IP Library › Granted Patent US 7,283,693
Granted Patent B2
US 7,283,693 · App. 11/296,855 · Granted Oct 16, 2007

Method to monitor structural damage occurrence and progression in monolithic composite structures using fibre Bragg grating sensors

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Quick Facts
Patent No.
US 7,283,693
App. No.
11/296,855
Granted
Oct 16, 2007
Kind
B2
Abstract

A method of monitoring structural damage in a composite structure manufactured by co-curing, co-bonding or secondary bonding of several sub-components ( 7, 8 ), using fibre optic Bragg grating sensors attached or embedded to or between (in the bonding line) said sub-components, comprising a first step of measuring the wavelength spectra ( 31, 33, 40 ) of said Bragg grating sensors at the end of the manufacturing of the part, and in a known load condition, considered as reference and a second step of identifying the occurrence of a failure of the structure and the progress of said failure detecting the release of the residual stresses/strains stored during the curing process by measuring changes ( 31 to 32, 33 to 34, 40 to 41 ) with respect to said reference wavelength spectra.

Claims (6)

1. A method of monitoring structural damage in a composite structure manufactured by co-curing, co-bonding or secondary bonding of several sub-components ( 7 , 8 ), using fibre optic Bragg grating sensors attached or embedded to or between (in the bonding line) said sub-components, characterised by comprising the steps of:

a) measuring the wavelength spectra ( 31 , 33 , 40 ) of said Bragg grating sensors at the end of the manufacturing of the part, and in a known load condition, considered as reference;

b) identifying the occurrence of a failure of the structure and the progress of said failure detecting the release of the residual stresses/strains stored during the curing process by measuring changes ( 31 to 32 , 33 to 34 , 40 to 41 ) with respect to said reference wavelength spectra.

2. A method according to claim 1 , wherein a change of the wavelength spectrum ( 31 to 32 ) consisting of a shift of the intensity peaks allows the identif-cation of a failure causing a longitudinal stress release.

3. A method according to claim 1 , wherein a change of the wavelength spectrum ( 33 to 34 ) consisting of a change in the distance between the intensity peaks allows the identification of a failure causing a transverse stress release.

4. A method according to claim 1 , wherein a change of the reflective spectrum ( 40 to 41 ) consisting of a general spectral distortion allows the detection of a failure causing a non-uniform longitudinal and/or transverse stress release.