Debonding is one of the most important damage forms in fiber-reinforced composite structures. This work was devoted to the debonding damage detection of lap splice joints in carbon fiber reinforced plastic (CFRP) structures, which is based on guided ultrasonic wave signals captured by using fiber optic Doppler (FOD) sensor with spiral shape. Interferometers based on two types of laser sources, namely the He-Ne laser and the infrared semiconductor laser, are proposed and compared in this study for the purpose of measuring Doppler frequency shift of the FOD sensor. Locations of the FOD sensors are optimized based on mechanical characteristics of lap splice joint. The FOD sensors are subsequently used to detect the guided ultrasonic waves propagating in the CFRP structures. By taking advantage of signal processing approaches, features of the guided wave signals can be revealed. The results demonstrate that debonding in the lap splice joint results in arrival time delay of the first package in the guided wave signals, which can be the characteristic for debonding damage inspection and damage extent estimation.
Ball, A. Structural health monitoring: current European project on operational reliability. Proceedings of WEAG/NATO Joint Workshop on Structural Health Monitoring, La Hague, France, 7–8 Octorber 1997.
[3]
Grondel, S.; Assaad, J.; Delebarre, C.; Moulin, E. Health monitoring of a composite wingbox structure. Ultrasonics？2004, 42, 819–824, doi:10.1016/j.ultras.2004.01.058. 15047390
[4]
Staszewski, W.J.; Lee, B.C.; Traynor, R. Fatigue crack detection in metallic structures with Lamb waves and 3D laser vibrometry. Meas. Sci. Technol？2007, 18, 727–739, doi:10.1088/0957-0233/18/3/024.
[5]
Takeda, N.; Okabe, Y.; Kuwahara, J.; Kojima, S.; Ogisu, T. Development of smart composite structures with small-diameter fiber Bragg grating sensors for damage detection: Quantitative evaluation of delamination length in CFRP laminates using Lamb wave sensing. Compos. Sci. Technol？2005, 65, 2575–2587, doi:10.1016/j.compscitech.2005.07.014.
[6]
Giurgiutiu, V. Tuned lamb wave excitation and detection with piezoelectric wafer active sensors for structural health monitoring. J. Intel. Mat. Syst. Struct？2005, 16, 291–305, doi:10.1177/1045389X05050106.
Kim, Y.; Ha, S.; Chang, F.K. Time-domain spectral element method for built-in piezoelectric-actuator-induced lamb wave propagation analysis. AIAA J？2008, 46, 591–600, doi:10.2514/1.27046.
[9]
Lu, L.; Ye, L.; Su, Z.; Yang, C. Quantitative assessment of through-thickness crack size based on Lamb wave scattering in aluminium plates. NDT. E. Int？2008, 41, 59–68, doi:10.1016/j.ndteint.2007.07.003.
Tsuda, H. Ultrasound and damage detection in CFRP using fiber Bragg grating sensors. Compos. Sci. Technol？2006, 66, 676–683, doi:10.1016/j.compscitech.2005.07.043.
[12]
Kageyama, K.; Murayama, H.; Uzawa, K.; Ohsawa, T.; Kanai, M.; Akematsu, Y.; Nagata, K.; Ogawa, T. Doppler effect in flexible and expandable light waveguide and development of new fiber-optic vibration/acoustic sensor. J. Lightwave Technol？2006, 24, 1768–1775, doi:10.1109/JLT.2005.863331.
[13]
Yashiro, S.; Okabe, T.; Takeda, N. Damage identification in a holed CFRP laminate using a chirped fiber Bragg grating sensor. Compos. Sci. Technol？2007, 67, 286–295, doi:10.1016/j.compscitech.2006.08.004.
Betz, D.C.; Thursby, G.; Culshaw, B.; Staszewski, W.J. Advanced layout of a fiber Bragg grating strain gauge rosette. J. Lightwave Technol？2006, 24, 1019–1026, doi:10.1109/JLT.2005.862442.
[16]
Park, H.J.; Song, M.H. Linear FBG temperature sensor interrogation with Fabry-Perot ITU multi-wavelength reference. Sensors？2008, 8, 6769–6776, doi:10.3390/s8106769.
[17]
Li, F.C.; Murayama, H.; Kageyama, K.; Shirai, T. Doppler effect-based fiber-optic sensor and its application in ultrasonic detection. Opt. Fiber Technol？2009, 15, 202–303.
[18]
Li, F.C.; Murayama, H.; Kageyama, K.; Shirai, T. Guided wave and damage detection in composite laminates using different fiber optic sensors. Sensors？2009, 9, 4005–4021, doi:10.3390/s90504005. 22412347
[19]
Li, F.C.; Su, Z.Q.; Ye, L.; Meng, G. A correlation filtering-based matching pursuit (CF-MP) for damage identification using Lamb waves. Smart. Mater. Struct？2006, 15, 1585–1594, doi:10.1088/0964-1726/15/6/010.
[20]
Li, F.C.; Meng, G.; Kageyama, K.; Su, Z.Q.; Ye, L. Optimal mother wavelet selection for lamb wave analyses. J. Intel. Mat. Syst. Struct？2009, 20, 1147–1161, doi:10.1177/1045389X09102562.
