The main objective of this study is to demonstrate the use of bonded COMPOSITE PATCHES in strengthening or repair of damaged structural elements. The high strength, light weight, formability and relative ease of application, make COMPOSITE materials an excellent option for use as external reinforcing systems for structures.A square aluminum plate with a central circular cutout is considered as a damaged structural element. The change in vibration response of damaged metallic plates reinforced with fiber reinforced polymer COMPOSITE materials (COMPOSITE patch) are presented in this study.Numerical studies using commercial finite element software were conducted to investigate the effects of variation in patch geometries and fiber orientation on free vibration responses of repaired plates. A quantitative measure for the effectiveness of the COMPOSITE PATCHES is taken to be the relative change in natural frequencies of the repaired plates compare to those of the damaged one. The results presented herein indicated that, for vibration response of a repaired aluminum plate with central cutout, a set of COMPOSITE PATCHES with different shapes and fiber angles can be found which change and improve vibration frequency of damaged plates.

This study investigates the impact of anisotropic and isotropic piezoelectric coefficients on vibrational energy harvesting using a piezoelectric patch integrated into plate-like structures. The research on energy harvesting in such configurations has garnered substantial attention in recent decades, with previous studies typically assuming isotropic piezoelectric coefficients (e_31=e_32). The investigation focuses on two common boundary conditions: cantilevered COMPOSITE plate (CFFF) and all-four-edges clamped (CCCC), employing a combination of analytical techniques and numerical simulations. The study presents comprehensive steady-state formulations for both the electrical and structural responses under harmonic force excitation. By comparing the voltage-frequency relationship between the analytical and numerical models, the accuracy of the analytical electroelastic model is verified. The findings highlight the potential for enhanced performance and increased output voltage in CFFF structures with an approximate rate between 5% to 8 % by minimizing the impact of the e_32 coefficient, whereas a decrease in output voltage is observed in CCCC structures. The findings emphasize that minimizing the impact of specific piezoelectric coefficients can lead to significant improvements in both performance and output voltage. This contributes to advancements in energy harvesting technology, highlighting the importance of optimizing piezoelectric materials to achieve better efficiency in energy harvesting applications. Additionally, the study shows that reducing the effects of e_32 in anisotropic piezoelectric harvesters can enhance energy harvesting from the vibration of a multilayer COMPOSITE cantilevered plate. This research contributes valuable insights into optimizing piezoelectric energy harvesting efficiency in plate-like structures, paving the way for advancements in energy harvesting technology.

This paper investigates the influence of temperature on the active vibration control of laminated COMPOSITE cantilever beams using collocative experimental and simulation techniques. The system identification toolbox of the MATLAB simulation tool is utilized to obtain the transfer function of the plant model. The adequate vibration attenuation of the glass-epoxy cantilever beam operating in various thermal environments is achieved using the proportional (P) and proportional-integral-derivative (PID) controllers. The vibration attenuation characteristics of the developed control algorithms are comprehensively investigated for a wide temperature range of –20 °C to 60 °C using PZT-5H PATCHES. Particular emphasis is given to the vibration control of the fundamental natural frequency of the laminated COMPOSITE cantilever beam. The obtained results of open and closed-loop models are presented in both time and frequency domains. The results indicate that for all the temperatures considered, the PID controller is found to be more effective in vibration attenuation than the P controller. The vibration attenuation performance of the cantilever beam considerably improved at the higher magnitude of temperature values. The natural frequency of the system is reduced continuously with an increase in temperature.

Considering the old methods of maintenance and repair of oil and gas pipelines such as welding or replacing a part of the damaged pipeline which include high costs and spending a lot of time, the important usage of novel methods with lower costs such as the use of COMPOSITE PATCHES can be highlighted. In this research, the strength of steel cracked pipe with COMPOSITE PATCHES of glass fibers and epoxy/polyester resins has been studied experimentally. A crack with a length of 15 mm in the longitudinal axis of the pipe is considered. The specimen was subjected to internal pressure by a hydraulic pump to evaluate the strength of the glass/epoxy and glass/polyester COMPOSITE PATCHES considering the effects of fiber distributions, fiber angles, number of layers, and dimensions. Also, a comparison has been made between glass/polyester COMPOSITEs in two modes of complete curing and initial curing. Finally, the experimental test results were compared with the numerical simulations obtained by Abaqus software and the accuracy and precision of the study were verified. Some of the obtained results indicate that arrangement and number of layers have significant roles in the pressure-bearing capacity of COMPOSITE PATCHES. In this paper, for the first time, the effect of COMPOSITE PATCHES with different fiber orientations and the number of layers as well as curing effects are considered for the cracked pipe. The results show that the pressure-bearing capacity of COMPOSITE PATCHES rises with increasing the number of COMPOSITE layers. Also, it can be seen that after complete curing of the glass-polyester COMPOSITEs, the pressure-bearing capacity rises about 3 times in 3- and 5-layer COMPOSITEs, and in 7-layer ones, it increases about 2 times.

In this paper, the first and second order approximations of Taylor expansion are used for calculating the change of each natural frequency by modifying an arbitrary parameter of a system with a known amount and based on this approximation, the inverse eigenvalue problem is transformed to a solvable algebraic equation. The finite element formulation, based on the classical laminated plate theory (CLPT) is presented for laminated COMPOSITE plates with piezoelectric PATCHES. Using the proposed FE model, sensitivity analysis is carried out, to find the effects of the changes made in the design parameters such as the piezoelectric patch thickness and the fiber angles in each layer on the natural frequencies of the structure. The inverse eigenvalue problem is solved in order to find the thickness of piezoelectric PATCHES and stacking sequence for relocating the natural frequencies.

Due to various benefits of COMPOSITE materials such as light weight, high strength and their excellent formability, the externally bonded COMPOSITE PATCHES have been proved to be a preferable method of repairing flaws and cracks in various engineering structures. In this paper, the behavior of various PATCHES such as COMPOSITE and metallic PATCHES has been studied by calculating the stress intensity factor and the T -stress via 3D finite element method. The study of the out-of-plane bending role in repair of plates with single-sided patch is another aims of this research. The results showed that the higher stiffness of the COMPOSITE patch leads to further reduction in stress intensity factor. It is found that in the studied specimens, the boron/epoxy patch has the better behavior compared with glass/epoxy one. Furthermore, using single-sided and double-sided PATCHES leads to change in the T -stress value. The largest change achieved by the crack angle equals to 0 and the smallest on achieved by the crack angle equals to 45 degrees. Increasing the adhesive thickness leads to increasing the stress-intensity factor in repaired plate. Finally, it is found that the out-of-plane bending has the significant effect on behavior of repair with single-sided COMPOSITE patch.

Extended finite element method (XFEM) is one of the strongest numerical methods that its basis is finite element method. In this method, using of enriching the nodes and increasing of their degrees of freedom (from 2 to 4 or even upto 10) virtually and without verifying the mesh and geometry of discountinuty, can model the system. In FEM crack geometry must be align with mesh edges which needs changing meshes in every steps of crack propagation and take so much time and too many analysis. One of the main objectives in this study is the expression of a novel method for modeling fatigue crack growth more easily and achieve the life of the structure by calculating the stress concentration factors. In this paper by using XFEM in ABAQUS, real 3D crack trajectory in single side repair has been simulated. Variation of fracture parameterin thickness direction of cracked panel with different patch lay-ups has been studied. In this paper, tests include mixed mode crack propagation. By examining the XFEM results of this research, FEM and experimental results of previous studies, it was found that the results of XFEM in comparison to experimental results have less error.

In the countries with natural gas, repair of gas transmission pips is a problem. In this study, the epoxy COMPOSITE with single wall carbon nanotubes reinforcements as patch was used and the von Mises stress distribution was determined. For this purpose, the tubular steel with thickness and length 6 mm 1.5 m was simulated in ANSYS software at both ends of the pipe patched-epoxy COMPOSITE single-walled carbon nanotubes with reinforcing particles ratios 0.01, 0.03, 0.05, 0.07, 0.1, 0.13 and 0.15 were applied. Then, according to the true values of internal pressure and external pressure, the stress of gas pipe distribution on the patch was determined. Von Mises stress results showed that, carbon nanotubes 0.01 times the maximum repair patch has 0.19 MPa von Mises stress is the maximum that occurred in the casing without PATCHES that 1.48 Mpa is, much less. It was also found to increase the percentage of carbon nanotube to 0.15, von Mises stress to the maximum reaches 0.43 MPa. As a result, it can be stated that the nanoCOMPOSITE patch greater ease in pipes, can be improved tensile properties are repaired areas. As well as increasing the percentage of nanotubes in COMPOSITEs, von Mises stress increases the maximum in the elderly.

BACKGROUND AND OBJECTIVE: The congenital anomaly of nose is the one of causes of cosmetic of face and repair of this defect is very difficult. In this article, it was reported a case of congenital hypo plastic nasal alar with failure in operation two times. CASE: A 19 year old female referred with hypo plastic nasal alar who had been already operated two times with a failure in repairing this defect. A COMPOSITE graft from ear with suitable size was inserted in the defect area of nose and it was improved. CONCLUSION: For repairing this anatomical defect and decreasing failure, this new surgical method is suggested.