This book is based around the concept of ‘adaptive structures’, by which we mean engineering structures which have the ability to adapt, evolve orchange their properties or behaviour in response to the environment around them. In recent years this concept has developed into a richly diverse area of research which includes topics such as structures, materials, dynamics, control, design and biological systems. The interdisciplinary fusion of these individual topic areas creates the possibility for new and exciting technological developments. These developments have been taking place in a wide range of industrial applications, but are particularly advanced in the aerospace and space technology sector.
Each chapter in this book represents the current state of the art in a particular aspect of adaptive structures, written by leading experts in their respective fields. But what about future developments beyond the current state of the art? Well, many chapters include discussions on future developments. More than this, we believe that by bringing together so many interrelated and yet diverse topics in a single volume one can get a sense of the huge future potential of this rapidly developing field of research. We hope that by viewing these combined chapters as a whole, the reader can enjoy the same sense of excitement and inspiration we felt when compiling this volume.
WHAT ARE ADAPTIVE STRUCTURES?
Humans have long been fascinated by nature’s ability to build structures which adapt to their environment. In contrast, our own structures often appear inefficient, static and cumbersome. In engineering, the term ‘adaptive structure’ has come to mean any structure which can alter either its geometric form or material properties. These are processes which are currently much simpler than those which can be observed in nature. The terms ‘smart’, ‘intelligent’ and ‘active’ have all been applied to describe both materials and structures which exhibit some or all of these properties (see the selection of authored and edited texts referenced below). Increasingly, the ability to adapt to a performance demand or environmental conditions has become a key design criterion for a range of structural and mechanical systems in recent years. It is precisely this type of requirement which has become a key driver in the development of adaptive structure technology.
The adaptation process itself can be passive, active, based on material properties, control, mechanical actuation or some combination of these. As performance limits on structural systems are increasinlgly being pushed to more extreme levels, especially with respect to minimising weight, there is a strong requirement to find more efficient ways to apply adaption processes. This brings significant scientific challenges relating to structural stability, vibration, control/actuation, sensing and material behaviour.
There are many examples of adaptive structures from a broad range of engineering applications, but much of the driving force for development has come from the aerospace and space engineering sectors. The need for a high level of material performance in terms of strength, flexibility and minimal weight, coupled with the need for deployment and operation in extreme environments, has led to some of the most advanced adaptive structures currently in existence. There has also been considerable interest in new concepts such as ‘morphing’ wings for aircraft.
As these more advanced concepts of adaptive structures become realisable, the interaction and integration of material behaviour, control, sensing and actuation becomes ever more critical.