Evaluation of Property Retention in E-Glass/Vinylester Composites after Exposure to Salt Solution and Natural Weathering

Abstract

E-glass fiber reinforced vinylester composites are attractive for use in civil infrastructure applications ranging from repair and rehabilitation to new structural systems due to their potential durability and low cost. However, these materials, generally cured under ambient conditions, must withstand changing and severe environmental conditions over extended periods of time. Data related to their degradation kinetics and property retention are largely anecdotal and lack the existence of both fundamental and mechanistic information and a data-base on the basis of which service life could be reasonably established. This study investigates the degradation of two E-glass architectures after exposure to salt solution, accelerated heat cycles based on a summer in Sydney, and actual outdoor weathering over an 18 month period in Sydney, Australia. It is seen that both tensile strength and modulus are reduced due to the various exposures with attendant degradation at the matrix, fiber, and interphase levels. Based on results of the study it is concluded that natural weathering can lead to rather severe degradation at the surface level, which if not corrected leads to rapid degradation through the thickness, emphasizing the criticality in use of surface coatings and/or veils/layers of mat. It is also shown that changes in Tg are due to both physical and chemical aging with overall effects to an extent being irreversible due to matrix hydrolysis and cracking, and fiber degradation.