Using of acoustic resonance for detection and identification of hidden defects in polymer layered composites

A method of non-destructive testing is proposed, which combines the acoustic load of the object of inspection and interferometric control of its surface displacements, formed as a result of an acoustic wave resonance in a hidden defect. The method is aimed at solving the problem of detection and identification of subsurface defects formed in structural elements made of polymer layered composite materials or contain protective paint coatings. At the same time, the defect is considered as an acoustic resonator filled with a medium in which only a longitudinal acoustic wave propagates. Usually such media are air or water. The novelty of the method is that it allows us not only to detect a hidden defect and establish its location, but also to determiВ¬ne its dimensions. The scheme of the experimental installation is given and the method is described. The research of the detection and identification of subsurface defects that most often occur in practice was conducted with the help of the model of the experimental installation. In products made of polymer layered composites, such defects are unbounded areas between layers during construction, internal damages such as cracks and areas of crumpling during its operation. The results of the experiments proved the effectiveness of the proposed method. The described method is also suitable for detection and identification of blistering of protective paint coatings, provided that they are filled with liquids or gases in which transverse acoustic waves do not propagate.