Adhesive

Materials science

Shear (geology)

Optical fiber

Layer (electronics)

Shear stress

Fiber optic sensor

Wavelength

Structural health monitoring

Physical chemistry

Polarization (electrochemistry)

Physics

Optics

Composite material

Fiber

Chemistry

Polarization-maintaining optical fiber

Birefringence

Optoelectronics

Fiber Bragg grating

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

The application of shear stress sensors in structural health monitoring remains limited because current sensors are either difficult to implement, they feature a low measurement resolution or the interrogation of the output signal is complex. We propose to use fiber Bragg grating-based sensors fabricated in dedicated highly birefringent microstructured optical fibers. When embedded in a host material, the orientation angle of the fiber should be chosen such that their polarization axes are aligned parallel with the direction of maximum shear stress when the host is mechanically loaded. We present experimental results of sensors embedded in the adhesive layer of single lap and double lap structural joints. These tests demonstrate that when the joints are tension loaded, the embedded sensors have a shear stress sensitivity of around 60 pm/MPa. We study the influence of the adhesive material on the sensor response, as well as the influence of sensor orientation and location in the bond line. Finally, we demonstrate the minimal thermal cross-sensitivity of the shear stress sensitivity of this sensor.

Fiber Bragg grating-based shear strain sensors for adhesive bond monitoring