SHM is a new and improved way of making a non-destructive evaluation. It involves the integration of sensors-probably made of smart materials, data transmission, computational power and processing ability inside the structure. It makes it possible to reconsider the design of the structure and the full management of the structure as a single unit and of the structure considered as a part of wider systems.
The safety and performance of all commercial, civil and military structural systems deteriorate with time. It is very important to know the state of the structure immediately by non-destructive inspection or by other methods when the structure receives any foreign object impact. Structural damage detection at the earliest possible stage is very important in critical areas such as in the aerospace industry to prevent major failures. With the advances in sensor systems, data acquisition, data communication and computational methodologies, instrumentation based monitoring has been a widely accepted technology to monitor and diagnose structural health and conditions for civil, aerospace and mechanical structural systems. A schematic arrangement of sub-systems in a health management system is shown in Figure 2.1.

Figure 2.1: Organization of a SHM system [Balagaes, 2001]