Dynamic Analysis of Sandwich Composite Beam with Magnetorheological Fluid Core
Date
2020
Authors
J, Vipin Allien.
Journal Title
Journal ISSN
Volume Title
Publisher
National Institute of Technology Karnataka, Surathkal
Abstract
Magnetorheological fluid (MRF) is a smart fluid which can change its
rheological properties under the influence of an applied magnetic field. Sandwich
structures with MRF as core have unique characteristics permitting to vary the stiffness
and damping properties under the influence of the applied magnetic field. Hence, MRF
core sandwich structures can be effectively utilized to suppress the vibration and
enhance the life of the structures. This study, investigates the dynamic characterization
of MRF core sandwich beams with two types of composite face layers viz. polymer
matrix composite and metal matrix composite.
The two-layer, four-layer and six-layered chopped strand mat glass fiber
reinforced unsaturated polyester resin polymer matrix composites (CGRP-PMC) were
prepared by the hand layup method. The tensile, flexural, impact, inter-laminar shear
strength (ILSS), fracture toughness properties were evaluated. The results have
revealed that the four-layered CGRP-PMC material has high impact strength, ILSS and
fracture toughness compared to two-layer and six-layered CGRP-PMC material. Free
vibration analysis was carried out to determine the natural frequency and damping ratio
of the CGRP-PMC materials. The result obtained from free vibration analysis indicated
that the natural frequency of six-layered CGRP-PMC is higher than two-layer and fourlayered CGRP-PMC materials. The density, tensile strength, flexural strength, impact
strength, absorbed energy, ILSS, fracture toughness, and damping ratio results of the
CGRP-PMC specimens were considered as attributes for the selection of the optimal
composite using multi-attribute decision making (MADM) techniques. The six-layered
CGRP-PMC material was selected as the optimal PMC based on the results of MADM
techniques.
The Al6082 and Al7075 aluminum alloy reinforced with (0, 1, 2, 3, 4, 5, 7.5,
10, 15 and 20) different weight percentages (wt%) of silicon carbide particles (SiCp)
metal matrix composites (MMCs) were fabricated through stir casting method. The
mechanical and dynamic properties such as density, hardness, tensile strength, impact
strength, natural frequencies and damping ratio of the MMCs were determined. Thevi
mechanical tests and free vibration analysis results revealed that the addition of SiCp
reinforcement increased the strength and stiffness of the MMCs. 15% SiCp/Al7075
MMC was selected as the best MMC based on the results obtained from MADM
techniques.
The MRF is prepared in-house at room temperature and contains 30% volume
carbonyl iron powder and 70% volume silicone oil. The rheological properties of the
MRF with and without the magnetic flux density were determined. The viscosity of
MRF increased with an increase in magnetic flux density and saturated at 0.63 T. The
shear stress of MRF increased and viscosity of MRF decreased with an increase in the
shear rate at zero magnetic flux density. Since the MRF is used as the core for sandwich
beams, the frequency sweep analysis was performed in the rheometer. The complex
shear modulus, storage modulus, loss modulus, shear stress and complex viscosity
properties of MRF increased with an increase in the applied magnetic flux densities.
The loss factor of MRF decreased with an increase in the magnetic flux densities. The
complex viscosity of MRF decreased with an increase in oscillatory frequency and
increased with increase in the applied magnetic flux density.
The two-layer, four-layer and six-layered CGRP-PMC prepared using hand layup technique is used as top and bottom layers of the sandwich beams and the in-house
prepared MRF is used as the middle core layer of the sandwich beams. The dynamic
characterization of CGRP-PMC sandwich beams enclosed MRF core is experimentally
investigated. The effect of various parameters such as magnetic flux density, the
thickness of CGRP-PMC layers and MRF core layer on the natural frequencies,
damping ratio and vibration amplitude suppressions of the CGRP-PMC-MRF core
sandwich beams are examined. From free vibration analysis, it was observed that the
natural frequency of the CGRP-PMC-MRF core sandwich beams decreases with
increase in the thickness of the MRF core layer. However, the damping ratio of the
CGRP-PMC-MRF core sandwich structure increased with increase in the thickness of
the MRF core layer. Also, the experimental forced vibration results reveal that CGRPPMC-MRF core sandwich beams have excellent vibration amplitude suppression
capabilities.vii
Dynamic characterization of (0, 5, 10, 15 and 20%) SiCp reinforced Al6082
alloy MMC sandwich beam with MRF core is experimentally investigated. The MRF
core of the sandwich beam is activated using a non-homogeneous magnetic field using
permanent magnets. The natural frequency, damping ratio and frequency amplitude
response of the MMC-MRF core sandwich beams were determined through
experimental free and forced vibration analysis at 0, 200, 400 and 600 gauss magnetic
flux densities. Vibration amplitude suppression capabilities of the MMC-MRF core
sandwich beams subjected to varying magnetic flux densities are determined. The
experimental results revealed that the natural frequency, damping ratio and vibration
amplitude suppression capabilities of the MMC-MRF core sandwich beams improved
with the increase in the applied magnetic flux density. The experimental forced
vibration results reveal that MMC-MRF core sandwich beams have excellent vibration
amplitude suppression capabilities.
Description
Keywords
Department of Mechanical Engineering, Magnetorheological fluid, Polymer matrix composite, Metal matrix composite, Sandwich beam, Free and forced vibration analysis, Vibration damping