An Electromagnetic Sensor with a Metamaterial Lens for Nondestructive Evaluation of Composite Materials

Abstract

This paper proposes the study and implementation of a sensor with a metamaterial (MM) lens in electromagnetic nondestructive evaluation (eNDE). Thus, the use of a new type of MM, named Conical Swiss Rolls (CSR) has been proposed. These structures can serve as electromagnetic flux concentrators in the radiofrequency range. As a direct application, plates of composite materials with carbon fibers woven as reinforcement and polyphenylene sulphide as matrix with delaminations due to low energy impacts were examined. The evaluation method is based on the appearance of evanescent modes in the space between carbon fibers when the sample is excited with a transversal magnetic along z axis (TMz) polarized electromagnetic field. The MM lens allows the transmission and intensification of evanescent waves. The characteristics of carbon fibers woven structure became visible and delaminations are clearly emphasized. The flaws can be localized with spatial resolution better than λ/2000.

Complementary Methods for Evaluation of Yttria Stabilized Zirconia Coatings used as Thermal Barrier Coating

“…Nowadays, multitudes of MM structural elements type are known, conferring special EM properties. Depending on the frequency of the incident EM field, the type and geometrical shape MM may have a high relative magnetic permeability either positive or negative [18], [19] and allow the EM waves amplification [20]. These properties strongly depend on the geometry of metamaterials more than on its composition [20], [21].…”

“…In the case of CSR, dimension of d is 20 mm (as the diameter of the large basis of the CSR) and k represents the wavenumber of the incident electromagnetic wave in free space, n and Z are related to dielectric permittivity and magnetic permeability by the relations [23] n Z The EM sensor is an absolute sendreceiver type [18,22], and has the principle scheme given in Fig. 1a and its construction in Fig.…”

“…(5). The functioning of the sensor is presented in [18]. The scattered field must be also focused such that it can be detected by the reception part of the sensor placed in image focal point.…”

“…The scattered field must be also focused such that it can be detected by the reception part of the sensor placed in image focal point. EM sensor with MM lens has been realized with two CSRs, tuned at 105MHz frequency [18], having a large basis face to face. The MM lens assure the possibility to apply of electromagnetic metamaterial in eNDE [21].…”

“…The detection principle is similar with the one of near-field electromagnetic scanning microscopy (NFESM) [18]. NFSEM imaging is a sampling technique, i.e., the specimen (in this case plate with thickness of coating) is probed point by point by raster scanning with the sensor over the specimen surface and recording for energy image pixel a corresponding electromagnetic signature.…”