Development of a highly sensitive strain sensor consisting of a nickel-carbon composite for new hybrid laminatesThursday (29.09.2016) 09:15 - 09:30 Part of:
Lightweight components comprised of fibre-reinforced plastics (FRP) have become more important for many different industrial applications in recent years. However, to take full advantage of this relatively new class of materials systems monitoring their state are a necessity. By means of methods such as Structure Health Monitoring (SHM), for example, permitted mechanical stresses within the composite structure can be measured, while the components remain unharmed and can be improved. At the same time SHM reduces maintenance costs due to the increased level of automation. Fibre-reinforced hybrid laminates with thermoplastic matrices offer numerous advantages over thermosetting resin-based laminates. These favourable characteristics include things such as the reduction of cycle times in the production and finishing of semi-finished products. Additional advantages to be mentioned are the improved formability, the good recyclability and the suitability of the in-line manufacturing utilised for mass production. One of the long-term objectives of the Federal Cluster of Excellence MERGE is the in-line integration of smart systems like sensors and actuators in fibre-reinforced hybrid laminates during the hot-pressing process for spatially resolved monitoring of lightweight components. This work aims to produce nickel-carbon thin films by DC-magnetron sputtering on polyimide substrates for the application as highly sensitive and temperature-compensating strain sensors in hybrid laminates. During the first step, commercially available polyimide films were investigated regarding to the suitability as a carrier substrate of the strain sensors. For this, they were processed by hot-pressing in hybrid laminates. In order to provide the most suitable polyimide substrate for thin-film depositing of Ni-C the samples underwent mechanical tests. The next step consisted of the deposition of Ni-C thin films by means of DC-magnetron sputtering under use different Ni-C plug targets and a mask to manufacture meander shape-strain gauges. These films were characterised regarding to their layer deposition rate, composition, structure, temperature coefficient of electrical resistance (TCR) and their sheet resistance. In order to verify that the Ni-C layers are temperature-resistant concerning the hot-pressing process, annealing tests were performed. As a result of this, a temperature-programmed Raman analysis was carried out and the change of the TCR and sheet resistivity were determined.