The review outlines modern trends in theoretical developments, novel designs and modern applications of sandwich structures. The most recent work published at the time of writing of this review is considered, older sources are listed only on as-needed basis. The review begins with the discussion on the analytical models and methods of analysis of sandwich structures as well as representative problems utilizing or comparing these models. Novel designs of sandwich structures is further elucidated concentrating on miscellaneous cores, introduction of nanotubes and smart materials in the elements of a sandwich structure as well as using functionally graded designs. Examples of problems experienced by developers and designers of sandwich structures, including typical damage, response under miscellaneous loads, environmental effects and fire are considered. Sample applications of sandwich structures included in the review concentrate on aerospace, civil and marine engineering, electronics and biomedical areas. Finally, the authors suggest a list of areas where they envision a pressing need in further research.

Review of current trends in research and applications of sandwich structures

Nondestructive test methods for concrete bridges: A review

Composite materials/structures are advancing in product efficiency, cost-effectiveness and the development of superior specific properties. There are increasing demands in their applications to loa...

/pdf/non-destructive-testing-and-evaluation-of-composite-25jy7cttmq.pdf

Non-destructive testing and evaluation of composite materials/structures: A state-of-the-art review

A review of ultrasonic testing applications in additive manufacturing: Defect evaluation, material characterization, and process control.

Mutual inductance is a key parameter of the inductively coupled circuits such as transformers and contactless energy transfer systems. This parameter is particularly required to design the power electronics associated with each application. However, its value is usually extracted from measurements performed in a previously built prototype, which is an expensive and time-consuming task. In this paper, an analysis of the mutual inductance between two planar circular windings is developed. The analysis takes into account the effect of the media that can be part of the complete system. As a result, an analytical calculation of the mutual inductance with respect to the main parameters of the system such as the number of turns of the coils, geometry, frequency of the currents, and the properties of the media can be carried out. The analysis can also be used to explore the tendencies of the mutual inductance for design purposes and, thus, it allows speeding up the design process. The analysis has been verified by means of experimental results.

Analysis of the Mutual Inductance of Planar-Lumped Inductive Power Transfer Systems

Nondestructive evaluation (NDE) research on composite materials has been ongoing for several decades, during which time their use has expanded significantly in the aerospace, marine, petrochemical, energy, construction and transport sectors. Initially, many composites were employed as fairings or reinforcements, but they are being increasingly used in primary and secondary load-bearing structures, where a mechanical failure has significantly greater safety implications. This increased scope has resulted in composite structures of significant thickness and complexity. Despite this, there has not been a corresponding increase in research pertinent to the detection and characterisation of defects in thick structures, apart from a brief period of interest by the NDE community in the early 1990s. This review critically assesses advances reported in the NDE of thick-section composites (structures of thickness above 15 mm are considered for the purposes of this review), and identifies future research opportunities to overcome the limitations of existing technologies.

Nondestructive evaluation of thick-section composites and sandwich structures: A review

The change in mutual impedance ΔZ12 due to eddy-current induction is considered for an arbitrary pair of air-cored coils located above a conducting plate. A general expression is derived for ΔZ12 and applied to the specific case of cylindrical coils with rectangular cross-section. A series of closed-form expressions for ΔZ12 is presented for the geometries that cover all of the possible coil configurations for which the orientation of the individual coils is either normal or tangential to the plate. Expressions are also obtained for ΔZ12 in the dipole limit and the results are compared with earlier work for dipole loops. The validity of the theory is tested against experimental measurements for representative high-symmetry coil systems above an aluminium-alloy plate. The theoretical calculations and experimental results are in excellent agreement over the experimental frequency range 100 Hz–50 kHz. The significance of the results for eddy-current non-destructive inspection using driver–pickup coils is discussed.

http://iopscience.iop.org/article/10.1088/0022-3727/37/13/021/pdf

Mutual impedance of air-cored coils above a conducting plate

Nondestructive evaluation of compressed cracks is a major challenge. A quantitative study of the effect of crack-tip closure on the pulse-echo ultrasonic sizing of delaminations in fibre-reinforced polymer-matrix composites (FRP) is presented. In particular, this study focuses on the interaction of ultrasound with a closed crack or kissing disbond, and their effect on the ultrasonic inspectability of FRP laminates consisting of carbon and glass plies. The compression of laminar cracks in these two different laminate types is clearly detectable via both pulse-echo and through-transmission ultrasonic measurements, but the reflected ultrasonic pulses in the two material types exhibit markedly different behaviour. The glass-fibre laminates show a drop in the reflected signal for crack openings up to approximately half the crack growth load, whereas the corresponding carbon-fibre laminates show the expected increase in the reflected signal as the crack opens. The origins of the observed effect of crack closure on the reflection and transmission of ultrasound are analysed in detail to ascertain possible mechanisms responsible for these effects.

https://research-information.bris.ac.uk/files/126268397/Glass_1_.pdf

Ultrasonic detection and sizing of compressed cracks in glass- and carbon-fibre reinforced plastic composites

Detection and characterisation of defects and damage that arise in marine composites is imperative, to ensure the safe and reliable operation of marine vessels and structures. This chapter discusses the types of defects occurring in marine composites, and introduces the concept of nondestructive testing (NDT) to inspect structures for flaws without reducing their future usefulness. The methodologies of point inspections, wide-area NDT and structural health monitoring are discussed, and examples are given of the performance of a range of techniques that fall within these categories.

M. E. Ibrahim

Papers

Nondestructive evaluation of thick-section composites and sandwich structures: A review

Mutual impedance of air-cored coils above a conducting plate

Ultrasonic detection and sizing of compressed cracks in glass- and carbon-fibre reinforced plastic composites

Nondestructive testing and structural health monitoring of marine composite structures

Effect of fibre-matrix interfacial strength on the explosive blast resistance of carbon fibre laminates