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New photonic composite materials for aircraft applications
|Piotr Lesiak 1, Tomasz Toliński 1, Andrzej W. Domański 1, Anna Boczkowska 2
1. Warsaw University of Technology, Faculty of Physics, Koszykowa 75, Warszawa 00-662, Poland
In the past decade, advanced composite materials have been widely used in a variety of load-bearing structures such as rotor blades, aircraft fuselage and wing structures. The unique properties of composite materials such as their high strength-to-weight ratio, high creep resistance, high tensile strength at elevated temperatures and high toughness have been attracting increasing interest in numerous automotive, aerospace, and sports applications.
Composite structures are frequently subjected to external excitations over a variety of vibration frequency ranges. Such a dynamic interference may cause the structures to suffer from fatigue damage and/or catastrophic failures. A typical composite material fails in a sequence of transverse micro-cracking, delamination and fiber failure. Non-destructive evaluation (NDE) techniques have been developed to detect internal or invisible damage. To the traditional NDE techniques belong: ultrasonic scan, an eddy current method, an X radiography, an acoustic emission method, and passive thermography. The NDE techniques are effective in detecting damages in materials and structures, but it is difficult to use them in operation due to the size and weight of the devices. Therefore, there is a strong interest in development of smart composite structures with integrated optical fiber sensors which would allow in-situ monitoring of both the manufacturing process and the service life. Compared to the traditional NDE techniques, fiber-optic sensors offer unique capabilities as: monitoring the manufacturing process of the composite parts, performing non-destructive testing once fabrication is complete, and enabling health monitoring and a structural control. Due to their minimal weight, small size, high bandwidth, high sensitivity, immunity to electromagnetic interference, possibility to operate in a hazardous environment and in the presence of electric currents fiber-optic sensors offer significant performance advantages over traditional sensors.
Composite structures are made of two or more components. This feature allows for introducing optical fiber sensors into the composite material. Typical optical fiber sensors are based on highly birefringent fibers where the output signal is a periodic function of the external strain or on fiber Bragg gratings where the output signal is a linear function of the external strain but this type of the fiber needs an additional equipment to encode the output signal. Due to a variety of sensing fibers and different responses to external perturbations there are a lot of possibilities to construct fiber-optic strain gauges precisely adjusted to particular needs and applications.In our research many types of the fiber optic sensors embedded in the composite materials have been investigated. We observed that interactions between composite material and optical fibers during manufacturing process are very significant. Lamination process can dramatically change strain sensitivity of the highly birefringent fibers. By using soft coatings of the optical fibers we protect them against stress introduce to the composite materials during manufacturing process. Additionally this research allows us to propose the new hybrid fiber optics sensing system which can measure separately temperature and strain.
Presentation: Oral at Nano and Advanced Materials Workshop and Fair, by Piotr Lesiak
See On-line Journal of Nano and Advanced Materials Workshop and Fair
Submitted: 2013-07-10 10:16 Revised: 2013-07-10 10:16