Structural health monitoring of aerospace composites
01 Jan 2019-pp 33-52
TL;DR: In this article, the authors reviewed the structural health monitoring of composite aerostructures and explained different techniques used to monitor the various failures occurring in the composite structures in aerospace industry.
Abstract: The health monitoring of aerostructures assists performance enhancement of existing structures. Continuous monitoring and different techniques involved in the structural monitoring help to increase the efficiency of structures, postpone the failures, and provide the prototype for future aerospace structures with better durability. Structural performance of aerospace composites depends on strength, stiffness, yield capacity, bending capacity, resistance against corrosion, impact and lightning, and fatigue due to cyclic loading. In structural monitoring, the four different stages followed to monitor any damage in aerospace composite structure are operation evaluation, data accession, feature extraction, followed by statistical modeling. This chapter on structural health monitoring for aerostructures elaborates the methods to detect and prevent the failures in the structures, as observed through a series of literature available based on the type of damages and techniques to detect them like cracking, fiber pullout, delamination and shearography, eddy current method, transient thermographic method, etc, respectively. In this chapter structural health monitoring of composite aerostructures is reviewed in detail. Different techniques used to monitor the various failures occurring in the composite structures in aerospace industry are explained in detail. Structures made of composite material used in aerospace fail due to fiber-matrix damage. Hence, it is important to analyze such damage like fiber buckling, fiber splitting, fiber cracking, fiber fracture, and fiber bending, and cracks in the matrix etc. to prevent catastrophic results.
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TL;DR: In this paper, the authors study the coverage of an RIS-assisted large-scale mmWave cellular network using stochastic geometry, and derive the peak reflection power expression of RIS and the downlink signal-to-interference ratio (SIR) coverage expression in closed forms.
Abstract: The use of millimeter-wave (mmWave) bandwidth is one key enabler to achieve the high data rates in the fifth-generation (5G) cellular systems. However, mmWave signals suffer from significant path loss due to high directivity and sensitivity to blockages, limiting its adoption within small-scale deployments. To enhance the coverage of mmWave communication in 5G and beyond, it is promising to deploy a large number of reconfigurable intelligent surfaces (RISs) that passively reflect mmWave signals towards desired directions. With this motivation, in this work, we study the coverage of an RIS-assisted large-scale mmWave cellular network using stochastic geometry, and derive the peak reflection power expression of an RIS and the downlink signal-to-interference ratio (SIR) coverage expression in closed forms. These analytic results clarify the effectiveness of deploying RISs in the mmWave SIR coverage enhancement, while unveiling the major role of the density ratio between active base stations (BSs) and passive RISs. Furthermore, the results show that deploying passive reflectors are as effective as equipping BSs with more active antennas in the mmWave coverage enhancement. Simulation results confirm the tightness of the closed-form expressions, corroborating our major findings based on the derived expressions.
97 citations
TL;DR: In this article, a review introduces several areas of importance in acoustic emission (AE) technology, starting from signal attenuation, which is a critical issue in any large-scale AE monitoring, but few systematic studies have appeared.
Abstract: This review introduces several areas of importance in acoustic emission (AE) technology, starting from signal attenuation. Signal loss is a critical issue in any large-scale AE monitoring, but few systematic studies have appeared. Information on damping and attenuation has been gathered from metal, polymer, and composite fields to provide a useful method for AE monitoring. This is followed by discussion on source location, bridge monitoring, sensing and signal processing, and pressure vessels and tanks, then special applications are briefly covered. Here, useful information and valuable sources are identified with short comments indicating their significance. It is hoped that readers note developments in areas outside of their own specialty for possible cross-fertilization.
69 citations
Cites background from "Structural health monitoring of aer..."
...A comprehensive monograph by Giurgiutiu [14] on SHM of aerospace composites appeared recently and AE monitoring for SHM was covered in depth....
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...However, there are more requirements developing in the SHM field for faster calculations and less sensor placements [14,119]....
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...In particular, smaller sized PWAS have added a new dimension to source location strategy as these allow mode discrimination and provide directional information [14] and phased array concept is also a useful addition [120]....
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...Conventional piezoceramic sensors still dominate AE applications to structures, although PWAS has started to become smaller and more functional for potential aerospace uses [14]....
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TL;DR: A full probabilistic method based on the Bayesian inverse problem is proposed to rigorously provide a robust estimate of the time of flight for each sensor independently and the results reveal that the proposed methodology is able to efficiently reconstruct the damage localization within a metallic plate without the need to assume a specific a priori time-frequency transform model.
63 citations
TL;DR: In this work, a HUMS was developed and implemented in an UAV based on 20 Fiber Bragg Gratings embedded into the composite front spar of the aircraft’s wing, a miniaturized data acquisition subsystem for gathering strain signals and a wireless transmission subsystem for remote sensing.
60 citations
TL;DR: In this article, the attenuation spectra are characterized in combination with four power law terms, with many showing linear frequency dependence, with or without Rayleigh scattering, and a new mechanism is proposed to explain some of the linear frequency dependencies.
Abstract: In this paper, ultrasonic attenuation of engineering materials is evaluated comprehensively, covering metals, ceramics, polymers, fiber-reinforced composites, wood, and rocks. After verifying two reliable experimental methods, 336 measurements are conducted and their results are tabulated. Attenuation behavior is determined over broadband spectra, extending up to 15 MHz in low attenuating materials. The attenuation spectra are characterized in combination with four power law terms, with many showing linear frequency dependence, with or without Rayleigh scattering. Dislocation damping effects are re-evaluated and a new mechanism is proposed to explain some of the linear frequency dependencies. Additionally, quadratic and cubic dependencies due to Datta–Kinra scattering and Biwa scattering, respectively, are used for some materials to construct model relations. From many test results, some previously hidden behaviors emerged upon data evaluation. Effects of cold working, tempering, and annealing are complex and sometimes contradictory. Comparison to available literature was attempted for some, but most often prior data were unavailable. This collection of new attenuation data will be of value in materials selection and in designing structural health monitoring and non-destructive inspection protocols.
52 citations
References
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TL;DR: In this paper, the authors provide an overview of methods to detect, locate, and characterize damage in structural and mechanical systems by examining changes in measured vibration response, including frequency, mode shape, and modal damping.
Abstract: This paper provides an overview of methods to detect, locate, and characterize damage in structural and mechanical systems by examining changes in measured vibration response. Research in vibration-based damage identification has been rapidly expanding over the last few years. The basic idea behind this technology is that modal parameters (notably frequencies, mode shapes, and modal damping) are functions of the physical properties of the structure (mass, damping, and stiffness). Therefore, changes in the physical properties will cause detectable changes in the modal properties. The motivation for the development of this technology is presented. The methods are categorized according to various criteria such as the level of damage detection provided, model-based versus non-model-based methods, and linear versus nonlinear methods. The methods are also described in general terms including difficulties associated with their implementation and their fidelity. Past, current, and future-planned applications of this technology to actual engineering systems are summarized. The paper concludes with a discussion of critical issues for future research in the area of vibration-based damage identification.
2,715 citations
15 Aug 1996-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio and excellent corrosion resistance as discussed by the authors.However, titanium usage is strongly limited by its higher cost relative to competing materials, primarily aluminum alloys and steels.
Abstract: Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio and excellent corrosion resistance. Titanium usage is, however, strongly limited by its higher cost relative to competing materials, primarily aluminum alloys and steels. Hence the advantages of using titanium must be balanced against this added cost. The titanium alloys used for aerospace applications, some of the characteristics of these alloys, the rationale for utilizing them, and some specific applications of different types of actual usage, and constraints, are discussed as an expansion of previous reviews of β alloy applications. [1,2]
1,938 citations
TL;DR: The focus of this paper is aircraft and aircraft engines but the broader focus is on the role of materials in creating lightweight structures, and there are examples used that are relevant to automotive applications once they are adjusted for cost.
1,746 citations
TL;DR: This paper is intended to serve as a summary review of the collective experience the structural engineering community has gained from the use of wireless sensors and sensor networks for monitoring structural performance and health.
Abstract: In recent years, there has been an increasing interest in the adoption of emerging sensing technologies for instrumentation within a variety of structural systems. Wireless sensors and sensor networks are emerging as sensing paradigms that the structural engineering field has begun to consider as substitutes for traditional tethered monitoring systems. A benefit of wireless structural monitoring systems is that they are inexpensive to install because extensive wiring is no longer required between sensors and the data acquisition system. Researchers are discovering that wireless sensors are an exciting technology that should not be viewed as simply a substitute for traditional tethered monitoring systems. Rather, wireless sensors can play greater roles in the processing of structural response data; this feature can be utilized to screen data for signs of structural damage. Also, wireless sensors have limitations that require novel system architectures and modes of operation. This paper is intended to serve as a summary review of the collective experience the structural engineering community has gained from the use of wireless sensors and sensor networks for monitoring structural performance and health.
1,497 citations
01 Jan 2003
TL;DR: A concise state-of-the-art survey of fiber-reinforced polymer composites for construction applications in civil engineering is presented in this article, which includes a historical review, the current state of the art, and future challenges.
Abstract: A concise state-of-the-art survey of fiber-reinforced polymer (also known as fiber-reinforced plastic) composites for construction applications in civil engineering is presented. The paper is organized into separate sections on structural shapes, bridge decks, internal reinforcements, externally bonded reinforcements, and standards and codes. Each section includes a historical review, the current state of the art, and future challenges.
1,362 citations