Chang Zhang

A hybrid piezoelectric/fiber optic diagnostic system for structural health monitoring

A hybrid piezoelectric/fiber optic diagnostic system has been developed for quick non-destructive evaluation and long term health monitoring of aerospace vehicles and structures. The hybrid diagnostic system uses piezoelectric actuators to input a controlled excitation to the structure and fiber optic sensors to capture the corresponding structural response. The system consists of three major parts: a diagnostic layer with a network of piezoelectric elements and fiber gratings to offer a simple and efficient way to integrate a large network of transducers onto a structure; diagnostic hardware consisting of an arbitrary waveform generator and a high speed fiber grating demodulation unit together with a high speed data acquisition card to provide actuation input, data collection, and information processing; and diagnostic software to determine the condition of the structure. This paper presents key development issues related to the manufacturing of the hybrid piezoelectric/fiber optic diagnostic layer and integration of a highly portable diagnostic hardware. Validation and proof testing of this integrated diagnostic system are also presented.

Practical issues in real-world implementation of structural health monitoring systems

Currently, there exist several different types of structural health monitoring (SHM) systems that are in the stage of development and/or are being tested for use in real-world applications. For a number of years, Structural Health Monitoring (SHM) systems have demonstrated feasibility in laboratory and controlled testing environments. Acellent has been developing and testing strategies to bring the SHM field to the next level. These include issues involved with system installation, calibration, reliability and connections for structures fabricated with composite materials. Composite structures are susceptible to hidden or barely visible damage caused by impacts and/or excessive loads that if unchecked may lead to lower structural reliability, higher life-cycle costs, and loss in operational capability. Current maintenance and inspection techniques for in-service composite structures can be labor-intensive and time-consuming. Utilization of an integrated sensor network system such as that developed by Acellent can greatly reduce the inspection burden through fast in-situ data collection and processing. Using a built-in network of actuators and sensors, Acellent Technologies is providing the tools required for a practical SHM system. In this paper, key development and testing issues concerning real-world implementation of the SHM system on composite structures are presented.

Potential applications of SMART Layer technology for homeland security

The SMART Layer (reg. TM) manufactured by Acellent is a thin flexible layer with a network of miniature piezoelectric actuators and sensors that can be embedded inside or mounted onto metal and composite structures to acquire information on structural integrity. Currently, SMART Layers (reg. TM) are used to assess the condition of structures and to monitor impact events. The layers can be used to perform built-in structural inspection by exciting the devices with a periodic or transient burst controlled input and analyzing the corresponding structural response. The technology can also be applied to areas concerned with Homeland Security. For example, the technology can be used for motion monitoring and monitoring of structures used in defense applications. By having a network of sensors that monitor loads on a structure, it is possible to monitor the movement of people by measuring the loads exerted by them. The SMART Layer (reg. TM) technology can be used to enhance the readiness of structures used for homeland defense such as manned and unmanned aircraft, missiles and radar systems. It can also be used to monitor a pipeline network for any terrorist related activity that can potentially damage the pipe system. A brief overview of such potential applications is presented here.