The use of free-space microwave non-destructive techniques: simulation of damage detection in carbon fibre reinforced composites

Munalli, Daniela; Dimitrakis, Georgios; Chronopoulos, Dimitrios; Greedy, Steve; Long, Andrew

Abstract

Microwave non-destructive testing (MNDT) methods represent an effective solution in detecting defects within composite structures with relatively low electrical conductivity. They offer the advantage to overcome the problems of traditional NDT techniques such as coupling, danger coming from ionizing radiation, limited depth of operation, large wavelengths, time consuming post processing. Near-field microwave and millimetre non-invasive inspections have been successfully used for detecting defects such as dis-bond and delamination in complex structures. In dielectric materials, they can be used for dielectric properties characterization , degree of porosity evaluation, degree of age-ing, anisotropy, dielectric mixture constituents determination , state of cure. When it comes to the analysis of carbon fibre reinforced polymers (CFRPs), the use of these non-destructive techniques is restricted by the composite relatively high conductivity of about 10 4 S/m. In this paper , the investigation of a free-space microwave method for non-destructive testing of unidirectional CFRPs has been carried out by means of a pair of standard gain horn antennas , covering a frequency range from 26.5 GHz to 40 GHz. With the simulations, experimental results related to the presence/severity of the analysed defects are linked to the variations of the measured scattering parameters S ij. The approach is based on the comparison between the electromagnetic signal reflected and transmitted through a healthy sheet material under test, when a radio frequency (RF) wave is incident on it, and the one reflected and transmitted by a damaged sheet. The eventual presence of the defect is revealed by measuring the mismatch between the two transmitted waveforms. The performance of this radio wave technique is investigated in relation to surface defects and also in relation to those types of defects that are less detectable with this method, such as delaminations, cavities and inclusions. The simulations make use of the finite integration technique (FIT) and the finite element method (FEM).

Citation

Munalli, D., Dimitrakis, G., Chronopoulos, D., Greedy, S., & Long, A. (2019). The use of free-space microwave non-destructive techniques: simulation of damage detection in carbon fibre reinforced composites

• Conference Name: 11th Symposium on NDT in Aerospace
• Start Date: Nov 13, 2019
• End Date: Nov 15, 2019
• Acceptance Date: Oct 25, 2019
• Publication Date: 2019
• Deposit Date: Nov 20, 2019
• Journal: 11 th Symposium on NDT in Aerospace -PARIS-SACLAY -Nov 13 to
• Volume: 15
• Public URL: https://nottingham-repository.worktribe.com/output/3345546