ELECTRONIC TEXTILES: Wearable Computers, Reactive Fashion and Soft computation


Electronic textiles, also referred to as smart fabrics, are quite fashionable right now. Their close relationship with the field of computer wearable‘s gives us many diverging research directions and possible definitions. On one end of the spectrum, there are pragmatic applications such as military research into interactive camouflage or textiles that can heal wounded soldiers. On the other end of the spectrum, work is being done by artists and designers in the area of reactive clothes: “second skins” that can adapt to the environment and to the individual. Fashion, health, and telecommunication industries are also pursuing the vision of clothing that can express aspects of people’s personalities,social dynamics through the use and display of aggregate social information.

In my current production-based research, I develop enabling technology for electronic textiles based upon my theoretical evaluation of the historical and cultural modalities of textiles as they relate to future computational forms. My work involves the use of conductive yarns and fibers for power delivery, communication, and networking, as well as new materials for display that use electronic ink, nitinol, and thermochromic pigments. The textiles are created using traditional textile manufacturing techniques: spinning conductive yarns, weaving, knitting, embroidering, sewing, and printing with inks.

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textile-berzowska

Students design fabric for charging mobile phones


students from Aalborg University in Denmark have designed a smart fabric technology which aims to make mobile phones and other hand held devices truly mobile. 

Students from Aalborg University have designed a smart fabric called Powertex which charges mobile phones

Four students from Aalborg University in Denmark have designed a smart fabric technology which aims to make mobile phones and other hand held devices truly mobile. 

Students Hans Christian Thiesen, Mads Gydegaard, Morten Ydefeldt and Marius Koppang were awarded the prize for their project involving a fabric which can charge mobile computers, mobile phones and other electrical devices. The fabric automatically charges a mobile phone or computer when they are placed on it and can be integrated into mats and table covers. Upholstery fabrics for seating are considered a key area of application.

Competing with 54 other entries from 17 countries, the novel smart textile product, called Powertex, won the Future Textiles International Prize Competition 2011, earning the students 6500 EUR in prize money.  The competition aims to promote smart textiles and shines the spotlight on Denmark as a pioneer in the field. The prize ceremony took place at TEKO Design + Business, VIA University College, in Herning Denmark.

Marius Koppang and Mads Gydegaard from Aalborg University

Powertex fabric to replace mobile phone charger

Powertex is said to be an ideal practical solution for meetings, as participants will be able to charge and use their laptops and mobiles without using power leads or adaptors. Another suggested application is the use of Powertex as an upholstery fabric in public transport systems and in public buildings and airports. Passengers or users will simply place their mobile devices on the seat in order to charge it.

“Our goal is to be free from cords and a whole collection of adaptors and to give users the possibility to recharge their gadgets on the go,”  the winning team, which studies industrial design at Aalborg University, said.

When the winner was announced, member of the winning team from Aalborg University, Marius Koppang said:

“It’s just euphoric! You had the biggest butterflies when they said it was someone from Aalborg University – and then Powertex – Ooh! Ah! “

Commenting on the joy of winning, Marius said: “It was just beautiful – I hadn’t experienced it before – it was beautiful – just awesome!”

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Fiber-reinforced composites


Fiber-reinforced composites (or fibrous composites) are the most commonly used form of the constituent combinations. The fibers of such composites are generally strong and stiff and therefore serve as the primary load-carrying constituent. The matrix holds the fibers together and serves as an agent to redistribute the loads from a broken fiber to the adjacent fibers in the material when fibers start failing under excessive loads. This property of the matrix constituent contributes to one of the most important characteristics of the fibrous composites, namely, improved strength compared to the individual constituent.

Woven fabrics that are used in composites can be grouped as two-dimensional (2-D) and three dimensional (3-D) structures. 2D-weaving is a relatively high-speed economical process. However, woven fabrics have an inherent crimp or waviness in the interlaced yarns, and this is undesirable for maximum composite properties.

In 2D-structures, yarns are laid in a plane and the thickness of the fabric is small compared to its in-plane dimensions. Single layer designs include plain, basket, twill and satin weaves which are used in laminates. Two-dimensional woven fabrics are generally anisotropic, have poor in-plane shear resistance and have less modulus than the fiber materials due to existence of crimp and crimp interchange. Reducing yarn crimp in the loading direction or using high modulus yarns improves fabric modulus. To increase isotropy, in-plane shear rigidity and other properties in bias or diagonal direction, triaxially woven fabrics are developed in which three yarn systems interlace at 60° angles as shown in Fig. 2. Other
mechanical properties required in relation to different loading conditions are: through thickness stiffness and strength properties, enhanced impact resistance, fatigue resistance,
dimensional stability, fraction thickness, damage tolerance, and subtle conformability.

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In 3D-fabric structures, the thickness or Z-direction dimension is considerable relative to X and Y dimensions. Fibers or yarns are intertwined, interlaced or intermeshed in the X (longitudinal), Y (cross), and Z (vertical) directions. For 3D-structures, there may be an endless number of possibilities for yarn spacing in a 3-D space.

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Fig. 2: Triaxial weaving

3-D fabrics are woven on special looms with multiple warp and/or weft layers. Fig. 3 shows various 3D-Woven structures. In polar weave structure, fibers or yarns are placed equally in circumferential, radial and axial directions. The fiber volume fraction is around 50%. Polar weaves are suitable to make cylindrical walls, cylinders, cones and convergent-divergent sections. To form such a shape, prepreg yarns are inserted into a mandrel in the radial direction.

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5-Direction construction                     Polar weave                                          Orthogonal weave

Fig.3: Schematics of various 3D-woven fabric structures for composites

Circumferential yarns are wound in a helix and axial yarns are laid parallel to the mandrel axis. Since the preform lacks the structural integrity, the rest of the yarns are impregnated with resin and the structure is cured on the mandrel. Polar weaves can be woven into nearnet shapes. A near-net shape is a structure that does not require much machining to each
the final product size and shape. Since fibers are not broken due to machining, net shapes generally perform better than machined parts.

In orthogonal weave, reinforcement yarns are arranged perpendicular to each other in X, Y and Z directions. No interlacing or crimp exists between yarns. Fiber volume fraction is
between 45 and 55 percent. By arranging the amount of yarn in each direction, isotropic or anisotropic preform can be obtained.

Except for the components that are fundamentally Cartesian in nature, orthogonal weaves are usually less suitable for net shape manufacturing than the polar weaves. Unit cell size can be smaller than polar weaves which results in superior mechanical properties. Since no yarn interlacing takes place in polar and orthogonal structures, they are also referred to as ´´nonwoven 3-D“ structures in the composites industry. However, it is more proper to label these structures as woven structures with zero level of crimp.

In angle interlock type of structures, warp (or weft) yarns are used to bind several layers of weft (or warp) yarns together as shown in Fig. 4. In place of warp or weft yarns, an additional third yarn may also be used as binder. Stuffer yarns, which are straight, can be used to increase fiber volume fraction and in-plane strength. If the binder yarns interlace vertically between fabric layers, the structure is called orthogonal weave.

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Fig. 4: Angle interlock fabric; (A) with and (B) without added stuffer yarns.
Fig. 5: Schematic of King’s 3-D machine

Angle interlock or multi-layer fabrics for flat panel reinforcement can be woven on traditional looms, mostly on shuttle looms. The warp yarns are usually taken directly from a creel. This allows mixing of different yarns in the warp direction. Other more complex 3D-Fabrics such as polar and orthogonal weaves require specialized weaving machines. Several weaving machines were developed to weave complex 3D-structures as illustrated in Fig. 5. Multilayer weaving into a three-dimensional preform consists of interlocking warp yarns in many layers. Whereas in conventional weaving all of the warp yarns are oriented essentially in one plane, in the structure.

A typical step for weaving a multilayer preform includes two, three, or more systems of warp yarns and special shedding mechanism that allows lifting the harnesses to a many levels as the number of layers of warp yarns. By this weaving method, various fiber architectures can be produced, including solid orthogonal panels, variable thickness solid panel, and core structures simulating a box beam or truss-like structure.

The most widely used materials in 2D- or 3D-weaving are carbon/graphite, glass, and aramid. Any material that can be shaped as a fiber can be woven into preforms, more or
less complicated. Woven preforms can be made of a single type of fiber material or different fiber and yarn materials can be used as a hybrid structure. Due to the nature of woven
structure geometry and weaving process, when selecting a fiber for weaving or for any other textile manufacturing process, fiber brittleness and bending rigidity need to be considered. or example, carbon and graphite fibers, which account for 90% of all 3D-woven preforms, are prone to break and fracture during weaving. Fig. 2.6 shows preform and composite samples made of carbon fibers.

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Fig. 6: Woven 3D-preform and composite samples made of carbon fibers

Ref:-

Development of the Weaving Machine and 3D Woven Spacer Fabric Structures for Lightweight Composites Materials- Book

By:-

Von der Fakultät Maschinenwesen
der
Technischen Universität Dresden
zur
Erlangung des akademischen Grades
Doktoringenieur (Dr.-Ing.)
angenommene Dissertation

Geotextile Fabric Types and Construction


Picturs of geotextiles

Image via Wikipedia

  • Materials.

Geotextiles are made from polypropylene, polyester, polyethylene, polyamide (nylon), polyvinylidene chloride, and fiberglass. Polypropylene and polyester are the most used. Sewing thread for geotextiles is made from KevlarL or any of the above polymers. The physical properties of these materials can be varied by the use of additives in the  composition and by changing the processing methods used to form the molten material into filaments. Yarns are formed from fibers which have been bundled and twisted together, a process also referred to as spinning. (This reference is different from the term spinning as used to denote the process of extruding filaments from a molten material.) Yarns may be composed of very long fibers (filaments) or relatively short pieces cut from filaments (staple fibers).

  • Geotextile Manufacture.

In woven construction, the warp yarns, which run parallel with the length of the geotextile panel (machine direction), are interlaced with yarns called fill or filling yarns, which run perpendicular to the length of the panel (cross direction as shown in fig 1-1). Woven construction produces geotextiles with high strengths and moduli in the warp and fill directions and low elongations at rupture. The modulus varies depending on the rate and the direction in which the geotextile is loaded. When woven geotextiles are pulled on a bias, the modulus decreases, although the ultimate breaking strength may increase. The construction can be varied imageso that the finished geotextile has equal or different strengths in the warp and fill directions.
Woven construction produces geotextiles with a simple pore structure and narrow range of pore sizes or openings between fibers. Woven geotextiles are commonly plain woven, but are sometimes made by twill weave or leno weave (a very open type of weave). Woven geotextiles can be composed of monofilaments (fig l-2) or multifilament yarns (fig 1-3). Multifilament woven construction produces the highest strength and modulus of all the constructions but are also the highest cost. A monofilament variant is the slit-film or ribbon filament woven geotextile (fig l-4). The fibers are thin and flat and made by cutting sheets of plastic into narrow strips. This type of woven geotextile is relatively inexpensive and is used for separation, i.e., the prevention of intermixing of two materials such as aggregate and fine-grained soil.

Nonwoven geotextiles are formed by a process other than weaving or knitting, and they are generally thicker than woven products. These geotextiles may be made either from continuous filaments or from staple fibers. The fibers are generally oriented randomly within the plane of the geotextile but can be given preferential orientation. In the spunbonding process, filaments are extruded, and laid directly on a moving belt to form the mat, which is then bonded by one of the processes described below.

(a) Needle punching. Bonding by needle punching involves pushing many barbed needles through one or several layers of a fiber mat normal to the plane of the geotextile. The process causes the fibers to be mechanically entangled (fig l-5). The resulting geotextile has the appearance of a felt mat.

(b) Heat bonding. This is done by incorpo-rating fibers of the same polymer type but having different melting points in the mat, or by using hetero filaments, that is, fibers composed of one type of polymer on the inside and covered or sheathed with a polymer having a lower melting point. A heat-bonded geotextile is shown in figure l-6.

(c) Resin bonding. Resin is introduced into  the fiber mat, coating the fibers and bonding the contacts between fibers.

(d) Combination bonding. Sometimes a combination of bonding techniques is used to facilitate manufacturing or obtain desired properties.

Composite geotextiles are materials which combine two or more of the fabrication techniques. The most common composite geotextile is a nonwoven mat that has been bonded by needle punching to one or both sides of a woven scrim.

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  • Geotextile Durability

Exposure to sunlight degrades the physical properties of polymers. The rate of degradation is reduced by the addition of carbon black but not eliminated. Hot asphalt can approach the melting point of some polymers. Polymer materials become brittle in very cold temperatures. Chemicals in the groundwater can react with polymers. All polymers gain water with time if water is present. High pH water can be harsh on polyesters while low pH water can be harsh on polyamides. Where chemically unusual environment exists, laboratory test data on effects of exposure of the geotextile to this environment should be sought. Experience with geotextiles in place spans only about 30 years. All of these factors should be considered in selecting or specifying acceptable geotextile materials. Where long duration integrity of the material is critical to life safety and where the in-place material cannot easily be periodically inspected or easily replaced if it should become degraded (for example filtration and/or drainage functions within an earth dam), current practice is to use only geologic materials (which are orders of magnitude more resistant to these weathering effects than polyesters).

  • Seam Strength

a. Joining Panels. Geotextile sections can be joined by sewing, stapling, heat welding, tying, and gluing. Simple overlapping and staking or nailing to the underlying soil may be all that is necessary where the primary purpose is to hold the material in place during installation. However, where two sections are joined and must withstand tensile stress or where the security of the connection is of prime importance, sewing is the most reliable joining method.

b. Sewn Seams. More secure seams can be produced in a manufacturing plant than in the field. The types of sewn seams which can be produced in the field by portable sewing machines are presented in figure 1-7. The seam type designations are from Federal Standard 751. The SSa seam is referred to as a “prayer” seam, the SSn seam as a “J” seam, and the SSd as a “butterfly” seam. The double-sewn seam, SSa-2, is the preferred method for salvageable geotextiles. However, where the edges of the geotextile are subject to unravelling, SSd or SSn seams are preferred.

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c. Stitch Type. The portable sewing machines used for field sewing of geotextiles were designed as bag closing machines. These machines can produce either the single-thread or two-thread chain stitches as shown in figure l-8. Both of these stitches are subject to unravelling, but the single-thread stitch is much more susceptible and  must be tied at the end of each stitching. Two rows of stitches are preferred for field seaming,  two rows of stitches are absolutely essential for secure seams when using the type 101 stitch.  since, with this stitch, skipped stitches lead to complete unravelling of the seam. Field sewing should be conducted so all stitching is exposed forinspection. Any skipped stitches should be over sewn.

d. Sewing Thread. The composition of the thread should meet the same compositional performance requirements as the geotextile itself, although it may be desirable to permit the thread to be made of a material different from the geotextile and being sewn. Sewing thread for geotextiles is usually made from Kevlar, polyester, polypropylene, or nylon with the first two recommended despite their greater expense. Where strong seams are required, Kevlar sewing thread provides very high-strength with relative ease of sewing.

  • Geotextile Functions and Applications

a. Functions. Geotextiles perform one or more basic functions: filtration, drainage, separation, erosion control, sediment control, reinforcement, and (when impregnated with sphalt) moisture barrier. In any one application, a geotextile may be performing several of these functions.

b. Filtration. The use of geotextiles in filter applications is probably the oldest, the most widely known, and the most used function of geotextiles. In this application, the geotextile is placed in contact with and down gradient of soil to be drained. The plane of the geotextile is normal to the expected direction of water flow. The capacity for flow of water normal to the plane of the geotextile is referred to as permittivity. Water and any particles suspended in the water which are smaller than a given size flow through the geotextile. Those soil particles larger than that size are stopped and prevented from being carried away. The geotextile openings should be sized to prevent soil particle movement. The geotextiles substitute for and serve the same function as the traditional granular filter. Both the granular filter and the geotextile filter must allow water (or gas) to pass without significant buildup of hydrostatic pressure. A geotextile-lined drainage trench along the edge of a road pavement is an example using a geotextile as a filter. Most geotextiles are capable of performing this function. Slit film geotextiles are not preferred because opening sizes are unpredictable. Long term clogging is a concern when geotextiles are used for filtration.

c. Drainage. When functioning as a drain, a geotextile acts as a conduit for the movement of liquids or gases in the plane of the geotextile. Examples are geotextiles used as wick drains and blanket drains. The relatively thick nonwoven geotextiles are the products most commonly used. Selection should be based on transmissivity, which is the capacity for in-plane flow. Questions exist as to long term clogging potential of geotextile drains. They are known to be effective in short duration applications.

d. Erosion Control. In erosion control, the geotextile protects soil surfaces from the tractive forces of moving water or wind and rainfall erosion. Geotextiles can be used in ditch linings to protect erodible fine sands or cohesionless silts. The geotextile is placed in the ditch and is secured in place by stakes or is covered with rock or gravel to secure the geotextile, shield it from ultraviolet light, and dissipate the energy of the flowing water. Geotextiles are also used for temporary protection against erosion on newly seeded slopes. After the slope has been seeded, the geotextile is anchored to the slope holding the soil and seed in-place until the seeds germinate and vegetative cover is established. The erosion control function can be thought of as a special case of the combination of the filtration and separation functions.

e. Sediment Control. A geotextile serves to control sediment when it stops particles suspended in surface fluid flow while allowing the fluid to pass through. After some period of time, particles accumulate against the geotextile, reducing the flow of fluid and increasing the pressure against the geotextile. Examples of this application are silt fences placed to reduce the amount of sediment carried off construction sites and into nearby water courses. The sediment control function is actually a filtration function.

f. Reinforcement. In the most common reinforcement application, the geotextile interacts with soil through frictional or adhesion forces to resist tensile or shear forces. To provide reinforcement, a geotextile must have sufficient strength and embedment length to resist the tensile forces generated, and the strength must be developed at sufficiently small strains (i.e. high modulus) to prevent excessive movement of the reinforced structure. To reinforce embankments and retaining structures, a woven geotextile is recommended
because it can provide high strength at small strains.

g. Separation. Separation is the process of preventing two dissimilar materials from mixing. In this function, a geotextile is most often required to prevent the undesirable mixing of fill and natural soils or two different types of fills. A geotextile can be placed between a railroad subgrade and track ballast to prevent contamination and resulting strength loss of the ballast by intrusion of the subgrade soil. In construction of roads over soft soil, a geotextile can be placed over the soft subgrade, and then gravel or crushed stone placed on the geotextile. The geotextile prevents mixing of the two materials.

h. Moisture Barrier. Both woven and nonwoven geotextiles can serve as moisture barriers when impregnated with bituminous, rubber-bitumen, or polymeric mixtures. Such  impregnation reduces both the cross-plane and in-plane flow capacity of the geotextiles to a minimum. This function plays an important role in the use of geotextiles in paving overlay systems. In such systems, the impregnated material seals the existing pavement and reduces the amount of surface water entering the base and subgrade. This prevents a reduction in strength of these components and improves the performance of the pavement system.

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Ref.:-

ENGINEERING USE OF GEOTEXTILES

-UNIFIED FACILITIES CRITERIA (UFC)

UFC 3-220-08FA
16 January 2004

Technical Textiles


Textiles are indispensable part of human life. They are used mainly to cover the human body for protection against all the adversities. Technological innovations have also made it possible for textile industry to offer technical solutions to the multiple end-users in the different industries.

Technical textiles are defined as textile materials and products used primarily for their technical performance and functional properties rather than their aesthetic or decorative characteristics. Other terms used for defining technical textiles include industrial textiles, functional textiles, performance textiles, engineering textiles, invisible textiles and hi-tech textiles.

An outstanding feature of the technical textile industry is the range and diversity of raw materials, processes, products and applications that it encompasses.

Technical textiles are used individually or as a component/part of another product. Technical textiles are used individually to satisfy specific functions such as fire retardant fabric for uniforms of firemen and coated fabric to be used as awnings. As a component or part of another product, they are used to enhance the strength, performance or other functional properties of that product as done by the tyre cord fabrics in tyres and interlining in shirt collars. They are also used as accessories in processes to manufacture other products like filter fabric in food industry or paper maker felt in paper mills.

Technical textiles have been slowly but steadily gaining ground due to one or more of the reasons such as: functional requirement, health & safety; cost effectiveness; durability; high strength; light weight; versatility; customization; user friendliness; eco friendliness; logistical convenience etc.

Unlike conventional textiles used traditionally for clothing or furnishing, technical textiles are used basically on account of their specific physical and functional properties and mostly by other user industries. Depending on the product characteristics, functional requirements and end-use applications the highly diversified range of technical textile products have been grouped into 12 sectors application wise:

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  1. Agrotech (Agriculture, horticulture and forestry)
  2. Buildtech (building and construction)
  3. Clothtech (technical components of shoes and clothing)
  4. Geotech (geotextiles, civil engineering)
  5. Hometech (components of furniture, household textiles and floor coverings)
  6. Indutech (filtration, cleaning and other industrial usage)
  7. Meditech (hygiene and medical)
  8. Mobiltech (automobiles, shipping, railways and aerospace)
  9. Oekotech (environmental protection)
  10. Packtech (packaging)
  11. Protech (personal and property protection)
  12. Sporttech (sport and leisure
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Technical Textiles in India – A dormant volcano prepares to erupt…


ABSTRACT:-

India is rising and moving ahead with opportunities in every sector. For the past four years India’s GDP has grown up to 8%, and is assumed to remain consistent at 8-9% for coming years. According to Goldman Sachs, India’s economy will exceed the economy of Europe and Japan by 2030 and that of the US by 2045.Such a growth is possible because of the increase in household incomes and the predicted growth in agriculture, manufacturing and service sectors. Also the consumer spending level is growing over 5% per annum which has resulted in the on-going growth of organized retail sectors.

Talking about the technical textile industry in India, it is said to be its initial stage as it contributes only 3% of total consumption. But, it would be wrong to say that India’s technical textile industry is still sleeping. It has woken up to the enormous potential of the technical textile sector and is predicted to grow faster in next two decades than the growth withstand by US and Europe in last three decades. This is said to become possible with the growing middle class, young and educated population. And Technical Textile would be one of the most promising sectors in this growth.

And the factors like, the global economic change, strong government support, the introduction of appropriate legislation, the development of tests and standards, and widespread recognition of the need for more trained personnel, etc. also playing the valuable role in driving the industry to the farthest destination. Thus it won’t be wrong to say that, “Technical Textiles in India- A sleeping volcano prepares to erupt.”

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