Real-time bonded area in-situ shear stress measurement of double butt strap joints based on FBG center wavelength analyses

One novel method which can achieve real-time bonded area in-situ shear stress measurement of double butt strap joints based on fiber Bragg grating (FBG) center wavelength analyses is proposed in this paper. Theory calculation model of this novel method is established to explain its feasibility. To verify the feasibility, testing experiment on one prototype is carried out. In the fabrication of the testing prototype of the double butt strap joint, four fiber Bragg gratings (FBGi, i = 1, 2, 3, 4) are embedded in the bonded area. After data analyses, shear stress measurement sensitivity coefficients of FBGi (i = 1, 2, 3, 4) show the same trend as theory calculation, and their values are 21.33 pm/MPa, 21.95 pm/MPa, 23.5pm/MPa and 21.2 pm/MPa, respectively. All these data confirm the feasibility and correctness of the novel bonded area in-situ shear stress measurement method.