欢度国庆 | 综述文章精选

1. Self-sensing concrete: from resistance-based sensing to capacitance-based sensing

D.D.L. Chung 

Yining Wei, Xiao Tang, Jing Shang, Lin Ju & Liangzhi Kou

https://doi.org/10.1080/19475411.2020.1790055

Abstract Two-dimensional (2D) materials have dominated nanoscience for the last two decades. Among all 2D materials, graphene, MoS2, and h-BN are extremely popular and have been tentatively scaled up to fabricate nanocomposites, energy storage devices, flexible electronics, etc., ex situ and in situ mechanical characterization of 2D crystals can help us understand their mechanical behavior and measure their mechanical properties, which are of great significance in both fundamental science and practical engineering. To date, a great effort has been devoted to both theoretical and experimental mechanics with a focus on unveiling mechanical behaviors and quantifying mechanical properties. Beyond original research, several insightful review works have been published with a specific focus on the mechanics of 2D materials. To have a complementary contribution to the overview of the mechanics of 2D materials, we would like to review the developed experimental techniques being used to mechanically characterize 2D materials. The working mechanism and associated advantages and disadvantages of the techniques will be briefly discussed. Based on the existence of arguments in mechanical properties and behaviors of 2D crystals, and immature mechanical characterization of 2D materials, more intensive and comprehensive studies are expected toward a full understanding of these novel and promising materials.

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Abstract With the development and applications of nano-electro-mechanical systems, academic interest in the mechanical behavior of piezoelectric structures at nanoscale is increasing. Interesting unconventional phenomena have been observed either experimentally or through molecular dynamics simulation. The most common and also important one is the size-dependent characteristics. Classical continuum mechanics with necessary modifications has been proven to be very powerful in explaining these particular characteristics in a relatively simple theoretical framework. This article reviews the recent advances in understanding the size-dependent dynamic responses of piezoelectric nanostructures from the viewpoint of modified continuum mechanics. Particular attentions are paid to three advanced theories of piezoelectricity (e.g. gradient piezoelectricity, surface piezoelectricity, and nonlocal piezoelectricity) and their abilities to predict unconventional vibration and wave characteristics in piezoelectric structures and devices at the nanoscale. The article could serve as a useful reference for the future research on or design of nanostructures with multifield couplings.

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Abstract Vitrimer is a new type of material that combine the advantages of thermoplastic and thermoset materials. The rapid dynamic exchange reactions at high temperature allow the topology of cross-linked networks to change and rearrange while keeping material structures and properties intact. The concept of vitrimer has emerged to provide a viable strategy for the recycling of high-performance polymer materials, and lots of research works have been carried out for the development of various types of vitrimers. In addition, the recycling strategies for vitrimers are particularly important to determine the performance and potential applications of the recovered materials. Therefore, it is an innovative and valuable perspective to discuss vitrimer materials according to their different recycling strategies. In this review, we start with a brief overview of vitrimers, and then, focus on recycling strategies for vitrimers. Specifically, we highlight the advantages and disadvantages of the two different recycling strategies: physical and chemical recycling methods, and then explore the feasibility of upcycling vitrimers using 3D printing technology. Finally, the impact of recycling strategies on vitrimer materials and the prospects for maximizing the use of vitrimer materials are discussed.

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Abstract Composite materials have been widely used in many industries due to their excellent mechanical properties. It is difficult to analyze the integrity and durability of composite structures because of their own characteristics and the complexity of load and environments. Structural health monitoring (SHM) based on built-in sensor networks has been widely evaluated as a method to improve the safety and reliability of composite structures and reduce the operational cost. With the rapid development of machine learning, a large number of machine learning algorithms have been applied in many disciplines, and also are being applied in the field of SHM to avoid the limitations resulting from the need of physical models. In this paper, the damage monitoring technologies often used for composite structures are briefly outlined, and the applications of machine learning in damage monitoring of composite structures are concisely reviewed. Then, challenges and solutions for quantitative damage monitoring of composite structures based on machine learning are discussed, focusing on the complete acquisition of monitoring data, deep analysis of the correlation between sensor signal eigenvalues and composite structure states, and quantitative intelligent identification of composite delamination damage. Finally, the development trend of machine learning-based SHM for composite structures is discussed.