Dynamisch mechanische Analyse von Epoxidharzen

Research output: ThesisMaster's Thesis

Abstract

Epoxy resins are due to their excellent mechanical and thermal properties the most used matrix resins in high performance fibre-reinforced composites. In order to measure thermo-mechanical properties, dynamic mechanical analysis (DMA) is an important test method, but has to be adjusted for the specific material. The present master thesis intents to examine various dynamic mechanical testing methods concerning significance and reproducibility for the determination of the thermo-mechanical properties for a selected epoxy resin. Tensile, bending and torsional loading are used for the determination of the dynamic storage modulus and the mechanical loss factor as functions of temperature for the cured state of the resin. Moreover, the possibility of dynamic mechanical characterisation of the curing process as well as the properties of the cured state in a single measuring run is examined. Comparing the different DMA techniques it turned out, that the best reproducible measurements are those under tensile and torsional loading. The statistical spread of moduli in the glassy state at a temperature of 23 °C is found to be around 24 MPa with the corresponding shear modulus of 1190 MPa, the glass transition temperature, with a mean value of 129°C, shows a standard deviation of 0,6°C. At lower as well as at higher temperatures an equal low statistical spread can be found. The stability of these DMA methods is based on the fixed clamping of the specimen. A negative influence of the effects related to the fixed clamping was not obvious. Less stable results with a standard deviation of the flexural modulus of around 200 MPa were found especially for the low temperature range at -60 °C due to instable clamping conditions in the 3-point bending clamping assembly. For the combined dynamic mechanical characterisation of the curing process and the cured state of the epoxy resin a DMA testing procedure based on torsional loading was developed. With this testing method it is possible to determine thermo-mechanical properties during the curing process as well as the characteristic temperature dependent property functions of the cured state in a single measurement. The resulting functions of shear modulus and loss factor are corresponding very well to the results of standard DMA tests.

Details

Translated title of the contributionDynamic mechanical analysis of epoxy resins
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
Award date18 Dec 2009
Publication statusPublished - 2009