Knitted fabric reinforcement warp knit

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. 

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. 

Production of monoaxiai reinforced warp-knitted fabrics (LiBA, 2010)... 

Fig. 1.3 Predicted and moduli for a range of reinforcement architectures 0 angle ply (for 0=0 to 45 to 90), cross-ply (0/90), eight-harness satin, and plain woven, triaxial woven fabric, braided (0=35° to 15°) and multiaxial warp knit ( - ), for the same fibre volume...

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]. 

A comparison of biaxial warp-knitted fabrics with conventional biaxial fabrics shows that warp-knitted fabrics have a partially higher stiffness than comparable fabrics due to the stretched reinforcement threads (Ploch, 1978). The overlapping... 

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). 

Pillar (0°) threads and weft yarns are connected via warp knitting. When using a stiff material for the warp yarns, the spacer fabric can also be reinforced in the z-direction see Fig. 8.13. 

Weft-knitted NCF can be produced as biaxial and multiaxial fabrics or as two- and three-dimensional near-net-shape textile structures. Warp and weft threads out of rovings are superposed and fixed together with loop systems. Due to the course-wise weft insertion the reinforcing threads remain noncrimped. Through the combination of weft insertion over the entire width or part of the width with or without support of a stitch-transferring device and by changing loop sizes on individual needles, three-dimensional near-net-shape preforms can be produced (Hufenbach, 2007). 

A. Peied and A. Bentur, Reinforcement of cementitious matrices by warp knitted fabrics . Mater. Struct. 31,1998, 543 550. 

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