MECHANISMS OF MOISTURE ABSORPTION BY CYANATE ESTER MODIFIED EPOXY RESINS

摘要

High modulus graphite/epoxy composites have been the materials of choice for aerospace applications. However, the use of conventional epoxy systems has drawbacks as a result of high water absorption. Cyanate ester act as a hardner for the curing of epoxy resin. The absorbed moisture is normally considered to be present in the free-volume of a polymer matrix, acting as plasticizer, there by degrading its mechanical performance especially at elevated temperatures [1]. The environment may be especially damaging if the temperature is not constant but varies rapidly over a wide range [2]. Sudden, large temperature changes, referred to as 'thermal spikes', are encountered, for example, by aircraft flying at supersonic speeds [3]. Thermal spikes may alter significantly the moisture absorption as well as the mechanical properties of cured polymer resin. The objective of this investigation was, to evaluate the relationships between material behaviour and variables such as maximum and minimum temperatures during a thermal spike, the duration of the spike, dry spiking and number of spikes.