TWI Frequently asked question

What is Comeld ^TM?

by Faye Smith

Comeld ^TM is the application of a proprietary material surface treatment technique ^[1] called Surfi-Sculpt ^® to a joint between composite materials and metals.

The photographs below show joints between a glass fibre reinforced polyester composite material and stainless steel. The control joint (left) was manufactured using conventional surface preparation techniques, whereas the Comeld ^TM joint (right) used conventional surface preparation techniques in conjunction with Surfi-Sculpt to produce a Comeld joint.

Control joint	Comeld TM joint

The graph below shows that the Comeld joint failed at a higher load and absorbed more energy before failure (corresponding to the area under the load-displacement curve) than the control joint. Comeld specimens have also been seen to fail in a more progressive manner than the sudden failure seen in control joints. This could have benefits in terms of in-service detection of deterioration in a structure before failure occurs.

Comeld joints can be produced from a wide variety of metals and composite materials - such as titanium joined to carbon fibre reinforced plastic or stainless steel joined to glass fibre reinforced plastic - and using a variety of processing techniques. In the joints shown above, the matrix of the composite was used as the adhesive; however, an additional adhesive layer may be used at the interface between the composite material and metal.

The performance benefits offered by Comeld joints cross a broad range of industrial sectors including aerospace, marine, motor-sport, military and specialist construction.

Further information

For more information on Comeld, contact Ewen Kellar at TWI.

Reference

1. Dance B G I and Kellar E J C: 'Workpiece Structure Modification'. International Patent Publication Number WO 2004/028731 A1.

Last Reviewed 2007 / Copyright © 2004 TWI Ltd