Tomorrow's answer – metal to composite joining breaches a new frontier

Citation

(2004), "Tomorrow's answer – metal to composite joining breaches a new frontier", Assembly Automation, Vol. 24 No. 3. https://doi.org/10.1108/aa.2004.03324caf.002

Tomorrow's answer – metal to composite joining breaches a new frontier

Tomorrow's answer – metal to composite joining breaches a new frontier

Keywords: Metals, Joining, Composite materials

For years, engineers and materials scientists have spent countless head scratching hours trying to develop a high strength means of joining composites to metals.

Fibre reinforced polymers used by themselves offer high strength and low weight. But their use in engineering invariably demands that they are joined to other materials, usually metals.

Poor mechanical performance, low fatigue resistance, and a deep-seated distrust of the joint's repeatability and integrity have, until now, coerced designers into over-conservativism. This negates the very essence of weight saving. But it could soon be a thing of the past.

With the advent of Comelde the world of composite-to-metal joining looks set for a surprise. Automotive, aerospace, medicine, oil and gas, renewable energy...the industrial applications for joining fibre reinforced plastic composites to metals are countless.

The heart of Comeld's success lies in a metal surface pretreatment, invented and patented by TWI, and dubbed Surfi-Sculpte.

The joint is produced by allowing the polyester resin and glass fibre composite to bond to the prepared surface of, in this case, stainless steel. A successful joint is created by allowing the polyester resin to bond to the prepared surface of the stainless steel. In some circumstances a further adhesive layer may be called for. Additional standard surface preparations like etching and priming have also been used to great effect (Plates 2 and 3).

Plate 2 The pretreated metal

Plate 3 A Comeld joint

The Comeld joint fails at a much higher load and absorbs far more energy before failure, than a conventional joint of identical dimensions (Figure 1).

Figure 1 Load displacement...with and without Comeld

This is a joining process of the near future. Formula One racing cars, high performance military jets, shipbuilders, energy suppliers... just about any industry that uses composites and metals in the same structure will be interested.

But these are early days in the development of Comeld. So assured is TWI by the recent and revelatory performance trials that launched a group sponsored project to explore its uncharted capabilities. To learn more contact Faye Smith at TWI. E-mail: faye.smith@twi.co.uk