Buried Thermoplastic Layer Diagnostics by the Use of Photo-Thermo-Acoustic Radiometry

Nondestructive evaluation of buried layers finds important applications in industry. In this paper we describe a fast, non-contact photothermal technique for thermoacoustic characterization of a thermoplastic layer sandwiched between two metal foils used in heat sealed food containers. For this particular application a non-contact measurement was required of the thickness of the polymer layer between two layers of aluminum in a heat sealed container rim at a speed of four locations of the container in 60 sec