@misc{CheilakouTsopelasAnastasopoulosetal.2018, author = {Cheilakou, E. and Tsopelas, N. and Anastasopoulos, A. and Kourousis, D. and Rychkov, Dmitry and Gerhard, Reimund and Frankenstein, B. and Amditis, A. and Damigos, Y. and Bouklas, C.}, title = {Strain monitoring system for steel and concrete structures}, series = {Procedia Structural Integrity}, volume = {10}, journal = {Procedia Structural Integrity}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2452-3216}, doi = {10.1016/j.prostr.2018.09.005}, pages = {25 -- 32}, year = {2018}, abstract = {The present work is part of a collaborative H2020 European funded research project called SENSKIN, that aims to improve Structural Health Monitoring (SHM) for transport infrastructure through the development of an innovative monitoring and management system for bridges based on a novel, inexpensive, skin-like sensor. The integrated SENSKIN technology will be implemented in the case of steel and concrete bridges, and tested, field-evaluated and benchmarked on actual bridge environment against a conventional health monitoring solution developed by Mistras Group Hellas. The main objective of the present work is to implement the autonomous, fully functional strain monitoring system based on commercially available off-the-shelf components, that will be used to accomplish direct comparison between the performance of the innovative SENSKIN sensors and the conventional strain sensors commonly used for structural monitoring of bridges. For this purpose, the mini Structural Monitoring System (mini SMS) of Physical Acoustics Corporation, a comprehensive data acquisition unit designed specifically for long-term unattended operation in outdoor environments, was selected. For the completion of the conventional system, appropriate foil-type strain sensors were selected, driven by special conditioners manufactured by Mistras Group. A comprehensive description of the strain monitoring system and its peripheral components is provided in this paper. For the evaluation of the integrated system's performance and the effect of various parameters on the long-term behavior of sensors, several test steel pieces instrumented with different strain sensors configurations were prepared and tested in both laboratory and field ambient conditions. Furthermore, loading tests were performed aiming to validate the response of the system in monitoring the strains developed in steel beam elements subject to bending regimes. Representative results obtained from the above experimental tests have been included in this paper as well.}, language = {en} } @misc{RamanVenkatesanFruebingGerhard2018, author = {Raman Venkatesan, Thulasinath and Fr{\"u}bing, Peter and Gerhard, Reimund}, title = {Influence of Composition and Preparation on Crystalline Phases and Morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) Relaxor-Ferroelectric Terpolymer}, series = {2018 IEEE 2nd International Conference on Dielectrics (ICD)}, journal = {2018 IEEE 2nd International Conference on Dielectrics (ICD)}, publisher = {IEEE}, address = {New York}, isbn = {978-1-5386-6389-9}, doi = {10.1109/ICD.2018.8514758}, pages = {4}, year = {2018}, abstract = {The influence of chemical composition and crystallisation conditions on the ferroelectric and paraelectric phases and the resulting morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer films with 55.4/37.2/7.3 mol\% or with 62.2/29.4/8.4 mol\% of VDF/TrFE/CFE was studied. Poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) with 75/25 mol\% VDF/TrFE was employed as reference material. Fourier-Transform Infrared Spectroscopy (FTIR) was used to determine the fractions of the relevant terpolymer phases, and X-Ray Diffraction (XRD) was employed to assess the crystalline morphology. The FTIR results show an increase of the fraction of paraelectric phases after annealing. On the other hand, XRD results indicate a more stable paraelectric phase in the terpolymer with higher CFE content.}, language = {en} } @misc{WangRychkovGerhard2018, author = {Wang, Jingwen and Rychkov, Dmitry and Gerhard, Reimund}, title = {Influence of Charge Density on Charge Decay in Chemically Modified Polypropylene Films}, series = {2018 IEEE 2nd International Conference on Dielectrics (ICD)}, journal = {2018 IEEE 2nd International Conference on Dielectrics (ICD)}, publisher = {IEEE}, address = {New York}, isbn = {978-1-5386-6389-9}, doi = {10.1109/ICD.2018.8514718}, pages = {4}, year = {2018}, abstract = {Previous work has shown that surface modification with orthophosphoric acid can significantly enhance the charge stability on polypropylene (PP) surface by generating deeper traps. In the present study, thermally stimulated potential-decay measurements revealed that the chemical treatment may also significantly increase the number of available trapping sites on the surface. Thus, as a consequence, the so-called "cross-over" phenomenon, which is observed on as-received and thermally treated PP electrets, may be overcome in a certain range of initial charge densities. Furthermore, the discharge behavior of chemically modified samples indicates that charges can be injected from the treated surface into the bulk, and/or charges of opposite polarity can be pulled from the rear electrode into the bulk at elevated temperatures and at the high electric fields that are caused by the deposited charges. In the bulk, a lack of deep traps causes rapid charge decay already in the temperature range around 95 degrees C.}, language = {en} } @misc{NguyenGerhard2018, author = {Nguyen, Quyet Doan and Gerhard, Reimund}, title = {LDPE/MgO Nanocomposite Dielectrics for Electrical-Insulation and Ferroelectret-Transducer Applications}, series = {2018 IEEE 2nd International Conference on Dielectrics (ICD)}, journal = {2018 IEEE 2nd International Conference on Dielectrics (ICD)}, publisher = {IEEE}, address = {New York}, isbn = {978-1-5386-6389-9}, pages = {4}, year = {2018}, abstract = {Published results on LDPE/MgO nanocomposites (3wt\%) show that they promise to be good electrical-insulation materials. In this work, the nanocomposites are examined as a potential (ferro-)electret material as well. Isothermal surface-potential decay measurements show that charged LDPE/MgO films still exhibit significant surface potentials after heating for 4 hours at 80 degrees C, which suggests good capabilities of LDPE/MgO nanocomposites to hold electric charges of both polarities. Open-tubular-channel ferroelectrets prepared from LDPE/MgO nanocomposite films show significant piezoelectricity with d(33) coefficients of about 20 pC/N after charging and are stable up to temperatures of at least 80 degrees C. Thus LDPE/MgO nanocomposites may become available as a new ferroelectret material. To increase their d(33) coefficients, it is desirable to optimize the charging conditions and the ferroelectret structure.}, language = {en} }