Developments in 3D knitted structures

Z. Guo , in Specialist Yarn and Fabric Structures, 2011

5.i Introduction to 3D knitted structures

Three-dimensional knitted fabrics accept been widely used in many fields, especially in technical textiles. The development of 3D knitted fabrics is based on 2nd knitted fabrics. Nevertheless, while a considerable amount of research has been performed on second knitted fabrics, by comparison little is known about the mechanical backdrop and applications of 3D knitted fabrics. This chapter provides a description of the three types of 3D knitted fabrics currently available, which are broadly categorized every bit multiaxial warp-knitted fabrics, infinite fabrics (or sandwich fabrics), and 3D knitted fabrics (or near-cyberspace-shaped knitted fabrics). The structures, backdrop, product, and applications of these different 3D knitted fabrics are described separately.

Read full chapter

URL:

https://world wide web.sciencedirect.com/science/article/pii/B9781845697570500052

Polymer-optical fibre (POF) integration into material fabric structures

Five. Schrank , ... T. Gries , in Polymer Optical Fibres, 2017

10.3.i Structure

Knitted fabrics are subdivided into warp and weft knitted fabrics. Both types of fabric consist of intertwined loops. Knitted fabrics usually possess high elasticity due to their loop construction. The difference between the 2 knitting processes is the formation of the loops. The loops of the warp knitting process are formed in rows in production management through collectively moved needles. The loops of the weft knitting process are formed orthogonal to the production management through individually moved needles. The basic structure of warp and weft knitted fabrics is shown in Fig. 10.seven [GVW15, WW14, DIN69].

Figure 10.7. Structure of warp and weft knitted fabrics [GVW15, IMS00].

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B9780081000397000105

Woven Material Media

Derek B Purchas , Ken Sutherland , in Handbook of Filter Media (Second Edition), 2002

2.4 Knitted Fabrics

Knitted fabrics are synthetic by the interlocking of a series of loops made from one or more yarns, with each row of loops caught into the preceding row. Starting with the frame knitting machine, which offset allowed production of a complete row of loops at in one case, the modern knitting industry has grown into one with highly sophisticated machinery. Knitted fabrics can be made flat or cylindrical (as well as fully fashioned, for the garment industry).

From the point of view of filtration, knitted fabrics are a lot more than open than are woven fabrics. Appropriately they are rarely used equally a medium in a single layer, but rather as a packed bed of many layers, in which format they work well every bit demisters and coalescers.

Knitted fabrics tin be made from yarns of quite wide diversity, but for industrial use they normally utilise single filaments as the yarn. By far the greatest proportion of knitted fabric is made from single wire or unmarried polymeric filament, and, as such, is covered after in this Handbook (in Chapter v to some extent, and in Chapter 6 in more detail).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9781856173759500031

Weft knitting, weft-knitted fabric and knitwear design

Jacquie Wilson , in Handbook of Textile Design, 2001

10.v Characteristics of weft-knitted fabrics

Knitted fabric is unique in that it possesses a loftier lodge of elasticity and recovery. Different woven cloth, which possesses a low caste of elongation, knitted textile can be stretched to a considerable length and nonetheless, when information technology is released, it will gradually render to its original shape and configuration. It is this feature of the fabric, plus the air permeability arising from its looped structure, that imparts to information technology the following backdrop: a loftier degree of wrinkle resistance (knitted apparel generally requires little ironing); good drape; a high degree of comfort; a porous nature allowing the skin to breathe freely; and elasticity allowing liberty of move.

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B9781855735736500151

Textile materials and structures for topical management of wounds

B.South. Gupta , J.V. Edwards , in Advanced Textiles for Wound Care (Second Edition), 2019

iii.12.4 Knitted fabrics

Knitted fabrics are categorised as either 'weft' or 'warp' constructed. Of the two, the faster and the more economical to produce is the weft-knitted fabric that can be accomplished with a single package of yarn. The warp-knitting process, even so, requires a warp beam, i.eastward., a running sail of yarns as does the weaving process. Loops are formed transversely in the example of the weft knitting and essentially vertically in the case of the warp knitting ( Fig. 3.13). Simplest or plain weft knits tend to be very extensible and dimensionally unstable. One could improve on these tendencies by using additional yarns that interlock the loops. In contrast, the warp-knitted structures are basically more interlocked and dimensionally highly stable. The knitted fabrics are more than flexible, compliant and conformable than are the woven fabrics, and one of them, the warp, likewise does non unravel as easily when cut to fit an application. A major limitation of knitted fabrics in some applications is porosity, which, owing to the nature of the loop structure, tends to exist high. The knitted nets and bandages can be draped more finer than the woven materials over areas that require three-dimensional conformability. One of the primary applications of knitted structures in wound care is in compression hosiery used for treatment of venous stasis.

Figure 3.thirteen. Weft-knit and warp-knit structures.

Read full chapter

URL:

https://world wide web.sciencedirect.com/scientific discipline/article/pii/B9780081021927000035

Manufacturing of textiles for civil engineering applications

T. Gries , ... O. Stolyarov , in Cloth Fibre Composites in Ceremonious Engineering, 2016

1.3.two.2 Warp-knitted fabrics

In a warp-knitting procedure, simultaneous yarn-feeding and loop-forming actions occur at every needle in the needle bar during the same knitting cycle (Spencer, 2001 ). The main difference from weft-knitted structures consists of the fact that all working needles on warp-knitting machines move simultaneously and, consequently, the loops are formed in a row simultaneously. Loop structures are formed in the warp yarn system in the length direction of the cloth. Thus, during i revolution of the shaft of the warp machine, from a few tens up to thousands of loops are formed. Warp-knitting features substantially higher performance compared with weft-knitting. In dissimilarity to weft-knitted fabrics, warp-knitted fabrics find widespread use in the reinforcement of diverse blended materials, including those for civil applied science applications. Manufacturing engineering for warp-knitted fabrics combines the benefits of weaving and knitting. Similar to weaving, yarns are wound from warp beams, and are located in the textile in 2 perpendicular directions. In the industry of technical fabrics, directly oriented warp- and weft-reinforcing, high-strength yarns are inserted to provide the necessary mechanical characteristics and dimensional stability of the fabric. The reinforcing yarns are and then combined with warp-knitting yarns.

Warp-knitted fabrics manufactured for ceremonious technology applications have the post-obit basic elements:

–

0° inlay yarns are straight yarns that are placed in the warp-knitted fabric in the auto's longitudinal (warp) direction

–

ninety° inlay yarns are the straight yarns that are placed in the warp-knitted fabric in the transverse (weft) direction

–

Inlay yarns in the diagonal direction are the directly yarns that are placed in the warp-knitted fabric in the diagonal management (e.g., ±   45°)

–

Warp-knitting yarns are the yarns that stitch-bond the material

It should be noted that inlay yarns do non participate in loop formation during the knitting procedure, but serve as reinforcing elements. Equally inlay yarns, high-strength rovings, hybrids, or multifilament yarns may exist used. The loop length of the warp-knitting yarns influences both the inner friction of the straight reinforcing yarns and other properties such as, for example, concrete penetration ability (Hanisch et al., 2006). The linear density of the filaments and the inlaid reinforcing yarn's hinge structure ordinarily differ in size by 1 or two orders of magnitude. The result of this manipulation is a structure with fundamentally new backdrop.

Planar warp-knitted fabrics may be uniaxial, biaxial, or multiaxial. In uniaxial structures, the weft yarn is inserted across the width of the textile (Padaki et al., 2006). This is also known as magazine weft insertion (Raz, 2000). Effigy 1.10a illustrates warp knit with a weft inlay yarn. As a outcome, a unidirectional construction that can sustain a load only in 1 particular management is produced. In comparison with woven fabrics, higher forcefulness due to the direct arrangement of the weft yarn is achieved. In biaxial structures along with weft inlaid yarns, additional yarns are incorporated into the knitted structure in the machine direction as shown in Figure 1.10b. The resulting structure combines the advantages of knitted and woven fabrics (Godou et al., 1998), and can deport loads in 2 directions. In addition to horizontal and vertical reinforcing yarns, additional diagonal yarns may be introduced at various angles to the car management of the fabric. These fabrics are chosen multiaxial or noncrimp fabrics, i.east., the reinforcing yarns are placed in the aforementioned plane but in dissimilar directions. Such structures may consist of several layers and have dissimilar orientations of their constituent yarns as shown in Figure i.10c (Raz, 2000).

Figure 1.ten. (a) Uniaxial, (b) biaxial, and (c) multiaxial warp-knitted structures.

The backdrop of warp-knitted fabrics are affected by the knitting design. Although there are a variety of knitting stitches, only a express number of them is used for the production of reinforcing fabrics. Typically two types of knitting stitches, namely colonnade (Figure one.11a) and tricot (Figure i.11b) stitches, are used in the warp-knitting process. In the pillar sew together, the same guide always overlaps the same needle. In the tricot sew, one thread crosses between wales respectively (Spencer, 2001).

Figure 1.eleven. Different run up types: (a) pillar and (b) tricot.

Warp-knitted fabrics with a tricot stitch embed the yarns or rovings with a flat, ribbon-shaped cross-section into the cloth structure. Due to the apartment shape of the roving, the contact surface between the filaments and the concrete increases. As well, in comparison to a round-shaped filament packet, the minimal penetration depth decreases past almost 50% (Janetzko et al., 2010). Thus, reinforcement structures are produced that can be hands penetrated past the concrete matrix, providing a proficient bond betwixt the filaments and the concrete. Warp-knitted fabrics with a tricot pattern show higher load-bearing chapters than specimens reinforced with colonnade-stitch textiles (Roye, 2007); all the same, the spacing width of the textiles between the individual rovings decreases due to the ribbon shape of the reinforcement yarn and the closed mesh of the knitting yarn (Effigy one.12a). For this reason, these reinforcement structures are further processed into structural parts mainly by lamination or spraying.

Figure i.12. Warp-knitted biaxial fabrics with (a) tricot stitches and (b) pillar stitches for concrete reinforcement.

Warp-knitted fabrics with colonnade stitches offer open-filigree reinforcement structures equally shown in Figure 1.12b. These grid textiles are very suitable for the product of concrete elements past using the casting process, where highly liquid concrete mixtures are used (Janetzko et al., 2010). Due to the openings within the textile, the concrete mixture can flow through the fabric layers to fill the formwork; withal, the contact surface betwixt the concrete and the reinforcing roving is low attributable to the circular shape of the roving (Roye, 2007).

Warp-knitted fabrics may also be produced with reinforced zones. Local reinforcement is created by locally applied yarns in reinforcement structures. The local reinforcements may be introduced directly during the manufacturing process or afterwards in an boosted procedure, eastward.g., with the help of sewing or embroidery techniques for tailored fiber placement (Kolkmann et al., 2005).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9781782424468000021

Types and product of textiles used for building and construction

Grand. Milwich , in Textiles, Polymers and Composites for Buildings, 2010

2.2.3 Flat knitting, weft knitting and warp knitting

Knitted fabrics ( Fig. two.half-dozen) are more flexible due to their mesh structure. Gear up-to-use goods can be produced in a unmarried processing stride by ways of electronically controlled flat knitting machines ('fully-fashioned applied science'). The electronic selection of needles offers a great variety of patterning. Warp/weft knitted textiles display reduced force, college elasticity, better shape retention and recovery from angle, and superior vapour manual when compared with woven fabrics. They are used for indoor applications, e.k. in mixed-fibre loftier stretch applications with normal elasticity (10–30% elongation) and elastane fibres (400% elongation).

2.half dozen. Knitted textile.

In contrast to the reduced strength and high elongation of standard knitted fabrics, elongation is reduced in weft-inserted warp-knit fabrics by inserting linear, uncrimped fibres into the fabric, allowing the use of these fabrics in load-conveying structural applications.

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B9781845693978500029

Textile structures

R. Fangueiro , F. Soutinho , in Fibrous and Blended Materials for Civil Technology Applications, 2011

iii.2.three Knitted fabrics

Knitted fabrics are fibrous structures characterized by a basic structure called loop, and are produced by the interlooping of i or more yarns. They can be produced using warp-knitting engineering, and also past weft-knitting applied science, producing fabrics with dissimilar characteristics and properties. In weft-knitted fabrics, loops are produced in courses from at to the lowest degree one yarn, while in warp- knitted fabrics loops are produced in wales using a number of yarns identical to the number of wales to be formed. In both structures, past varying the blazon of loops produced, the loop length, the yarn linear density, the embrace gene and the density of wales and courses, a wide range of structural combinations tin be achieved.

The tensile behaviour of knitted fabrics is strongly restricted past its loop germination. During the application of a tensile load, the loops change their shape in guild to accommodate the applied load. In this part of the deformation pocket-size loads atomic number 82 to large displacements, which is the typical behaviour of low-stiffness materials. When this type of structure is used as reinforcement, the mechanical properties of the composite material may be considerably hindered, as the resin may bear the initial load and fail before the load is transferred to the reinforcing fibers (Bruer, 2005).

The lack of stiffness of these structures at the initial stage of loading may be overcome by the introduction of directly yarns in various directions, or by prestressing the structure in a particular direction in order to attain jamming weather condition and firsthand transfer of the practical loads to the load-bearing yarns. Very of import contributions to this subject have been made by Araújo et al. (2009) in a enquiry work undertaken to better the stiffness in the coursewise direction of weft-knitted fleece glass-fiber fabrics to be used in 3D tubular or second apartment preforms for technical applications. In this work, the effects of fiber orientation were analyzed by comparison the tensile testing results obtained for unlike types of fleece structures. The fleece construction was chosen for this work for its relative advantages and information technology may be manufactured in 3D complex shapes in electronic apartment knitting machines. For some applications, the knitting or basis yarns work as a scaffold to agree the laid-in or the pile yarns, which are the reinforcing yarns, in the proper position for increasing the stiffness in the coursewise direction (Araújo, 2007).

Other disadvantages of these structures for specific applications are their depression thickness and loftier consumption of yarn in relation to the covering degree. A potential limitation of knitted fabrics is their high porosity which, unlike woven fabrics, cannot be reduced below a certain value determined past the construction. As a result, applications requiring very depression porosity usually incorporate woven materials (Scardino, 2009).

Warp-knitted fabrics accept a larger potential for apply in civil technology applications due to the power to pattern the backdrop of the fabric in each management according to the application needs. Notwithstanding, weft-knitting is the most suitable cloth technology to produce 3D complex-shaped fabrics that could be explored for some particular applications in civil construction.

In a warp-knitted cloth (Fig. three.7), loops are formed from a separate yarn, called warp, mainly introduced in the longitudinal fabric management. In this structure, neighbouring loops of 1 course are not being created from the same yarn. These structures bear witness mechanical properties very similar to those of woven fabrics; all the same, they are very flexible and, depending on the construction, they can be elastic or inelastic.

3.vii. Warp-knitted fabric.

Some special warp-knitted structures, named weft-inserted warp knits, can be produced with maximum stability due to the laid-in yarn systems in biaxial directions. Commonly they are used for manufacturing composites, and this is of huge interest as these structures preserve the yarn backdrop and, due to their flexibility, fulfil pattern performance requirements from complete dimensional stability to directional elongation. In improver, they provide higher yarn-to-cloth tensile translation efficiencies, greater in-plane shear resistance, and improve handling in open structures when compared to wovens.

Thus, for reinforcement information technology is possible to utilise weft-inserted warp-knitted fabrics characterized by an insertion of yarns in the weft direction and multibar weftinserted warp-knit at the same time where yarns are inserted in both warp and weft directions. The reinforcing yarns are introduced in the structure without crimp, assuasive the optimization of mechanical backdrop (Scardino, 2009; Goran, 2005; Araújo, 2009).

The equipment used for the production of warp-knitted fabrics are Tricot and Raschel looms. The offset, Tricot, is not able to produce complex structures, is finer in gauge and is more rapid, while the Raschel produces more circuitous structures only is slower in production (Gries, 2005).

The warp-knitted structure is extremely versatile, and can be engineered with a multifariousness of mechanical backdrop like to those of woven fabrics (Goran, 2005).

Read total chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B978184569558350003X

Yarn to Fabric

R.H. Gong , in Textiles and Way, 2015

14.6.4 Knitted Structures

Knitted fabrics more often than not have lower modulus and dimensional stability than woven fabrics due to the loop formation in the structure. Notwithstanding, knitted structures can conform to circuitous shapes more easily without developing creases, and knitting is a more than flexible process in terms of forming preshaped structures. In that location are two basic types of knitting machines, warp knitting and weft knitting, defined by the loop yarn feeding direction. Warp-knitted structures have better structural stability and are more suitable as reinforcement material for composites. Knitted 3D fabrics may be divided into 3 varieties, multiaxial warp-knitted fabrics, spacer fabrics and fully-fashioned fabrics ( Guo, 2011). Multiaxial warp-knitted fabrics are basically multiple yarn layers stitched together during knitting, every bit illustrated in Figure xiv.nineteen. In addition to the warp yarns forth the length and the weft yarns across the width, yarn layers on a diagonal or along other angles can exist used. The structure has loftier in-aeroplane stability and modulus, considering the yarns are aligned at multiple angles and are crimp-free. The multiaxial structure as well has good conformability to complex shapes. When used as composite reinforcements, these structures are considered to be 3D solid fabrics and take been used in a variety of blended applications such every bit wind turbines, and machine and aeroplane components (Arnold, Hufnagl, Stopp, Puffi, & Sfregola, 2004; Guo, 2011).

Figure 14.19. Multiaxial warp-knitted structure.

Spacer fabrics are composed of ii-airplane fabrics connected by pile fibres or yarns. These can be fabricated by knitting (Ikenaga & Taniguchi, 2010; Shirasaki & Yukito, 2006) weaving (Bottger, 2000; Roell, 1996), or a nonwoven method (Le Roy, 1995; Poillet & Le Roy, 2003). They are essentially the same as the double fabrics described before in the section on pile fabrics, although the two linked fabrics are used as a single assembly instead of being separated after. Spacer fabrics can be used on their own in applications such as seat covers to offer greater permeability and absorption performance than offered past single-layer fabrics. They tin can besides be used in composites, and the space between the ii surface fabrics may be filled with a variety of materials to provide the required properties for detail applications, e.g. as partition walls for improved racket and oestrus insulation.

Three-dimensional shell structures may be produced during knitting past controlling knitting parameters such equally the sew together density, sew type and number of working needles in one course (Kazuyoshi, 2008; Kobata & Nakai, 2001; Nobuo & Takahiro, 2010; Roell, 2000). These are produced using flatbed weft knitting machines with two or more needle beds. Iii-dimensional knitted fabrics are used in seamless products such as hats, gloves, socks and seat covers. They can also be used in composite materials for applications such as jet engine vanes and T-shaped connectors (Guo, 2011). When compared with 3D woven structures, 3D-knitted fabrics take a lower modulus simply ameliorate elasticity and shock absorbency.

Read full chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B9781845699314000143

Knitted textile design

N. Francis , B. Sparkes , in Textile Blueprint, 2011

3.one Introduction

A knitted fabric designer needs to understand the creative potential of knitting technology and work in partnership with bachelor technology and technical expertise. The following chapter is an introduction to the fundamental principles relating to the design and manufacture of weft knitted fabric and way knitwear. In that location are few texts on this subject and nigh take been written past knitting technologists. This chapter has been approached from a blueprint perspective but includes information from a diversity of technological sources. The aim has been to provide a useful overview of the bailiwick that explains its diversity and complexities in an accessible form.

Read full chapter

URL:

https://world wide web.sciencedirect.com/science/commodity/pii/B9781845696467500032