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Application of natural fiber-polymer composites (NFPCs) in different industrial applications provides competitive edge due to their lightweight, higher specific mechanical properties than glass fibers, sustainability, and lower cost involved in production. There are certain challenges associated with natural fibers and their reinforcement in composites such as poor bonding between the fibers and matrix due to their contradictory nature of characteristics, moisture absorption, lower thermal properties, and poor interfacial adhesion between the natural fiber and polymer matrix. The challenges involved in NFPCs need to be overcome to produce materials with relatively equivalent properties to those of conventional composites and other metallic structures. Several researchers around the globe have conducted investigations with the primary attention being paid to the modification of natural fibers and matrix by employing surface treatments and other chemical treatment methods. In order to address the need for eco-friendly and sustainable materials in different domains, a comprehensive review on natural fibers and their sources, available matrix materials, modification techniques, mechanical and thermal properties of NFPCs, is needed for better understanding of the behavior of NFPCs. This work provides the information and holistic view of natural fiber-reinforced composites based on the results obtained from modification techniques, with the view of focusing the review in terms of different chemical and physical treatment techniques, modification of fibers and matrix, and enhanced mechanical and thermal properties in the composites.

The prime objective of this research study was the investigation the new natural cellulosic fiber extracted from the stem of Abutilon Indicum plants as an alternative reinforcement in greener composite materials for structural applications. Abutilon Indicum a flowering plant with unique medicinal values are abundantly found in India and other south Asian countries. The fibers extracted from the stem of the Abutilon Indicum plant are proven to be sustainable, ecofriendly, and novel and hence this fiber is chosen for characterization study. In this experimental investigation the physical, chemical, thermal, morphological, crystallinity, chemical constituents, and surface characteristics of raw Abutilon Indicum fibers (AIF) were analyzed. Chemical analysis results convey the presence of higher cellulose content of (56.12 wt.%) in AIF. The diameter (175 μm) and density (1.170 g/cm3) of AIFs are determined by physical analysis of the raw fibers. Such lower density values observed in AIF make it as a perfect material for lightweight applications. Crystalline properties of AIFs are determined from X‐ray diffraction tests with a crystalline index of 77.35%, and crystalline size of 2.20 nm, which attributes to the presence of cellulose‐1β and the crystallites are ordered in nature. Thermal stability of 175°C, maximum degradation temperature upto 302.6°C and kinetic activation energy of 86.95 kJ/mol of AIF are established based on thermo gravimetric analysis. Morphological and surface characteristics of AIF through a scanning electron microscope (SEM) and atomic force microscope (AFM) analysis revealed that the raw fibers display a relatively finer surface. Research findings of the AIF mentioned above conclude that the AIFs prove to be an ideal, alternative reinforcement in greener composite materials for sustainable and cleaner production of components in structural applications.

Epoxy granite composites with its wide range of applications in machine tool industries are manufactured by molding process and require post cast machining operations to meet the desired dimensional accuracy for assembly of machine tool structures. In this research work, milling of epoxy granite composites are carried out based on the experimental design from Response Surface Methodology (RSM) techniques and further the optimal solutions are determined by a novel hybrid algorithm AHP-TOPSIS. Central Composite Design (CCD) model is applied with three factors-three levels and the measured output responses are thrust force, tangential force and surface roughness. Experimental combinations of 20 different trials are performed using high speed steel end mill cutter of diameter 10mm with three levels of input parameters: speed; fibre content and feed rate at a uniform depth of cut. The relative importance matrix formulated proved to be highly consistent with its consistency ratio to a maximum of 0.000641 which lies below the higher range of 0.1. Consistency ratio of 0.000641 reveals that the optimal solutions determined will be highly reliable and the decision making is much more judicious. Optimal solution determined from hybrid AHP-TOPSIS methods are: speed 1800 rpm; feed rate 0.03 m/min and 0% percent fibre content. Functional relationships among parameters and responses established by RSM are consistent upto 95% and its significance is tested by analysis of variance. Comparison among predicted and experimental values of three measured responses convey that the percentage variations are minimum with up to 2.03% for surface roughness, 2.50% for thrust force and 2.71% for tangential force components. This research work provides a systematic procedure and clear framework for determination of optimal machining conditions by hybrid methodology on the basis of technique for order preference by similarity to ideal solution (TOPSIS) combined with analytical hierarchy procedure (AHP) for attribute weights and further analyzes the influence of machining parameters over measured responses.

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