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Robust Polymer Planar Bragg Grating Sensors Embedded in Commercial-Grade Composites
Stefan Kefer1, Theresia Sauer2, Steffen Hessler1
1Applied Laser and Photonics Group, Aschaffenburg University of Applied Sciences, Wuerzburger Strasse 45, 63743 Aschaffenburg, Germany.
Polymers
|March 27, 2020
Summary
Polymer planar Bragg grating (PPBG) sensors can be embedded directly into carbon fiber reinforced polymer (CFRP) components during manufacturing. These integrated sensors accurately measure deflection and detect plastic deformations in CFRP materials.
Area of Science:
- Materials Science
- Optical Engineering
- Composite Materials
Background:
- Traditional polymer-based optical sensors face limitations due to temperature sensitivity.
- Integrating sensors directly into composite materials during production is challenging but desirable for structural health monitoring.
Purpose of the Study:
- To demonstrate the functionality and performance of polymer planar Bragg grating (PPBG) sensors integrated into commercial-grade carbon fiber reinforced polymer (CFRP) components.
- To evaluate the sensor's response to mechanical loading, including deflection and plastic deformation.
- To assess the suitability of PPBG sensors for in-situ monitoring during composite manufacturing.
Main Methods:
- CFRP specimens were fabricated with integrated PPBG sensors using a heated mechanical press (7 bar, 120 °C for 2 h).
- Flexural experiments were conducted to measure the Bragg wavelength shift in response to specimen deflection.
- Plastic deformation detection was analyzed by correlating Bragg signal offset to deformation levels.
- Results were validated by comparing with experiments on CFRP without integrated sensors and with externally attached sensors.
Main Results:
- Integrated PPBG sensors maintained a strong, evaluable signal after the curing process.
- A linear relationship was observed between the sensor's Bragg wavelength and the CFRP specimen's deflection.
- The embedded PPBG sensors successfully detected plastic deformations, showing a linear correlation between deformation and Bragg signal offset.
- PPBG sensors based on cyclic olefin copolymers demonstrated resilience to temperature-related limitations.
Conclusions:
- PPBG sensors can be successfully integrated into commercial-grade CFRP components during manufacturing.
- The integrated sensors provide reliable measurements of deflection and plastic deformation.
- PPBG sensors offer a promising solution for structural health monitoring in composites, overcoming temperature limitations of conventional optical sensors.
