Abstract
Microwave imaging and defectoscopy are promising techniques for dielectric composite evaluation. Their most significant advantage is their relatively high penetration depth. Another feature worth noting is that traditional methods could not acquire an internal content with such a low impact on both the sample and surrounding environment, including the test operator, compared to other techniques. This paper presents microwave non-destructive and noninvasive methods for quality evaluation of layered composite materials using an open-ended waveguide probe. Pure |S11| parameters only exceptionally give a clear answer about the location of material cracks. Therefore, this makes it necessary to analyze these parameters simultaneously along with several other factors, such as stand-off distance, probe type or wave polarization. The purpose of the work was to find the dependency between the physical state of a layered composite powerplant pipeline and the S-matrix parameters response (reflection and transmission parameters) in a Ku frequency band that has not yet been extensively researched. Lower-frequency measurements broaden the application possibility for thicker composites, mainly because of a higher penetration depth and measurement setup availability. Different methods have been shown, including reflection and transmission/reflection methods, both in close proximity and in stand-off distance. The measurements are based on a low-complexity experimental setup.
Highlights
The number of composite materials surrounding us is growing at an above-average rate in many fields, e.g., automotive hydrogen tank and car chassis, avionics-fuselages, aircraft wings, or industrial applications—layered powerplant pipelines
These measurements aimed to investigate the frequency candidates that are sensitive to delamination cracks
The probe aperture was oriented such that the electric field vector was orthogonal to the delamination edge to provide a higher resolution
Summary
The number of composite materials surrounding us is growing at an above-average rate in many fields, e.g., automotive hydrogen tank and car chassis, avionics-fuselages, aircraft wings, or industrial applications—layered powerplant pipelines. Critical application areas make non-destructive testing of composite materials crucial for cost optimization, repeatability, and quality control throughout the whole product lifetime. Microwave imaging techniques are often applied in the noninvasive and non-destructive testing (NDT) of dielectric materials, due to their unique characteristics, such as high penetration depth, low measurement setup complexity, in-touch or stand-off operation zone, lack of requirement for a coupling agent, and environmental safety. Due to the lossy nature of dielectric materials and the following internal dissipation, electromagnetic waves can heat, dry, or disinfect dielectric surfaces and structures. Many efforts have been made to use microwaves for retrieving information, such as material composition, and for imaging internal structures. Researches focus on imaging systems for biomedical applications, civil engineering, and industrial applications
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