Towards micro-structured optical fiber sensors for transverse strain sensing in smart composite materials

We developed a highly birefringent micro-structured optical fiber that, in combination with a fiber Bragg grating sensor, allows measuring transverse strains in reinforced composites. The first generation of this dedicated fiber sensor featured a hydrostatic pressure sensitivity of −15 pm/MPa and yielded a transverse strain sensitivity of −0.16 pm/µε when embedded in a carbon fiber reinforced polymer. The second generation of this sensor has now been fabricated and hydrostatic pressure experiments and FEM simulations show that this generation returns a sensitivity of more than twice that of the first generation. FEM simulations additionally show an increased sensitivity when this sensor is embedded in a reinforced composite, achieving an unprecedented transverse strain sensitivity of 0.29 pm/µε. We explain how the optimized micro-structure yields this record-high sensitivity. In addition we demonstrate the selectivity of the bare fiber sensor, which remains insensitive to temperature changes or axial strain. This sensor can therefore play an important role in the domain of structural health monitoring.

[1]  Jonathan C. Knight,et al.  Photonic crystal fibres , 2003, Nature.

[2]  K. Hill,et al.  Fiber Bragg grating technology fundamentals and overview , 1997 .

[3]  H. Bartelt,et al.  Fiber Bragg Gratings in Germanium-Doped Highly Birefringent Microstructured Optical Fibers , 2008, IEEE Photonics Technology Letters.

[4]  Wim De Waele,et al.  Transversal Load Sensing With Fiber Bragg Gratings in Microstructured Optical Fibers , 2009, IEEE Photonics Technology Letters.

[5]  Hugo Thienpont,et al.  Highly birefringent microstructured fibers with enhanced sensitivity to hydrostatic pressure. , 2010, Optics express.

[6]  P. Russell,et al.  Photonic Crystal Fibers , 2003, Science.

[7]  R. Batra,et al.  Modeling damage in polymeric composites , 2008 .

[8]  Wim De Waele,et al.  Multi-axial strain transfer from laminated CFRP composites to embedded Bragg sensor: I. Parametric study , 2010 .

[9]  J. P. Carvalho,et al.  Discrimination of strain and temperature using Bragg gratings in microstructured and standard optical fibres , 2005 .

[10]  H. Bartelt,et al.  Response of FBGs in Microstructured and Bow Tie Fibers Embedded in Laminated Composite , 2009, IEEE Photonics Technology Letters.

[11]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[12]  John Canning,et al.  Ultrafast femtosecond-laser-induced fiber Bragg gratings in air-hole microstructured fibers for high-temperature pressure sensing. , 2010, Optics letters.

[13]  J M W Brownjohn,et al.  Structural health monitoring of civil infrastructure , 2007, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[14]  J. Canning.  Fibre gratings and devices for sensors and lasers , 2008 .

[15]  Youngjoo Chung,et al.  Enhanced transverse load sensitivity by using a highly birefringent photonic crystal fiber with larger air holes on one axis. , 2010, Applied optics.

[16]  W. Bock,et al.  Measurement of pressure and temperature sensitivities of a Bragg grating imprinted in a highly birefringent side-hole fiber. , 2003, Applied optics.

[17]  Hugo Thienpont,et al.  Microstructured Optical Fiber Sensors Embedded in a Laminate Composite for Smart Material Applications , 2011, Sensors.

[18]  John Canning,et al.  Sensitivity enhancement of fiber Bragg gratings to transverse stress by using microstructural fibers. , 2006, Optics letters.

[19]  Joris Degrieck,et al.  Strain Measurements of Composite Laminates with Embedded Fibre Bragg Gratings: Criticism and Opportunities for Research , 2010, Sensors.