Abstract
In this paper, stability analysis of sandwich toroidal shell segments (TSSs) with carbon nanotube (CNT)-reinforced face sheets featuring various types of auxetic cores, surrounded by elastic foundations under radial pressure is presented. Two distinct types of auxetic structures are considered for the core, including re-entrant auxetic structure and graphene origami (GOri)-enabled auxetic structure. The nonlinear stability equilibrium equations of the longitudinally shallow shells are formulated using the von Kármán shell theory, in conjunction with Stein and McElman approximation while considering Winkler–Pasternak's elastic foundation to simulate the interaction between the shell and elastic foundation. The Galerkin method is employed to derive the nonlinear stability responses of the shells. The numerical investigations show the influences of various types of auxetic-core layers, CNT-reinforced face sheets, as well as elastic foundation on the stability of sandwich shells.
Key Words
carbon nanotube-reinforced composite; elastic foundation structures; radial load; stability analysis; toroidal shell segment; various auxetic
Address
Farzad Ebrahimi: Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran
Mohammadhossein Goudarzfallahi and Ali Alinia Ziazi: Mechanical Engineering Department, Science and Research branch, Islamic Azad University, Tehran, Iran
Abstract
This paper presents the development of an educational management model for analyzing the dynamic instability of nanocomposite sandwich beams. The model aims to provide a comprehensive framework for understanding the behavior of sandwich micro beams with foam cores, featuring top and bottom layers made of smart and porous functionally graded materials (FGM) nanocomposites. The bottom layer is influenced by an external electric field, and the entire beam is supported by a visco-Pasternak foundation, accounting for spring, shear, and damping constants. Using the Kelvin-Voigt theory to model structural damping and incorporating size effects based on strain gradient theory, the model employs the parabolic shear deformation beam theory (PSDBT) to derive motion equations through Hamilton's principle. The differential quadrature method (DQM) is applied to solve these equations, accurately identifying the improvement in student understanding (ISU) of the beams. The impact of various parameters, including FGM properties, external voltage, geometric constants, and structural damping, on the DIR is thoroughly examined. The educational model is validated by comparing its outcomes with existing studies, highlighting the increase in ISU with the application of negative external voltage to the smart layer. This model serves as a valuable educational tool for engineering students and researchers studying the dynamic stability of advanced nanocomposite structures.
Abstract
Functionally graded-carbon nanotube (FG-CNT) is expected to be a new generation of materials with a wide range of potential applications in technological fields such as aerospace, defense, energy, and structural industries. In this paper, an exact finite strip method for functionally graded-carbon nanotube sandwich plates is developed using first-order shear deformation theory to get the exact natural frequencies of the plates. The face sheets of the plates are made of FG-CNT with continuous and smooth grading based on the power law index. The equations of motion have been generated based on the Hamilton principle. By extracting the exact stiffness matrix for any strip of the sandwich plate as a non-algebraic function of natural frequencies, it is possible to calculate the exact free vibration frequencies. The accuracy and efficiency of the current method is established by comparing its findings to the results of the literature works. Examples are presented to prove the efficiency of the generated method to deal with various problems, such as the influence of the length-to-height ratio, the power law index, and a core-to-face sheet thickness of the single and multi-span sandwich plates with various boundary conditions on the natural frequencies. The exact results obtained from this analysis can check the validity and accuracy of other numerical methods.
Key Words
exact finite strip method; first order shear deformation theory; free vibration; functionally graded-carbon nanotube; sandwich plate
Address
Shahabeddin Hatami, Mohammad J. Zarei and Seyyed H. Asghari Pari: Department of Civil Engineering, Yasouj University, Iran
Abstract
Using the mechanical treatments for mechanical properties improvement was rarely in the development scope before. This research approves through analytical ways that surface impacts can improve the quality of the surface significantly. This fact is approved for deposited titanium on silicone substrate. The new algorithm called minimum resultant error method (MREM) which is a direct combination of nanoindentation, FEM and dimensional analysis through a reverse method is utilized to extract the mechanical characteristics of the coating surface before and after impact. This method is extended to the time dependent behavior of the material to obtain strain rate coefficient. To implement this new approach, a new analysis technic is developed to define the residual stress field caused by surface impact as initial condition for nanoindentation. Analyzing the model in micro and macro scale at the same time was one of the main resolved challenges in this study. The result was obtaining of the constants of Johnson-Cook constitutive equation. Comparing the characteristics of the coating surface before and after impact shows high improvement in yield stress (34%), Elastic modulus (7.75%) and strain hardening coefficient (2.8%). The main achievement is that the strength improvement in titanium thin layer is much higher than bulk titanium. The yield strength shows 41.7% improvement for coated titanium comparing with 24% for bulk material. The rate of enhancement is about 6 times when it comes to the Young's modulus.
Abstract
Nanotechnology, the science of manipulating matter at the nanoscale, offers remarkable opportunities for innovation across various fields. Nanomaterials, which form the cornerstone of advanced materials, drive forward new ideas and groundbreaking applications. In the textile industry, traditional antibacterial and antifungal garments are typically treated with chemical compounds to inhibit bacterial growth. However, these treatments often lack durability, losing effectiveness after multiple washes. To address this limitation, the application of green nanotechnology in developing high-performance textiles emerges as a promising solution. This study explores the integration of nanocomposites into the polymer layers of footballs to enhance their stability and performance. By embedding nanoparticles within the polymer matrix, the durability and resilience of the footballs are significantly improved, leading to better control and performance on the field. This innovative approach not only extends the lifespan of the footballs but also provides economic advantages by reducing the frequency of replacements. Additionally, the enhanced stability contributes to a more consistent and reliable playing experience, promoting improved safety and performance for athletes.
Key Words
durability; football stability; nanocomposites; nanotechnology; performance enhancement; polymer layers
Address
Huayun Tian and Lu Li: Department of Physical Education, Wuhan University of Technology, Wuhan 430076, Hubei, China
Abstract
This paper presents nonlinear vibration analysis of a composite cylindrical shell. The core of the shell is made of functionally graded (FG) porous materials and layers is fabricated of carbon nanotubes (CNTs) reinforced nanocomposites. To increase the accuracy of results, neutral surface position is considered. First-order shear deformation theory is used as displacement field to derive the basic relations of equation motions. In addition, von-Karman nonlinear strains are employed to account geometric nonlinearity and to enhance the results' precision, the exact position of the neutral surface is considered. To governing the partial equations of motion, the Hamilton's principle is used. To reduce the equation motions into a nonlinear motion equation, the Galerkin's approach is employed. After that the nonlinear motion equation is solved by multiple scales method. Effect of various parameters such as volume fraction and distribution of CNTs along the thickness directions, different patterns and efficiency coefficients of porous materials, geometric characteristics and initial conditions on nonlinear to linear ratio of frequency is investigated.
Address
Zhihui Liu, Kejun Zhu and Xue Wen: College of Mechanical and Energy Engineering, Shaoyang University, Shaoyang, Hunan, 422000, China/ Key Laboratory of Hunan Province for Efficient Power System and Intelligent Manufacturing, Shaoyang University, Shaoyang, Hunan, 422000, China
Abhinav Kumar: Department of Nuclear and Renewable Energy, Ural Federal University Named after the First President of Russia Boris Yeltsin, Ekaterinburg 620002, Russia
Abstract
The insecticidal efficiency of orange (Citrus sinensis) peel essential oil (OP-EO) is limited because of its low stability under environmental conditions. Nanoemulsion formulations show promise in overcoming this limitation. Therefore, this study aimed to formulate and characterize the OP-EO nanoemulsion form (OP-EON) and investigate its insecticidal properties against two significant storage pests, Rhyzopertha dominica (Fabricius, 1792), and Tribolium castaneum (Herbst, 1797). The OP-EON (4:3:3:90 w/w, EO: Tween 80: Ethanol: water) was successfully created using an ultrasonic homogenizer. The major chemical components of the OP-EO were determined to be D-limonene (87.93%), myrcene (3.62%), and α-pinene (1.34%) through GC-MS analysis. The OP-EON was characterized using TEM (50-100 nm), Zeta sizer (the mean droplet particle size of 58.60 nm, the ζ-potential value of -12.6 mV, and the polydispersity index of 0.486), and FT-IR analysis. After 7 days, exposure to 500 ppm of the OP-EON resulted in 50% and 30% mortality rates in R. dominica and T. castaneum, respectively. Exposure to 1000 ppm of OP-EON resulted in 90% and 55% mortality in R. dominica and T. castaneum, respectively, after 7 days. Overall, these results clearly showed the potential to exceed the limits of the insecticidal activity of the OP-EO with its nanoemulsion form.
Abstract
Nanotechnology is one of the leading edges of science and technology today, holding out the promise for revolutionary advances in just about any discipline. With the integration of nanoscale concepts into K-12 STEM education comes a special opportunity pertaining to the cultivation of future innovators and scientists who are more adept at traveling in this burgeoning field. It discusses some strategies and frameworks for effectively bringing nanotechnology into the K-12 curriculum. Hands-on activities, interdisciplinary approaches, and age-appropriate educational materials have been used with an emphasis on improving student engagement and enhancing understanding in nanoscale phenomena. Thus, early exposure to the principles of nanotechnology can be effectively used by teachers to develop curiosity, critical thinking, and problem-solving skills, which are necessary for technological advancement. These results highlight the potential of nanotechnology education integration in the development of future STEM professionals. It results in an increase in the enrollment rate. Hence, this proves that there is a lasting impact of the intervention on the choice that students made while in school.
Key Words
DQM; K-12 curriculum; nanoscale; nanotechnology; STEM education
Address
Yawen Su: Normal College, Jimei University, Xiamen 361005, Fujian, China
Maryam Shokravi: Energy institute of higher education, Mehrab High School, Saveh, Iran
M.H. Fakhar: Department of Mechanical Engineering, Kashan Branch, Islamic Azad University, Kashan, Iran
