In this paper, a simple four-variable first-order shear deformation theory is further applied to solve the bending and free vibration problems of antisymmetrically laminated functionally graded carbon nanotube (FG-CNT)-reinforced composite plates. The adopted four-variable theory contains only four unknowns in its displacement field which is less than the Reddy’s first-order theory. The equations of motion are derived from the Hamilton’s principle with the help of specific boundary conditions. Laminated FG-CNT-reinforced plates with different distribution types of carbon nanotube through the thickness are considered. The material properties of individual layer are estimated by using the extended rule of mixture. Analytical solutions of various simply supported antisymmetric cross-ply and angle-ply laminates are given for case study. The effects of carbon nanotube volume fraction, length to width ratio and thickness to width ratio on the non-dimensional fundamental frequency and the central deflection are investigated for antisymmetrically laminated FG-CNT-reinforced plates.
It is difficult for the existing point monitoring methods to find the initial crack on the civil infrastructure. In this article, by adopting the area monitoring method, the sensitive skin and the relative sensing system is proposed, which has the ability to real-time monitor the initial crack on the surface of civil infrastructure. The system is composed of three main parts: sensitive skin, secondary processor, and terminal processor. The concrete specimen experiments show that the system can monitor the structural surface crack with the width down to 0.02 mm and reflect the shape and length of the crack effectively. Because the whole circuit is digital and the most consumed sensitive skin is inexpensive, the system may have excellent performance in cost, accuracy, and sensitivity.
In the field of structural health monitoring of concrete bridges, one of the most challenging problems is the crack identification. In our previous study, we proposed a crack-sensitive skin to monitor the crack initiation and development in a structure and to visualize them remotely using computer. However, the material used in the sensitive skin is not suitable for large-scale structural monitoring. In this article, magnetic wire smart film is proposed for crack monitoring of large-scale concrete structures. Fabrication of the smart film, the working principle of the film, and the application of the film on a real bridge will be presented and discussed. The results show that the smart film is a good technique for crack monitoring of large-scale concrete structures.
In order to explore the dynamic characteristics of the linear-arch beam tri-stable piezoelectric energy harvester (TPEH), a magnetic force model was established by the magnetic dipole method, and the linear-arch composite beam nonlinear restoring force model was obtained through experiments. Based on the Euler–Bernoulli beam theory, a system dynamic model is established, and the influence of the horizontal distance, vertical distance and excitation acceleration of magnets on the dynamic characteristics of the system is simulated and analyzed. Moreover, the correctness of the theoretical results is verified by experiments. The results show that the system can be mono-stable, bi-stable and tri-stable by adjusting the horizontal or vertical spacing of the magnets under proper excitation. The potential well of the system in the tri-stable state is shallow, and it is easier to achieve a large-amplitude response. Increasing the excitation level is beneficial for the large-amplitude response of the system. This study provides theoretical guidance for the design of linear-arch beam TPEH.
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