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Research on composites in Germany
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Comp osites Eng ineering; Vol. 4, No.8, pp. 853-855. 1994 Copyright © 1994 Elsevier Science Ud Printed in Great Britain. All rights reserved 0961-9526/94 57.00+ .00
Pergamon
0961·9526(94) EOOO38-7
RESEARCH ON COMPOSITES IN GERMANY Karl Schulte Technical University Hamburg-Harburg, Polymer Composites Section, D-21071 Hamburg , Germany
(Received 5 March 1994;final version accepted 13 May 1994) Abstract-During the 1980sit was thought that composite materials would grow into one of the major materials used in structural design. However, as the expected economic success did not appear, a number of companies decided to discontinue their support for composite materials research and development and withdrew from business. It is the opinion of the author that there is no reason to complain, the composite community has come back to reality. Reality in Germany means that there is, and there will be, further improvements in composites research and application. Reality means that the penetration of composites applications into new markets will continue, but at a slower rate , This expansion of application can be recognized: the superior composite properties are mentioned in an increasing number of new industries and with improving technology a gradual substitution of conventional materials occurs. I. TRENDS AND PERSPECTIVES
The German aerospace industry remains at the forefront of introducing composite materials into structures. With each new aircraft developed, the amount of composite materials used for structural primary parts is increasing. The German glider industry, which holds more than 50070 of the world market , builds its aircraft entirely out of composite materials. Aircraft presently designed for civil air transportation will use an increasing amount of composites. For future aircraft there are plans to manufacture the wing and fuselage from composites. However, this means that there is a new challenge for the aerospace industry, mainly the scaling-up of composites technology so it can also be used for wide-body aircraft. In its turn, the German helicopter industry is moving towards building entire helicopter fuselages from composites. The reasons for this continuous interest in the materials are performance improvements, weight savings and associated fuel savings. In addition, reduced maintenance costs can be expected as the use of composites leads to a large reduction in fatigue problems, and corrosion maintenance is greatly reduced. This is especially important for civil transportation. Of further importance is that the certification process, an essential component of the wide acceptance of composites, has now been experienced by the commercial airframe manufacturers. The aviation authorities have developed experience in dealing with composite structural systems and feel confident in their certification. Hence, this is no longer an issue for not selecting composites on an equal basis with metals. The groundtransportation industry has to build light-weight and fuel-efficient vehicles. It can be recognized that also in this area composite materials have increasingly been taken into account. The German high-speed train, Intercity Express (ICE), already uses a number of composite parts, and currently the change of the four-wheeled undercarriage from a steel construction to an entire composite construction is under consideration. The use of a composite element for the frame of the buggy gives a weight reduction of approximately 25%, enabling minimization of power capacity, energy consumption and wear. The high elastic properties of the composite frame provide a high torsional compliance which prevents the train from running off the rails even at speeds up to 350 km h- 1 , without additional primary hydraulic dampers. The high damp ing properties of the composite frame reduce sound emission and noise transmission within the structure, required for environmental protection. Currently two prototypes of a composite bogie are being test-run with the ICE. After the tests have been completed, there are plans for the bogie to be used on all Intercity Express trains. 853
854
K. Schulte
The German company Neoplan, a manufacturer of city and long-distance buses, is manufacturing a city bus with the hull entirely built of composites. This construction leads to weight savings, and therefore a smaller engine can be used. Further, twin-wheels are no longer necessary. The German automotive industry, and here especially the Daimler-Benz Company, has recognized the great potential of composite materials. Further fuel savings can only be achieved from now on, if cars have a lower weight. One way to achieve weight reduction is to build the frame out of aluminium alloys. However, polymer-matrix composites will have a greater potential. As an example, a composite leaf spring link can replace both the metallic spring link and the helico spring of a conventional rear suspension design. The German mechanical engineering industry now recognizes the advantages of composites. (In order to further improve the performance of their machines, there is a need to substitute conventional materials and composites possess the required properties.) The German industry producing textile machines, cigarette machines, wrapping machines and print machines is incorporating more and more composite parts into its constructions. Mainly by substituting conventional materials, it can remain competitive in the world market. One of the key future successes of the composites industry lies in this field. 2. OVERVIEW OF SOME INDUSTRIAL APPLICATIONS
In an industrial context, composite materials in Germany mainly means polymermatrix composites. Only a few industrial companies have an interest in metal-matrix composites, but German industry has developed some of the most prominant applications. Together with bigger companies like German Aerospace, Hoechst, MAN, AkzoEnka, Volkswagen and Mercedes, a lot of smaller and medium-size company technology centers and material suppliers are successfully working in the field of advanced composite materials in Germany. One example of a technology center is the Composites Technology Automation GmbH in Hamburg. This company offers a unique spectrum of products and services, ranging from high-performance composite parts to complex automated facilities for plastic, metal and glass processing. A strong, creative team of experienced engineers and skilled craftsmen uses advanced equipment for the various tasks in design, engineering and manufacturing. The aerospace group in the composite division succeeded in obtaining substantial orders for aerospace hardware (e.g. rocket fairings for the Arianne rocket and packboards for the emergency slide system for the new Airbus A330/340), thus achieving a quantum leap from a development- and prototype-oriented activity to full production. In addition, high-performance composite parts for applications for the automotive, medical and industrial equipment industries are under development or in advanced prototype phases. One example is a fiber-reinforced piston for a diesel engine for small trucks which has already entered serious production. The aluminium piston being partly reinforced by aluminium oxide fibers is produced via a squeeze-casting technique. Thermoplastic composites with a polyamide 12 (PA12) matrix and glass-fiber fabrics complement Hiils's range of engineering plastics. Prepregs with satin-weave glass-fabric and unidirectional fiber reinforcement are available. Prepregs with carbonand aramid-fiber fabric can be manufactured on request. The company's capacity for post-forming should be especially highlighted. Even finished components can be tailored to special needs after local heating . Hiils can form plastics and rubber composites (K + K composites), that is to say certain rubbers can be directly bonded to the prepreg or laminate surface by vulcanization without primers. In this way hard/soft combinations, for example, can be manufacured for noise- or vibration-damping applications. Rubber-toughened epoxy-resin systems have been developed by a small company (Hanse Chemie in Hamburg). Albiflex is an epoxy resin in which silicon as a second phase is mixed during processing. Even at low volume fractions of the silicon phase, which does not alter the cross-link density and therefore the properties of the epoxy, the toughness of the material increases by a factor of 3. One application of the Albiflex resin may be to
Research on composites in Germany
855
increase the resistance against impact and interlaminar fracture of fiber-reinforced composite laminates. 3. COMPOSITE MATERIALS RESEARCH IN GERMANY
Composite materials research in Germany covers nearly the entire research field. This means strong efforts are being made in polymer-matrix, metal-matrix and ceramic-matrix composites. Research is performed at universities, industry and independent research institutions. Funding of research is possible mainly via contracts both from industry and from the German Science Foundation. However, presently there is great complaint among scientists, because the recession has reduced the available money. With the German unification the number of scientists working in composite materials has increased. Among the traditional, and in the western hemisphere well-known scientific centers, now further research establishments work on composite materials. They are mainly located in the south-east of Germany in the state of Saxony. After a strong evaluation, which took place in the last few years, the research establishments are now settled, and starting to do research at a high level.
Comp osites Eng ineering; Vol. 4, No.8, pp. 853-855. 1994 Copyright © 1994 Elsevier Science Ud Printed in Great Britain. All rights reserved 0961-9526/94 57.00+ .00
Pergamon
0961·9526(94) EOOO38-7
RESEARCH ON COMPOSITES IN GERMANY Karl Schulte Technical University Hamburg-Harburg, Polymer Composites Section, D-21071 Hamburg , Germany
(Received 5 March 1994;final version accepted 13 May 1994) Abstract-During the 1980sit was thought that composite materials would grow into one of the major materials used in structural design. However, as the expected economic success did not appear, a number of companies decided to discontinue their support for composite materials research and development and withdrew from business. It is the opinion of the author that there is no reason to complain, the composite community has come back to reality. Reality in Germany means that there is, and there will be, further improvements in composites research and application. Reality means that the penetration of composites applications into new markets will continue, but at a slower rate , This expansion of application can be recognized: the superior composite properties are mentioned in an increasing number of new industries and with improving technology a gradual substitution of conventional materials occurs. I. TRENDS AND PERSPECTIVES
The German aerospace industry remains at the forefront of introducing composite materials into structures. With each new aircraft developed, the amount of composite materials used for structural primary parts is increasing. The German glider industry, which holds more than 50070 of the world market , builds its aircraft entirely out of composite materials. Aircraft presently designed for civil air transportation will use an increasing amount of composites. For future aircraft there are plans to manufacture the wing and fuselage from composites. However, this means that there is a new challenge for the aerospace industry, mainly the scaling-up of composites technology so it can also be used for wide-body aircraft. In its turn, the German helicopter industry is moving towards building entire helicopter fuselages from composites. The reasons for this continuous interest in the materials are performance improvements, weight savings and associated fuel savings. In addition, reduced maintenance costs can be expected as the use of composites leads to a large reduction in fatigue problems, and corrosion maintenance is greatly reduced. This is especially important for civil transportation. Of further importance is that the certification process, an essential component of the wide acceptance of composites, has now been experienced by the commercial airframe manufacturers. The aviation authorities have developed experience in dealing with composite structural systems and feel confident in their certification. Hence, this is no longer an issue for not selecting composites on an equal basis with metals. The groundtransportation industry has to build light-weight and fuel-efficient vehicles. It can be recognized that also in this area composite materials have increasingly been taken into account. The German high-speed train, Intercity Express (ICE), already uses a number of composite parts, and currently the change of the four-wheeled undercarriage from a steel construction to an entire composite construction is under consideration. The use of a composite element for the frame of the buggy gives a weight reduction of approximately 25%, enabling minimization of power capacity, energy consumption and wear. The high elastic properties of the composite frame provide a high torsional compliance which prevents the train from running off the rails even at speeds up to 350 km h- 1 , without additional primary hydraulic dampers. The high damp ing properties of the composite frame reduce sound emission and noise transmission within the structure, required for environmental protection. Currently two prototypes of a composite bogie are being test-run with the ICE. After the tests have been completed, there are plans for the bogie to be used on all Intercity Express trains. 853
854
K. Schulte
The German company Neoplan, a manufacturer of city and long-distance buses, is manufacturing a city bus with the hull entirely built of composites. This construction leads to weight savings, and therefore a smaller engine can be used. Further, twin-wheels are no longer necessary. The German automotive industry, and here especially the Daimler-Benz Company, has recognized the great potential of composite materials. Further fuel savings can only be achieved from now on, if cars have a lower weight. One way to achieve weight reduction is to build the frame out of aluminium alloys. However, polymer-matrix composites will have a greater potential. As an example, a composite leaf spring link can replace both the metallic spring link and the helico spring of a conventional rear suspension design. The German mechanical engineering industry now recognizes the advantages of composites. (In order to further improve the performance of their machines, there is a need to substitute conventional materials and composites possess the required properties.) The German industry producing textile machines, cigarette machines, wrapping machines and print machines is incorporating more and more composite parts into its constructions. Mainly by substituting conventional materials, it can remain competitive in the world market. One of the key future successes of the composites industry lies in this field. 2. OVERVIEW OF SOME INDUSTRIAL APPLICATIONS
In an industrial context, composite materials in Germany mainly means polymermatrix composites. Only a few industrial companies have an interest in metal-matrix composites, but German industry has developed some of the most prominant applications. Together with bigger companies like German Aerospace, Hoechst, MAN, AkzoEnka, Volkswagen and Mercedes, a lot of smaller and medium-size company technology centers and material suppliers are successfully working in the field of advanced composite materials in Germany. One example of a technology center is the Composites Technology Automation GmbH in Hamburg. This company offers a unique spectrum of products and services, ranging from high-performance composite parts to complex automated facilities for plastic, metal and glass processing. A strong, creative team of experienced engineers and skilled craftsmen uses advanced equipment for the various tasks in design, engineering and manufacturing. The aerospace group in the composite division succeeded in obtaining substantial orders for aerospace hardware (e.g. rocket fairings for the Arianne rocket and packboards for the emergency slide system for the new Airbus A330/340), thus achieving a quantum leap from a development- and prototype-oriented activity to full production. In addition, high-performance composite parts for applications for the automotive, medical and industrial equipment industries are under development or in advanced prototype phases. One example is a fiber-reinforced piston for a diesel engine for small trucks which has already entered serious production. The aluminium piston being partly reinforced by aluminium oxide fibers is produced via a squeeze-casting technique. Thermoplastic composites with a polyamide 12 (PA12) matrix and glass-fiber fabrics complement Hiils's range of engineering plastics. Prepregs with satin-weave glass-fabric and unidirectional fiber reinforcement are available. Prepregs with carbonand aramid-fiber fabric can be manufactured on request. The company's capacity for post-forming should be especially highlighted. Even finished components can be tailored to special needs after local heating . Hiils can form plastics and rubber composites (K + K composites), that is to say certain rubbers can be directly bonded to the prepreg or laminate surface by vulcanization without primers. In this way hard/soft combinations, for example, can be manufacured for noise- or vibration-damping applications. Rubber-toughened epoxy-resin systems have been developed by a small company (Hanse Chemie in Hamburg). Albiflex is an epoxy resin in which silicon as a second phase is mixed during processing. Even at low volume fractions of the silicon phase, which does not alter the cross-link density and therefore the properties of the epoxy, the toughness of the material increases by a factor of 3. One application of the Albiflex resin may be to
Research on composites in Germany
855
increase the resistance against impact and interlaminar fracture of fiber-reinforced composite laminates. 3. COMPOSITE MATERIALS RESEARCH IN GERMANY
Composite materials research in Germany covers nearly the entire research field. This means strong efforts are being made in polymer-matrix, metal-matrix and ceramic-matrix composites. Research is performed at universities, industry and independent research institutions. Funding of research is possible mainly via contracts both from industry and from the German Science Foundation. However, presently there is great complaint among scientists, because the recession has reduced the available money. With the German unification the number of scientists working in composite materials has increased. Among the traditional, and in the western hemisphere well-known scientific centers, now further research establishments work on composite materials. They are mainly located in the south-east of Germany in the state of Saxony. After a strong evaluation, which took place in the last few years, the research establishments are now settled, and starting to do research at a high level.