A miniaturized composite impact monitor and its evaluation research

Shenfang Yuan, Peipei Liu , Lei Qiu
Sensors and Actuators A: Physical, Volume 184, September 2012

Abstract

From the Prognostic and Health Management (PHM) standpoint, the main purpose of the structural health monitoring is to help the maintenance of aircraft structures. Here, aiming at on-line applications, this paper puts forward a new digital impact localization method. Different from traditional processing methods, the new one is achieved in a digital way by turning the outputs of PZT sensors directly into digital queues and localizing the impact occurring area based on the digital queues obtained. Depending on this method, a PZT sensor array based impact monitor with advantages of miniaturized size, low weight and low energy consumption is developed which can meet the strict on-line application requests. Details of the new impact monitor design are presented in this paper. Meanwhile, a series of experiments, including evaluations on complex composite structures, have been conducted to verify the performance of the new digital impact monitor. This new monitor shows its potential for on-line structural PHM applications on aerospace vehicles.

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Additional Information

Programs about Prognostic and Health Management (PHM) have been widely researched in recent years for aerospace vehicles. From the PHM standpoint, the main purpose of the structural health monitoring (SHM) is to help the maintenance of aircraft structures. Impact usually causes inner damage in composite materials which in general cannot be found easily. This undetected, hidden damage can cause significant loss of structure strength or stiffness. Because of this, impact and impact caused damage monitoring is a very important monitoring object in the area of composite structural health monitoring and management.

For damage monitoring, it may not be requested to be performed on line. But impact is an instant event, and aircraft structure may suffer from impacts during both its service and maintenance, which are caused mainly by bird strikes, tool drop, runway stones or ballistic impacts. These impact events have to be monitored on line. On-line aircraft application does not allow too much additional weight, size and power consumption attachment caused by the PHM systems. Hence, this research puts forward a new digital impact localization method. Different from traditional methods, the new one is achieved in a digital way by turning the outputs of PZT sensors directly into digital queues without ordinary data acquisition modules, such as charge amplifier, filter circuit and A/D converter. A simple impact occurring area localization and energy grade estimation method is also presented relying on the digital arrival queues. Depending on these methods, a PZT sensor array based miniaturized impact monitor with advantages of miniaturized size, low weight and low energy consumption is developed which can meet the strict on-line application request. Here, a compromise is made with approximate impact area, rather than the accurate location, as the monitoring object. Using the information obtained, further structural maintenance can be managed more reasonably.

A series of experiments, including evaluations on complex composite structures, have been conducted to verify the performance of the new digital impact monitor. Taking advantage of history information obtained concerning the impact occurring area, energy grade and times, traditional NDT methods can be scheduled only when it is necessary and only a localized inspection has to be done. Consequently this can save a lot of time, make the inspection highly efficient and significantly reduce the maintenance cost. This new monitor shows its potential for on-line structural PHM applications on aerospace vehicles.