Dual technology structural health monitoring: comparison between indipendent technologies for a stronger result

Since the end of the 1980s, the concept of smart or intelligent materials and structures has become more and more present in the minds of engineers. These new ideas were particularly welcome in the fields of aerospace and civil engineering. The concept of Smart Materials/Structures can be consider as a step in the general evolution of man-made objects. There is a continuous trend from simple to complex in human production, starting from the use of homogeneous materials, supported by nature and accepted with their natural properties, followed by muti-materials in particular, composite materials, allowing us to create structures with properties adapted to specific uses. The next step consists of making the properties of the materials and structures adapt to changing environmental conditions. This requires making them sensitive, controllable and active. In effect, almost all achievements in this field are only intended to make materials/structures sensitive, by embedding sensors. In this context it is possible to include Structural Helth Monitoring. Structural Health Monitoring (SHM) is an improve and a new way to make a Non Distructive Evaluation (NDE); it aims to give, at every moment during the life of a structure, a diagnosis of the state of the costituent materials, of the different parts costituing the structure as a whole. The state of the structures must remain in the domain specified in the design, although this can be alterated by the action of the environment, by the normal aging due to usage and by accidental events [3]. A SHM strategy consists of many important components including sensing network, possibly smart materials, data transmission, data processing and analysis, damage assessment and decision making [3]. SHM has the great potential to offer significant economic and life-safe benefits and this technology is deal with monitoring the structural health of aircraft, buildings and dams; improving the efficiency of turbines and industrial equipment, and much more. This is schematically presented in the figure below, where the organization of a typical SHM system is given in detail.