Abstract
This contribution demonstrates the functionality of polymer planar Bragg grating (PPBG) sensors integrated into commercial-grade carbon fiber reinforced polymer (CFRP) components. Multiple CFRP specimens are generated by curing a stack of pre-impregnated fibers inside of a heated mechanical press, exposing the polymer sensor to a pressure of 7 bar and a temperature of 120 °C for 2 h. After integration, the sensor still exhibits a strong and evaluable signal. Subsequent flexural experiments reveal a linear response of the integrated sensor’s Bragg wavelength to the CFRP specimen’s maximum deflection. Additional findings demonstrate that the embedded PPBG can be used to detect plastic deformations of a CFRP workpiece, whereas a linear correlation of plastic deformation to the resulting Bragg signal offset is determined. A plausibility check of the obtained results is delivered by a comparison of three-point flexural experiments on bulk CFRP workpieces, without integrated sensors and additional specimens featuring external optical sensors affixed to their surface. It is found that PPBGs based on cyclic olefin copolymers are able to overcome the temperature-related limitations of traditional polymer-based optical sensors and can thus be directly integrated into commercial-grade composites during production.
Highlights
In recent years, the usage of carbon fiber reinforced polymers (CFRP) for lightweight and high-performance applications, such as the aerospace industry and civil engineering, has increased dramatically, since this material class combines excellent mechanical properties with low weight and density [1,2]
This study demonstrates that cyclic olefin copolymers (COC)-based polymer planar Bragg grating (PPBG) can successfully be integrated into commercial-grade CFRP components
According to the authors’ best knowledge, this is the first assessment of a polymer-based optical sensor integrated into a composite structure under environmental influences this harsh
Summary
The usage of carbon fiber reinforced polymers (CFRP) for lightweight and high-performance applications, such as the aerospace industry and civil engineering, has increased dramatically, since this material class combines excellent mechanical properties with low weight and density [1,2]. Their true mechanical behavior cannot be fully represented by classical theories. Immense resources have to be invested for the detection of damage, delamination and material fatigue. While there are several modern and sophisticated approaches for the structural health monitoring of composites [7,8], most damage inspection methods
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