This paper investigates the possibility of converting vibrations to electricity. A numerical and an experimental study of a magnetic levitation harvester are proposed. The system can be highly efficient when the electrical parameters are correctly tuned. Mechanical and electrical interaction of the harvester is described by an electromechanical coupling. Fixed value, linear and nonlinear electromechanical coupling models are presented and compared. It has been shown that the nonlinear electromechanical coupling model is more suitable for higher oscillations of the magnet. The obtained results show that nonlinear resonance and recovered energy can be controlled by the simple configuration of the magnet coil position. The recovered energy from the top branch is significantly higher, but this solution is much harder to obtain.

Nonlinear dynamics of a rotating flexible slender beam with embedded active elements is studied in the paper. Mathematical model of the structure considers possible moderate oscillations thus the motion is governed by the extended Euler–Bernoulli model that incorporates a nonlinear curvature and coupled transversal–longitudinal deformations. The Hamilton’s principle of least action is applied to derive a system of nonlinear coupled partial differential equations (PDEs) of motion. The embedded active elements are used to control or reduce beam oscillations for various dynamical conditions and rotational speed range. The control inputs generated by active elements are represented in boundary conditions as non-homogenous terms. Classical linear proportional (P) control and nonlinear cubic (C) control as well as mixed ( $$P-C$$P - C ) control strategies with time delay are analyzed for vibration reduction. Dynamics of the complete system with time delay is determined analytically solving directly the PDEs by the multiple timescale method. Natural and forced vibrations around the first and the second mode resonances demonstrating hardening and softening phenomena are studied. An impact of time delay linear and nonlinear control methods on vibration reduction for different angular speeds is presented.

In this research, an analysis of polymer composite with the matrix of L285-cured hardener H286 and six reinforcement layers of carbon fabric GG 280 T was provided. It involved a comparison of the dynamical behavior responses for three cases of composite structures in the context of the presence of the mass share modifier. The samples with the addition of a physical modifier with varying mass percentages were investigated by being subjected to dynamic tests with specific parameters, i.e., constant excitation amplitude and vibration frequency in the vicinity of the base resonance zone. The analysis allowed for indicating the relationship between the composition of the prepared composites and their dynamic response via stiffness characteristics. In addition, the investigation resulted in determining the range of harmful dynamical operating conditions, which may contribute to damage to the composite structures.

The aim of this study was to determine the effect of a selected physical modifier with different granularity and mass percentage on the dynamics of aerospace polymer composites. The tests were carried out on samples made of certified aerospace materials used, among other purposes, for the manufacture of aircraft skin components. The hybrid composites were prepared from L285 resin, H286 hardener, GG 280T carbon fabric in twill 2/2 and alumina (Al₂O₃, designated as EA in this work). The manufactured composites contained alumina with grain sizes of F220, F240, F280, F320 and F360. The mass proportion of the modifier in the tested samples was 5% and 15%. The tested specimens, as cantilever beams fixed unilaterally, were subjected to kinematic excitation with defined parameters of amplitude and frequency excitation in the basic resonance zone of the structure. The results, obtained as dynamic responses, are presented in the form of amplitude–frequency characteristics. These relationships clearly indicate the variable nature of composite materials due to modifier density and grain size. The novelty of this study is the investigation of the influence of the alumina properties on system dynamics responses.

This paper presents a theoretical vs. experimental modal analysis of a composite thin-walled beam featuring a circumfer-entially asymmetric stiffness (CAS) profile characteristics. The adopted lamination scheme results in the complex elastic deformation modes exhibiting mutual coupling of flapwise bending, transverse shear and torsion. The analytical model used in this study is based on the authors previous research and takes into account most classical and non-classical effects specific for thin-walled composite structures. The theoretical outcomes are compared to experimental ones obtained by two different test methods, namely an impact hammer test and a laser vibrometer test. In this second experiment the macro fibre composite (MFC) patch actuators have been used to excite the system. For comparative purposes two different transducer types providing different excitation load have been examined. The performed analytical and laboratory experiments demonstrate extremely high consistent findings irrespective of the means of excitation. Therefore, the laser-based motion analysis system combined with piezo-actuator excitation may be considered as a feasible and accurate method for static and dynamic experiments on systems exhibiting complex deformation modes. These include also highly flexible structures where the deformations can not be measured by conventional contact methods e.g. due to the influence of an accelerometer mass. The discussed laser-based motion measuring technique can also be used in future modal analysis experiments on rotating beams.