Influence of Stacking Sequence and Seawater Aging on Mechanical, Thermal, and Viscoelastic Properties of Hybrid kenaf/Flax/Glass Fiber-Reinforced Sustainable Composites

Hybrid fiber-reinforced composites are gaining prominence in engineering for their lightweight, high-strength, and eco-friendly potential. This study explores the performance of sustainable hybrid kenaf/flax/glass fiber composites in marine environments. Natural fibers like kenaf and flax offer renewable, biodegradable alternatives to synthetic reinforcements, reducing environmental impact. Three five-layer stacking sequences, namely, GKKKG, GKFKG, and GFKFG were fabricated using hand lay-up and vacuum bagging methods, then exposed to seawater for 50 days. Specimens were tested as per ASTM standards using Izod impact, Shore D hardness, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Among the configurations, GFKFG demonstrated superior durability, with minimal degradation in impact strength (18.2%), energy absorption (12.7%), and hardness (2.3%). TGA results showed aged samples retained slightly higher residual mass and exhibited delayed, less intense thermal peaks. DMA revealed GFKFG had the highest storage modulus, while GKFKG showed the best damping behavior. These findings highlight the potential of hybrid natural/synthetic fiber composites especially GFKFG as sustainable alternatives for marine applications, combining mechanical resilience with reduced ecological footprint.