Physical, Mechanical, and Thermal Properties of Natural Fiber-Reinforced Epoxy Composites for Construction and Automotive Applications  
[PERSON]  
CSIR--Central Salt and Marine Chemicals Research Institute, Bhavnagar 364002, India  
1  
[PERSON]  
1  
[PERSON]  
2 Department of Technology and Automation, Crestochowa University of Technology,  
42-201 Czestochowa, Poland  
2  
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due to its excellent abrasion properties, good electrical insulating quality, resistance to moisture and chemical attacks, high mechanical strength, and appreciable resilience [8; 9; 10]. Epoxy can be cured without using a curing agent or heating at room temperature without pressure [11]. [PERSON] [8] was the first to discover epoxy resins in 1909. However, the first commercial production of epoxy resin began in the late 1940s. Epoxy adhesives became commercially available in the early 1950s, and continuous innovations have been made in various applications. In 1953, the Shell Chemical Corporation initiated field tests to evaluate epoxy systems as surfacing materials on highways [8; 12]. Additionally, in 1953, the first application of epoxy seal coating as test patches in industrial plants was made. Later, in 1957, epoxy polymer concrete was used as the first wearing course to repair popouts and spalled areas on the surfaces of bridge decks in California [8]. Nowadays, epoxy resins are used as a polymer with natural fiber reinforcements in countless construction applications and automobile sectors, such as thin-layer non-skid surfacing for roads and bridges, aerospace industries, and housing [8; 9; 12]. Several researchers are working on toughening/strengthening agents to enhance the properties of epoxy resin in structural and automotive applications [13; 14; 15]. Incorporating nano-silica, thermoplastic components, inorganics, carbon fibers, graphene, clay, and carbon nanotubes improves the toughness of epoxy resin [16]. The common physical and mechanical properties of epoxy resin are shown in Table 1[17; 18; 19; 20]. The epoxy matrix is composed of resin and hardener, which are usually mixed in a ratio of 10:1. The epoxy resin has a wide range of applications including uses for coatings, aerospace industries, composites, the bio-medical field, and electronics material. Figure 1a shows the properties of NFRCs and their applications. Figure 1b shows various steps involved during NFRCs fabrication. Few reviews are available on construction materials with synthetic and natural fiber. Still, no review covers the physical, mechanical, and thermal properties of the NFRCs used in different applications such as automotive and construction. This review paper focuses on natural fiber-reinforced epoxy composites' physical, mechanical, and thermal characteristics. Moreover, the various chemical and physical treatments and their effects on the physical, mechanical, and thermal behaviour of the NFRCs are presented. These properties are critical for the effective design and use of composite materials in construction and automotive construction applications. This review has been divided into the following sections:  
1. Epoxy-based composites based on reinforcement;
2. Physical and mechanical properties of natural fibers;
3. Physical properties of the natural fiber-reinforced epoxy composites;
4. Mechanical properties of the natural fiber-reinforced epoxy composites;
5. Thermal behaviour of the natural fibers reinforced epoxy composites;
6. Physico-chemical treatment of the natural fibers;
7. Applications of natural fiber-reinforced epoxy-based composites;
8. Summary and future perspectives.