Thandavamoorthy Raja, Yuvarajan Devarajan, Deepak Kohli, Ranganathaswamy Madihalli Kenchappa, Nagendra SVH, Mukul Saxena, Jayanta Kumar Nath, Kulmani Mehar
Natural fibers are increasingly recognized as sustainable materials supporting the transition toward circular and eco-friendly material technologies due to their biodegradability, renewability, and low density. This review provides a critical overview of natural fiber resources, including their classification, chemical composition, and structural characteristics. Various fiber extraction techniques are discussed, comparing conventional methods such as water retting and mechanical decortication with emerging green approaches including enzymatic treatments, ionic liquids, and microwave or ultrasound-assisted extraction, highlighting their effects on fiber morphology, crystallinity, and surface properties. The physicochemical, thermal, and mechanical properties of major natural fibers are summarized using literature-based ranges to clarify their reinforcement potential in polymer composites. Key application areas are reviewed across automotive, construction, biomedical, packaging, and renewable energy sectors, with attention to material performance and industrial feasibility. Emerging research directions, including hybrid composites, nanofiber reinforcements, surface functionalization for antimicrobial behavior, and smart bio responsive materials, are also highlighted. Finally, major challenges are discussed, including variability in fiber quality due to agro-climatic conditions, scalability limitations of eco-friendly extraction processes, durability under environmental stress, and the lack of standardized testing protocols. Addressing these issues is essential for advancing the broader adoption of natural fiber – based materials in sustainable engineering applications.