Multi-Layer Fabrics: the art of weaving several layers in a fabric
Multi-layer fabrics - design, properties, and concepts
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 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:
- interlacing and
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.