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Structural health monitoring (SHM) is increasingly being considered by the aerospace industry as a new and innovative technique to enhance the safety and reliability of structures, maximize structure operational efficiency, and minimize their operational cost. This article summarizes the latest developments in SHM systems based on SMART Layer technology in aerospace‐related applications. The systems consist of three major components: sensor/actuator network, integrated hardware, and diagnostic software. Two types of SHM systems in terms of their applications are introduced: one is the onboard system and the other is the off‐board system. The onboard SHM system has all components integrated with the host structures, and data can be automatically taken and processed. However, the off‐board system requires only the sensor network to be integrated with the structures, while the hardware and software are detached from the structures and form a portable stand‐alone unit. Data are taken only when the unit is reconnected to the sensor network. A variety of applications of both onboard and off‐board systems are discussed, including monitoring damage in composite pressure vessels and large composite barrels, cracks in the pipes of liquid rocket engines, multisite damage in riveted joints, bondlines in composite repairs, detection of impacts on the thermal protection systems (TPS) of space vehicles, and monitoring composite rocket motor cases.

Life extension programs for military metallic aircraft are becoming increasingly important as defense budgets shrink and world economies realign themselves to an uncertain future. For existing military weapon systems, metallic corrosion damage costs an estimated $8 billion per year. One approach to reducing this cost is to develop a reliable method to detect and monitor corrosion in hidden metallic structure with the use of corrosion sensors which would give an early indication of corrosion without significant disassembly, thereby reducing maintenance costs. This presentation describes the development, analysis, and testing of a fiber optic corrosion sensor developed jointly with the Virginia Polytechnic Fiber & Electro-Optics Research Center and sponsored by Wright Laboratory Materials Directorate, contract #F33615-93-C-5368. In the sensor which was researched under this contract, the normal cladding is removed in the sensor region, and replaced with aluminum alloy and allowed to corrode on coupons representative of CIKC-135 body structure in an ASTM B 1 17 salt spray chamber and a Boeing developed Crevice Corrosion Cell. In this approach, the optical signal output of the sensor was originally designed to increase as corrosion takes place, however interaction with the corrosion byproducts yielded different results than anticipated. These test results to determine a correlation between the sensor output and the structural degradation due to corrosion are discussed.

The results of a study recently completed by Boeing Aerospace & Electronics to investigate the use of NiTiNOL Shape Memory Metals as the sensor and actuator components of active vibration suppression systems are presented. Two different test set-ups consisting of aluminum cantilever beams with NiTiNOL wires fastened along both sides were developed. The test article for the first set-up was a very flexible, low frequency beam which utilized NiTiNOL wires for both sensing and actuation. The test article for the second set-up was a much stiffer, high frequency beam which utilized NiTiNOL wires for sensing and piezoelectric ceramics for actuation. The settling times of both beams were significantly reduced through the use of the NiTiNOL wire sensors and actuators. Analytical simulations were developed which correlated well with the experimental results. The results of the study demonstrated the feasibility of using NiTiNOL sensors and actuators for active vibration control of structural members.