Failure analysis of FRP composites exposed to real marine environment

Abstract

Fiber reinforced polymer (FRP) composites find ever growing application possibilities in marine structures. Due to harsh environmental operational conditions, failure prediction of such structures is an imperative in this industry sector. For this reason, samples of epoxy/glass and polyester/glass with various fiber layout configurations have been submerged under the sea for prolonged periods (6 and 12 months). On contrary to usual accelerated laboratory experiments, these type of tests in real sea environment and for prolonged periods are rarely done. They are useful to obtain more realistic environmental input parameters for structural modeling of marine structures. Changes in mass, marine microbiology growth, tensile strength and morphological structures were analyzed after submersion and compared with samples exposed to room environment. All samples exhibited an increase in mass due to seawater absorption and microorganism growth in the organic resins used as matrix materials. The dynamic and level of decrease in tensile strength showed dependency on the fiber layout configuration. Optical and scanning electron microscopical investigation showed significant matrix morphological changes primarily due to salt crystal formation and the impact of sea microorganisms embedding in the resin. Results of this experimental work will be used as realistic input parameters for subsequent failure analysis numerical tool that can be applied for life-time behavior predictions of marine structures.