Brillouin spectral response depending on strain non-uniformity within centimeter spatial resolution and its application to internal damage detection in large-scale composite structures

The authors propose a technique to detect centimeter internal damages in largescale composite structures, using an optical fiber network running throughout the structure. A Brillouin-based distributed strain sensing system with centimeter-order spatial resolution (prepump pulse Brillouin optical time domain analysis (PPP-BOTDA)) was utilized to detect residual non-uniform strain in the damaged area. First, Brillouin spectral response depending on the strain profile within the spatial resolution was revealed. The spectral response depending on strain non-uniformity was experimentally quantified with consideration of the general characteristics of the Brillouin gain spectrum. Then, the damage detection procedure was proposed, based on the spectral response. Finally, impact damage detection of a composite sandwich structure was numerically conducted to illustrate the effectiveness of the proposed technique. The developed system is quite useful in a first inspection of largescale composite structures in aerospace applications.

[1]  Hiroshi Naruse,et al.  Application of Brillouin Scattering-Based Distributed Optical Fiber Strain Sensor to Actual Concrete Piles , 2002 .

[2]  D. Zenkert,et al.  Handbook of Sandwich Construction , 1997 .

[3]  Nobuo Takeda,et al.  Delamination monitoring of laminated composites subjected to low-velocity impact using small-diameter FBG sensors , 2005 .

[4]  Anthony W. Brown,et al.  Characterization of the Brillouin-loss spectrum of single-mode fibers by use of very short (<10-ns) pulses. , 1999, Optics letters.

[5]  David J. Webb,et al.  Temperature non-uniformity in distributed temperature sensors , 1993 .

[6]  X. Bao,et al.  Structural monitoring by use of a Brillouin distributed sensor. , 1999, Applied optics.

[7]  Hiroshi Naruse,et al.  Dependence of the Brillouin gain spectrum on linear strain distribution for optical time-domain reflectometer-type strain sensors. , 2002, Applied optics.

[8]  Zuyuan He,et al.  Distributed strain measurement with millimeter-order spatial resolution based on Brillouin optical correlation domain analysis. , 2006, Optics letters.

[9]  Anthony W. Brown,et al.  Spatial resolution enhancement of a Brillouin-distributed sensor using a novel signal processing method , 1999 .

[10]  Toshio Kurashima,et al.  Brillouin characterization of fiber strain in bent slot-type optical-fiber cables , 1992 .

[11]  Akiyoshi Shimada,et al.  Deformation of the Brillouin Gain Spectrum Caused by Parabolic Strain Distribution and Resulting Measurement Error in BOTDR Strain Measurement System , 2003 .

[12]  Kinzo Kishida,et al.  Pulse pre-pump method for cm-order spatial resolution of BOTDA , 2005, International Conference on Optical Fibre Sensors.

[13]  Kazuro Kageyama,et al.  Distributed Strain Sensing from Damaged Composite Materials Based on Shape Variation of the Brillouin Spectrum , 2004 .

[14]  K. Nishiguchi,et al.  Pulsed pre-pump method to achieve cm-order spatial resolution in Brillouin distributed measuring technique , 2004 .

[15]  Lufan Zou,et al.  Detection of buckling in steel pipeline and column by the distributed Brillouin sensor , 2006 .

[16]  Nobuo Takeda,et al.  “Segment-wise model” for theoretical simulation of barely visible indentation damage in composite sandwich beams: Part I – Formulation , 2008 .

[17]  Robin Olsson,et al.  Impact on composite structures , 2004, The Aeronautical Journal (1968).

[18]  Nobuo Takeda,et al.  Real-time Detection of Debonding between Honeycomb Core and Facesheet using a Small-diameter FBG Sensor Embedded in Adhesive Layer , 2007 .

[19]  T. Horiguchi,et al.  Tensile strain dependence of Brillouin frequency shift in silica optical fibers , 1989, IEEE Photonics Technology Letters.