Electromagnetic Inspection of Carbon-Fiber- Reinforced Polymer Composites With Coupled Spiral Inductors

Abstract

This paper presents a new type of an electromagnetic sensor for nondestructive testing of carbon-fiber-reinforced polymer composites. The sensor utilizes coupled planar spiral inductors operating typically in the range of 10-500 MHz. The method proposed here shows some similarity to the eddy current technique, but as will be shown, the principles of operation are different as the sensitivity to defects is mostly due to the magnetic field components tangential to the surface of a material. It is shown that the method is applicable to 3-D inspection of carbon-fiber-reinforced composites widely employed in the aerospace industry.Index Terms-Carbon-fiber-reinforced polymer (CFRP), composite material structures, coupled spiral inductors, eddy currents, nondestructive testing (NDT).

Detection of Impact Damage in Carbon Fiber Composites Using an Electromagnetic Sensor

“…However, there are some differences between the two methods, which are listed in Table 1. For the original design of the CSI sensor [14], the characteristic impedance of the coplanar transmission line is around 80 Ω, which implies that around 5% energy is reflected during the signal transfer from the SMA connector (normally 50 Ω) to the coplanar waveguide (CPW) transmission line. Here, for the optimised sensor the central track of the CPW line on the upper side shown in Fig.1 (c) is increased to 1.0 mm [17] resulting in reducing the reflected energy to 0.05 %.…”

“…Recently, a new kind of electromagnetic (EM) sensor with coupled spiral inductors (CSI) for CFRP composites [14][15][16] has been proposed. This sensor has several advantages, such as its low power consumption, low cost, potential for high speed scanning, non-contact, one-sided scanning capability and no need for piezoelectric transducers (e.g., Lamb waves) or couplants (e.g., ultrasonic testing).…”

“…The ability to detect an air gap and cracks intentionally produced in a four-layer CFRP plate was reported [14]. Furthermore, the authors optimised the CSI sensor for better impedance matching [17] and extended the applications to the detection of subsurface grooves [18], delamination caused by three-point bending [17] and impact damage [19].…”

Portable automated Radio-Frequency scanner for Non-Destructive Testing of Carbon-Fibre-Reinforced Polymer composites

“…One of promising techniques that successfully addresses the aforementioned challenges is radio-frequency inductive testing (RFIT) [14,15] with a single sensor built of two coupled spiral inductors manufactured on a printed circuit board (PCB). First of all, as it has been shown in [14], the point spread function (PSF) of the sensor is strongly anisotropic, thus, enabling the characterization of such materials like CFRP.…”

“…First of all, as it has been shown in [14], the point spread function (PSF) of the sensor is strongly anisotropic, thus, enabling the characterization of such materials like CFRP. Second of all, the measurement with the RFIT sensor allows easily determining the depth of defects buried in the CFRP materials and obtain a cross-sectional scan by the appropriate combination of measurements data at a few frequencies.…”