Aircraft operators are faced with increasing requirements to extend the service life of air platforms beyond their designed life cycles, resulting in heavy maintenance and inspection burdens as well as economic pressure. Structural health monitoring (SHM) based on advanced sensor technology is potentially a cost-effective approach to meet operational requirements, and to reduce maintenance costs. Fiber optic sensor technology is being developed to provide existing and future aircrafts with SHM capability due to its unique superior characteristics. This review paper covers the aerospace SHM requirements and an overview of the fiber optic sensor technologies. In particular, fiber Bragg grating (FBG) sensor technology is evaluated as the most promising tool for load monitoring and damage detection, the two critical SHM aspects of air platforms. At last, recommendations on the implementation and integration of FBG sensors into an SHM system are provided.

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Piezoelectric transducers have a long history of applications in nondestructive evaluation of material and structure integrity owing to their ability of transforming mechanical energy to electrical energy and vice versa. As condition based maintenance has emerged as a valuable approach to enhancing continued aircraft airworthiness while reducing the life cycle cost, its enabling structural health monitoring (SHM) technologies capable of providing on-demand diagnosis of the structure without interrupting the aircraft operation are attracting increasing R&D efforts. Piezoelectric transducers play an essential role in these endeavors. This paper is set forth to review a variety of ingenious ways in which piezoelectric transducers are used in today’s SHM technologies as a means of generation and/or detection of diagnostic acoustic waves.

Highway safety and vehicle performance are two important considerations in the design of a heavy vehicle combination. In this paper a performance measure called the 'rearward amplication ratio' ( RWA) is used as a control criterion in the design of a vehicle-handling controller. This approach is diVerent to conventional control techniques. The RWA is de ned as the ratio of the peak lateral acceleration at the rearmost trailer's centre of gravity (CG ) to that of the lead unit during a lane-change manoeuvre. The vehicle under consideration is a six-axle truck/full trailer, which usually exhibits a high level of RWA leading to roll-over during obstacle avoidance manoeuvres.In this study, several control strategies are examined, namely active yaw control at the truck CG, active yaw control at the dolly CG and active yaw control at the trailer CG. These could be employed individually or in combination. The eVect of an active control torque applied to various vehicle units is examined by using an optimal linear quadratic regulator approach combined with a simpli ed four degrees-of-freedom linear vehicle model. The controller performance index parameters are determined for the vehicle based on acceptable RWA target values. The sensitivity of the controller to tyre cornering stiVness variation is further evaluated.Simulation results indicate that the RWA can be reduced without signi cant change of the uncontrolled vehicle trajectory when active yaw torque is applied to the dolly. The controller can be more eVective in improving the dynamic performance and roll stability of this type of commercial vehicle, if applied to the lead unit (truck) or to the last unit (trailer). However, the path of the vehicle will be strongly in uenced and driving diYculties can be experienced. For active yaw control at the dolly CG, the optimal controller is found to be most sensitive to the dolly's tyres' cornering stiVness variations and least sensitive to steering axle from the RWA point of view. It is also found that the controller is most sensitive to steering axle parameter variations for path following.