Identification of Defects in a Carbon Fiber Reinforced Polymer using Eddy Current Sensors

Abstract

The Carbon Fiber Reinforced Polymer (CFRP) is a strong and lightweight composite that leads to its extensive use in critical applications like manufacturing of aircraft's, nuclear reactors, and high-speed vehicles. In many applications, it is essential to monitor the systems at regular intervals after their use without damaging the system. To fulfill the need, we are using one of the most emerging and promising electromagnetic principles based Eddy Current Sensors for monitoring of the CFRP laminates in an entirely non-destructive manner. In the eddy current sensor method, a spiral shaped current called eddy current is induced based on the Faraday's law in the conductive test surface by using a current carrying inductive coil. The induced eddy current follow the Lenz's law and generates its own magnetic field that leads to a magnetic coupling between the test surface and the coil. The path of induced eddy current and correspondingly its magnetic field is affected when the probe is on the defect. Hence, the voltage across the coil will be altered when the probe encounters the defect. The change in voltage that appears across the coil is used to trace the presence of a defect in the test surface. There are various parameters like frequency of operation, ferrite core material, ferrite core dimension, number of turns in the coil, Copper wire gauge that affects the outcome of the system. We have performed a number of experiments and analyzed various samples having different impact damages to design the eddy current coil and the electronic circuitry. There are few more methods in the area of non-destructive evaluation, out of which ultrasonic is the most advanced technology that has been developed. We compare the results of our system with the ultrasonic method and claim that the designed system is capable of tracing the impact damages equivalently to the most advanced ultrasonic method.