Innovative composite curing
A new method can create aerospace composites with significantly less energy than traditional technology whilst optimising production. The prototype tool produces composite materials of the same standard used in the aerospace industry. Reducing the overall energy use during component production will have a dramatic impact on profitability.
With demand for air passenger transport greater than ever, innovations in aerospace manufacturing will help lower costs and reduce environmental impact.
Background
The Centre for Intelligent Dynamic Communications (CIDCOM) of the University of Strathclyde in partnership with Spirit AeroSystems have developed a prototype surface curing tool where heat is transferred through surface conduction. During the curing process, thermal energy is used to harden polymer resins and bind carbon fibre strands within the composite material. Autoclaves are traditionally used but have high capital costs and energy consumption.
Surface curing differs by transferring thermal energy into the composite material from a heated surface. Up to 30% less energy compared to autoclaves for an equivalent composite component can be achieved using surface curing.
Smart cure tracking
Whilst the prototype tool is able to reduce the amount of energy required to create a given composite part, its real innovation is the ability to optimise the manufacturing process. The tool achieves this by tracking the exothermic response of the polymer resin during curing.
These thermosetting resins require significant thermal energy input before the chemical structure begins to harden into the desired strong form. During this process, the polymer will emit significant heat, lowering the energy requirement to maintain a given temperature. This reduction was successfully tracked using a combination of sensitive hardware and signal processing algorithms that targeted the change.
By using a large number of discrete heaters embedded within the tool surface and temperature sensors for feedback, a customised heating profile could be generated for composite components with different sizes and shapes. Microcontrollers were used to control individual heaters grouped into larger zones but also relayed data to a single computer to allow centralised management of the manufacturing process.
Dynamic scanning calorimetry testing was used to validate that the test components reached the required standard of cure to be used within the aerospace industry.
Future work
The next stage in the collaboration between CIDCOM and Spirit AeroSystems is to increase the size of the tool and develop a flexible surface to allow more complex components to be created. With increased size comes increased complexity for control, so a large portion of research will need to be devoted to building an effective communication system. With the successes of the initial stages, it is believe that further innovations will allow improved and greener composite manufacturing.