An investigation of the crack propagation in a carbon fiber bonded joint using backface strain measurements with FBG sensors

Andrea Bernasconi; Lorenzo Comolli

doi:10.1117/12.975143

17 October 2012 An investigation of the crack propagation in a carbon fiber bonded joint using backface strain measurements with FBG sensors

Andrea Bernasconi, Lorenzo Comolli

Author Affiliations +

Proceedings Volume 8421, OFS2012 22nd International Conference on Optical Fiber Sensors; 84214Y (2012) https://doi.org/10.1117/12.975143
Event: OFS2012 22nd International Conference on Optical Fiber Sensor, 2012, Beijing, China

Abstract

Carbon-fiber structures has many advantages over traditional materials, but special care must be taken when bonded joints are used. A crack can propagate and cause the failure of the structure. The presence of a crack and its length can be monitored in example by means of backface strain measurements. In this work the backface technique is applied by using an array of 10 Fiber Bragg Grating (FBG) sensors applied on a carbon-fiber bonded joint. This is an interesting solution because these sensors can be embedded in carbon-fiber structures nearly without producing a load effect thanks to their small cross section. Special care must be used with FBG sensors because the expected strain profile is non-homogeneous (computed using a FEM analysis) and the FBG spectra can be altered and prevented from correct measurements (simulations using a T-matrix model were conducted). The specimen was tested with a pulsating tensile force, so that a crack developed and propagated below the optical sensors. The comparison of the observed crack position and the one inferred from the measured position of the minimum of the longitudinal strain pattern showed a good correlation, with errors lower than 10% except a small range where a 20% error was observed.

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Andrea Bernasconi and Lorenzo Comolli "An investigation of the crack propagation in a carbon fiber bonded joint using backface strain measurements with FBG sensors", Proc. SPIE 8421, OFS2012 22nd International Conference on Optical Fiber Sensors, 84214Y (17 October 2012); https://doi.org/10.1117/12.975143

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