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• A geometrically exact model (GEMP) is developed for mosaic multi-stable composites. • Besides GEMP, a common model based on classical laminated‐plate theory is used. • Mosaic bi-stable and tri-stable composite laminates with large rotations are studied. • Lagrange multiplier is used to apply linear and non-linear continuity conditions. • Effect of dimensions of mosaic multi-stable laminates on static behavior are studied. Multi-stable composite laminates are composite materials that exhibit multi-stable states, making them highly suitable for use in morphing structures. These materials are capable of maintaining each stable state without expending any energy. As a result, they are used extensively in numerous applications and garnered the interest of scholars and aerospace organizations. In the context of practical applications, such as morphing structures, it is insufficient for designers to rely solely on common bi-stable composite laminates that exhibit large deformations and medium rotations to achieve their desired objectives. Consequently, based on the objectives of the design, there are two potential resolutions to address this limitation. A designer may utilize mosaic multi-stable composite laminates to achieve a morphing structure that exhibits high flexibility, significant deformation, and substantial rotation. The utilization of a series connection between a bi-stable composite laminate and a symmetric composite laminate results in the formation of a mosaic bi-stable composite laminate with variable stiffness. Furthermore, the amalgamation of two asymmetric composite laminates with inverted orientations engenders a mosaic tri-stable composite laminate. The present research examines the static characteristics of mosaic bi-stable and tri-stable composite laminates. It also seeks to analyze the factors affecting the behavior of these types of laminates. A geometrically exact model was formulated for this objective. Apart from the geometrically exact model, a widely used and uncomplicated model relying on the conventional Classical Laminated-Plate Theory (CLPT) and Von-Karman nonlinear strains was employed. The proposed models were validated through finite element simulations. The system's static equations were derived using the virtual work principle and the Rayleigh-Ritz method. The present study examines and explores quasi-static snap-through behavior between stable states through the application of concentrated forces. The findings indicate a high level of concurrence between the outcomes derived from the geometrically exact model and the finite element analyses, particularly in composite laminates exhibiting significant deformations and rotations. [ABSTRACT FROM AUTHOR]

Nowadays, environmental energy resources, especially mechanical vibrations, have attracted the attention of researchers to provide energy for low-power electronic circuits. A common method for environmental mechanical energy harvesting involves using piezoelectric materials. In this study, a spiral multimode piezoelectric energy harvester was designed and fabricated. To achieve wide bandwidth in low frequencies (below 15 Hz), the first three resonance frequencies of the beam were designed to be close to each other. To do this, the five lengths of the substrate layer were optimized by the Taguchi method, using an L27 orthogonal array. Each experiment of the Taguchi method was then simulated in ANSYS software. Next, the optimum level of each design variable was obtained. A test rig was then constructed based on the optimum design values and some experimental investigations were conducted. A good correlation was observed between measured and the finite element results. [ABSTRACT FROM AUTHOR]

In this paper, static and dynamic behavior of bi-stable composite laminates with $$[0-90]_{T}$$ stacking sequence and piezoelectric layers is studied. The governing equations of system were obtained using Rayleigh-Ritz method and Hamilton's principle. In order to improve the accuracy of results, a set of higher-order shape functions were employed. The dynamic response of the system under various electrical fields applied to the piezoelectric actuators was studied, and the effects of the presented shape functions on short-circuit natural frequency and the lowest electrical field required for snap-through were analyzed. The results obtained from the developed analysis have been compared with the conventional and FEM models. Good correlation was observed between the proposed model and the finite element method. [ABSTRACT FROM AUTHOR]

Hydraulic engine mounts are generally applied to the aerospace and automotive applications for the purpose of cabin noise and vibration reduction. By careful selection of mount design parameters, at a certain frequency called the notch frequency, the dynamic stiffness will be smaller than the static stiffness. Following the notch frequency there will be a frequency, called the peak frequency, where the dynamic stiffness is much higher than the static stiffness. Increase in the dynamic stiffness above the static stiffness is not desirable because of the increase in transmitted force to the airframe or the chassis. Here in this paper, a new hydraulic engine mount design is proposed that uses two working fluids. This new design has two notch frequencies and two peak frequencies. Under special conditions, the peak frequency can be eliminated. As a result, one can obtain a hydraulic engine mount design with only one notch frequency but no peak frequency, by using a controllable fluid or a high viscosity fluid as one of the working fluids. The new hydraulic engine mount design, its mathematical model, and some discussions on the simulation results are presented. [ABSTRACT FROM PUBLISHER]

• A geometrically exact model is rendered to study the behavior of bi-stable laminate. • A model based on classical laminated-plate theory with Von-Karman strains is used. • Bi-stable laminates with very large displacements and large rotations are studied. • The effect of lateral length of square laminates on the statics behavior is studied. • The aspect ratio effect of rectangular laminates on the statics response is studied. The present study aimed to analyze the stable states and the snap-through forces of square and rectangular bi-stable composite laminates with [0 3 /90 3 stacking sequence and large to very large displacements and medium to large rotations. Also, the effect of lateral length and aspect ratio of these laminates on their stable states and snap-through forces were analyzed. For this purpose, a realistic geometric exact model of plate (GEMP) was developed based on continuum mechanics. In addition, the analysis was also performed with a commonly used model based on classical laminated‐plate theory (CLPT) with Von-Karman strains. FEM simulations were used to validate the results of these theoretical models. The static equations of the system were derived using the principle of virtual work and Rayleigh-Ritz method. Good consistency was observed between the results of the proposed GEMP and the FEM models, especially for laminates with very large displacements and large rotations. [ABSTRACT FROM AUTHOR]

• Energy harvesting from moving harmonic and continuous mass on simply supported beam. • Theoretical and experimental study of energy harvesting from moving mass. • Increase in the harvested power by adding the mass and the speed of the moving part. • Decrease in the harvested power by increasing the length of moving continuous mass. In this paper, energy harvesting from a simply supported beam using piezoelectric materials has been performed. Two different models for the moving objects were considered. First, the passing object was modeled as a concentrated mass with some amount of unbalances. The coupled governing equations of the beam, the piezoelectric patch, and the moving mass were obtained and discretized using assumed mode method. The beam response and the output voltage were calculated for different values of moving mass and unbalances. In the second model, the passing object was studied as a distributed mass. The governing equations of the system were extracted at three stages, namely entrance, main, and exit of the object from the beam. To validate the numerical findings, two test setups were erected, and the beam midpoint deflection and the piezoelectric power were measured experimentally. A good degree of correlation was found between numerical and measured values. [ABSTRACT FROM AUTHOR]

The coupling between polarization and strain gradients is called flexoelectricity. This phenomenon exists in all dielectrics with any symmetry. In this paper, energy harvesting from a Timoshenko beam is studied by considering the flexoelectric and strain gradient effects. General governing equations and related boundary conditions are derived using Hamilton's principle. The flexoelectric effects are defined by gradients of normal and shear strains which lead to a more general model. The developed model also covers the classical Timoshenko beam theory by ignoring the flexoelectric effect. Based on the developed model, flexoelectricity effect on dielectric beams and energy harvesting from cantilever beam under harmonic base excitation is investigated. A parametric study was conducted to evaluate the effects of flexoelectric coefficients, strain gradient constants, base acceleration and the attaching tip mass on the energy harvested from a cantilever Timoshenko beam. Results show that the flexoelectricity has a significant effect on the energy harvester performance, especially in submicron and nano scales. In addition, this effect makes the beam to behave softer than before and also it changes the harvester first resonance frequency. The present study provides guidance for flexoelectric nano-beam analysis and a method to evaluate the performance of energy harvester in nano-dielectric devices. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the amount of energy which can be harvested by a cantilever beam type piezoelectric energy harvester from a bridge vibration. The sources of vibration are vehicles traversing the bridge. Two types of masses are considered as models for traversing vehicles: concentrated and distributed masses. The mass of the harvester is assumed negligible compared to that of the bridge. First, the problem of moving mass travelling with a constant speed over a beam is considered. The formulations for both concentrated and distributed masses are presented. The obtained results are then compared to the data available in the literature, in order to validate the model of a beam with a moving mass. Next, a mathematical model for the harvester is proposed, which is composed of an Euler–Bernoulli beam as a substrate, a tip mass, and a single piezoelectric patch whose electrodes are connected to a changeable resistance. To validate the model, the harvester is fabricated and tested on a shaker. The electroelastic frequency response functions of the system are measured by low-amplitude chirp excitation tests. The optimal resistive load at the resonance frequency, obtained from theory and experiments, are compared. Finally, the acceleration time histories for the beam at mid-span, where the harvester is located, are calculated for two mass types and used as base excitation signals to the harvester. These signals are replayed on an electromagnetic shaker to simulate the bridge vibrations on the fabricated harvester and the experimental results are compared with theoretical ones. Good agreement is observed. [ABSTRACT FROM AUTHOR]