Multi-Layer Fabrics: the art of weaving several layers in a fabric

Introduction

Technical textiles are the fastest growing sector in the textile industry. Therefore, it is highly essential to develop all techniques and types of equipment in order to decrease the production time especially with the use of electronically equipped modern looms and communicated with computers.

The automatization of woven design is one of the ways to facilitate the work and to increase the production, especially in the conventional weaving of complex structure, due to the time consuming and difficulties involved in the manual design (e.g., the combination of weaves, seeking of stitches and introducing it, generating of lifting plan, doing cross-sections, etc. However, a number of CAD/CAM fabric woven structures with complicated weaves have been developed and represented in the form of 2D and 3D matrices.

Some of these researches depended on mathematical functions to describe and generate automatically the 2D and 3D weaves. In other words, the algorithm of the Kronecker Product was applied to describe weaves. In addition, other CAD/CAM software’s that deal with geometric modeling of woven structures have been developed to visualize the fabric appearance before weaving (Liao & Adanur, 1998; Lomov, Perie, Ivanov, Verpoest, & Marsal, 2011; Smith & Chen, 2009). However, they do not discuss all the problems due to the wide variety of weaves and stitching ways.

Definition Multilayer fabrics

A multilayer fabric consists of several layers woven above each other with a maximum of 12 woven layers or 22 warp yarn layers and 23 weft yarn layers (unidirectional layers). The connection can be realized by connection yarns in the third dimension or by interlocking. As a result, the delamination resistance of the fabric increases and the manual labor of stacking different layers on top of each other could be decreased. All types of yarns can be used and combined. This combination could be different layers with different types of yarns but also in one-layer different types of yarns can be used.

Woven multilayer fabrics are composed of warp and weft yarns which interlace with one another according to the weave design

Multi-layer fabric

Multi-layer fabric

A multilayer fabric with woven layers consists of a number of woven layers stacked on top of each other and held together with connection yarns in the third dimension (Z-direction). The geometry of the woven layers can be customized.

3D Weaving

The term 3D weaving is commonly used in reference to the weaving of cloths that have pre-designed three-dimensional shapes (multilayer fabrics) or can be directly manipulated by interlocking and non-interlocking methods into a 3D shape immediately after being woven. It is also used to describe the weaving of fabrics with substantial thicknesses, many times greater than the diameters of the yarns used to produce the fabrics.

3D Shape Weaving

Conventional projectile/rapier-dobby/ Jacquard looms can be used to produce certain three-dimensional shapes by weaving multiple layers of fabric interlinked to each other, similar to a ‘double cloth, treble cloth ‘formation, so that after being woven the layers of 2D fabric can be manipulated into the required 3D shape; for example, a dobby/jacquard loom can be used to produce the cellular structures. For obvious reasons, this method is also termed multilayer weaving.

It is highly essential to have knowledge and understanding of double/treble cloths which are basic for the formation of multilayer fabric

Double cloths structures—The simplest structure of double cloth is composed of two series of warp threads and two series of weft threads. One series of each kind forming an upper or face fabric, and the other, an under or back fabric. It is necessary for the face picks, to be arranged in definite order with the backing picks, and the face ends with the back ends

Treble cloths structure—In treble cloths there are three series of warp and weft threads which form three distinct fabrics one above the other. Except for the forties, when a face pick is inserted all the center and back ends are left down; when a center pick is inserted all the face ends are raised, and all the backing ends are left down, while a backing pick is inserted all the face and central ends are raised.

The face ends and picks interweave with each other to form face fabric, the Centre ends and picks form Centre fabric and backing ends and picks form back fabrics. By interweaving the Centre ends or picks with the face and backing picks or ends, the three fabrics are joined together, and the resulting cloth is equal in thickness and weight to the three single fabrics.

These shaped structures are essentially based on 2D weaves, where the weft and warp yarns are in the horizontal plane, by convention in the x and y directions, of the fabric. No yarn lengths are present in the z-direction of the fabric to give the 3D shape its thickness; the thickness is given by the diameters of the warp and weft yarns.

Projectile/ Rapier-Jacquard looms are used to produce directly woven thin, complex, 3D-curved geometries. the thickness is given by the diameters of the warp and weft yarns. The conventional 2D multilayer weaving can be used to construct 3D fabrics, but for profiled 3D fabrics (i.e. thick fabrics with a designed shape – termed shaped 3D fabrics) specially built looms are required.

2D Multilayer Weaving of 3D fabrics, two techniques are used:

  1. interlacing and
  2. non-interlacing

A multilayer fabric with interlocking is not kept together with an extra connection yarn system in the third dimension. The interlocking happens as the warp and/or weft yarns are switched between the different layers. The transition of the warp and weft yarns can be customized according to the application.

Multilayer woven fabrics are conventionally represented with the usual weave notation of black and white squares. This notation is based on the top view of the woven fabric. Side view of multilayer woven fabrics contains more important information, namely the routes of warp yarns between layers of weft yarns.

In this study, possibilities of woven structures with any numbers of layers and corresponding warp and weft yarns are described. Formulas are derived to describe horizontal, vertical, and diagonal symmetries which lead to identifying the fully independent structures. The results serve as the theoretical ground to determine all the possible mechanical properties by using woven reinforcements.

Detailed weaving structure of multilayer woven fabric

  1. Non Crimp yarn layers

    A multilayer fabric with non-crimp layers consists of unidirectional layers stacked on top of each other. The stacking can be in 0-degree direction or a combination in 0- and 90-degree direction. The whole package is then held together by connection yarns in the third dimension.

  2. Woven layers

    A multilayer fabric with woven layers consists of a number of woven layers stacked on top of each other and held together with connection yarns in the third dimension (Z-direction). The geometry of the woven layers can be customized.

  3. Interlocking

    A multilayer fabric with interlocking is not kept together with an extra connection yarn system in the third dimension. The interlocking happens as the warp and/or weft yarns are switched between the different layers. The transition of the warp and weft yarns can be customized according to the application.

  4. Combination

    A combined multilayer fabric is a combination of different types of multilayer fabrics. This can be for example a multilayer fabric with NC layers except for the outer layers which are woven layers and can be interlocked.

  5. Tubular fabrics

    A tubular fabric is characterized by the hollow spaces in the 3D woven fabric. These hollow spaces can be customized in shape and dimension. The surfaces can be profiled or flat each with several different connection possibilities. With profiled faces oblique or oblique in combination with horizontal connections (for example a honeycomb structure) are possible.

    Flat surfaces can have vertical connections, oblique connections or a combination of oblique and horizontal connections. These openings can be used for utilities, can be filled with reinforcement matrix, with foam…

    It is possible to combine different yarn types in one woven fabric. Different layers can consist of other yarns but also within one woven layer periodically another yarn type can be used.

  6. Pile fabrics

    A pile fabric consists of a woven layer with perpendicular cut pile yarns as with normal velvet.

  7. Loop pile fabrics

    A loop pile fabric consists of a woven layer with perpendicular loops of pile yarns.

  8. Complex fabrics

    This category includes all woven fabrics that cannot be divided into five main categories. The woven fabrics can be a combination of different techniques, a jacquard woven fabric or an asymmetrical woven fabric.

Design for Double/ multilayers of weaving design for multilayers fabric

Design for Double/ multilayers of weaving design for multilayers fabric


New Architectural Approach to the Designing of multilayer fabrics by using various types of yarns to give desired apparel properties

Usually at least three layers are identified as follows:

  • Inner Layer provides body comfort by keeping the skin dry. Also called base layer or first layer.
  • Mid Layer provides warmth. Also called insulating layer.
  • Outer Layer protects from wind and/or water. Also called outer layer which works as protection over the other two layers.

Often clothes combine two adjacent layers, as in the case of warm undergarments that provide both comfort and insulation.

The inner or base layer

The purpose of the inner layer is to draw the sweat away from the skin to the next layers, which makes the wearer feel warmer and more comfortable. The transfer of moisture happens due to capillary action, sometimes called wicking. The used materials are called wicking materials.

When moisture has moved from the skin into (nonabsorbent) clothing, it has more surface area and will evaporate faster. If a piece of clothing does not transfer moisture well, it is not strictly an inner layer garment at all, but simply a comfortable mid-layer garment.

  • Wool is a combination of wicking and water-repelling properties and, along with silk, is the most expensive of the materials used for base layers. How comfortable wool feels against skin varies greatly, with Merino wool being softer. Wool is highly odor resistant.
  • Synthetic materials such as Polyester, polyethylene, and microfiber-based fabrics are inexpensive. They have excellent water wicking properties.
  • Wicking fabrics are modern technical fabrics which draw moisture away from the body. They are made of high tech polyester, which, unlike cotton, absorbs very little water. Cotton will absorb 7% of its weight in water, polyester only 0.4%. Cotton will, therefore, hang onto your sweat, making your garment heavy and unpleasantly clammy. Wicking polyester has a special cross-section and a large surface area, which picks up moisture and carries it away from your body, spreading it out, to evaporate easily on the outside of the fabric. So, you stay cool and dry. They can also carry specialist finishes, such as anti-bacterial agents which reduce odors, and insect repellent. However, in the absence of such anti-odor treatment, they quickly become notoriously foul-smelling. This is because their hydrophobicity causes them to strongly absorb the short-chain fatty acids that are responsible for body odor.
  • Silk is expensive. It feels comfortable but is less warm, weaker and harder to take care of.
  • Cotton is usually inexpensive. It absorbs moisture easily and is slow to dry out. When wet or damp, cotton loses its insulative abilities and becomes more thermally conductive than other materials. This makes it suitable for warm temperatures but potentially dangerous for cold and/or wet conditions. You will commonly hear that cotton is better forgotten because it is so cold when wet.

Mid Layer

The mid layer is needed in cold weather to provide additional insulation. The use of multiple thin layers facilitates adjustment of warmth. The mid layer should be more loose-fitting than the inner layer, as this leaves insulating air between the layers. However, if best possible moisture transfer is desired, too great a gap between any adjacent layers of clothing may reduce the moisture transfer by capillary action from one piece of clothing to another.

On the other hand, very loose-fitting layers can allow more removal of moisture (and heat) via air circulation. Capillary pressure is the main force responsible for the movement of moisture along or through a fabric, where the force of the surface tension between the liquid and the walls of a narrow gap or pore overcome the forces between the molecules of the liquid, moving it into empty gaps until the forces even out.

Permeability is the measure of a fabric’s ability to transport moisture through itself and is determined by a combination of sizes of spaces within it and the connections between the spaces.

  • Wool is the traditional mid layer material with several good properties: it has good insulation even when wet, absorbs moisture but does not feel wet even when it holds significant moisture and transfers moisture.
  • Fleece made from PETE or other synthetics has many of the features of wool but is lighter. It provides good insulation even when wet, absorbs very little moisture, and dries quickly. Although no longer commonly used in the industrialized world, natural sheepskin fleece could also serve the mid layer function.
  • Down has a very good warmth: weight ratio, and can be packed down (squeezed) to take very little room. On the downside, it is expensive, makes a thick garment, dries slowly, loses its insulating properties when wet or compressed, and stops lofting properly after being washed several times.
  • Synthetic Fiberfill such as Polyester fiber is used similarly to down but does not have as good a warmth: weight ratio. However, it is less expensive, provides better insulation when wet, dries quickly, and absorbs very little moisture. There are brands of very fine fiberfill like Thinsulate, PrimaLoft or Thermolite, that provides higher warmth for a given thickness.
  • Cotton, as with the inner layer, is a cheap alternative, but a reasonable choice only when low insulation and moisture transfer is needed. Most people involved in outdoor activities would agree that cotton is a very poor material to wear in the outdoors because you MAY need to insulate yourself and unless you are not moving, you WILL need moisture transfer.

Outer Layer

A waterproof breathable (hard shell) jacket

Breathability

Some people will refer to wicking fabrics as being breathable – that is, they let air in and sweat out. Breathable showerproof and waterproof fabrics have tiny pores in the fabric, larger than water vapor molecules (so these can get out) but much smaller than drops of rain (so these can’t get in)

The outermost clothes are called the shell layer, but only if they block wind or water, or have good mechanical strength. Ideally, the shell layer lets moisture through to the outside (that is, is breathable), while not letting wind and water pass through from the outside to the inside. While this is enabled to some degree by modern materials, even the best and most expensive materials involve a slight trade-off between breathability and water- and wind resistance.

If heavy sweating is expected, one should avoid wearing any shell layer garments unless their protective properties are essential. For example, when one is jogging, no traditional shell layer is likely to be able to transfer enough moisture to keep the wearer feeling dry. But as more air permeable membranes emerge, when combined with pit zips the amount of moisture being transferred outwards would be sufficient for cardiovascular pursuits. As a general rule, one should consider using sufficiently warm mid-layer clothes.

Both “soft” and “hard” shell jackets and layers exist. Hard shells are commonly woven fabric and do not rip. Softshell may rip easier but are more flexible.

  • Plastic raincoats protect completely from water and wind, but let through no moisture. To compensate for that, such raincoats usually have flap-covered holes and are very loose-fitting at the bottom to allow air circulation.
  • Waterproof breathable (hard shell) materials are waterproof and somewhat breathable. Their essential element is a thin, porous membrane that blocks liquid water, but lets through water vapor (evaporated sweat). The more expensive materials are typically more breathable. The best-known brand is Gore-Tex, while one study shows that eVent, a newer material, has the best breathability, although it has less wind resistance.
  • Water resistant (soft shell) most materials block water only partially, however as technology in the outdoor industry moves forward more fully waterproof soft shells are emerging such as Polartec neoshell or DryQ Elite. On the other hand, they are usually more breathable and comfortable, thinner, and cheaper than completely waterproof materials. Water-repellent coatings are often used. Before waterproof-breathable shells were invented, the “60/40” (60% cotton, 40% nylon) parka was widely used. Soft shells are not water “proof”.

The term soft shell is increasingly used to describe garments that combine partial or full water resistance with partial or full wind breaking ability. Softshell fabrics come in numerous varieties with many garments offering a combination, such as a wicking layer. In many cases, insulation is combined in an attempt to replace several layers with a single highly flexible one. One of the most unique characteristics of the woven softshell fabrics is the combination of wind-proofness, a high level of water resistance, and stretch — in many cases four-way stretch. Solid plastic films and micro-perforated laminates typically breathe much less and do not stretch at all.

Summary

The integration of performances in interactive textile fabric system has so far been rather complicated since they are based on multilayer or three-dimensional principles. These structures are today mainly put together by means of several processes, which is laborious and time-consuming. This has combined the principle of a three-dimensional multilayer weaving process and interactive textiles structures in order to enable the manufacturing of interactive textile structure in one process.

The process is using a manual reconstructed loom and the approach has been to use the 3D structures in order to integrate and organize conductive and compressive spacer layers as a textile capacitive structure. In this paper, it is seen that a three-dimensional structure enables the development of interactive textiles in one process. Future research will focus on developing other types of interactive structures.


Acknowledgment:

Technical and technological Facts in this write up have been selected from various reputed sources. I do also acknowledge the research contents done by other research institutions and organizations.