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New knitting technologies move beyond apparel

by Adrian Wilson | 23 Mar, 2015

When Germany’s Mario Goetze scored the winning goal in the 2014 FIFA World Cup Final against Argentina in July last year, most football fans would have been unaware of a behind-the-scenes victory being enjoyed by sports giant Nike.

But crucially for Nike – and in a blow for its main rival Adidas – Goetze was wearing boots incorporating Flyknit uppers produced by flat knitting, in one of the very latest developments for textile technology.

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At successive ITMA shows over the past 20 years, the development of 3D knitting technology by major machine builders, notably Japan’s Shima-Seiki, Italy’s Santoni and Stoll of Germany, have wowed the crowds with the infinite possibilities of sealmless, 100% CAD created designs.

And other industries have certainly taken note.

Adidas and Nike first introduced running shoes with uppers made from seamless knitted fabrics prior to the 2013 Olympic Games and in 2014 both also claimed to be first in the introduction of the 3D knitting technology to football boots before last year’s tournament in Brazil.

In February 2014, Adidas introduced its limited edition Samba Primeknit boots, billed as combining ‘the comfort and responsiveness of playing barefoot with the protection of a traditional design’.

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The Samba has an upper that is knitted from heel-to-toe, and the yarns employed in its construction are designed to provide stability and strength that is equal to conventional boots, while being fully coated for extreme water resistance.

The advanced production techniques employed to make Primeknit also allow the one-layer upper to be constructed with performance-specific zones and without any wastage of material.

The boots were launched in March 2014 and retailed on the Adidas store website for £220, quickly selling out.

Nike subsequently launched a new Magista football boot based on its Flyknit technology, followed by the Dynamic Fit collar, which extended the boots above the ankle.

nike2

To protect the foot from water and cold, Nike’s design team developed a special application of NikeSkin coating for the Flyknit. The coating is less than 0.1 mm thick – thinner than a sheet of paper – and applied as a hot melt onto the knit to help protect from water.

Not to be outdone once again, Adidas then unveiled the Primeknit FS – billed as the world’s first all-in-one knitted football boot and sock hybrid to provide ‘a bespoke second-skin’ from toe to calf.

Still being tested by players, Adidas believes the one-piece design and strong light yarns of the Primeknit FS can provide new levels of flexibility and comfort combined with the stability and strength of conventional boots.

Reinforcements
Meanwhile, there is currently strong growth in the sales of multiaxial knitting machines for the production of fabrics employed in the reinforcement for composites.

In their simplest form, unidirectional (UD) fabrics – or ‘non-crimp fabrics’ as they are known in certain parts of the world – are made up of multiple plies of parallel fibres, each laying in a different orientation or axis – hence the term ‘multi-axial’.

multiaxia

Multiaxials effectively allow composite manufacturers to layers in their optimum form in a single, highly-engineered structure. These can then be shaped and set with resin to make specific parts.

Some of the advantages UD fabrics over competing reinforcements include:

  • The reinforcing fibres can be placed at different angles to optimise the performance of a finished composite.
  • Non-crimped fibres result in higher tensile and flexural properties in a finished composite.
  • There is reduced ‘print-through’– a fabric’s pattern showing through its resin coating on a surface – which is especially important on boat hulls and in automotive applications.
  • The fabrics are easier to cut and handle.
  • The straight uncrimped fibres allow good resin penetration and flow which is ideal for certain composite processes, while the stitching assists resin migration through the layers (the so-called ‘Z-direction’) maximising infusion rates.

For many years now, multiaxial fabrics made from carbon, glass and other speciality fibres such as aramid have been used extensively in the manufacture of sporting equipment, from tennis rackets and cycles to surfboards and kayaks, where every extra gram is critical in improving performance and significant weight advantages are made possible.

They are also engineered specifically for wind blade manufacturing. The Wind Energy market has seen enormous growth over the last 15 years, with blades now being produced over 80 metres in length. This has led to more focus on ensuring that all the reinforcements used in the manufacture of the blades are fully optimised to achieve the best mechanical performance. Carbon and E-glass multiaxials are also used in the marine sector in the hulls and other components.

Aerospace
In the aerospace industry, the use of carbon fibre as the basis for composite parts (often referred to as CFRP – carbon fibre reinforced plastics) has grown from representing just 10% of a commercial aircraft body 20 years ago to more than 50% in the latest models, such as the Airbus A380 and Boeing’s 787 Dreamliner. In addition, the US military is now using more carbon fibre than ever before in its aircraft and many other items of equipment.

airbusmultiaxial

Now it’s believed a similar switch to composite adoption will take place in the automotive industry.

It has been estimated that for the production of around 1,000 planes a year, the total amount of CFRP required is 50,000 tonnes, based on an average of 50 tonnes being used in each of them.

However, if even just 100 kg of CFRPs were to be employed in the projected 100 million cars soon to be built each year, the demand would be 10 million tonnes – significantly more than all of the global production of carbon fibre that is currently available.

Such developments point to an exciting future for some of the advanced textile technologies that will be exhibited at ITMA 2015 – and often moving far beyond the apparel and home furnishing markets for which they were originally developed.

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