Trucos para la elaboración de la mayonesa: aplicaciones

At that time, Arall also began to gain international momentum and was about to take off. In 1988, one year after the conference in Seven Springs, a second conference was held in Delft.

At this conference, the French company Aerospatiale presented their study on a fuselage shell for an Airbus A320. However, the results were disappointing. Arall was clearly not suited for fuselages. The US Air Force was looking at top parts (dorsal covers) for their T-38 jet trainers to replace magnesium covers, which suffered from serious fatigue problems. A lot of marketing effort was put into this dorsal cover by Bill Evancho’s group at ALCOA. In October of the same year, the first commercial application of Arall was achieved by the ALCOA marketing people on the C-17 military transport aircraft. This aircraft suffered from heavy weight problems towards its rear, and therefore the large cargo door situated there would be manufactured from Arall by McDonnell Douglas.

The Wall Street Journal described this victory as follows: “The guys in the Arall programme are more aggressive than the run-of-the-mill metallurgists at ALCOA”, says Richard Pettit, an engineer at McDonnell Douglas, which agreed to use Arall in the cargo door of its C-17. “They got their material used on an airplane much faster than usual.” As this quote shows, the introduction of this new aircraft material was even considered to be rapid. Several other locations where Arall could be used on this new aircraft, such as the wing and the fuselage, were studied – also in Delft. Only the cargo door, with dimensions of 5.6 x 9.7 metres was successful. It was manufactured from Arall-3 and led to 26% weight savings. However, it also turned out to be a highly complex product when manufactured from Arall:

stretch forming, roll forming, routing, bonding and riveting of many different components were necessary. The Arall panels that could be produced by ALCOA were too small and had to be connected together with expensive titanium straps. This clearly revealed the great Achilles’ heel of Arall: per kilogram the laminate was already about eight to ten times as expensive as aluminium. With the complex production steps that were necessary, this cost factor became even worse. Only about thirty C-17s were built with Arall

cargo doors. The weight reduction efforts for this aircraft were soon followed by a cost reduction round. Arall ‘fell off’ the aircraft just after take-off.

However, this is part of the story of the rise and fall of Arall in the U.S., which will be told in the next chapter.

“I got the habit of a continuous building project on my house from my father”, said Geert Roebroeks, when he gave me a tour of his premises. His house is situated at the side of a dike, near Den Bommel, a tiny village in the south-west of the Netherlands, on one of the islands of the province Zuid-Holland. It is an old house with a wide view over the polders, but in a continuous state of renovation. Roebroeks has been used to this since he was a boy, because during his whole life his father has done the same. One of Roebroeks’ most recently started projects is the construction of a swimming pool in his garden. When it is eventually finished, the plan is to build a foldable, aluminium covering for it. It is one of the many never-ending projects on the premises. His former Delft colleague and roommate, Leo Meijers, was his neighbour for a long time, but in the end could no longer keep up the fight against degradation and the struggle to modernise a centuries old house. From the time when as a student he was continuously

tinkering with his Citroën Deux Cheveaux, such struggles have become a way of life for Roebroeks. He still owns one, which is under constant maintenance in one of his sheds. A restless person in a creative but not stressful manner, Roebroeks has a reputation for finding practical solutions quickly. This is reflected in his speech, for he speaks very rapidly, even in English. For this reason, some engineers at the German aircraft manufacturer DASA – now renamed EADS – preferred to call Gunnink instead of Roebroeks, since they could not keep up with his speaking pace and his quick train of thought.

Roebroeks commutes daily in the rush hour between his old, charming house in the polder and the colourful, high tech aerospace faculty building in the ‘Randstad’, the busiest part of the country. Like many others in the Glare project, he has maintained his ties to Delft for a large part of his life. He did the work for his Master’s thesis in the lab in Delft in the composites group, studying the adhesion between aramid fibres and the epoxy plastic of the composite, a weak point. This fibre is difficult to bond chemically to another material, which is exactly what has to be done in a composite if it is to function properly. Another weak point of the fibre is that it can easily be split into separate small fibres, so-called ‘fibrils’. Roebroeks used this latter characteristic of aramid to combat the former. He invented a process to roughen the fibre in such a way that small fibrils appeared on the surface of the fibre. These small ‘branches’ improved the adhesion between the epoxy and the fibre. The epoxy was effectively entangled in the branches of the fibres, establishing a firm connection. This was a major step forward for aramid fibre in its competition with the much more successful carbon fibre. For composites, three main fibre types are used, i.e. glass, aramid and carbon, of which carbon is the stiffest and strongest fibre. In composites, aramid found it hard to compete against carbon. The fibre did not behave well under compressive loads, splitting easily under such conditions.

Moreover, the aramid absorbed moisture and was sensitive to environmental degradation. In the cellar of the laboratory in Delft, Roebroeks built a big machine with his own hands, using rough stones that scoured the fibres and produced surface fibrils. In the lab he worked in the same spirit that he would later show with respect to his house. The aramid producer AKZO was at the time in the midst of a legal fight with Du Pont regarding a possible infringement of a patent belonging to Du Pont by AKZO on a similar aramid fibre with the trade name ‘Kevlar’. AKZO was happy with Roebroeks’

process, as it strengthened their legal position as well as increasing the

number of possible application of the aramid fibre. A patent was filed, the first of many for Roebroeks. All the others would be on a new variant of fibre-metal laminates: Glare.