In recent days, natural fiber reinforced polymer composite is more popular due to its extensive properties suitable for various potential applications. The attention towards natural fibers is because of low cost, biodegradable, recyclability, nonabrasive, combustible, lightweight, and nontoxic properties. However, there is a need for furthermore fundamental knowledge for the raw materials processing and fabrication of composite structures, which is still challenging in current days. Natural fiber sources exist all over the world, which is obtained from animals, plants and minerals. The quality of the natural fibers depends on the extraction methods and different processing techniques. These natural fibers surface characteristics could be enhanced by selecting suitable surface treatment and chemical treatment. These fiber treatments reduce the water intake percentage, improve the adhesive nature, and enhance the overall performance of resulting polymer composites. Among all the chemical treatments, alkaline treatment (NaOH) is the most preferred chemical treatment because of its effectiveness and its low cost. This review article proposes the natural fibers detailed classification, composition, structure, properties, and extraction methods, chemical and surface treatments. We also summarize the previous research work findings on the fibers treatment, properties of natural/natural hybrid polymer composites and natural/synthetic hybrid polymer composites with applications.

The continuous delivery of E-waste from petroleum-based products creates ecological and environmental problems due to non-biodegradable polymers, which release harmful chemicals and toxic gases. This results in biodegradable polymers/fibers appearance, which are biocompatible and degrade in the surrounding environments without causing any environmental pollution and these relieve environmental burden. However, the bio-based materials are unable to meet certain properties in the way of flexibility, dielectric properties, electrical properties, water and gas vapor barrier properties. The current day's research focus is towards the implementation of biodegradable composites properties by introducing different nanostructures. The biopolymers/biofibers

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The continuous demands for reducing environmental impact and energy consumption are the major driving factors for the development of natural fiber (NF)-reinforced composites (NFRCs). The huge demand for sustainable materials in industries leads to the usage of NFs in product developments. These NFs are more attractive due to their lightweight, cost-effectiveness, ease of availability, and environmentally friendly aspects. Green composites are the best alternatives in place of petroleum-based composites which meet the current industrial requirements. In recent years, researchers are more focused on the development of NF composites as a potential candidate in real-life applications due to economic advantages. This review gives a brief overview of NFs introduction, types, economic aspects, and the recent developments in NFRCs with an analysis of mechanical, thermal, and dielectric properties. Moreover, the water absorption behavior, applications, and challenges in using NFs are also studied in this review. Additionally, this review will motivate the researchers for further developments and exist as foundation literature for upcoming researchers.

The main challenging things in railway vehicles are to reduce the consumption of energy for transportation and to decrease the emission of harmful gasses by limiting the consumption of fuel sources. These drawbacks can be overcome by lightweight structures designed for the vehicle bodies and frameworks. The composite materials with fiber reinforcements are the preferred choice for manufacturing lightweight structures to reduce the overall weight of the rail vehicle. The fiber reinforced polymer (FRP) materials possess light‐weightiness, high strength, high stiffness value and are more durable in nature. The researchers are continuously putting their efforts into new innovations in concern towards the replacement of existing conventional materials by FRP composites in railway applications. This review focuses on the overview of FRP composites, the role of composites in past rail vehicles, the rail vehicle component selection and methodology and FRP composites used for various railway components manufacturing with their challenges. Also, this review included the data of FRP composites used in various countries for different railway components applications. Hence, this review is beneficial for the upcoming researchers as a foundation literature to work on railway vehicle applications using variety of FRP materials. Moreover, the challenges are quoted in this review through the comprehensive analysis of literature and hence it provides the information in the form of research gap, so that it would be helpful for the researchers to overcome all the challenges in their upcoming research works.

The composite industry was attracted by natural fiber reinforced polymer materials for various valuable engineering applications due to its ecofriendly nature, less cost, and enhanced mechanical and thermal properties. This present work aimed at incorporating sisal and kevlar woven fabrics with the epoxy matrix and studying the effect of Pongamia pinnata shell powder on the sisal/ kevlar hybrid composite. Six different laminates were prepared using hand layup method with filler percentage varying 2, 4, and 6 wt%. The prepared laminates cut according to the ASTM standards for performing different mechanical tests. Results reveal that the reduction of void percentage was observed at higher filler contents, while the incorporation of kevlar fabric enhances the impact strength by 279%, tensile strength by 89.77%, and tensile modulus value by 2% in comparison with pure natural fabric laminate L-1. The flexural strength and interlaminar shear strength were higher for 2% filler composites, while the highest flexural modulus and hardness values were observed for 6% filler-filled composites. The water absorption percentage was maximum for sisal laminate L-1 and minimum for kevlar laminate L-2. The fractured tensile and flexural specimens were analyzed by scanning electron microscopy.

This review article discusses the environmental and economic effects of recycling, as well as sustainable thermoplastic polymer recycling technologies. Several researchers have utilized recycled thermoplastics as matrices in the production of a variety of natural and synthetic‐based composites, which is also the focus of this study. All of the industries (food and packaging, construction and building, transportation, and indoor usage) where recycled thermoplastics have a large market share (food and packaging, construction and building, transportation, and indoor usage) are covered in this review. The desirable properties of thermoplastic polymers, such as corrosion resistance, low density, and user‐friendliness, have caused plastic production to surpass aluminum and other metals in use over the past 60 years. Furthermore, recycling is one of the most important measures available to mitigate these effects and is one of the most dynamic segments of the plastics industry at present. Increased landfilling and incineration of plastics have a negative impact on the ecosystem, and the continued increase in the production of virgin fossil plastic also has a negative impact on the environment. Consequently, this continuous production could lead to the depletion of fossil fuel resources, an increase in environmental emissions during processing, and eventual incineration. Increasing numbers of nations are adopting the circular economy concept in an effort to avoid all of these problems. This concept emphasizes the reuse of products and resources, as well as the recycling of materials according to the waste hierarchy, rather than their cremation or disposal in the environment.

The present experimental investigation focuses on the development of Areca/ Sisal/Carbon reinforced epoxy hybrid composites under various stacking sequences and involves the assessment of their mechanical and morphological properties to evaluate their use in some railway interior applications. Nine different combinations of laminates were prepared by using the manual hand layup technique. Mechanical experiments such as tensile, flexural, impact, inter-laminar shear strength and hardness tests were performed and the results envied the positive values which suggest the use of composites prepared in the study to be employed in some railway interior parts. The morphology of the composites was scrutinized using scanning electron microscopy and exposed the proper agglomeration of fibers in the matrix which in turn has influenced better mechanical properties. The experimental results convey that the hybridization of natural and synthetic fibers in polymer matrix would be an exciting prospect to be utilized in some railway interior applications.