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Gewählte Doctoral Thesis:

Christoph Winkler (2021): Process and material features influencing piezoresistive wood adhesives.
Doctoral Thesis - Institut für Holztechnologie und Nachwachsende Rohstoffe, BOKU-Universität für Bodenkultur, pp 197. UB BOKU obvsg FullText

Data Source: ZID Abstracts
Abstract:
The use of piezoresistive adhesive bond lines in timber construction offers various advantages over classic sensors and is intended as an option to monitor structural timber components during operation. The thesis systematically deals with different material- and process-specific variables with impact on the piezoresistive properties of piezoresistive wood bonds and presents the currently available fundamental theoretical inputs from other fields of application. For this purpose, electrically conductive adhesives based on polyurethane polymers and various carbon allotropes were produced, and their adhesive strengths and electrical and piezoresistive properties were initially investigated in an experimental design. The results showed that increased piezoresistive sensitivity can only be achieved with low filler concentrations and that low press temperatures favour this. The reduction of high instabilities of the piezoresistive reaction (electrical drift, low reproducibility and increased base resistance after loading) which accompanied high sensitivities could be achieved through higher filler concentrations, increased glue spread, longer pressing times and thermal postcuring. The results also show that, despite high filler concentrations, the minimum requirement of 10 MPa when testing the tensile shear strength according to EN 302-1 (A1) can be achieved. It could be shown that, depending on the frequency, a significantly increased signal-to-noise ratio compared to classical resistance measurements with the help of impedance spectroscopy was possible. Finally, a material-based model could be derived from the different high sensitivities and the direction of the change in resistance, which enables both a qualitative estimation of the relative sensitivity and can explain inverse piezoresistivity in anisotropic materials.

Betreuer: Teischinger Alfred
1. Berater: Konnerth Johannes

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