Dresden, Germany
Dresden, Germany

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Heuer H.,Fraunhofer Institute for Ceramic Technologies and Systems | Heuer H.,TU Dresden | Schulze M.,Fraunhofer Institute for Ceramic Technologies and Systems | Pooch M.,Fraunhofer Institute for Ceramic Technologies and Systems | And 14 more authors.
Composites Part B: Engineering | Year: 2015

Eddy current testing is well established for non-destructive testing of electrical conductive materials [1]. The development of radio frequency (RF) eddy current technology with frequency ranges up to 100 MHz made it possible to extend the classical fields of application even towards less conductive materials like CFRP [2][3](Table 2). It turns out that RF eddy current technology on CFRP generates a growing number of valuable information for comprehensive material diagnostic. Both permittivity and conductivity of CFRP influence the complex impedance measured with RF eddy current devices. The electrical conductivity contains information about fiber texture like orientations, gaps or undulations in a multilayered material. The permittivity characterization influenced by dielectric properties allows the determination of local curing defects on CFRP e.g. hot spots, thermal impacts or polymer degradation. An explanation for that effect is seen in the measurement frequency range and the capacitive structure of the carbon rovings. Using radio wave frequencies for testing, the effect of displacement currents cannot be neglected anymore. The capacitive structures formed by the carbon rovings is supposed to further strengthen the dielectric influences on eddy current measurement signal [3]. This report gives an overview of several realized applications and should be understood as a general introduction of CFRP testing by HF Radio Wave techniques. © 2015 The Authors. Published by Elsevier Ltd.


Grant
Agency: European Commission | Branch: FP7 | Program: CP-IP | Phase: NMP.2013.4.0-1 | Award Amount: 12.40M | Year: 2013

GLADIATOR (Graphene Layers: Production, Characterization and Integration) will enable the scalable production of cheaper, higher quality and larger area graphene sheets. The project will achieve this by optimizing the performance of CVD graphene (using doping), by increasing the throughput and size of CVD batch reactors, and by improving the process by which graphene is transferred for the CVD catalysts to the application substrate. GLADIATOR directly targets the gobal market for transparent electrodes (estimated to be worth over 11,000 million USD in 2016) and will demonstrate that the performance and price of indium tin oxide can be matched by graphene (transparency > 90%, sheet resistance < 10 Ohm/sq, cost < 30 Eur/ square meter). The new production technologies will be demonstrated by making ultraviolet organic photodiodes (possible application as fire sensors) and large area flexible OLEDs. CVD graphene production will be optimized using new diagnostic and process control instrumentation based on Raman spectroscopy and spectrometric ellipsometry; the quality of graphene layers post-transfer will be assured using new non-contact in-line eddy current measurements and THz imaging. CVD production costs per unit area will be reduced not only by the process parameter optimization, but also by developing methods to re-use the catalysts and by increasing the size of the reactor chamber. The process safety will be addressed, too. A critical issue for graphene, especially as a transparent electrode, is how to achieve homogenous large area coverage. GLADIATOR will extend the size of graphene layers beyond that of the CVD tools by implementing a novel patchwork process using a transfer process with high yields and negligible impact upon the properties of the graphene. Transfer processes will be developed for rigid and flexible substrates appropriate for organic large area electronics (OLAE), and substrate and barrier properties will be optimized for use with graphene.


Bardl G.,TU Dresden | Nocke A.,TU Dresden | Cherif C.,TU Dresden | Pooch M.,Fraunhofer Institute for Ceramic Technologies and Systems | And 6 more authors.
Composites Part B: Engineering | Year: 2016

Ensuring the correct fiber orientation in draped textiles and 3D preforms is one of the current challenges in the production of carbon-fiber reinforced plastics (CFRP), especially in resin transfer molding (RTM). Small deviations in fiber angle during preforming have a considerable effect on the mechanical properties of the final composite. Therefore, this paper presents an automated method for determining local yarn orientation in three-dimensionally draped, multi-layered fabrics. The draped fabric is scanned with a robot-guided high-frequency eddy current sensor to obtain an image of the sample's local conductivity and permittivity. From this image, the fiber orientation not only of the upper, but also of the lower, optically non-visible layers can be analyzed. A 2D Fast Fourier Transform is applied to local segments of the eddy current image to determine the local yarn orientation. Guidelines for processing the eddy current data, including phase rotation, filtering and evaluation segment size, are derived. For an intuitive visualization and analysis of the determined yarn orientation, reference yarn paths are reconstructed from the determined yarn angles. The developed process can be applied to quality inspection, process development and the validation of forming simulation results. © 2016 The Author(s). Published by Elsevier Ltd.


Muhl S.,Fraunhofer Institute for Electron Beam and Plasma Technology | Klein M.,Suragus GmbH | Torker M.,Fraunhofer Institute for Electron Beam and Plasma Technology | Richter A.,TU Dresden
Digest of Technical Papers - SID International Symposium | Year: 2015

Slot die coated silver nanowires as OLED anode are developed. The influence of the coating parameters ∗shuttle velocity' and 'coating gap' on the single layer properties transmittance and sheet resistance anisotropy is examined The influence on the OLED performance is explored. ©2015 SID.


Heuer H.,Fraunhofer Institute for Ceramic Technologies and Systems | Heuer H.,TU Dresden | Schulze M.,Fraunhofer Institute for Ceramic Technologies and Systems | Pooch M.,Fraunhofer Institute for Ceramic Technologies and Systems | And 3 more authors.
54th Annual British Conference of Non-Destructive Testing, NDT 2015 | Year: 2015

Eddy current testing is well established for non-destructive testing of electrical conductive materials [1]. The development of radio frequency (RF) eddy current technology with frequency ranges up to 100 MHz made it possible to extend the classical fields of application even towards less conductive materials like CFRP [2][3]. It turns out that RF eddy current technology on CFRP generates a growing number of valuable information for comprehensive material diagnostic. Both permittivity and conductivity of CFRP influence the complex impedance measured with RF eddy current devices. The electrical conductivity contains information about fiber texture like orientations, gaps or undulations in a multilayered material. The permittivity characterization influenced by dielectric properties allows the determination of local curing defects on CFRP e.g. hot spots, thermal impacts or polymer degradation. An explanation for that effect is seen in the measurement frequency range and the capacitive structure of the carbon rovings. Using radio wave frequencies for testing, the effect of displacement currents cannot be neglected anymore. The capacitive structures formed by the carbon rovings is supposed to further strengthen the dielectric influences on eddy current measurement signal [3]. This report gives an overview of several realized applications and should be understood as a general introduction of CFRP testing by HF Radio Wave techniques.


Klein M.,Suragus GmbH | Herzog T.,Suragus GmbH | Hillmann S.,Fraunhofer Institute For Zerstorungsfreie Pruifverfahren | Schulze M.,Fraunhofer Institute For Zerstorungsfreie Pruifverfahren | And 2 more authors.
Galvanotechnik | Year: 2012

Many thin-films, simple and complex composite materials (e.g. carbon fiber composites) and layer systems (e.g. photovoltaic cells) can be characterized with the help of advanced eddy current testing technology as numerous quality parameters affect the local electrical conductivity. This paper presents measurement results gained with high-resolution eddy current spectroscopy and transmission eddy current testing at different layer systems. Detectable characteristics in thin-films and layer systems are sheet resistance, thickness, electrical conductivity, inhomogeneities or the depiction of structures. In many applications there are specific defects that are detectable with the underlying method. Presented examples from photovoltaics show finger failures, cracks, diffusion and deposition effects. Detectable effects in carbon fiber materials are missing fiber bundles, lanes, suspensions, missing sewing threads and angel errors in hidden layers.

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