As part of the late 1930s rationalization program at Auto-Union, the design team recognized that DKW’s wooden-bodied Front series would need to be modernized. However, steel was a scarce strategic resource in Germany so Auto-Union engineers turned to the question of alternative, non-strategic materials for body panels. One of these alternatives was phenoic resin plastics.
At the beginning of February 1936, a meeting was held in Chemnitz between the technical design team at Auto-Union and Dynamit AG, a subsidiary of the IG Farben chemical conglomerate. Dynamit was determined to forge closer ties with Auto-Union and had initiated a partnership agreement with the company for the development of plastic body panels. Auto-Union presented the Dynamit team with technical drawings of a Front vehicle door, with the request to make the door from plastic material. Dynamit used phenolic resin impregnated paper sheets, which were pressed together under high pressure to create a strong and flexible panel.
On September 25, 1936, Dr. Leysieffer of Dynamit presented the Auto-Union board with the plastic door panel for inspection. Auto-Union were satisfied and provided Dynamit with body panel plans for a complete DKW F7 body. In July 1937, Dynamit delivered panels for three complete car bodies. The structure of these bodies was as follows - the floor was made of sheet metal, to which was attached the synthetic side panels, rear body and two front cowl sides. The windscreen frame, firewall and doors were mounted together. The roof was composed of two parts. All of these panels were connected to one another by means of flanges and screws.
Between 15 September and the end of October 1937, the three assembled cars were vigorously road tested. Although they largely proven themselves, cracks developed in the wheel-arches where they joined the side panels. On October 4th, 1937, the members of the board of directors of Dynamit visited the Audi and Horch plants and inspected the plastic bodied cars after their trials. Despite the cracks uncovered during testing, the tests results were considered positive and Auto-Union ordered a set of body presses.
In parallel, in mid-1937, an Auto-Union engineer by the name of Romen had developed a process for extracting fibres from paper waste using a specific filtration process. A 10% synthetic resin mix was added to the wet paper mat and formed under relatively low pressure. It was an inexpensive material but had limited tensile strength and was difficult to form in varying thickness, which limited its possible use to the roof panel and wheel covers. To refine this process further, Auto-Union turned to the company, Zenith of Leutkirch, which already had a fairly similar product on the market.
Another company, Deisting of Kierspe, which manufactured Bakelite dashboards and buttons, decided they wanted to have a piece of the Auto-Union cake. Deisting’s material, was composed of very thin strips of wood compressed together with an 8% synthetic resin, and exhibited excellent structural integrity. The downside, however, was the high pressure required for forming, as well as the amount of time required for the moulded panels to dry. Another problem appeared when it was realised that Brangs from Solingen held an exclusive license for this process.
Dynamit however used its influence to put an end to these explorations and in 1938 a further 4 DKW F7 were built with plastic bodies. Between 31 August and 29 October these cars were subjected to crash tests, which Auto-Union showed itself a pioneer in automobile safety. To do this, DKW built a sloping track near Potsdam with, at its lower end, a device designed to flip the car over. A standard F7 with composite wood and plywood bodywork, an F7 Export with all-steel bodywork and the new plastic bodied F7 were launched down the track at an average speed of around 45 to 50 kilometres per hour. With surprise and satisfaction, it was observed that the plastic cars behaved much better than their wooden or sheet metal counterparts.
Next the cars were studied for frontal or lateral impact. On the grounds of the Auto-Union test center, a kind of catapult was mounted on a car axle and guided by 2 concrete rails. A tree trunk was fixed on the carriage and used as a ram, thus simulating an unexpected encounter with a plane tree or an opposing car.
The first tests took place in January 1939 and once again F7s were used. Indeed, Auto-Union only envisaged the mass production of plastic bodies for the DKW range. The other brands of the group, Audi, Horch and Wanderer, were to remain steel bodied. For comparative tests, an Opel Kadett was used. The ram was launched at the car immobilized across the concrete rails at 40 kilometres per hour, causing significant damage such that the potential occupants would not have survived the impact. Further tests were carried out in March 1940, crash testing an Opel Kadett and a new F8 Meisterklasse model. The F8, whose chassis, more elaborate than that of its predecessor, lent itself better to the mounting of a plastic body. The door jambs were made of steel and the roof frame, as well as the windshield uprights, had been reinforced. During the test carried out at 50 kilometres per hour, the DKW suffered much less damage than the Opel Kadett. Additionally, the Meisterklasse’s 2-stroke engine was still operating after the impact. The very last crash tests took place in September 1941. By this stage, although the effectiveness of Duroplast panels was apparent, the war was in full swing and automobile production was no longer a priority.
In parallel with the later phases of the DKW F9 project, a study was carried out to substitute steel for Duroplast panels. As this car was intended for the middle-class, it was clear that only a few of the body panels would be made of synthetic material. Doors, bonnet and the boot would be made of Duroplast. Auto-Union planned to test a pre-series of this model in India to assess the behaviour of synthetics panels in tropical conditions. Of course, the war prevented this plan from progressing.
The problem of painting plastic parts, according to the technical reports of the time, was never fully resolved. The problem was that Duroplast was too smooth surface and its low permeability prevented adhesion of the paint. However, the biggest problem with Duroplast was logistical. At an extraordinary meeting which took place in February 1944 meeting devoted solely to synthetic materials, it appeared that to manufacture 200,000 bodies per year, it would have required no less than 20 heavy presses. Wolfgang Barthel, plastic specialist and inventor of the Duroplast used for the bodywork of the AWZ P70 and later of the Trabant, thought that this number of machines would not have been sufficient and that this technological approach would have led Auto-Union to a dead end. In the case of steel bodies, no less than 80 die-stamping presses would have been necessary, and at the time of this meeting, DKW only had 7....
Nevertheless, on 31 March 1944 at special board meeting in Chemnitz, DKW decided that plastic bodies were the future and plans were made for the order of the necessary presses and machinery as soon as the war was over. On 8 May 1945 all those plans came to nothing.
It would only be after the war, under the auspicious of the nationalized East German VEB, that the project was successfully concluded. The former Audi works at Zwickau would successfully develop plastic body panels constructed of cotton waste pressed with phenolic resin for the AWZ P70. This construction method would be carried over to the Trabant and would be used in more than a million vehicles.
The development of the Trabant: https://dkwautounionproject.blogspot.com/2017/07/trabant-east-german-peoples-car.html
The development of the DKW F9: https://dkwautounionproject.blogspot.com/2017/07/1939-dkw-f9-prototype.html
The history of the Werner DKW F9: https://dkwautounionproject.blogspot.com/2021/08/the-werner-dkw-f9.html
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