A comparative study on the impact performance of water-exposed balsa-cored sandwich structures

This study aims to examine how moisture absorption affects the impact behavior of a recently developed sandwich structure designed for use as a water-resistant system in the marine industry. For this purpose, two types of balsa-cored sandwich systems were manufactured, one with conventional glass fiber-epoxy (GE) skins and the other with novel fiber metal laminates (FML) skins. Subsequently, the specimens were exposed to environmental aging through distilled water immersion for 100 days before impact testing. Low-velocity impact behavior was studied using Charpy tests, while high-velocity impact tests were conducted with a light gas gun. The experimental results showed that FML sandwich systems exhibited significantly better impact characteristics compared to GE systems. Before aging, the Charpy impact strength and high-velocity impact absorbed energy of FML systems were 187% and 49% higher than those of GE ones. Another main finding was the impact properties of the FML systems showed a lower decline due to moisture aging compared to the GE systems, for both low- and high-velocity impacts. The reduction of Charpy impact strength and high-velocity impact absorbed energy due to moisture aging in GE systems with sealed edges was about 15%, and 3%, respectively, and for sealed edges FML systems was less than 12% and 1%, respectively. The results also indicated that the high-velocity impact properties of both sandwich systems studied were not significantly affected by moisture aging. In general, the findings suggest that FML skins significantly enhance both the impact resistance and environmental durability in marine balsa-cored sandwich structures. Graphical abstract