Analysis of structural changes in microwave- and ultrasound-modified carbon-fiber-reinforced polymer composites by low-coherence reflectometry

Background and Objectives: Low-coherence reflectometry has traditionally been used to study the microstructure of biological tissues. Currently, the scope of its application is expanding, and the method is increasingly being employed to assess the characteristics of layered structures. The paper discusses possible physical mechanisms underlying the decrease in the scattering coefficient in the near-infrared region, attributed to an increased structural homogeneity of the polymer component at the supramolecular level. Materials and Methods: The low-coherence reflectometry method was applied to analyze the structure of carbon-fiber-reinforced polymer composite materials in their initial state and after microwave or ultrasonic treatment. An OSC 1300 SS optical coherence tomograph operating in B-scan mode was used as the instrumental platform for reflectometric measurements. Results: Analysis of the statistical and correlation characteristics of B-scan images of the surface layer of both pristine and modified composites has revealed that the modification leads to a reduction in the scattering coefficient of the probing radiation (wavelength 1300 nm) within the polymer matrix of the composite. The maximum effect is achieved when ultrasonic radiation with a frequency of 44 kHz and a power density of 10 W/cm2 is used as the modifying agent. Conclusion: Further development of this research direction could facilitate the use of optical coherence tomography as a rapid, non-destructive method for quality control of the binder-filler interface in the surface layers of polymer composites.