|M.Sc Student||Zehavi Assaf|
|Subject||Ageing of Polymer-Epoxy-Polymer Joints|
|Department||Department of Materials Science and Engineering||Supervisor||Professor Emeritus Arnon Siegmann (Deceased)|
The Research deals with two aspects of ageing of an epoxy-amine system: The first deals with the changing of mechanical properties and chemical structure of this system, containing different amounts of a modifier, after various ageing times, in different environments. The second aspect deals with the energy needed to propagate a crack, so called energy release rate, in polymer-epoxy-polymer joints, determined using a four point delamination technique.
Epoxy samples containing different amounts of a modifier were aged in various environments (water; vacuum, 100oC; air, 70oC, 95%RH). The presence of the modifier has a crucial effect on the ageing rate in wet environments, significantly decreasing the storage modulus and the glass transition temperature. In the absence of the modifier a minor decrease was observed in these parameters. Incorporating the modifier increases the amount of absorbed water. No significant changes were observed in vacuum-aged epoxy. FTIR spectroscopy shows chemical changes including post-curing effects due to a wet-environment ageing.
The energy release rate of the joints was measured by propagating a crack, using four point bending. A significant decrease (>50%) in the energy release rate was measured already after one day of water-ageing. The Humidity-ageing yielded a reduction of 50% in the energy release rate only after more than a month. A correlation between the significant decrease in the storage modulus and the energy release rate after water-ageing is discussed.