Twisted yarn-reinforced composites

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. 

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). 

Impregnated yams are considered as composites with unidirectional reinforcement (twist of the yarns used in composite reinforcement is normally negligible) with the given fibre volume fraction Vj this value is determined by the dimensions of the cross-section of the yam (which can differ from point to point in the unit cell, but most often assumed to be constant) and the amount of fibres inside the yam, given by the fibre count or yam linear density ... 

Fabric composites have mechanical properties similar to those of laminates made from orthogonal uni-directional layers. However, fibre curvature arising from yarn twist and weave crimp makes fabric reinforcement less efficient than in the case of aligned straight fibres. 

Carbon (sometimes referred to as graphite) fibre is the reinforcement material of choice for advanced composites. Carbon fibres have a higher fatigue resistance than glass or aramid. Carbon fibre properties depend on the structure of the carbon used and are typically defined as standard, intermediate and high modulus fibres. Several thousand fibres are twisted together to form a yarn which may be used by itself or woven into a fabric. The yarn or fabric is combined with a resin, usually epoxy, and wound or moulded to shape to form a wide variety of products. 

A textile composite reinforced by woven or nonwoven fabrics, knits, or braids is a material of great interest Conventional textile composites are developed as the combination of various synthetic fibers and resins. On the other hand, material developed by the combination of natural fibers and natural-resource-based resin may be called a textile biocomposite. Natural fibers are first changed into bundle form, known as slivers, and then spun into a continuous yam. Spun yams are often twisted around each other to make a heavier yarn, called a twisted or plied yarn. Such spun yams are processed into final textile products such as woven fabrics, knits, and braids. The textile biocomposites described in this chapter are natural-resource-based resin composites reinforced by such spun yarns or textile products. Section 10.1 describes the elastic properties oftwisted yam biocomposites of ramie, and Section 10.2 introduces the development and evaluation of bladed yarn composites made from jute. 

---