C. Edwards et al., Laser generated ultrasound: efficiency and damage thresholds in carbon fibre reinforced composites, IEE P-SCI M, 148(4), 2001, pp. 139-142
Citations number
19
Categorie Soggetti
Eletrical & Eletronics Engineeing
Journal title
IEE PROCEEDINGS-SCIENCE MEASUREMENT AND TECHNOLOGY
Laser techniques are beginning to be used for non-contact ultrasonic inspec
tion of carbon fibre reinforced composites in industry. The ultrasound is n
ormally generated with a high-power pulsed laser and is detected with a las
er interferometer. Other non-contact detection methods can also be used, su
ch as simpler laser beam deflection techniques and air coupled transducers.
The authors compare the generation efficiency and damage thresholds of a f
undamental Nd:YAG laser (1.06 mum), and a TEA CO, laser (10.6 mum) which is
normally preferred for carbon-fibre reinforced composites). A Nd:YAG laser
with an optical parametric oscillator (OPO) tunable up to 4 mum is also ex
amined. The laser energy is absorbed within the optical absorption depth; t
he temperature rise is affected by the wavelength and laser pulse duration.
It is essential to remain in the thermoelastic regime in order not to dama
ge the material. A modified Michelson interferometer is used to detect the
absolute displacement of the ultrasound. Optical beam deflection techniques
and air-coupled transducers are also evaluated as detectors.