Opening the door for adhesives

Dec 22, 2011 | Fasteners & adhesives

An epoxy adhesive from Henkel has solved a joining problem for a company producing gullwing doors for Land Rovers – At its plant in Hixon, Staffordshire, Alpha Manufacturing designs, prototypes and manufactures components and assemblies for customers across a variety of industries, from automotive to construction.

One recent application involved the production of gullwing doors for Land Rovers which, due to weight considerations, needed to be made from aluminium. When it came to joining the component parts of the door units, however, some thought had to be given to the method used.

Welding was rejected due to possible heat discolouration and distortion.

In addition, the doors are constantly being opened and closed in all weather conditions, meaning the door units had to be watertight, Welding may not have created the seal that was required.

As an alternative, the company looked into the use of adhesives. Here, no fettling/dressing operation would be needed, resulting in a more cost effective solution combined with a relatively simple application. However, manufacturing considerations made the selection of the right adhesive technology a crucial factor.

“One issue was the actual powder coating of the units,” said Mike Willis, quality engineer at the company. “A large amount of heat from the ovens would have to go into the parts – so any adhesive would have to be able to perform at high temperatures. In addition, during the powder coating process the doors would distort a little, so the selected adhesive had to be somewhat flexible, while still remaining strong.”

Many different adhesives were trialled, but most could not cope with the oven temperature in the powder coating plant, with the stiffener which is positioned through the centre of the unit peeling away from the main body of the door.

The company then turned to Henkel, which suggested Loctite Hysol 9514. Trials revealed this was ideal because of its high temperature resistance and high shear and peel strength. In this application, the adhesive was also used to fill any gaps between the stiffener and the door to ensure the unit was watertight.

Simple to apply, this is a single part epoxy adhesive with a service temperature range of -55°C to +200°C. It has a tensile strength of 44 N/mm2 and a peel strength of 9.5 N/mm. As this application has shown, its viscosity and sag resistant characteristics allow for the filling of large gaps.

Willis commented: “I feel that in the future designers should place more emphasis on incorporating different joining methods while they are developing new parts for manufacture.”


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