Eco-friendly composite aircraft structures
Plastics reinforced with carbon fibres could soon make aircraft structures based on aluminium a thing of the past. Such composites have high strength-to-weight ratio, resulting in high mechanical performance with reduced fuel consumption and emissions. LRI is an innovative manufacturing process for obtaining integrally stiffened panels. The process utilises a dry fibre preform, in which a liquid resin is injected. Scientists compared two different LRI methods with EU funding of the project ACID (Advanced composite integrated skin panel structural testing). The result should be a greener process to produce carbon fibre-reinforced aircraft structures. The project manufactured and tested two geometrically similar wing skin panel coupons to evaluate their performance. Moreover, a third panel with different geometry but same manufacturing technique was tested. The two stiffened panels were made by attaching stiffeners to a thin panel, while the third one was an integrally stiffened panel. The focus was on gathering information on the failure load and mode. The findings should lead to better material and process development. All specimens were compressed to failure. Results demonstrated that despite the LRI manufacturing process used, no detected damage occurred prior to final break. In all cases, linear potentiometers demonstrated similar displacement readings and extensometers measured same stiffness. Except for the conventional measurement systems, ACID also employed distributed systems based on digital image correlation and optic strain measurements. These systems help decrease time and costs associated with strain measurements utilising a large number of strain gauges and rosettes. The use of these advanced systems could help with panel structural testing in other areas making use of composites such as the renewable energy and automotive sectors.
Composite, aircraft structures, liquid resin infusion, skin panel, structural testing