Laserhyphen;excited thermalhyphen;wave image magnitude and phase were acquired by photoacoustic detection in the 10ndash;1000hyphen;Hz modulation frequency range on epoxy/aluminum interface systems with surface (black) and bulk (white) laserhyphen;absorbing epoxy, different planar interface distances, surface and subsurface flaws, and different surface angle boundaries. The following conclusions were reached from the thermalhyphen;wave results: (1) thermally thin epoxy on aluminum layer thicknesses can be estimated from variable modulation frequency data; (2) planar and subsurface defect interface structures of epoxy/aluminum systems are best studied by examining both magnitude and phase images; (3) thermalhyphen;wave images are more straightforward to interpret for the systems that absorb light at the irradiated surface rather than in the bulk. These conclusions are consistent with thermal diffusion length and thermalhyphen;wave reflection effects predicted by theory for surface lighthyphen;absorption conditions.
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