Marine Coolant Fluids’ Effect on the Mechanical Properties of Glass Fiber-Reinforced Composites

Abstract

This study examines the effect of coolant and antifreeze solutions such as distilled water, ethylene glycol-based antifreeze with organic acid technology (OAT), and ethylene glycol-based antifreeze with inorganic inhibitors and glycerol (IAT/HOAT) on the tensile strength of glass fiber-reinforced polyester (GFRP-P) and vinyl ester (GFRP-VE) composites. Standardized specimens were produced and immersed in these solutions for three months at room temperature. Following exposure, tensile tests were conducted using the universal testing machine, supported by microscopic analysis to evaluate surface damage and internal structural changes such as composite layer delamination. The tensile test results show the highest decrease in tensile strength for GFRP-P specimens immersed in HOAT antifreeze (16.3%), whereas GFRP-VE specimens exhibit only a minimal reduction (3.4%). This difference is attributed to the higher chemical aggressiveness and alkalinity of the HOAT antifreeze. Furthermore, the decrease in the tensile strength of GFR-P exposed to OAT antifreeze is 6.1%, whereas GFRP-VE demonstrates a significantly smaller reduction of 1%, which can be attributed to the less aggressive chemical composition of the OAT formulation compared to HOAT. In contrast, the influence of distilled water on GFRP-P specimens is manifested as a tensile strength decrease of 12.7%, whereas GFRP-VE specimens show a reduction of 11%, attributed to the fluid’s density and the rate of hydrolytic degradation. These results contribute to a deeper understanding of the effects of various coolant media on the performance of GFRP in marine cooling systems, highlighting GFRP-VE as a more suitable matrix for prolonged exposure to coolant environments.