PSI - Issue 5

Alejandro Carvajal-Castrillón et al. / Procedia Structural Integrity 5 (2017) 729–736 Alejandro Carvajal-Castrillón/ Structural Integrity Procedia 00 (2017) 000 – 000

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Despite 12 different angles of attack were tested, only five distinct operational conditions were identified by the pattern recognition techniques. This happens because of the testing nature: loads were applied in very similar fashions through the complete testing procedures and some angles of attack were close to each other, having similar strain distribution patterns. These results show the capability of the whole system to acquire, send and process strain measurements from FBGs with pattern recognition techniques, being able to separate diverse operational conditions to which the structure can be subjected on a realistic environment. A strain data acquisition system was developed using FBG sensors to measure strains on the composite main beam of an UAV wing using an on-board miniaturized interrogation system. Operational tests showed that the system is capable of measuring strains alongside the beam on different operational conditions. In combination with the acquisition system, an outdoor data transmission subsystem was designed for sending strain information from the UAV to a ground station, using a WLAN with the IEEE 802.11 protocol. This system, by means of a densely packaged request and reply procedure, proved to be fast enough to send strain information while keeping up the sensing speed of the FBG interrogator. Test on the system resulted on short delays between the time the strain is measured on the structure and received on ground. This acquisition and transmission systems are suitable for remote monitoring of the composite structure’s strain field through its complete lifetime operation. Operational tests were performed to the aircraft’s healthy structure on ground, acquiring strain data from the embedded sensors and processing the structural strain distribution over all the tests with an OBS and DS2L-SOM methodology. This experiment resulted in five separated operational conditions, demo nstrating the system’s capability to detect different structural behaviors belonging to the normal operational loads of the aircraft when the structure is in its healthy condition. These developments comprise a system suitable for SHM applications in aerospace composite material components, as it can uncouple the structural operational conditions from its damage state, allowing to potentially perform effective damage detection remotely and during the airframe operation. 5. Conclusions

Acknowledgements

The authors are thankful to the Centro Integrado para el Desarrollo de la Investigación (CIDI) at Universidad Pontificia Bolivariana for funding this project with internal settlement number 636B-06/16-57.

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