Static and dynamic analysis of the mechanical behavior of complex hybrid structures

Abstract

The work presented in this thesis focuses on analyzing the mechanical behavior and vibrations of hybrid structures. The objective is to propose sandwich structures with aluminum skins and different core configurations: magnetorheological elastomer (MRE) and honeycomb, offering adjustable stiffness and damping capabilities through the application of a magnetic field. These materials are known as smart materials. A bibliographic review is presented, including a detailed overview of the literature on the evolution of materials science, from early human discoveries to the latest advancements in smart materials, as well as innovative concepts for adaptive hybrid structures as intelligent systems. The study conducted consists of two parts: The first part is a comparative study of the mechanical behaviour under static 3-point bending of four sandwich beams with four core configurations: magnetorheological elastomer (MRE), honeycomb, MRE/honeycomb and MRE/honeycomb/MRE. The specimens were fabricated in the motor dynamics and vibroacoustics laboratory. The analysis includes a numerical simulation using ABAQUS software with finite element method modelling. The numerical results are validated by experimental tests. The results obtained show that the developed hybrid beams present better performance in terms of stiffness and damping due to the adjustment of the magneto-mechanical properties of the MRE materials integrated in the core. The second part concerns experimental modal analysis. Performing a modal analysis test generally requires measuring the vibrational response of the structure as well as the excitation force at different points, thereby enabling the calculation of the Frequency Response Function (FRF). The excitation is applied using an impact hammer, and the response is recorded with an accelerometer. Consequently, the identified modal parameters are: resonance frequencies, damping, and mode shapes. These tests are conducted for the sandwich beams with the proposed core configurations and under different boundary conditions. A numerical simulation of the modal analysis was performed using ABAQUS software through finite element modelling on the same types of specimens. The numerical and experimental results are compared and discussed. This study explores the advantages of MRE materials as smart materials, where dynamic mechanical properties can be controlled by an applied magnetic field, opening up prospects for designing innovative solutions for more resilient and reliable structures in applications requiring both high strength and effective vibration control