APPLICATION TECHNOLOGY
The growth of lightweight composite materials
Here bigHead Bonding Fasteners Ltd, based in Dorset, UK, looks at the development of lightweight composite materials and how it is contributing to the growth of bonding fasteners.
T
he development of composites and plastics and their migration into applications habitually dominated by traditional materials such as wood and metal has been significant. Lighter, stronger, versatile and more
mechanically stable, modern composite materials have found a home in almost every industrial sector. The issue of reducing weight or ‘light-weighting’ has become central to innovation in the automotive sector. High oil prices and increasing regulatory pressure to reduce carbon emissions will only enhance this trend. Initially, lightweight composite materials such as carbon fibre
were only used in very high end applications such as aerospace and super cars, as costs were very high and production processes slow. Increasingly, major car makers are introducing carbon fibre into their luxury models and many are examining ways to replace structural elements traditionally made in heavier metal with lightweight carbon fibre. As the volumes of carbon fibre production increases, the costs will fall and the number of applications in premium and standard car models will increase. The expansion of carbon fibre and other lightweight composite
materials presents challenges as well as opportunities. One of the key challenges is how to securely fasten to such materials. Traditional fastening systems designed for sheet metal, such as rivets, bolts and clinched fixings are incompatible with carbon fibre. Increasingly therefore, design engineers are turning to bonding and bonding fasteners as a solution. Interestingly, this is exactly how design engineers solved the same problem in the 1970s when GRP became a popular material.
“ The issue of reducing weight or ‘light-weighting’ has become central to innovation in the automotive sector.”
The development of the bonding fastener Bonding fasteners were invented by bigHead in 1966 to solve
a fastening problem that traditional fasteners could not; how to achieve a strong mechanical fastening in a composite material, such as GRP. bigHead came up with the unique bigHead bonding fastener design; a fixing, such as a threaded stud or collar, is welded to a flat perforated head which is embedded in the composite material.
132 Fastener + Fixing Magazine • Issue 75 May 2012 The perforated head helps spread the load directly into the
composite material while the welding process means there is an almost infinite variety of fixings that can be used. Like all the best inventions it was simple and effective but also versatile in solving a problem. In its 45 year history bigHead has made over 5,000 types of bigHead bonding fasteners for specific customer applications, and customers show no sign of diminishing their need for flexible design. The growth in performance and acceptance of adhesives
has gone hand in glove with the growth of bonding fasteners. Whereas the original bonding fasteners were embedded in the GRP when laid up or formed, most manufacturers today surface bond bigHead fasteners with adhesive. The perforated head allows the adhesive to flow through and lock the fastener in position when cured. A substrate like carbon fibre is left undamaged and the load continues to be effectively spread through the perforated head and adhesive to the substrate. The expansion and refinement of adhesives continues to broaden the scope and range of bonding fasteners across many industries.
From prototype to production The phrase ‘time is money’ has never been truer, whether
for the assembly of a car or the construction of a building. Streamlining a production process has therefore become a critical factor for success. bigHead typically supplies Tier 1 and Tier 2 sub-assembly manufacturers who provide completed modules to their customers for final assembly. By integrating the bonding fasteners within their module, Tier 1 and 2 suppliers help their customers streamline final assembly. In this streamlined process simple product design and reliability have become even more critical. As bonding fasteners become integral to the product they are
bonded to, the strength and reliability of the welding technology that forms the bigHead is of central importance. The bigHead welding technology also enables an enormous range of different bigHead fasteners to be made quickly and reliably, and often in small runs to support customer prototyping and testing. bigHead can test fasteners for specific applications and provide customers with critical data to help them optimise design and performance. bigHead’s automated
welding technology is designed to ensure a perfect weld
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