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- Curriculum Vitae
Dirk Lehmhus, Matthias Busse, Axel S. Herrmann, Kambiz Kayvantash (Ed.): Structural Materials and Processes in Transportation, Wiley-VCH, 2013
Dirk Lehmhus, Stefan Bosse, Matthias Busse, Chapter 17, Sensorial Materials, pp. 517-548
This book is meant to provide an introduction to current developments in the field of structural materials for the transportation industry. This includes rail, maritime, automotive, and aerospace industries, with a focus on the last two. Deliberately excluded from the scope are purely functional materials.
Quite literally, structural characteristics of materials are the backbone of any engineering design. They provide self-supporting capabilities to components where mechanical stability is a secondary concern. Whenever the bearing of mechanical loads becomes the primary role, and materials are optimized in view of this demand, we speak of structural materials. Solutions that address this challenge are what this book revolves around. The perspective chosen to deal with the topic is that of materials science and engineering. We have structured our work accordingly by dedicating the central parts to the main material classes.
However, any structural material we see in a specific application is in fact a combination of material and process. Its properties are defined by both, and thus, treating one aspect while neglecting the other is not a viable option. Besides, it is development tools which are built on similarly advanced modeling and simulation techniques that finally enable usage of emerging materials by allowing their evaluation in diverse application environments. With this in mind, we have included these aspects in our book. In all of them, the perspective is forward-facing: We do not intend to comprehensively cover the fundamentals of the various fields. Instead, we have attempted to identify major trends and highlight those that we see at the threshold to practical application.
Materials are evolving. So are the processes associated with them, as well as the tools and methodologies that allow their development and application. The rate of change in material development is dictated by external pressure. We have defined the major periods in the development of early mankind by the structural materials that dominated them. When bronze technology evolved, stone had to yield. The same occurred to bronze once iron became available on a larger scale. In transportation, we have seen change from wood and other natural materials to metal, and nowadays to composites. The rate of change steps up once pressure rises. The period of time that one material prevails appears to become shorter and shorter. On the other hand, since the shift from natural to technical materials, we mostly observe additions to the spectrum of materials rather than complete replacement. This may not be true for individual exponents of a material class, but definitely so for the classes themselves. Transportation, in all its width, is currently under considerable pressure to increase resource efficiency. One major handle to achieve this is lightweight design. This affords either new structural concepts or new materials offering improved performance. Very often, both go hand in hand. While such general pressure strengthens the motivation to search for entirely new approaches, it will also fuel inter-area competition.
The past has shown that this may significantly speed up developmental processes within one class of materials. A good example in this respect is the recent evolution of highstrength steels, which took place at least partly in response to aluminum-centered automotive body designs entering volume production. A comparable situation can be observed in the commercial aircraft industry, where large-scale introduction of carbon-fiber-reinforced composites challenges the established status of aluminum alloys. New production processes support such tendencies are enablers of crossfertilization between modes of transport: considering their properties, automotive design could profit greatly from application of carbon-fiber-based composites, too, but the sheer cost of state-of-the-art aerospace materials and processes forbids immediate takeover. Adaptation of processes to match another industry’s needs, like transition from single part to large-scale series production, can help diminish such barriers. As a result, we currently see an extremely high rate of change in the range of available materials for load-bearing structures in the transport industry. With this in mind, it is the conviction of editors and authors of this book that a work is needed that familiarizes materials scientists, design engineers, and innovation managers in industry with developments in structural materials science and engineering that are likely to find their way into high-technology products within the next 5–10 years. We do give some background on the various materials and technologies, but the major focus is on what is currently on the verge of application.
Besides our primary target audience, we are confident that students and graduates in mechanical engineering, as well as academic researchers in the field, will find this compilation helpful to first get and then adjust their bearings through a highly dynamic field of research. In this sense, we intend our book to serve as a guideline for both groups. As such, it is meant to give them the first idea of the respective material class as well as a clear vision of where the present focus of developmental work will lead it within the near to mid-term future. This knowledge base shall allow them to decide which material classes and subclasses to study in more detail in view of their specific interest. Suggestions on where to search for in-depth fundamental information and keep track of future advances shall complete the picture.
The book is structured along the major material classes relevant for transport industry structural applications. All of these are treated in separate parts, starting with metals (Part I) and proceeding via polymers (Part II) and composites (Part III) to cellular materials (Part IV). Each part covers associated processes on the level of its individual chapters, that is, for the exemplary case of metals separately for iron-, aluminum-, magnesium-, and titanium-based materials (Chapters 1–4). In a further section (Part V), selected aspects of modeling and simulation techniques are being treated. Highlights have been set here in terms of modeling approaches covering multiple scales of material description (Chapter 13) and adaptation of artificial intelligence (AI) techniques to material modeling (Chapter 14). The use of fundamental ab initio techniques in designing new metallic material compositions and states is treated in yet another subsection (Chapter 15). Finally, specific trends that go beyond an individual class of materials are discussed in Part VI.
An example are hybrid design approaches, which attempt to locate the optimum material for a purpose at the place where best use can be made of its properties, thus leading to complex, multimaterial structures (Chapter 16). In extrapolating trends already discussed in terms of structural health monitoring for composite materials (Chapter 8), material-integrated sensing and intelligence, summarized under the descriptive term of sensorial materials, are covered in Chapter 17. Additive manufacturing as an approach with promise for highly versatile production and structural complexity that in some respects cannot be reached by other processes is presented in the final chapter (Chapter 18).
We have attempted to organize each of the main chapters in Parts I–IV and Part VI in a similar way. In these predominantly material-related chapters, we start with some fundamentals and go on to detail new developments. In this, we do not separate material and process because of the close link between both. However, we do subdivide the chapters according to distinctions that are already established for the respective class of materials. An example is the distinction between wrought and cast alloys realized in the chapters on aluminum and magnesium. A similar approach, though adapted to the specifics of such composites, is reflected in the separation between processes involving thermoplastic versus those employing thermoset matrices in the chapter on polymer matrix composites. The major chapters are concluded with a section on further reading for intensified study and a hint at major organizations, conferences, or other events dedicated to the respective topic.