We endeavour to develop the technologies and the methods required to enable a complete life cycle monitoring system of composite material structures.
Illustration of life cycle monitoring (S Minakuchi 2011)
At the stage of the production process monitoring is commonly restricted to temperature measurements at several locations within the laminate. The material is subsequently checked for production errors either visually or with ultrasonic inspection. Our goal is to use flexible electronics in combination with optical sensor technology to monitor the residual strains during the production process and to link this to the degree of polymerization of the material. Since strain fields in the structure act along multiple axes, the consortium targets multi-axial strain sensors. In addition to the sensor development, the consortium also endeavours to identify industrial solutions in terms of compatibility with the fabrication processes.
Current standard inspection techniques such as visual surveillance, ultrasonic inspection and radiography do not answer the need for continuous in-service and in-situ monitoring. Moreover these techniques are labour-intensive and therefore expensive. In the few cases where in-situ monitoring is employed, the sensors monitor the load history without providing a diagnosis of the health of the material (for example monitor the evolution of properties such as the stiffness of the material or localize and quantify the appearance of damage). The current state of the art in sensor technology does not allow measuring all strain components present during loading of a structure. Moreover they are mostly mounted on the surface of the structure while a representative assessment of the integrity of the structure can only be obtained when they are embedded. The last figure illustrates the advancement upon the state-of-the-art in in-situ strain monitoring targeted by our project proposal.