Non-contact detection of impact damage in carbon fibre composites using a complementary split-ring resonator sensor

In this paper, a new non-contact method for detection of impact damage in carbon fibre-reinforced polymer composites with a complementary split-ring resonator sensor is proposed. The resonance frequency is evaluated as an indicator of the presence of damage. The resonator is made on a printed circuit board, and in the experimental setup it is positioned close to the area of interest. Electromagnetic models are built, and from the resonant responses the appropriate frequency range used for the test is determined. The active sensing element in the resonator is found from the analysis of the magnetic field distribution. The parametric study performed shows that a larger frequency change occurs for a wider impacted region, which is of great use for practical applications. The proposed method is validated by the experimental results, where a frequency shift of 65 MHz was observed for a 0.36 mm deep dent.