by Mark Saxton 2010
In recent years, there have been significant developments in the science and applications of intelligent, or 'smart', materials. These can be defined as materials with one or more properties (e.g. mechanical, thermal, optical, or electromagnetic properties) that can be varied in a predictable or controllable way in response to external stimuli, such as, for example, stress, temperature, moisture, pH and electric or magnetic fields. Such materials are now used in a vast number of applications, from photochromic lenses for sunglasses to military and aerospace uses.
Smart structures incorporate smart materials and exhibit one or more of the following features:
A smart structure is thus an integrated system comprising actuators, sensors and a control system.
At a more sophisticated level, smart materials become intelligent when they have the ability to respond intelligently and autonomously to dynamically-changing environmental conditions.
The technologies encompassed by intelligent materials are very diverse and include electrorheological fluids, fibrous materials, ceramics, photonics, microsensors, signal processing, piezoelectrics, dielectric elastomers, biomimetics, shape memory alloys, neural networks, nanotechnology, conducting and chiral polymers, liquid crystals, microactuators, biotechnology and information processing.
Potential applications are similarly widespread and have excited interest in industrial, military, commercial, medical, automotive and aerospace fields. Embedded fibre-optic sensing systems are employed in many engineering disciplines to monitor critical characteristics. Several smart skins programmes have been initiated for both civil and military aircraft. Large space structures are also candidates for the incorporation of smart structural systems because of the variable service conditions in which they operate.
Useful Classification Codes and Controlled Indexing Terms
The wide variety of materials and applications results in intelligent materials cropping up in many parts of the Inspec Classification scheme. The most relevant sections are:
Inspec has a set of controlled terms for intelligent/smart material technology:
Other related areas
There is an extensive range of topics related to intelligent materials/structures. Some of the most useful (and most popular) codes and terms are:
Section A (Physics Abstracts)
Section B (Electrical and Electronics Abstracts)
Section C (Computer and Control Abstracts)
Section E (Manufacturing and Production Engineering)
The Advanced Materials journal in the Key Abstracts series has one particular chapter covering intelligent materials.
Other controlled terms which may have some connection with smart materials technology include:
carbon fibre reinforced plastics
electric sensing devices
electroactive polymer actuators
fibre reinforced composites
shape memory effects
Finally, turning to the question posed by the title "Are Smart Materials Intelligent?", we would probably answer "not yet", but major progress has been made in recent years, with increasingly more complex and sophisticated systems under development.
Inspec will continue to cover the interdisciplinary fields of research to keep you up to date with progress towards this goal.