Mechanical properties of natural fibers

Table 2 Mechanical Properties of Natural Fibers in Comparison to Conventional Reinforcement Fibers...

The mechanical properties of natural fibers depend on cellulose type because each type of cellulose has a specific cell geometry and the geometrical conditions determine the mechanical properties. 

These are covered with a sheath of para-crystaUine polyglucosan material surrounded by hemicellulose [29]. In most natural fibers, these micro-fibrils orient themselves at an angle to the fiber axis called the micro-fibril angle. The ultimate mechanical properties of natural fibers are found to be dependent on the microfibrillar angle. Gassan et al. have performed calculations on the elastic properties of natural fibers [30]. 

J. Gassan and A.K. Bledzki. Dynamic-mechanical properties of natural fiber-reinforced plastics the effect of coupling agents. In Fourth International Conference on Woodfiber-Plastic Composites, Madison, WI, May 12-14, 1997, pp. 76-80. 

Table 23.1 Mechanical properties of natural fiber-reinforced PLA composites [47]...

Improved fiber matrbc adhesion and thereby improved mechanical properties can be accomplished by engineering a superior processing condition in preparing the bio-composites, by altering the polymer architecture of the matrix or by the surface treatment on the fiber [47]. Table 23.1 showed mechanical properties of natural fiber-reinforced PLA composites. 

Torres, F.G., Arroyo, O.H., Gomez, C. Processing and mechanical properties of natural fiber reinforced thermoplastic starch biocomposites. J. thermoplast. compos, mater. 20,... 

J.R. Guedes, L.M. Rodrigues, D.R. Mulinari, Mechanical Properties of Natural Fibers Reinforced Polymer Composites Palm/Low Density Polyethylene XIV SLAP/XII CIP 2014. (Porto de Galinhas, Brazil—1, 2014)... 

Peponi L, Biagiotti J, Torre L, Kenny JM, Mondragon I (2008) Statistical analysis of the mechanical properties of natural fibers and their composite materials. I Natural fibers. Poly Compos 29(3) 313-320 II 322-325... 

The slightest amount of water can significantly affect the mechanical properties of natural fiber-reinforced composites. Water absorption in a fibrous composite is dependent on many factors such as temperature, fiber loading, orientation of fibers, permeability of fibers, surface protection, area of the exposed surfaces, diffusivity, void content, hydrophilicity of the individual components, etc. 

Mishra S, Naik JB (2005) Effect of treatment of maleic anhydride on mechanical properties of natural fiber polystyrene composites. Polym Plastics Technol Eng 44 663-675... 

Oksman K, Mathew AP, Langstrom R (2009) The influence of fiber microstracture on fiber breakage and mechanical properties of natural fiber reinforced polypropylene. Compos Sci Technol 69 1847-1853... 

As expected, the nominal values of the various properties vary widely from system to system and are also dependent on processing and testing conditions. Even though a very different group of fibers and polymer matrices were presented here, some general trends can be identified. Perhaps, the main one is that fiber hybridization even with a small amoxmt of glass fibers can significantly improve the physical and mechanical properties of natural fiber polymer composites. Moreover, these properties can be... 

K. Adekunle, S.-W.Cho, R. Ketzscher and M. Skrifvars, Mechanical properties of natural fiber hybrid composites based on renewable thermoset resins derived from soybean oil, for use in technical apphcations.. Appl. Polym. Sci. 124, 4530-4541 (2012). 

T. Lundin, Effect of Accelerated Weathering on the Physical and Mechanical Properties of Natural Fiber Thermoplastic Composites, University of Wisconsin, Madison, M.S. thesis (2001). 

The investigations mentioned above, are focused principally on the processing and mechanical response of polymers reinforced with natural fibers, without considering that their mechanical properties decrease after exposition to alkaline environmental of cement materials or weather. Natural fibers reduce their mechanical properties after exposition to alkaline environment of the cement matrix, nevertheless the use of polymeric matrix as a binder aroimd the natural fibers provides protection for them. However, if the interface of composites is not good, and/or matrix is not alkaline resistant, hydration products like calcium hydroxide will migrate to interface, and polymer composite will deteriorate. Several studies have demonstrated that the mechanical properties of natural fibers decrease after exposure to alkaline environment of the cement matrix due to three different mechanisms [30-39] ... 

Effect of Physical Treatment on Mechanical Properties of Natural Fiber Reinforced Composites... 

EFFECT OF CHEMICAL TREATMENT ON THE MECHANICAL PROPERTIES OF NATURAL FIBER-REINFORCED POLYMER COMPOSITES... 

Yoshida, K., Kurose, T., Nakamura, R., Noda, J., and Goda, K., Effect of yarn structure on mechanical properties of natural fiber twisted yarns and green composites reinforced with the twisted yarn, J. Soc. Mater. Sci. Jpn., 61 (2), 111-118 (2012) (in Japanese). 

The cellulose component of natural fibers may be degraded or cross-linked upon electron beam irradiation of high energy [108]. The chain sdssion of cellulose may occur at higher irradiation dosage and it may cause deterioration in the mechanical properties of natural fibers [14,109,110]. The irradiation may considerably change the structure, reactivity, physicochemical, and mechanical properties of cellulose. 

Mechanical properties of natural fiber reinforced composites are mainly influenced by the level of dispersion and interfacial adhesion between the matrix and fibers and microscopy is one of the most effective methods for morphological observations. In this study, scanning electron microscope (SEM) was used to investigate the dispersion of natural fiber and interfacial morphologies and the images are shown in Figures 3.2 (film surface) and 3.3 (cryo fractured surface). The SEM pictures show the differently shaped particles and the more or less spherical lignin-based particles. 

It should be mentioned here that the molecular weight and molecular weight distribution of the polymer matrix would also influence the rheological and mechanical properties of natural fiber reinforced composites. Not much research has been conducted so far in order to elucidate the role of the matrix flow properties on rheological properties of NFC. 

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