FRP embedded micro-sensors on multifunctional substrates for curing process control

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An important challenge for the development of innovative highperformance fiber reinforced plastics for light-weight constructions is the local monitoring of the nascent material structure using embedded sensors to allow further reducing the weight of fiber composite structures. Novel sensors for on-line monitoring of strains and of the curing behavior of fiber composite materials are highly desired and can have an enormous influence on the dimensional stability, the mechanical and physical characteristics, and the service life of a component. Furthermore, material damage resulting from excessiveloads could with the aid of sensors remaining integrated in the material be avoided or detected at an early stage so that the maintenance of the support structures can be more targeted and carried out more efficiently. A prerequisite for integrated sensors is that the compound material is not mechanically weakened. In a first approach, the materials, the microfabrication processes and the design of the sensors will be chosen in such a way that the initially introduced "foreign body" disappears almost completely from the material compound and the sensor system mechanically no longer disturbs the structure. Beyond that, it would be fascinating when the composite mechanical properties could even improve by the sensor embedding. In a second approach, this research project thereforeaims at the development of integrated sensors based on very thin polymer films that can even enhance the impact strength of the epoxy based composite. Amorphous thermoplastics are possible candidates being already in use for toughening. By means of micro sensors for temperature, impedance, and strain that are produced on thin foilsand subsequently integrated into the composite material, information can be obtained from the internal state of the material which can serve as control data during production. The sensor-based monitoring of local material state will allow optimization of the production processes, shortening of storage times and a sophisticated qualityassurance.