LIGHTWEIGHT MANUFACTURING
elements, mounting brackets, and other structural and semi-structural items that would have traditionally been made from steel or aluminium. In such instances, the weight-saving is considerable.” Before TFP, it hasn’t always been possible to satisfy a full range of loading conditions with fi xed fi bre orientations, even through the build-up of multiple layers. Each layer must be individually cut, often from prepreg, which results in considerable waste and is very labour intensive. Prepreg materials also have their own nuances and barriers to entry: they must be kept at a low temperature to prevent the thermoset resin from ageing, and the cutting technology required can be complex and expensive. This limits the scope for mass production and raises the cost of fi nished products. By comparison, the thermoplastics that are generally
A ShapeTex suspension link
used as part of a TFP matrix can be kept at room temperature and have much improved impact resistance when compared to thermoset resins. One of ZSK’s innovations that has
resulted in the evolution of TFP’s accessibility is the introduction of its Fast Fibre Laying technology. This technique allows intermediate layers of thread to be laid down extremely quickly and with minimal stitches, focusing on anchorage and changes of thread orientation. The top layer is then stitched down thoroughly, fi xing the layers below. This is much faster than stitching through every layer to the base layer at regular intervals and complements the fl exible manufacturing footprint that is inherent to TFP.
The automated process extends to
switching between thread or bobbin changes and is highly scalable. Each ZSK machine head can lay between 1 and 3kg of carbon fi bre preform per hour and can handle two rovings of up to 60,000 fi bres each. Machines with up to eight heads can create components simultaneously to considerably reduce cycle time. TFP is a simple concept, but a complex one to refi ne. Designers need to understand the draping simulation (where to add or remove material to ensure that 2D preforms will successfully press into a 3D structure) and where and how stitches should be applied for optimal distortion and intended strength. Due to this complexity, ZSK has established research and training centres both in Europe and Seattle, USA. These
Elemental application
TFP components have already made it into series automotive production. For instance, the Elemental Motor Company has used the technique to develop part of the rear structure of its track-focused road car, the RP1. Carbon fi bre had previously been ruled out on a cost and fragility basis, before the company was introduced to the technique by Shape Group.
36
www.engineerlive.com According to Elemental’s
composites manager, Peter Kent, TFP “changed our view of how carbon composites could help achieve weight and cost targets. We found it created pre-forms quickly, is cost effective, and durable. The resulting structural rear bodywork on the Elemental RP1 is tough enough to withstand impacts such as extensive stone chips and has a complex 3D shape with
compound curves. This is at odds with the traditional qualities of carbon fi bre components. “We have been able
to design a bodywork component with Shape and ZSK in carbon composite using TFP, which can act as a structural component, carrying bodywork and the rear luggage bins, while experiencing considerable aerodynamic forces.”
RP1 arch next to its preform
centres enable engineers to familiarise themselves with the process, but also to better understand its signifi cant potential. “TFP principles can be applied
to more than just the manufacture of carbon composites,” concludes Sobizack. “For a range of industries, a twin-head embroidery machine, for example, can be used to stitch an embedded component such as electrical wiring, heating elements, strain gauges or antennae. This enables a more widespread utilisation of smart textiles embedded with elements such as RFID components. Even complex wiring systems can be embroidered for applications such as next generation automotive or aerospace interiors; the potential is vast.” ●
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