Impact damage detection of composite materials by fiber Bragg gratings

Zoran Djinovic; Michael Scheerer; Milos Tomic

doi:10.1117/12.887065

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5 May 2011 Impact damage detection of composite materials by fiber Bragg gratings

Zoran Djinovic, Michael Scheerer, Milos Tomic

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Proceedings Volume 8066, Smart Sensors, Actuators, and MEMS V; 80660T (2011) https://doi.org/10.1117/12.887065
Event: SPIE Microtechnologies, 2011, Prague, Czech Republic

Abstract

Usage of fiber-optic Bragg gratings (FBG) for strain measurement is well-known technique in structural health monitoring (SHM). However, this technique based on shift of spectral peak, suffers from different spurious signals, particularly caused by thermal effect. We present here a method for impact damage detection of composite materials based on FBG without thermal disturbance. This method is based on the broadening of the spectral peak in dependence on the FBG separation from the impact damage. We used a sensing configuration where an Optical Spectrum Analyzer was interrogated with an array of 10 FBGs with central wavelength between 812 and 817nm that were bonded on a CFRP composite plate with 8 plies. We performed two groups of impact experiments: by impact energy of about 10J and 20J. We found there was no any significant shift of the spectral peak after the impact. Contrary, we confirmed in the last experiments the spectral peak broadening caused by impact load. The spectrum broadening primarily depends on the strain gradient generated into the FBGs, i.e. into the damaged area. We made a correlation between the peak width and FBG-impact damage separation. There are three characteristic regions; near to impact, abrupt region and almost even region.

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Zoran Djinovic, Michael Scheerer, and Milos Tomic "Impact damage detection of composite materials by fiber Bragg gratings", Proc. SPIE 8066, Smart Sensors, Actuators, and MEMS V, 80660T (5 May 2011); https://doi.org/10.1117/12.887065

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