Wireless power transfer for structural health monitoring of composite structures

Details

Supervisors

Flandre, Denis ; Francis, Laurent

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil électricien

Abstract

We, here, lay down the base ground and framework for the design of the wireless power transfer unit of a sensor node for structural health monitoring of composite structures. Composite structures like aircraft, wind turbine blades or car are prone to hidden damages. Carbon ber composite risk of failure also increases with lifetime due the environmental impacts. These factors are leading the industry to look toward condition-based maintenance techniques. This requires the development of structural health monitoring techniques assessing parameters like strain, temperature or humidity within the structure at regular time intervals. In this context, the need for insertion techniques and powering of electronics within the composite has arisen. This work focuses on the wireless power transfer through resonant magnetic coupling for a receiver embedded into carbon ber reinforced composites. A complete analytic model of coupled coils separated by a conductive sheet was rst developed. The equations obtained were used to numerically evaluating the impact of the composite plies on the self-inductance, quality factors, mutual inductance of the system and so on the power transfer eciency. Following that, a design ow using the 3D simulation software CST was put in place. The ber composite was approximated as an homogeneous media of eective conductivity of 7500 S/m, approximation which was experimentally veried. This was done by implanting three PCB test coils in composite material. The results of measurements on the coils were then compared to simulation results obtained with CST in which similar 3D coils were inserted into the equivalent homogeneous material. To do so, a custom composite fabrication technique was put in place to embed pancake coils into composite samples. It was concluded that the combination of CST simulations and of the homogeneous material approximation could predict the coils self-inductances as accurately in CFRP as in air. Finally, this process was applied to small pancake coils and following aircraft application constraints. They were inserted 1- and 2-plies deep into industrial pre-impregnated composite. With those specimens, it is proved that power can be transferred within the composite achieving 0.6% and 0.45% power transfer eciencies for the 1- and 2-plies deep samples respectively.