Metal bonding — General information. Features

A bit of background is in order here.

Metal bonding began around 1942, under the influence of two events:

• the discovery by Prof. Castan, of the CIBA company, of epoxy adhesives, which made it possible for the first time to produce very strong bonds on metals, thanks to their very high adhesion and mechanical strength;

• the Second World War, which led the Americans to mass-produce aircraft and warships, and thus to seek faster assembly methods than conventional mechanical assemblies (welding, riveting, bolting).

So we gradually became bolder, replacing all-mechanical assemblies with mixed assemblies (welded-glued, crimped-glued), then with all-glued assemblies for secondary parts.

After the end of the war, aircraft manufacturers, both civil and military (Boeing, De Havilland, Fokker, then Sud Aviation, Aérospatiale, Dassault...) were ready to make greater use of bonding for increasingly important metal parts: stiffeners, flaps, rudders, rudder reinforcements, helicopter blades.

The advent of composite materials between 1965 and 1975, for which bonding is the main assembly method, and the development of new thermostable, high-temperature-resistant adhesives, combined with the very high demands of space research, further boosted bonding's rapid progress (see [BM 4 221] ).

The automotive industry began using structural metal bonding from 1965-1970, initially for bonding hood and door stiffeners only, then for hardware, and finally since 1980 for the increasingly frequent bonding of composite parts, such as those on the body of the Renault Espace (for example).

The electronics industry has taken advantage of one of the great advantages of bonding, namely the ability to assemble very small parts, and has used cyanoacrylate, epoxy and acrylic adhesives to assemble surface-mounted devices (SMD) at very high speeds, made possible by accelerated cross-linking using UV rays, for example.

Finally, seeing the success of bonding in aeronautics, all industries adopted it (skis as early as 1965, followed by bicycles, mechanics and watchmaking in the 1970s and 1980s).

In this article, we'll concentrate on the bonding of metals and confine ourselves to knowledge specific to this field. For some general concepts and definitions concerning bonding, we refer the reader to the articles "Bonding of materials. Mechanisms. Classification of adhesives". , "Bonding materials. Characteristics and application of adhesives". , "Bonding...