COMPARISON OF SEAWATER EFFECTS ON MECHANICAL AND VISCOELASTIC PROPERTIES OF EPOXY COMPOSITES WITH GLASS, CARBON AND THEIR HYBRID FABRIC REINFORCEMENTS

Increasing demand for high performance materials with enhanced durability in marine environments has led to the developments of hybrid polymer composites consisting of different fibers as epoxy reinforcements. The goal is to harness various properties of individual constituents of the composites. In the current study, fiber reinforced polymer composite (FRPC) laminates were fabricated using SC-780 epoxy resin reinforced with E-glass (G), carbon (C) and hybrid of carbon/Eglass fabrics, and conditioned in seawater at room temperature. Hybridized fibers consisted of profiles 1: (2G-9C-2G); 2: (G-C-G - alternating sheets), and 3: (5C-3G-5C). Properties of these fibers were targeted to utilize their inherent features while reducing overall cost and absorption characteristics of their composites leading to enhanced durability. Unconditioned hybrid composites showed average enhancements of 25, 47 and 103% in flexural strength and 19, 58 and 94% in flexural modulus for Profiles 1, 2 and 3 respectively when compared to E-glass composites. Similarly, viscoelastic characterization through dynamic mechanical analysis showed -10, 8 and 21 % enhancements in storage moduli at 30 degrees C for profile 1, 2 and 3 respectively compared to E-glass composites. When immersed in sea water, E-glass/epoxy composites and profile 3 hybrid composites had highest weight gain while the profile-1 hybrid had the least absorption. While the flexural strength decreased for all composites, there was slight increase in the flexural modulus. Storage modulus decreased for carbon/epoxy and profile 2 composites steadily. On the other hand it increased initially for other composites before reversing the trend. Glass transition temperature (Tg) decreased for all composites upon exposure to sea water.