Warp-knitted fabric-reinforced composites

Ko, F.K., Oastorc, C.M., Yang, J.M. and Chou, T.W. (1986). Structure and properties of multi-layer, multidirectional warp knit fabric reinforced composites. In Composites 86 Recent Advances in Japan and the United Slates, Japan Society for Composite Materials, Tokyo. 

Three dimensional structures of multiaxial warp knitted fabrics have been recently developed for multidirectional reinforcement of composites. Multilayers of linear yams are assembled in warp (0°), weft (90°) and bias ( 0) directions to provide in-plane reinforcement in specific directions and they are stitched together by knitting yams to provide structural integrity and through the thickness reinforcement [1,2,3,4,5]. 

For the production of composites, it is normally desired that textiles used for reinforcement possess great tensile strength and an extreme stiffness. The Young s modulus of textiles has to be significantly higher than that of the matrices used (for example, plastics). Conventional warp-knitted fabrics cannot fulfill these demands. Therefore, weft-reinforced, warp-knitted fabrics (Fig. 8.3) were developed to increase the stiffness of warp-knitted fabrics. 

Normally, the stresses of fiber-reinforced composite components are not mono- or biaxial. Therefore, for the use of biaxial textiles it is necessary to lay several layers in different orientations above one another to reinforce a component with regard to multiaxial loading. This procedure generates a large quantity of waste by cutting the layers in different orientations. It also increases the amount of time for the production of a composite component. Warp-knitted, multiaxial multi ply fabrics (MAG) were developed to eliminate the aforementioned disadvantages (Fig. 8.5). 

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