Cold-temperature and simultaneous aqueous environment related degradation of carbon/vinylester composites

The effects of non-cryogenic, cold temperature conditions especially as related to freeze–thaw cycling both in the presence of aqueous solutions, and just ambient humidity, on carbon fiber composites is not well understood. Based on processing characteristics and lower cost, vinylester resin systems are increasingly being used in civil infrastructure and in off-shore applications. The use of these systems with carbon fibers causes some concern due to the current lack of appropriate finish on the fibers. In addition the use of ambient cure processes such as wet layup and resin infusion raise concerns of durability since these resin systems typically do not achieve full conversion and are thus susceptible to moisture induced degradation. This paper reports on results of short-term exposure of thin ambient cured carbon/vinylester specimens, processed following wet layup procedures similar to those used in rehabilitation of structural components, to freeze and freeze–thaw cycling. It is shown that freeze–thaw can cause significant reduction in mechanical properties and in glass-transition temperature with immersion in salt water having a larger effect on fiber-matrix bond deterioration and matrix cracking than other exposures.