioned thermoplastic technologies
• Develop fast, efficient and reliable automated manufacturing processes
• Assess the weight reduction provided by thermoplastic technologies
• Develop optimum manufacturing solutions (additive manufacturing, Linear friction welding, machining) for manufacture of metallic components in the door locking mechanism
• Build an integrated and complete new Tier 1 supply chain
• Reduce impact cost of Non Recurrent Activities
• Decrease the environmental footprint
The project has been successful in demonstrating that an aircraft door can be manufactured by use of thermoplastic material, supported by a number of innovative techniques for metallic parts still required. This can potentially reduce the environmental footprint of the manufacture by up to 30%
The main gain achieved is the reduced cost for assembling thanks to a semi-automated welding process that can avoid the manual operations of drilling and mechanical fasteners installation.
The second gain is the reduction in waste material using parts produced by Additive Manufacturing techniques, since there is no removed and scrapped material from the original raw material block as produced by mechanical milling (fly-to-buy ratio is near 5% for the latter technique)
The final gain for thermoplastic material use is the reduced cost for manufacturing (no autoclave process) and the weight reduction compared to a conventional aluminium door that is estimated approximately equal to -48% (the main gain is on external skin and intercostals).
There is some additional cost for the thermoplastic door compared to a conventional aluminium door. The cost for production of a single composite door is €90k compared to €48k for the aluminium. However, with an assumed learning curve slope of 87%, the cost of the thermoplastic door reduces to €64k by the production of the 40th door.
