دانلود رایگان مقاله ترک بازدید ازدحام برای برآورد محل شکاف در فیبر کربن، پلاستیک، شیشه

Abstract

The present study proposes crack swarm inspection (CSI) for estimating crack location and size in carbon composite laminates from the surface voltage distribution. This technique generates a large number of virtual microscopic cracks, and calculates the surface voltage distribution of the composites using anisotropic electric potential functions and doublet strings. Using genetic algorithms, the virtual microscopic cracks formed a swarm to coincide with the measured surface voltage; thereby, the crack sizes and locations are estimated from the position of the crack swarm. The CSI was applied to crack detection in carbon laminated composite plates; it was confirmed that the existence of cracks in each partitioned section was detected with >80% probability, in reference to the crack location and size information. Furthermore, we also confirmed that the estimation accuracy was affected by the electric current density in the thickness direction, and addressed the recommended electrode interval based on the minimum size of the estimated crack.

4. Conclusions

This paper proposed crack swarm inspection, with the goal of estimating crack locations and sizes from the surface voltage distribution of a cracked composite material by introducing a genetic algorithm for crack analysis with doublets. By applying the technique to cracked CFRP laminated plates, the estimation accuracy was validated for the electric conductivity, voltage measurement points, and crack depth. The lower the electric conductivity in the thickness direction, the more difficult crack detection becomes, because the voltage change distribution caused by crack development does not have sharp peaks in regions close to the crack. It is possible to detect cracks with voltage measurement points by installing electrodes at smaller intervals than the width of the cracks to be detected. Furthermore, it was confirmed that 7-mm cracks were detected with a degree of accuracy of over 80%. It was also confirmed that the electric current density in the thickness direction around the crack location affects the estimation accuracy. By calculating the equivalent electric conductivity, the proposed method can be extended to multidirectional laminates. Because the accuracy of the estimation depends on the electric conductivity ratio (rz/rx), this method would be more accurate in multidirectional laminates, which have smaller rx compared with unidirectional laminates.