Real-time Detection of Debonding between Honeycomb Core and Facesheet using a Small-diameter FBG Sensor Embedded in Adhesive Layer

Abstract

The authors have developed a novel technique to detect debonding in honeycomb sandwich structures using small-diameter fiber Bragg grating (FBG) sensors. A small-diameter FBG sensor is embedded in the adhesive layer between the core and the facesheet during the curing process of the adhesive layer. After the curing process, the reflection spectrum from the small-diameter FBG sensor is distorted because the formation of fillets induces a non-uniform strain distribution in the adhesive layer. However, after debonding, the core with the fillets peels off the facesheet, and, as a result, the reflection spectrum recovers its original shape due to the release of the non-uniform strain. Debonding can thus be detected with high sensitivity in real time from the recovery in the shape of the reflection spectrum. In addition, a more reliable debonding detection technique using a small-diameter chirped FBG sensor is proposed, in which two indicators in the reflection spectrum have been successfully used for a more reliable judgment of debonding.

Keywords

honeycomb sandwich panel debonding fillet small-diameter fiber Bragg grating sensor health monitoring

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References

Vinson, J. R. (1999). The Behavior of Sandwich Structures of Isotropic and Composite Materials, Technomic Publishing Company, Lancaster .

Zenkert, D. (1997). The Handbook of Sandwich Construction, EMAS Publishing, London .

Abrate, S. (1997). Localized Impact on Sandwich Structures with Laminated Facings , Appl. Mech. Rev., 50(2): 69-82 .

Blaise, E. and Chang, F.-K. (2001). Built-in Diagnostics for Debonding in Sandwich Structures under Extreme Temperatures, In: Chang, F.-K. (ed.), Structural Health Monitoring-The Demands and Challenges, CRC Press, Boca Raton , pp. 154-163.

Bocherens, E. , Bourasseau, S. , Dewynter-Marty, V. , Py, S. , Dupont, M. , Ferdinand, P. and Berenger. H. (2000). Damage Detection in a Radome Sandwich Material with Embedded Fiber Optic Sensors , Smart Mater. Struct., 9(3): 310-315 .

Bourasseau, N. , Moulin, E. , Delebarre, C. and Bonniau, P. R. (2000). Health Monitoring with Lamb Waves: Experimental Approach , NDT & E International, 33(6): 393-400 .

Diamanti, K. , Soutis, C. and Hodgkinson, J. M. (2005). Lamb Waves for the Non-destructive Inspection of Monolithic and Sandwich Composite Beams , Composites Part A: Applied Science and Manufacturing, 36(2): 189-195 .

Paolozzi, A. and Peroni, I. (1996). Experimental Assessment of Debonding Damage in a Carbon-fibre Reinforced Plastic Sandwich Panel by Frequency Variations , Compos. Struct., 35 (4): 435-444 .

Lestari, W. and Qiao, P. (2005). Damage Detection of Fiber-reinforced Polymer Honeycomb Sandwich Beams , Compos. Struct., 67(3): 365-373 .

10.

Okabe, Y. , Mizutani, T. , Yashiro, S. and Takeda, N. (2002). Detection of Microscopic Damages in Composite Laminates with Embedded Small-diameter Fiber Bragg Grating Sensors , Compos. Sci. Technol., 62(7-8): 951-958 .

11.

Takeda, S. , Okabe, Y. and Takeda, N. (2002). Delamination Detection in CFRP Laminates with Embedded Small-diameter Fiber Bragg Grating Sensors , Composites Part-A: Applied Science and Manufacturing, 33(7): 971-980 .

12.

Takeda, S. , Minakuchi, S. , Okabe, Y. and Takeda, N. (2005). Delamination Monitoring of Laminated Composites Subjected to Low-velocity Impact Using Small-diameter FBG Sensors , Composites Part A: Applied Science and Manufacturing, 36(7): 903-908 .

13.

Huang, S. , Ohn, M. M. , Leblanc, M. and Measures, R. M. (1998). Continuous Arbitrary Strain Profile Measurements with Fiber Bragg Gratings , Smart Mater. Struct., 7(2): 248-256 .

14.

Peters, K. , Pattis, P. , Botsis, J. and Giaccari, P. (2000). Experimental Verification of Response of Embedded Optical Fiber Bragg Grating Sensors in Non-homogeneous Strain Fields , Opt. Laser Eng., 33(2): 107-119 .

15.

Guemes, J. A. , Diaz-Carrillo, S. and Menendez, J. M. (1998). Measurement of Strain Distribution in Bonded Joints by Fiber Bragg Gratings , Smart Structures and Materials 1998: Sensory Phenomena and Measurement Instrumentation for Smart Structures and Materials, 3330, SPIE , 264-271 .

16.

Kersey, A. D. , Davis, M. A. , Patrick, H. J. , LeBlanc, M. , Koo, K. P. , Askins, C. G. , Putnam, M. A. and Friebele, E. J. (1997). Fiber Grating Sensors , J. Lightwave Technol., 15(8): 1442-1463 .

17.

Okabe, Y. , Tsuji, R. and Takeda, N. (2004). Application of Chirped Fiber Bragg Grating Sensors for Identification of Crack Locations in Composites , Composites Part A: Applied Science and Manufacturing, 35(1): 59-65 .

18.

Huang, W. P. (1994). Coupled-mode Theory for Optical Waveguides: An Overview , J. Opt. Soc. Am. A., 11(3): 963-983 .

19.

Steenkiste, R. J. V. and Springer, G. S. (1997). Strain and Temperature Measurement with Fiber Optic Sensors, Technomic Publishing Company, Lancaster , pp. 162-171.

20.

Minakuchi, S. , Okabe, Y. and Takeda, N. (2005). Real-time Damage Detection of Honeycomb Sandwich Structures Using Small-diameter Fiber Bragg Grating Sensors , In: Proceedings of the 7th International Conference on Sandwich Structures (ICSS-7), Aalborg, Denmark, pp. 383-392 .

21.

Yamada, M. and Sakuda, K. (1987). Analysis of Almost-periodic Distributed Feedback Slab Wave-guides via a Fundamental Matrix Approach , Appl. Opt., 26(16): 3474-3478 .

22.

Gafsi, R. and El-Sherif, M. A. (2000). Analysis of Induced-birefringence Effects on Fiber Bragg Gratings , Opt. Fiber. Technol., 6(3): 299-323 .

23.

Okabe, Y. , Yashiro, S. , Tsuji, R. , Mizutani, T. and Takeda, N. (2002). Effect of Thermal Residual Stress on the Reflection Spectrum from Fiber Bragg Grating Sensors Embedded in CFRP Laminates , Composites Part A: Applied Science and Manufacturing, 33(7): 991-999 .