Intrinsically monitored carbon fiber composites using electrical properties

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The research project "Intrinsically monitored carbon fibre composites" deals with the interaction of electrical and mechanical properties of carbon fibre reinforced plastics for the purpose of condition monitoring. The hypothesis is pursued that both component strains and structural damage in carbon fibre composites can be measured using electrical measurement techniques. Thus, instead of dedicated sensors, the load-bearing material itself can be used for load measurement and thus lead to an integration of sensory functions with high material conformity. Elastic component strains lead to changes in shape and piezoresistive effects leading to a reversible change in the electrical resistance. Fiber cracks and delaminations can be observed by irreversible changes of the electrical paths. The suitability of the carbon fiber as a sensor depends largely on whether it is stretched or not. Ondulations lead to a significant reduction and scattering of the sensory property. In this project, therefore, pultrusion is proposed for the first time as a manufacturing technology for carbon fiber-based strain sensors. Pultrusion is a promising technology for the production of strain sensors due to its process-inherent prestressing on the sensorically active carbon fibers. The goal is to create a continuous process for the production of integrated strain sensors based on carbon fibers. The sensors produced in this way are then integrated into glass and carbon fiber reinforced plastics and tested for their achievable strain measurement accuracy.