Yam-reinforced composites

The flexural properties in terms of flexural stress, strain and chord modulus (between 0.25% and 0.75% of the yield point) of the flax yam reinforced composites with SPI, PH2-SPI and PH4-SPI composites are presented in Fig. 9.8. As in the case of tensile properties, flax yarn reinforced PH2-SPI composites showed significantly higher chord modulus and flexural stress, 7.8 GPa and 105 MPa, respectively, than the SPI (2.8 GPa and 48.9 MPa)... 

In this chapter, we define some important terms and parameters that are commonly used with fibers and fiber products such as yams, fabrics, etc., and then describe some general features of fibers and their products. These definitions, parameters, and features serve to characterize a variety of fibers and products made from them, excluding items such as fiber reinforced composites. These definitions and features are generally independent of fiber type, i.e. polymeric, metallic, glass or ceramic fibers. They depend on the geometry rather than any material characteristics. 

All these mechanical results demonstrate the ability of 3D woven fabrics to be adjusted to requirements and cover a wide range of mechanical properties by modifying weaving or manufacturing parameters such as spacing between yams or fibre volume fraction of the composite. Databases of materials can be built in order to help design or selection of these 3D textile reinforced composites. 

Clearly, the mechanical properties of woven fabric-reinforced composites are dominated by the type of fibre used, the weaving parameters, and the stacking and orientation of the various layers. However, there are additional subtleties which also affect composite performance. For example, some authors have noted the possibility of slightly altered mechanical properties depending on whether the yams are twisted prior to weaving in addition, damage accumulation under static and cyclic loading is different in laminates fabricated from twisted or untwisted yam. "... 

Prewo, K. M., and Brennan, J. J. (1982). Silicon carbide yam reinforced glass matrix composites./. Mater. Sci. 17 i20f-i206. 

Zaixia F, Zhangyu YC, Haim L. Investigation on the tensile properties of knitted fabric reinforced composites made from gf-PP commingled yam preforms with different loop densities. J Thennoplast Compos Mater 2006 19 113—26. 

Fiber reinforced composites, depending on the properties needed, can be fabricated in three different ways. Very short fibers can be used as filler, short fibers can be organized with random orientation and long fibers can be laid in one direction to form unidirectional composites. Short staple fibers may also be twisted together to form continuous yams to fabricate unidirectional composite laminates similar to those made using long fibers. Several unidirectional laminates may be combined by layering in different directions to form laminar composites. Yarns may also be woven or knitted into fabrics to form similar laminar composites. 

Lodha, R and Netravah, A.N., Phytagel modified soy protein isolate resin and unidirectional flax yam reinforced green composites, Polym. Comp., 2005, 26, 647. 

Kim JT, Netravah AN (2011) Development of ahgned-hemp yam-reinforced green composites with soy protein resin effect of pH on mechanical and interfacial properties. Compos Sci Technol 71(4) 541-547... 

Similarly, Fig. 15 presents the stiffness of bidirectionally reinforced composites, compared to the precursor reinforcements. Interestingly, the stiffness of the bidirectionally reinforced PE-based composite of 77 GPa reported by Cohen et al. [87] exceeded that of the unidirectional PE-based composites of 73 GPa reported by Marais and EeiUard [31]. However, this may be because Cohen et al. used a precursor UHMWPE yam with a tensile modulus of 164 GPa, almost twice the stiffness of the precursor UHMWPE fibre reported by Marais and FeiUard [31]. 

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