Dynamic characterization and parametric instability analysis of rotating magnetorheological fluid composite sandwich plate subjected to periodic in-plane loading:

Vibration analysis of a multifunctional hybrid composite honeycomb sandwich plate

Abstract: In the present study, the free and forced vibration responses of the composite sandwich plate with carbon nanotube reinforced honeycomb as the core material and laminated composite plates as the to...

Dynamic stability enhancement of laminated composite sandwich plates using smart elastomer layer

Abstract: The dynamic stability of composite sandwich plates with a smart elastomer layer subjected to an axial periodic load is investigated. A finite element model of the composite sandwich plate with Magn...

Assessment of dynamic properties of hybrid ribbon reinforced multifunctional composite sandwich plates: Numerical and experimental investigation

Abstract: This study investigates numerically and experimentally the effect of longitudinal ribbon reinforcement in conventional honeycomb structure on the various dynamic characteristics of a hybrid composite sandwich plate. Longitudinal strips are considered to be embedded along the transverse directions at various locations of a honeycomb core material without and with carbon nanotubes (CNT) reinforcement in a composite sandwich plate. The governing differential equations of motion of the various hybrid honeycomb composite sandwich plate configurations with strips inserted in conventional honeycomb structures as core layer having top and bottom face composite layers are derived using higher order shear deformation theory (HSDT) and solved numerically using a four noded rectangular finite element. Further, experimental investigations are performed by fabricating the various strips embedded hybrid honeycomb core material with and without CNT reinforcement to evaluate the shear and loss moduli using the alternative dynamic approach. The efficacy of the developed finite element formulation is demonstrated by comparing the experimental and numerical results obtained in terms of natural frequencies and loss factors for the various prototypes of honeycomb composite sandwich plates. Also, the effect of variation in CNT content and thickness of longitudinal ribbon reinforcement in conventional honeycomb core material and ply orientation of the face sheets on the various dynamic properties of hybrid composite structures are studied under various end conditions. This study proposes that the ribbon reinforcement location and the addition of CNTs in honeycomb core materials strongly influence the stiffness, damping and transverse vibration displacements of the ribbon reinforced hybrid composite sandwich plates.

Static and dynamic instability analysis of tapered CNTRC sandwich plates under uniform and non-uniform in-plane loadings using spline finite strip method

Abstract: This paper presents the buckling analysis of rectangular sandwich plates with pure polymeric tapered cores and functionally graded carbon nanotube (FG-CNT) reinforced composite face sheets under static and harmonic dynamic loads. One uniform and four linearly-varying patterns are considered for the applied in-plane loads. The effective material properties of face sheets, in which the polymeric matrix is reinforced with aligned single-walled carbon nanotubes (SWCNT), are estimated using the extended rule of mixture. A higher-order zigzag shear deformation theory, which has the same number of dependent unknowns as the first-order theory, is employed to express the plate's displacement field. The governing equations are derived using Hamilton's principle and discretized by the spline finite strip method. The dynamic instability regions of plates with uniform and variable thickness are obtained by employing Bolotin's method. The accuracy of the present method is demonstrated by considering the problems for which solutions are available. A detailed numerical study is conducted to examine and compare the effects of different parameters, including the taper angle, type of the applied in-plane load, static and dynamic load factors, length-to-width ratios, the volume fraction of CNT, distribution pattern of CNTs along the thickness direction, temperature, and boundary conditions on the behavior of sandwich plate.

Vibration characteristics and optimal design of composite sandwich beam with partially configured hybrid MR-Elastomers

Abstract: The free and forced vibration characteristics of a sandwich beam with composite face layers and partially configured carbon nanotubes reinforced magnetorheological elastomer (hybrid MR elastomer) c...

Vibration suppression capabilities of magnetorheological materials based adaptive structures

Abstract: This paper discusses the investigation of vibration suppression capabilities of magnetorheological (MR) materials in adaptive structures. Homogeneous three-layered adaptive beams with MR materials sandwiched between two elastic layers were considered. By varying the externally applied magnetic field level over the MR layer, the stiffness and damping properties of the adaptive beam can be varied. These variations in the damping and stiffness properties can be used to tune the vibration characteristics of the adaptive beams such as natural frequencies, vibration amplitudes, mode shapes and loss factors. In this study, theoretical investigation of the MR adaptive beams vibration behavior based on the energy approach is accomplished. Experiments were performed to observe the theoretically predicted vibration responses in real time. From both studies, vibration suppression capabilities of MR adaptive beams were observed in the forms of shifts in natural frequency values, variations in loss factors, and vibration amplitudes.

Dynamic analysis of magnetorheological elastomer-based sandwich beam with conductive skins under various boundary conditions

Abstract: The dynamic analysis of a three-layered symmetric sandwich beam with magnetorheological elastomer (MRE) embedded viscoelastic core and conductive skins subjected to a periodic axial load have been carried out under various boundary conditions. As the skins of the sandwich beam are conductive, magnetic loads are applied to the skins during vibration. Due to the field-dependent shear modulus of MRE material, the stiffness of the MRE embedded sandwich beam can be changed by the application of magnetic fields. Using extended Hamilton’s principle along with generalized Galarkin’s method the governing equation of motion has been derived. The free vibration analysis of the system has been carried out and the results are compared with the published experimental and analytical results which are found to be in good agreement. The parametric instability regions of the sandwich beam have been determined for various boundary conditions. Here, recently developed magnetorheological elastomer based on natural rubber containing iron particles and carbon blacks have been used. The effects of magnetic field, length of MRE patch, core thickness, percentage of iron particles and carbon blacks on the regions of parametric instability for first three modes of vibration have been studied. These results have been compared with the parametric instability regions of the sandwich beam with fully viscoelastic core to show the passive and active vibration reduction of these structures using MRE and magnetic field. Also, the results are compared with those obtained using higher order theory.

Analytical solutions for vibrations of laminated and sandwich plates using mixed theory

Abstract: A semi-analytical method has been presented in this paper to evaluate the natural frequencies as well as displacement and stress eigenvectors for simply supported, cross-ply laminated and sandwich plates by using higher order mixed theory. Models based on equivalent single layer as well as layerwise (LW) theories have been formulated. By assuming a non-linear variation of axial displacements through the plate thickness, the warping of the transverse cross-section has been considered. Hamilton’s principle has been employed to derive the equilibrium equations. The proposed LW model fulfills a priori the continuity of displacements as well as the transverse and the normal stress components at each interface between two adjacent layers. Results obtained by present higher order mixed theory have been found in good agreement with those obtained by three-dimensional elasticity solutions. After establishing the accuracy of present results for orthotropic plates, new results for thin and thick sandwich plates have been presented which can serve as benchmark solutions for future investigations.

Vibration analysis of a multi-layer beam containing magnetorheological fluid

Abstract: Magnetorheological (MR) materials exhibit rapid variations in their rheological properties when subjected to varying magnetic field and thus offer superior potential for applications in smart structures requiring high bandwidth. MR sandwich structures can apply distributed control force to yield variations in stiffness and damping properties of the structure in response to the intensity of the applied magnetic field and could thus provide vibration suppression over a broad range of external excitation frequencies. This study investigates the properties of a multi-layered beam with MR fluid as a sandwich layer between the two layers of the continuous elastic structure. The governing equations of a multi-layer MR beam are formulated in the finite element form and using the Ritz method. A free oscillation experiment is performed to estimate the relationship between the magnetic field and the complex shear modulus of the MR materials in the pre-yield regime. The validity of the finite element and Ritz formulations developed is examined by comparing the results from the two models with those from the experimental investigation. Various parametric studies have been performed in terms of variations of the natural frequencies and loss factor as functions of the applied magnetic field and thickness of the MR fluid layer for various boundary conditions. The forced vibration responses of the MR sandwich beam are also evaluated under harmonic force excitation. The results illustrate that the natural frequencies could be increased by increasing the magnetic field while the magnitudes of the peak deflections could be considerably decreased, which demonstrates the vibration suppression capability of the MR sandwich beam.

Vibration characteristics of MR cantilever sandwich beams: experimental study

Abstract: The concept of vibration controllability with smart fluids within flexible structures has been of significant interest in the past two decades. Although much research has been done on structures with embedded electrorheological (ER) fluids, there has been little investigation of magnetorheological (MR) fluid adaptive structures. In particular, a body of research on the experimental work of cantilever MR beams is still lacking. This experimental study investigates the controllability of vibration characteristics of magnetorheological cantilever sandwich beams. These adaptive structures are produced by embedding an MR fluid core between two elastic layers. The structural behaviour of the MR beams can be varied by applying an external magnetic field to activate the MR fluid. The stiffness and damping structural characteristics are controlled, demonstrating vibration suppression capabilities of MR fluids as structural elements. MR beams were fabricated with two different materials for comparison purposes. Diverse excitation methods were considered as well as a range of magnetic field intensities and configurations. Moreover, the cantilever MR beams were tested in horizontal and vertical configurations. The effects of partial and full activation of the MR beams were outlined based on the results obtained. The controllability of the beam's vibration response was observed in the form of variations in vibration amplitudes and shifts in magnitudes of the resonant natural frequency.