Civil infrastructures are normally one of the most expensive investments in a nation. To ensure the security of our homeland, the integrity of critical infrastructural systems must be assessed periodically. The assessment of the performance and reliability of the infrastructures can be carried out effectively and efficiently through the use of a network of smart sensors. The smart sensors will constantly interrogate the state of the structural health and detect any initiation or progression of damage in the infrastructures. Proper warnings can be issued prior to structural failure to prevent catastrophic loss of lives and properties. In addition, the infrastructural health monitoring system can request a comprehensive structural performance re-evaluation when the deterioration of the structure has threatened the integrity. This paper reviews the current state of the art on applying smart piezoelectric sensors in infrastructural health monitoring. Experimental results for using smart sensors to detect the damage on some typical infrastructural components are presented. With the goal of constructing an automated on-line structural health monitoring system to constantly assess the integrity of critical infrastructural systems, this paper illustrated the promise of using the smart piezoelectric sensors in homeland security.
An important way of increasing the payload in a reusable launch vehicle (RLV) is to replace heavy metallic materials by lightweight composite laminates. Engineers and scientists have studied many metallic materials thoroughly, due to the long history of practical usage in many aerospace and aeronautical structures. Compared to metallic materials, composite laminates are a relatively new material and therefore require more attention to ensure the safety and reliability. Among various parts and systems of the RLV, this study focuses on tanks containing cryogenic fuel. Historically, aluminum alloys have been used as the materials to construct fuel tanks for launch vehicles. To replace aluminum alloys with composite laminates or honeycomb materials, engineers have to make sure that the composites are free of defects before, during, and after launch. In addition to robust design and manufacturing procedures, the performance of the composite structures needs to be evaluated constantly. In recent years, the impedance-based health monitoring technique has shown its promise in many applications. This technique makes use of the special properties of smart piezoelectric materials to identify the change of material properties due to the nucleation and progression of damage. A major advantage of this technique is that the procedure is nondestructive in nature and does not perturb the properties and performance of the materials and structures. This paper reports the results of applying the impedance-based nondestructive testing technique to the damage identification of composite laminates at cryogenic temperature. These materials have potential application for fuel tanks in future RLV’s.
An important way of increasing the payload in a reusable launch vehicle (RLV) is to replace heavy metallic materials by lightweight composite laminates. Compared to metallic materials, composite laminates are a relatively new class of materials and therefore require more attention to ensure the safety and reliability when they are used. Among various parts and systems of the RLV, this study focuses on tanks containing cryogenic fuel. Historically, aluminum alloys have been used as the materials to construct fuel tanks for launch vehicles. To replace aluminum alloys with composite laminates or honeycomb materials, engineers have to make sure that the composites are free of defects before, during, and after launch. In addition, the performance of the composite structures needs to be evaluated constantly. In recent years, the impedance-based health monitoring technique has shown its promise in many applications. A major advantage of this technique is that the procedure is nondestructive in nature and does not perturb the properties and performance of the materials and structures. This paper reports the results of applying the impedance-based nondestructive testing technique to the damage identification of composite laminates at cryogenic temperature. These materials have potential application for fuel tanks in future RLV’s. Regular and single-crystal piezoceramic sensor/actuators are tested to assess their performance under cryogenic temperature.
Civil infrastructures are generally the most expensive investments in a country. Concrete has been used extensively in the construction of most of the civil infrastructures. Structures made of concrete have long life span and are rarely replaced once they are erected. During the service life, the concrete ages and deteriorates leading to the loss of structural integrity. One of the major factors for the deterioration of concrete is the attack from environmental factors such as sulfate and acid. This paper presents some experimental results on the effects of environmental attacks on the system performance of impedance-based structural health monitoring. Two types of environmental factors are investigated - sulfate attack and acid attack. The experimental results show that impedance-based health monitoring technique is capable of identifying the change in the material property of concrete due to chemical attacks. Another interesting observation is that the impedance-based monitoring technique appears to be sensitive to the moisture contents in the concrete cube.
Conference Committee Involvement (2)
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems
7 March 2005 | San Diego, California, United States
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems
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