A U.K.-based manufacturer of weft-knitted technical textiles has developed the ability to commercially manufacture 3D carbon fiber preforms for composites that require no post knitting fabrication or cutting.
Inside Composites says that Preform Technologies completed a two-year Knowledge Transfer Partnership (KTP) project with the University of Derby to modify and adapt a Stoll CMS 822 HP v-bed weft (flat) knitting machine to retain its full functionality while knitting carbon fiber.
Sylvan Whalley, CEO of Preform Technologies, describes making preforms out of carbon fiber as “the holy grail of 3D knitted composite reinforcements.” The result is shaped parts that promise to require no fabrication or cutting to fit a mould tool.
The challenge of the project was not in the knitting, but in dealing with the electrical conductivity of carbon fiber. Items such as power supplies, motors, solenoids, onboard computers and printed circuit boards, touch screen interfaces and USB data transfer ports are all vulnerable.
When using carbon fiber in weaving, multi-axial warp knitting, braiding and other functions, the vulnerable electronics and motors are often separated from the machine. This can be done by housing them in different rooms and connecting via cables.
With electronically controlled flat knitting machines, however, using cables longer than a few meters may result in essential signaling being interrupted. The solution lies in taking numerous measures to protect motors, circuit boards and other components, which is largely what the company accomplished.
Whalley expects the company’s technological advancement to produce shaped carbon fiber preforms in volume for the automotive, aerospace and marine industries.