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Future safety and maintenance strategies for industrial components and vehicles are based on combinations of monitoring systems, which are permanently attached to or embedded in the structure, and periodic inspections. The latter belong to conventional nondestructive evaluation (NDE) and can be enhanced or partly replaced by structural health monitoring systems. However, the main benefit of this technology in the far future will consist in systems can be designed differently based on an improved safety philosophy that includes continuous monitoring. This approach will increase the efficiency of inspection procedures and reduce inspection time. The Dresden branch of Fraunhofer IZFP has developed network nodes, miniaturized transmitters and receiver systems for active and passive acoustic techniques and sensor systems that can be attached to or embedded in components or structures. These systems have been used to demonstrate intelligent sensor networks for monitoring of aerospace structures, railway systems, wind energy generators, pipes and others. Defects have been detected and monitored during full scale fatigue tests. This paper will discuss opportunities and future trends in nondestructive evaluation and health monitoring based on new sensor principles and advanced microelectronics. It will outline various application examples of monitoring systems based on acoustic techniques and will denote further needs for research and development.

The presented paper describes a condition monitoring for Aircraft structures based on the evaluation of acoustical Lamb waves. Methods for effective sensor near signal processing are required to detect wave modes and to reduce noise as much as possible. Frequently, a further necessity exists to integrate the measuring technique into the monitored structure. To meet these requirements, sensor near units for signal processing have to be developed, which can be connected as nodes within a network. A compact, sensor near signal processing structure has been realized containing components for analog preprocessing of acoustic signals, their digitization, algorithms for data reduction and network communication. The core component is a digital signal processor (DSP), which performs the basic algorithms necessary for filtering, down sampling, mode selection and correlation of spectral components particularly effective. As a first application, impact detection and characterization of delaminations were realized for a fiber composite plate. Starting from the simulation of wave propagation, characteristic signal parameters were determined. In some experiments, it could be proven that impact locations and delaminations can be derived from the detected Lamb waves. This work is continued to develop special structural health monitoring systems (SHM) for selected aircraft components (e. g. stringer elements, panels)