Smart composite patches for aircrafts
When older metallic and newer composite aircraft components become fatigued, cracked or otherwise damaged, repair integrity is critical for passenger and crew safety. Adhesively bonded composite patches with enhanced corrosion resistance and sealing are becoming an important alternative to fastening for interfacing between the patch and the component.EU funding of the project www.iapetus.eu (IAPETUS) revolutionized hot bond field repair through exploitation of carbon nanomaterials in both the patch and the adhesive. Their use enabled a multi-functional repair solution that includes innovative bond curing, curing monitoring and continuous health monitoring of metallic and composite aircraft components.The electrically conductive smart composite repair patches are made of a carbon fibre (graphite) epoxy system with matrix materials containing carbon nanotubes. The latter improves homogeneity of thermal and electrical properties to facilitate homogeneous heating. The team developed two novel curing methodologies — direct resistance and induction heating. The former relies on passage of electrical current and the latter on application of a magnetic field through the electrically conductive carbon fibres and carbon nanotube network. A new generation of adhesives with carbon nanotube additives for improved strength, control of thermal expansion and higher electrical and thermal conductivity enabled direct heating polymerization.Scientists developed sensor technology such as wireless impedance monitoring and infrared thermography. This technology can detect changes in the nanotube network, patch and/or adhesive and compare results to conventional non-destructive inspection techniques. This technology was applied to conventional and newly developed smart patch repairs of both composite and aluminium demonstrators.IAPETUS demonstrated that their revolutionary composite patch repair technology had better patch curing and mechanical loading behaviour than conventional mechanically bolted patches. The solution also decreases the time and costs associated with repairs significantly. With continuous health monitoring, even if a defect does show up, maintenance will be timely and cost-efficient while ensuring the safety of airline passengers. IAPETUS has contributed to environmentally friendly and safe air transport and has globally promoted EU's position in the aerospace sector.
Keywords
Aircraft, structural health monitoring, metallic, composite, patches, carbon nanomaterials, hot bond field repair, direct resistance, induction heating, sensor, impedance, thermography
