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American Society for Testing and Materials

Natural fibers are getting attention from researchers and academician to utilize in polymer composites due to their ecofriendly nature and sustainability. The aim of this review article is to provide a comprehensive review of the foremost appropriate as well as widely used natural fiber reinforced polymer composites (NFPCs) and their applications. In addition, it presents summary of various surface treatments applied to natural fibers and their effect on NFPCs properties. The properties of NFPCs vary with fiber type and fiber source as well as fiber structure. The effects of various chemical treatments on the mechanical and thermal properties of natural fibers reinforcements thermosetting and thermoplastics composites were studied. A number of drawbacks of NFPCs like higher water absorption, inferior fire resistance, and lower mechanical properties limited its applications. Impacts of chemical treatment on the water absorption, tribology, viscoelastic behavior, relaxation behavior, energy absorption flames retardancy, and biodegradability properties of NFPCs were also highlighted. The applications of NFPCs in automobile and construction industry and other applications are demonstrated. It concluded that chemical treatment of the natural fiber improved adhesion between the fiber surface and the polymer matrix which ultimately enhanced physicomechanical and thermochemical properties of the NFPCs.

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A Review on Natural Fiber Reinforced Polymer Composite and Its Applications

Characterization and Properties of Natural Fiber Polymer Composites: A Comprehensive Review

Functionalization is an important way to breed new properties and applications for a material. This review presents an overview of the progresses in functionalized hexagonal boron nitride (h-BN) nanomaterials. It begins with an introduction of h-BN structural features, physical and chemical properties, followed by an emphasis on the developments of BN functionalization strategies and its emerging properties/applications, and ends with the research perspectives. Different functionalization methods, including physical and chemical routes, are comprehensively described toward fabrication of various BN derivatives, hetero- and porous structures, etc. Novel properties of functionalized BN materials, such as high water solubility, excellent biocompatibility, tunable surface affinities, good processibility, adjustable band gaps, etc., have guaranteed wide applications in biomedical, electronic, composite, environmental and "green" energy-related fields.

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Functionalized hexagonal boron nitride nanomaterials: emerging properties and applications.

Synthetic structural materials with exceptional mechanical performance suffer from either large weight and adverse environmental impact (for example, steels and alloys) or complex manufacturing processes and thus high cost (for example, polymer-based and biomimetic composites) Natural wood is a low-cost and abundant material and has been used for millennia as a structural material for building and furniture construction However, the mechanical performance of natural wood (its strength and toughness) is unsatisfactory for many advanced engineering structures and applications Pre-treatment with steam, heat, ammonia or cold rolling followed by densification has led to the enhanced mechanical performance of natural wood However, the existing methods result in incomplete densification and lack dimensional stability, particularly in response to humid environments, and wood treated in these ways can expand and weaken Here we report a simple and effective strategy to transform bulk natural wood directly into a high-performance structural material with a more than tenfold increase in strength, toughness and ballistic resistance and with greater dimensional stability Our two-step process involves the partial removal of lignin and hemicellulose from the natural wood via a boiling process in an aqueous mixture of NaOH and Na2SO3 followed by hot-pressing, leading to the total collapse of cell walls and the complete densification of the natural wood with highly aligned cellulose nanofibres This strategy is shown to be universally effective for various species of wood Our processed wood has a specific strength higher than that of most structural metals and alloys, making it a low-cost, high-performance, lightweight alternative

https://www.fpl.fs.fed.us/documnts/pdf2018/fpl_2018_song001.pdf

Processing bulk natural wood into a high-performance structural material

This paper is a review on the tensile properties of natural fiber reinforced polymer composites. Natural fibers have recently become attractive to researchers, engineers and scientists as an alternative reinforcement for fiber reinforced polymer (FRP) composites. Due to their low cost, fairly good mechanical properties, high specific strength, non-abrasive, eco-friendly and bio-degradability characteristics, they are exploited as a replacement for the conventional fiber, such as glass, aramid and carbon. The tensile properties of natural fiber reinforce polymers (both thermoplastics and thermosets) are mainly influenced by the interfacial adhesion between the matrix and the fibers. Several chemical modifications are employed to improve the interfacial matrix–fiber bonding resulting in the enhancement of tensile properties of the composites. In general, the tensile strengths of the natural fiber reinforced polymer composites increase with fiber content, up to a maximum or optimum value, the value will then drop. However, the Young’s modulus of the natural fiber reinforced polymer composites increase with increasing fiber loading. Khoathane et al. [1] found that the tensile strength and Young’s modulus of composites reinforced with bleached hemp fibers increased incredibly with increasing fiber loading. Mathematical modelling was also mentioned. It was discovered that the rule of mixture (ROM) predicted and experimental tensile strength of different natural fibers reinforced HDPE composites were very close to each other. Halpin–Tsai equation was found to be the most effective equation in predicting the Young’s modulus of composites containing different types of natural fibers.

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A review on the tensile properties of natural fiber reinforced polymer composites

A commercial phenol formaldehyde based resole thermosetting resin (Hexion “J2027L”) was filled with ceramic-based fillers (Envirospheres “slg”) to increase its strength and fracture toughness. By testing viscosity, strength, and fracture toughness at a range of filler addition levels, the optimal addition level of SLG was able to be determined in terms of workability, cost, and performance. It was found that the fracture toughness of this resin could be significantly increased through the addition of the slg filler. The results show that composite with 20% by weight of the slg produces the best balance between ease of casting and impact performance.

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Fracture Toughness of Phenol Formaldehyde Composites: Pilot Study

The shrinkage of vinyl ester particulate composites has been reduced by curing the resins under microwave conditions. The reduction in the shrinkage of the resins by microwaves will enable the manufacture of large vinyl ester composite items possible (H.S. Ku, G. Van Erp, J.A.R. Ball, and S. Ayers, Shrinkage Reduction of Thermoset Fibre Composites during Hardening using Microwaves Irradiation for Curing, Proceedings, Second World Engineering Congress, Kuching, Malaysia, 2002a, 22-25 July, p 177-182; H.S. Ku, Risks Involved in Curing Vinyl Ester Resins Using Microwaves Irradiation. J. Mater. Synth. Proces. 2002b, 10(2), p 97-106; S.H. Ku, Curing Vinyl Ester Particle Reinforced Composites Using Microwaves. J. Comp. Mater., (2003a), 37(22), p 2027-2042; S.H. Ku and E. Siores, Shrinkage Reduction of Thermoset Matrix Particle Reinforced Composites During Hardening Using Microwaves Irradiation, Trans. Hong Kong Inst. Eng., 2004, 11(3), p 29-34). In tensile tests, the yield strengths of samples cured under microwave conditions obtained are within 5% of those obtained by ambient curing; it is also found that with 180 W microwave power, the tensile strengths obtained for all duration of exposure to microwaves are also within the 5% of those obtained by ambient curing. While, with 360 W microwave power, the tensile strengths obtained for all duration of exposure to microwaves are 5% higher than those obtained by ambient curing. Whereas, with 540 W microwave power, the tensile strengths obtained for most samples are 5% below those obtained by ambient curing (H. Ku, V.C. Puttgunta, and M. Trada, Young’s Modulus of Vinyl Ester Composites Cured by Microwave Irradiation: Preliminary Results, J. Electromagnet. Waves Appl., 2007, 20(14), p. 1911-1924). This project, using 33% by weight fly ash reinforced vinyl ester composite [VE/FLYSH (33%)], is to further investigate the difference in fracture toughness between microwave cured vinyl ester particulate composites and those cured under ambient conditions. Higher power microwaves, 540 and 720 W with shorter duration of exposure are used to cure the composites. Short-bar method of fracture toughness measurement was used to perform the tests. Plastic (PVC) re-usable molds were designed and manufactured for producing the test samples. The results show that the fracture toughness of specimens cured by microwave conditions are generally higher than those cured under ambient conditions, provided the power level and duration of microwave irradiation are properly and optimally selected.

An Evaluation of Fracture Toughness of Vinyl Ester Composites Cured under Microwave Conditions

A commercial phenol formaldehyde based resole thermosetting resin supplied by Borden Chemical Australia Pty. was reinforced with ceramic-based fillers (SLG) to increase its fracture toughness. This is the second study of the same series. By testing fracture toughness and viscosity at a range of filler addition levels, the optimal addition of SLG was determined in terms of workability, cost and performance. The composites obtained were post-cured in conventional oven as in the previous study. The original contributions of this paper include lowering the cost of the composite (35% w/t of SLG) by 50 % but at the same time its the fracture toughness was reduced only by 20 % (compared to the neat resin), and increasing the fire resistance of the resins tremendously. It was also found that the values of fracture toughness of the samples in this study were higher than those obtained in the previous study when the percentage by weight of SLG varies from 0 to 35%. The shapes of the plots of fracture toughness against percentage by weight of SLG were also different. The possible reasons for the differences were explained.

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Fracture Toughness of Phenol Formaldehyde Composites Reinforced with E-spheres

Phenol formaldehyde was filled with glass powder (GP) to optimize the strength and impact toughness of the composite for structural applications by a research center at the University of Southern Queensland. To reduce costs, the center wished to fill as much of the glass microspheres as possible to maintain sufficient strength and impact toughness in the composites in structural applications. In this project, we varied the weight percentages of the GP in the composites, which were then subjected to tensile tests. The best weight percentage of GP that could be added to the phenolic resin to give the optimum yield, tensile strengths, Young's modulus, and cost was found to be about 10%. The contribution of this study was the finding that if the tensile properties are the most important factors to be considered in the applications of the composites, GP is not a suitable filler.

M. Trada

Papers

A review on the tensile properties of natural fiber reinforced polymer composites

Fracture Toughness of Phenol Formaldehyde Composites: Pilot Study

An Evaluation of Fracture Toughness of Vinyl Ester Composites Cured under Microwave Conditions

Fracture Toughness of Phenol Formaldehyde Composites Reinforced with E-spheres

Tensile tests of phenol formaldehyde glass-powder-reinforced composites: pilot study