Damage detection of CFRP laminates via self-sensing fibres and thermal-sprayed electrodes

Structural components made of carbon/graphite fibre-reinforced polymers (CFRP) are frequently deployed in environments where solid particle impacts can generate surface degradation and damage. Recently, several nondestructive evaluation methods have been proposed to detect any damages for composite materials. However, many of them are not suited for real-time health monitoring in large scale due to their complexity and cost. This study proposes a new monitoring system to quantify the extent of damage using carbon fibres themselves as self-sensing sensors. This approach utilises recently developed thermal spray process to deposit copper electrodes directly onto composite surfaces. These electrodes are used to measure electrical resistances along the carbon, which are processed to estimate damage state via inverse analysis. In this study, in order to determine appropriate distributions of electrodes to identify damage parameters, several simulations are carried out under different electrode spacing conditions. To improve the estimation accuracy, an error sensitivity analysis is also carried out with various data processing schemes. In addition, preliminary tests are conducted for actual CFRP laminates with thermal-sprayed electrodes to verify the concept of the proposed method. Here, electrical resistance changes are measured with an artificially introduced damage. Although further refinements are necessary, increased resistances due to the damage among electrodes are obtained.