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

Stress Intensity Fctor for Intermal and Extemal Surface Cracks in Cylindrical Vessels

Innovative honeycomb-based structures have been paid substantial attention in recent years due to their superb mechanical performances and specific functions. The presented study made acomprehensive overview on the development of the innovative honeycomb-based structures in the past two decades, including filled-type, embedded, tandem, hierarchical, auxetics with Negative Poisson's Ratio (NPR), etc. Mechanical performances of these structures were commented with advantages and disadvantages, related on their geometric configurations, mechanical performance and dynamic response, respectively. The challenges as well as future directions were also analyzed. The achievements provide significant guidelines in designing of new generation light-weight honeycomb-based structures.

Recent advances in novel metallic honeycomb structure

Nature has provided us with extraordinary resources to tackle design challenges facing in modern society nowadays. The multistate structures inspired by animal shell have proven effective to improve the impact resistance of composite laminate. This study aims to identify the crash responses and crashworthiness characteristics of bio-inspired sandwich structures composed of carbon fiber reinforced plastic (CFRP) panels and aluminum honeycomb. The crash responses, failure mode as well as the effects of core side length, height and impact velocity on peak load and energy absorption were explored herein. The differences of crashworthiness characteristics between the CFRP aluminum honeycomb sandwiches and bare CFRP panel were quantified. Two typical load-displacement relations, namely single-peak and double-hump curves, were observed in the tests. It was noted in the energy-displacement curve, where the slopes corresponding to the failure stages of the upper and lower face-sheets, were greater than that in the honeycomb failure stage, indicating that the bare aluminum honeycomb was of lower energy absorption capacity than the CFRP face-sheet. By comparison, the honeycomb filling was an effective way to improve the impact resistance of CFRP structure, yielding higher energy absorption and lower peak load during the impact. It was also found that the crashworthiness characteristics were more sensitive to the core length than to the core height; and the specific energy absorption (SEA) varied insignificantly with the increase in the core height. It was noted that the peak load, absorbed energy and SEA increased significantly under high impact velocity.

Dynamic crash responses of bio-inspired aluminum honeycomb sandwich structures with CFRP panels

Mechanical properties of sandwich composites with 3d-printed auxetic and non-auxetic lattice cores under low velocity impact

Experimental study on the fatigue behaviour of honeycomb sandwich panels with artificial defects

Modelling the fatigue behaviour of composites honeycomb materials (aluminium/aramide fibre core) using four-point bending tests

Honeycomb sandwich panels are used because of their high stiffness, good fatigue resistance and low weight. These panels are used in a variety of applications, but particularly in the aerospace industry. When this is the case a simple knowledge of the static properties is not sufficient and additional information about the fatigue properties is required. In real situations these panels can be affected by manufacturing defects and impacts, and it is important to know the effects of these defects and the behaviour of the damaged panel; it also important to determine the location of the defect. In our investigation these defects will be simulated by a blind hole in the centre of the lower face sheet. Static and fatigue tests (four-point bending) with acoustic-emission monitoring were carried out on sandwich panels with defects. The load/displacement and the S-N fatigue curves are presented and analyzed.

A fatigue characterization of honeycomb sandwich panels with a defect utrujenostna karakterizacija satastih sendvi^nih panelov z napako

Transport by pipelines is more used at the present time to transfer liquid or gas sources of energy from the location of extraction to the region of use. With the reduction of oil reserves, hydrogen became an interesting source of energy. To avoid any risk of explosion or escape during hydrogen transport and to reduce the problem of pollution and fatal consequences, mechanical properties of steels used for the manufacturing of pipes should be known. In the paper the results of experimental analyses of the hydrogen effect on mechanical properties of API 5L X52 pipe steel regarding its resistance to fatigue and fracture are presented. Kljucne reci

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Hydrogen effect on fatigue and fracture resistance of a pipe steel uticaj vodonika na otpornost prema zamoru i lomu čelika za cevi

This study is a summary of works performed on fatigue crack propagation, that it is by carrying out experimental tests, or numerical simulations, or those using empirical models, relating principally to thick plates in three points bending, in tension and to thick tubes under internal pressure. The objective is to give the broadest possible comparison of various results allowing the follow-up of the shape evolution of semi-elliptic surface defect during its propagation in fatigue. This review work enabled us to conclude that the form variation of a semi-elliptic defect propagating by fatigue in a cylinder under internal pressure, can be obtained by tests on thick plate in tension, or by the use of model proposed by Mahmoud [36, 37] obtained on plate in tension, and model proposed by Boukharouba et al. [31] obtained and validated by the experimental results on tube under internal pressure.

Joseph Gilgert

Papers

Experimental study on the fatigue behaviour of honeycomb sandwich panels with artificial defects

Modelling the fatigue behaviour of composites honeycomb materials (aluminium/aramide fibre core) using four-point bending tests

A fatigue characterization of honeycomb sandwich panels with a defect utrujenostna karakterizacija satastih sendvi^nih panelov z napako

Hydrogen effect on fatigue and fracture resistance of a pipe steel uticaj vodonika na otpornost prema zamoru i lomu čelika za cevi

Some Insights into the Fatigue Crack Propagation in Tubes Under Internal Pressure — Proposition of Predicting Models