Advanced layout of a fiber Bragg grating strain gauge rosette

A temperature-compensated strain-sensing scheme based on fiber Bragg gratings (FBGs) that is suitable for strain mapping applications is described. FBGs are bonded to a backing patch, together with an extra grating that is used for temperature compensation/measurement. The patch provides a simpler and more robust way of attaching the FBGs to a structure than directly mounting a bare fiber, though it was necessary to design it in such a way that there was minimal reduction in the strain transferred from the structure to the sensing fibers. Finite element (FE) analysis was used to help design the patch, which was then constructed accordingly. The authors have demonstrated experimentally that the use of the backing patch produces a reduction in strain sensitivity of only around 4%, which is slightly better than theoretically predicted values. The temperature measuring FBG had to be bonded in such a way that it experienced the changes in temperature, but not the strain, to which the structure was subjected. A design for doing this was developed and proven. The use of a backing patch to develop a rosette configuration of Bragg gratings, each having a different peak reflective wavelength, is described. The rosette configuration is one that is frequently used with electrical strain gauges and allows here to determine both the magnitude and the direction of strain.

[1]  Daniel C. Betz.  Application of optical fibre sensors for structural health and usage monitoring , 2004 .

[2]  Peter David Foote,et al.  Applications of optical fiber sensors in aerospace: the achievements and challenges , 2000, Symposium on Applied Photonics.

[3]  R. Kashyap.  Fiber Bragg Gratings , 1999 .

[4]  J. D. Cronkhite,et al.  Exploitation of Structural Loads/Health Data for Reduced Life Cycle Costs , 1998 .

[5]  Wieslaw J. Staszewski,et al.  Monitoring on-line integrated technologies for operational reliability — monitor , 2000 .

[6]  Daniel Betz,et al.  Smart sensing of aviation structures with fiber optic Bragg grating sensors , 2000, Smart Structures.

[7]  R. Measures.  Structural Monitoring with Fibre Optic Technology , 2001 .

[8]  L. Staudigel,et al.  Test of a fiber Bragg grating sensor network for commercial aircraft structures , 2002, 2002 15th Optical Fiber Sensors Conference Technical Digest. OFS 2002(Cat. No.02EX533).

[9]  Brian Culshaw,et al.  Measuring Strain Using Optical Fibres , 2000 .

[10]  Brooks A. Childers,et al.  Use of 3000 Bragg grating strain sensors distributed on four 8-m optical fibers during static load tests of a composite structure , 2001, SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[11]  Nigel Bruce Aldridge,et al.  Operational Load Monitoring for Aircraft & Maritime Applications , 2000 .

[12]  P. D. Foote.  Optical fibre Bragg grating sensors for aerospace smart structures , 1995 .

[13]  S. G. Allison,et al.  Use of 3000 Bragg grating strain sensors distributed on four eight-meter optical fibers during static load tests of a composite structure , 2001 .

[14]  Terrence J Barnes.  The FAA Operational Loads Monitoring Program - Achievements And Problems , 2000 .

[15]  S. R. Hunt,et al.  Validation of the Eurofighter Typhoon structural health and usage monitoring system , 2001 .

[16]  Christian Boller,et al.  Next generation structural health monitoring and its integration into aircraft design , 2000, Int. J. Syst. Sci..

[17]  Christian Boller,et al.  Ways and options for aircraft structural health management , 2001 .