The characteristic features of nondestructive testing (NDT) methods, equipment, and technology employed in quality control of polymer composite products in various branches of industry. Various aspects of the application of acoustic, radiation, optical, thermal (infrared), and radio-frequency NDT methods and equipment are discussed. Recommendations are made for the choice of methods and equipment for revealing typical hidden flaws in polymer composites.In comparison with metals, polymer composites have a considerably inhomogeneous structure, anisotropic properties, a variety of types of structure (unidirectional, longitudinal-transverse, combined), specific properties (heat, electrical, and acoustic insulation), small values of density (0.02-2.0 g/cm3), a large spread of physical and mechanical characteristics, etc. Moreover, almost all polymer composites are nonmagnetic and, depending on the filler used, are mainly dielectrics or poor conductors.Not all nondestructive testing (NDT) methods used for metal products [1], therefore, can be used to inspect polymer composites and products made of them. For example, the sensitivity of radiation methods [2, 3] when revealing flaws in such composites is one-third to one-quarter that when doing the same in steel, while high-frequency ultrasonic methods are ineffective for inspection of polymer composites because of strong scattering and damping of high-frequency waves (above 1 MHz).The specific nature of defects (external and internal) in polymer composites causes some difficulties in the choice of equipment and development of methods for detecting the defects. External defects include scratches and wrinkles, irregularities of the decorative layer, separation of the filler texture, visible disruption of the filament orientation, and the adherence of the binder. Internal defects include delamination and cracks, cavities, porosity, extraneous inclusions, uneven distribution of the binder (portions with insufficient or excess resin), and incomplete curing.The norms for allowable defects in polymer composites are determined by the conditions and technical capabilities of the NDT equipment [4].Most often, the defects in polymer composite products are revealed [5], and what caused those defects is determined (Table 1) by using acoustic, radiation, optical, thermal, radio-frequency, and other methods that can check almost all characteristics of composites (Table 2). We briefly describe the salient features of the principal methods.Acoustic methods include ultrasonic, acoustic impedance, collision (free oscillations), resonance, velocimetric, reverberation, and acoustic emission methods.Acoustic NDT equipment employs ultrasound of the frequency range from 50 Hz to 50 MHz. The intensity of the oscillations is less than 1 W/cm 2. Acoustic methods are divided into two groups, depending on the form and reception of waves: active methods, which use emission and reception of acoustic waves, and passive methods, which are based only on reception of waves. In each group, methods are dis...
