Highly efficient fiber-reinforced composites find extensive application in diverse industries. Yet, conventional fiber-reinforced composites have significant environmental impacts during both manufacturing and disposal. Environmentally friendly fiber-reinforced composites have garnered significant attention within the framework of sustainable development. Utilizing natural fibers in place of synthetic fibers and progressively decreasing the use of synthetic fibers are the main approaches to achieving a balance between economic progress and environmental quality. Attention is increasingly being drawn to natural fiber-reinforced biocomposites that exhibit outstanding environmental performance, exceptional physical and mechanical capabilities, and biological features. The lightweight and high-strength characteristics of these biocomposites enable them to significantly decrease the weight of structures, making them increasingly popular in many industries. The objective of this review is to evaluate the effectiveness of hybrid fiber-reinforced biocomposites in marine applications, specifically examining their mechanical characteristics, resistance to seawater, and ability to absorb moisture, all while advocating for sustainable material methodologies. To achieve this objective, the paper delineates the distinction between synthetic and natural fibers, examines the benefits of hybrid fiber-reinforced biocomposite materials, and addresses the obstacles and effective approaches in their production and application in seawater. Considering the review analysis, it can be inferred that the use of fiber-reinforced biocomposites in maritime applications shows significant potential and has abundant untapped growth prospects in the future years.

Fiber-reinforced composites are widely utilized across various industries, including aerospace, automotive, and marine, due to their outstanding mechanical properties and lightweight characteristics. Natural fibers, as promising reinforcements, have the potential to replace synthetic fibers in certain areas to meet the growing demand for environmental protection and sustainability. These biocomposites offer numerous benefits, including reduced carbon footprints, diminished reliance on non-renewable resources, and increased natural biodegradability. In addition, utilizing such eco-friendly materials is a critical strategy for balancing industry progress and environmental protection. Kenaf fiber, a superior bast fiber known for its excellent mechanical properties and high cellulose content, presents considerable advantages for enhancing the performance of biocomposites. This review explores the potential of kenaf fiber-reinforced biocomposites for marine applications, focusing on their fabrication and testing methods to evaluate their physicochemical and mechanical properties. This paper examines the chemical composition and mechanical properties of the kenaf fiber, investigates the excellent performance advantages of kenaf fiber-based biocomposites by hybridization manufacturing, and provides an overview of the status and challenges of applying such biocomposites in marine environments. Based on this review, it is evident that kenaf fiber-reinforced biocomposites have significant superiority for marine applications with the advancement of manufacturing techniques.

Unmanned maritime vehicles (UMVs) have become essential tools in marine research and monitoring, significantly enhancing operational efficiency and reducing risks and costs. Fiber-reinforced composites have been widely used in marine applications due to their excellent characteristics. However, environmental concerns and the pursuit of sustainable development goals have driven the development of environmentally friendly materials. The development of eco-friendly biocomposites for UMV construction can effectively reduce the environmental impact of marine equipment. This study investigates the effects of seawater aging on kenaf/flax/glass-fiber-reinforced composites under artificial seawater conditions and determines their ranking for UMVs using the Analytic Hierarchy Process (AHP). These hybrid composites, fabricated with various stacking sequences, were prepared using a combination of hand lay-up and vacuum bagging techniques. All plant fibers underwent sodium hydroxide treatment to eliminate impurities and enhance interfacial bonding, while nano-silica was incorporated into the epoxy matrix to improve overall performance. After 50 days of immersion in artificial seawater, mechanical tests were conducted to evaluate the extent of changes in mechanical properties. Subsequently, the AHP analysis was performed based on three main criteria and thirteen sub-criteria to determine the most suitable configuration for marine applications. The results demonstrate that the stacking sequence plays a critical role in resisting seawater-induced degradation and maintaining mechanical performance. GKFKG exhibited the highest retention rates for both tensile strength (86.77%) and flexural strength (88.36%). Furthermore, the global priority vector derived from the AHP analysis indicates that hybrid composites consisting of kenaf, flax, and glass fibers consistently ranked highest. The optimum configuration among these hybrid composites was determined to be GKFKG, followed by GFKFG, GKKKG, and GKGKG.

Recently, with concern for the environment and the request for sustainable materials, more researchers and manufacturers have focused on the substitute solution of synthetic fiber reinforcement composites in industry applications. Green hybrid composites with natural components can present excellent sustainability, possess superior mechanical behavior, and reduce hazards. Hybridization technology allows new materials to inherit their raw materials’ characteristics and generate new properties. The current study designed novel double-walled shell structures (DS1R4L, DS2R8L, and DS5R12L), containing two thin walls and different numbers of ring and longitudinal stiffeners, as unmanned maritime vehicle (UMV) components. A normal single-walled cylindrical shell was used as a control. These models will be made of hybrid kenaf/flax/glass-fiber-reinforced composites, GKFKG and GFKFG, created in the ANSYS Workbench. The mechanical responses (deformation, stress, and strain characteristics) of models were examined under three loading conditions (end force, end torque, and hydrostatic pressure) to evaluate the influence of both material change and structural configuration. Compared to the single-walled structure, the double-walled configurations display minimized deflection and torsional angle. Moreover, GKFKG-made structures are better than GFKFG-made ones. The research contributes positively to advancing the application of hybrid kenaf/flax/glass-fiber-reinforced composites in UMV structures and promotes the development of green sustainable materials.