Oversizing No More Necessary
Textile-based Sensors Enable Safe Monitoring of CFRP Components
Scientists of TU (Technische Universität) Dresden, Germany, are developing textile-based sensor networks designed to be integrated in heavy-duty fiber composites in a way that fits the respective material. They are due to detect global and local loads as well as changes in structure, so that oversized CFRP components can be dispensed with.
Fiber-reinforced components, such as rotor blades for wind power plants, are frequently designed larger than necessary. This is done to make up for missing information concerning their residual bearing capacity during component application, due to, e.g. ageing, overload or load history. Conventional methods to monitor the structure, however, can only provide information to a certain extent.
Strain gages, for example, include downsides such as adhesive failure as a result of environmental impact or sensitivity to temperature, making them unreliable for long-term measurements. CFRP-compatible integration into heavy-duty components has therefore been possible only to a certain extent, as yet.
The Tessy Project: Predictable, Reliable Lightweight Structures
The Tessy research project (Monitoring CFRP Structures Using Textile-Based Sensory Systems Integrated Using Textile Technologies) is funded by the German Federal Ministry of Economic Affairs and Energy. Scientists from the Institute of Textile Machinery and High Performance Material Technology (ITM), the Institute of Lightweight Engineering and Polymer Technology (ILK) and the Institute of Electronic Packaging Technology (IAVT) at TU Dresden work together on this project, developing textile-based sensor systems based on carbon fibers connected to an electrical circuit. Taking advantage of the electrical conductivity of the carbon fibers, the researchers measure the fibers’ electrical resistance, which directly depends on the load placed on the reinforcing structure.
The major challenge for the scientists, in addition to intelligent connection and arrangement of the sensor fibers, is damage-free integration of the sensor carbon fibers into the textile reinforcing structure. Fiber displacement and pores occurring during infiltration with a polymer matrix may deteriorate both sensor functionality and the load-bearing capacity of the component.
The scientists are therefore analyzing and evaluating how sensor layout affects the infiltration of semi-finished textiles, if using conventional techniques. In addition, materials are also tested with respect to component performance so as to gain insight into potential damage to reinforcement structures caused by the integration of sensor filaments and their electrical contacts.
Oversizing no Longer Required
Unlike conventional structural monitoring systems, the novel sensor systems are suitable to detect not only local and global, but also static and dynamic loads and structural deformation over the entire service life of a component. Simulation-based analytical procedures due to be developed as part of the project will enable immediate statements on the residual load-bearing capacity of a component.
CFRP-compatible integration will also lead to long-term sensor stability throughout the service life of the overall structure. Prof. Dr.-Ing. habil. Chokri Cherif, Director of the ITM, states: “These novel sensors facilitate precise localization of all changes critical to the structure.” He explains that potential damage can be detected at an early stage and expensive subsequent repair be avoided.
In the long run, these textile-based sensors will make safety-related oversizing of CFRP components unnecessary. “In addition to saving both resources and energy, this will also reduce CO2 emissions during production,” explains Cherif.
TU Dresden - Institut für Leichtbau u. Kunststofftechnik
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