International Journal of Science Engineering and Advance ISSN 2321-6905

Technology, IJSEAT, Vol 2, Issue 12 December-2014

Analysis of Sandwich Beam

M Siva Prasad#1, P Satish Reddy #2, Matta Manoj #3, N.Guru Murthy #4
ME Department, Prasiddha College of Engg and Technology, Anathavaram
1
sivaprasadmuppanapalli@gmail.com, 2satish2436@gmail.com, 3mattamanoj13@gmail.com,
4
murthy408@gmail.com

Abstract- Sandwich beams are composite systems materials. In general, these structures require high
having high stiffness-to-weight and Strength-to- reliability assurance for which, the prediction of the
weight ratios and are used as light weight load maximum load that the structure can withstand.
bearing components. The use of thin, strong skin
sheets adhered to thicker, lightweight core materials A sandwich structured composite is a special class of
has allowed industry to build strong, stiff, light, and composite materials that is fabricated by attaching
durable structures. Due to the use of viscoelastic two thin but stiff skins to a light weight but thick
polymer constituents, sandwich beams can exhibit core. The core material is normally low strength
time-dependent behaviour. This study examines the material, but its higher thickness provided the
behaviour of sandwich beams driven by the sandwich composite with high bending stiffness with
viscoelastic rubber core. Finite element (FE) method overall low density. Open and closes cell structured
is used to analyze the overall transient responses, foams like polyvinylchloride, polyurethane,
harmonic responses and the static responses of the polyethylene or polystyrene foams, and honey combs
sandwich systems subject to a concentrated point are commonly used core materials. Open and closed
load at the mid span of the beam. cell metal foam can also be used as core materials.
Laminates of glass or carbon fiber reinforced
In this study the skin, i.e. the top and bottom layers thermoplastics or mainly thermo set polymers
are made up of mild steel while the core is made up (unsaturated polyesters, epoxies...) are widely used as
of rubber. The stress, strain, and deformation fields skin materials. Sheet metal is also used as skin
are analyzed. The core thickness is varied keeping the material in some cases. The core is bonded to the
skin thickness constant and the behaviour of the skins with an adhesive or with metals components by
sandwich beam is studied under static and dynamic brazing together.
conditions.
There are different types of sandwich structures.
Keywords- Sandwich, viscoelastic, Metal composite material (MCM) is a type of
deformation fields sandwich formed from two thin skins of metal
bonded to a plastic core in a continuous process
I. Introduction
under controlled pressure, heat, and tension.
Sandwich Beams are extensively used in the Recycled paper is also now being used over a closed-
construction of aerospace, civil, marine, automotive cell recycled craft honeycomb core, creating a
and other high performance structures due to their lightweight, strong, and fully repulpable composite
high specific stiffness and strength, excellent fatigue board. This material is being used for applications
resistance, long durability and many other superior including point-of-purchase displays, bulkheads,
properties compared to the conventional metallic recyclable office furniture, exhibition stands, and

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 International Journal of Science Engineering and Advance ISSN 2321-6905
Technology, IJSEAT, Vol 2, Issue 12 December-2014

wall dividers. To fix different panels, among other Sandwich structures can be widely used in sandwich
solutions, a transition zone is normally used, which is panels; these kinds of panels can be in different types
a gradual reduction of the core height, until the two such as FRP sandwich panel, aluminum composite
fiber skins are in touch. In this place, the fixation can panel etc. FRP polyester reinforced composite
be made by means of bolts, rivets, or adhesive. honeycomb panel (sandwich panel) is made of
polyester reinforced plastic, multi-axial high-strength
The strength of the composite material is dependent glass fiber and PP honeycomb panel in special
largely on two factors: antiskid tread pattern mould through the process of
1. The outer skins: If the sandwich is constant temperature vacuum adsorption &
supported on both sides, and then stressed by means agglutination and solidification.
of a force in the middle of the beam, then the bending Sandwich theory describes the behavior of
moment will introduce shear forces in the material. a beam, plate or shell which consists of three layers -
The shear forces result in the bottom skin in tension two face sheets and one core. The most commonly
and the top skin in compression. The core material used sandwich theory is linear and is an extension of
spaces these two skins apart. The thicker core first order beam theory. Linear sandwich theory is of
material the stronger the composite. This principle importance for the design and analysis of sandwich
works in much the same way as an I-beam does. beams, which are of use in building construction,
vehicle construction, airplane construction and
2. The interface between the core and the refrigeration engineering.
skin: Because the shear stresses in the composite
material change rapidly between the core and the Historically, the first use of the concept of sandwich
skin, the adhesive layer also sees some degree of construction dates back to Sir William Fairbairn in
shear force. If the adhesive bond between the two England, 1849. The idea to combine two different
layers is too weak, the most probable result will materials to increase the strength of a structure was
be delamination. first used in the 1930s. In 1940, sandwich
Sandwich beams are composite systems having low construction was used extensively in building the
weight and high strength and stiffness characteristics. English Mosquito bomber during the War II. The
Typical sandwich beams consist of two thin skin Mosquito was implemented with a plywood
layers separated by a thick inner core. The use of sandwich construction. In the United States the core
thin, strong skin sheets adhered to thicker, was originated. In the late 1940’s, Hexcel
lightweight core materials has allowed industry to Corporation was formed and it has played the most
build strong, stiff, light, and durable structures. When role in the development of sandwich construction.
the skins and core are joined together, they function Sandwich beams are widely used in a variety of
as a single structural component containing all the applications such as satellites, railroads and
advantages of each component. Sandwich beams automobiles to name a few (Vinson, 2005).
have high stiffness-to-weight and strength-to-weight
ratios and are used as light weight load bearing Due to the use of polymer constituents,
components. Tensile and compressive stresses are sandwich beams can exhibit time dependent
mainly carried by the skins, while transverse shear behavior. Visco elasticity is the study of time-
stresses are predominantly experienced by the core. dependent materials showing a combined elastic solid
Typically, materials such as steel and aluminum and viscous fluid behavior when subjected to external
sheets are used for the skins. The main function of mechanical loadings. The response of viscoelastic
the core is to increase the flexural rigidity of the materials is determined not only by the current state
sandwich beam, minimizing transverse deformation. of the load, but also by the history of the loading.
Honeycombs, foams, and corrugated cores made of
polymers or metals are typically used.

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 International Journal of Science Engineering and Advance ISSN 2321-6905
Technology, IJSEAT, Vol 2, Issue 12 December-2014

Sandwich beams are generally thick experimental data reported in the literature.
structures in which the thickness is not negligible as Parametric studies show that the variation of core
compared to other dimensions. Thus, shear thickness has a significant effect on the natural
deformation accounts for a significant amount of frequencies and mode shapes and maximum
transverse deflection. In polymer foam cores, shear deflections.
deformation often continues to increase under a
constant load (stress). The strength of a sandwich
beam is determined by the resistance of the skins or
core to failures. Ideally, the skins should be designed
to resist axial stresses, whereas the core should be
designed for limited shear. Although the distribution
of the shear stress through the thickness in sandwich
beams is not uniform, for design purposes the shear
stress through the core thickness is often assumed
uniform.

Selection of materials in designing the

structural and/or mechanical components play an
important role and is fixed based on the strength,
stiffness, cost and other mechanical properties such Fig-1 Sandwich Structure
as hardness, toughness, wear resistance etc.. II. Modelling of Sandwich beam
Materials selected in view of the above requirements A sandwich beam whose core thickness is varied is
may not have internal damping capacity. When the modeled using ANSYS. The specifications of the
structures are subjected to harmonic loads of high beam are as follows:
frequencies, conventional damping techniques such
as providing external dashpots, arranging dynamic
DIMENSIONS OF THE BEAM
vibration absorbers may not have control on the
dynamic response of the structures resulting in failure a=0.02m…… thickness of the skin
at resonance frequencies.
Arrangement of soft core material that requires more w=0.2m…….width of the beam
energy to deform provides internal damping of
structures known as sandwich treatment. Sandwich P=5000N…… load acting on the beam
treatment will reduce the amplitude of oscillation
l=1m………...length of the beam
depending upon the location, volume and mechanical
properties of core layer in the structure. It is also Dimension of core varies.
important to study the effect of sandwich treatment
on static response of the structure in order to confirm
the safe design. When a sandwich structures with thin
soft core is transversely loaded, the two faces tend to
act as two independent beams, bending along their
centroids, rather than along the neutral axis of the
beam as a whole.
In this thesis static and dynamic analysis of sandwich
beams with different core thickness under simply
supported condition is studied. The results of the
present model agree well with the analytical and

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 International Journal of Science Engineering and Advance ISSN 2321-6905
Technology, IJSEAT, Vol 2, Issue 12 December-2014

Fig-2 Modelled Beam

Fig-1.1 Dimensions of Beam
III.Static Analysis
Table-1Variation of core thickness

Condition Thickness(m)

1 0.01

2 0.015

3 0.02

4 0.025

5 0.03

Fig-3 Von Misses Stress for 0.01m thick

Table -2 MATERIAL PROPERTIES

PARAMETER SKIN CORE

Material Mild Steel Rubber

Young’s 210GPa 0.2GPa

Modulus

Poisson’s Ratio 0.303 0.48

Density 8050kg/m3 1100kg/m3

Fig-4 Von Misses Stress for 0.015m thick

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 International Journal of Science Engineering and Advance ISSN 2321-6905
Technology, IJSEAT, Vol 2, Issue 12 December-2014

Fig-6 Von Misses Stress for 0.03 m thick

Variation of Deflection and stress with thickness

Fig-5 Von Misses Stress for 0.02 m
thick Thickness (m) Deformation Stress(Pa)

0.01 0.0024 0.912e7

0.015 0.00186 0.810e7

0.02 0.00146 0.725e7

0.025 0.00118 0.654e7

0.03 0.00097 0.596e7

Fig-5 Von Misses Stress for 0.025 m thick

Fig-7: graph between deflection and core thickness

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 International Journal of Science Engineering and Advance ISSN 2321-6905
Technology, IJSEAT, Vol 2, Issue 12 December-2014

Fig-8 Graph between Vonmisses stress and

Core Thickness

From this we can note that the deflection is

decreasing with that of the core thickness. It is the
Fig-10: Fifth Mode Shape
same as in case of the stress also. This decrease will
continue in the same fashion as the skin thickness is Modal Frequencies
constant. When the value of the skin changes then an
optimum value could be found out. Mod
e
IV Modal Analysis shap 0.015 0.025
e 0.01m m 0.02m m 0.03m
Six Mode shapes are considered and modal analysis
is done for every thickness value. 39.98 61.42
1 7 45.41 50.88 56.54 9
The following are the mode shapes for the thickness
value of 0.02m 158.5 239.1
2 4 179.35 199.8 219.76 5

240.8 256.6
3 5 262.75 260.6 258.62 2

264.9 292.9 338.4

4 8 267.70 6 316.54 2

351.2 437.1 515.5

5 1 394.96 2 477.38 8

494.8 598.9 589.6

6 9 548.86 0 594.21 2

V Harmonic Analysis

Fig-9: First Mode Shape

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 International Journal of Science Engineering and Advance ISSN 2321-6905
Technology, IJSEAT, Vol 2, Issue 12 December-2014

Fig-11 First mode frequency for beam with core

thickness 0.01m
Fig-14 graph for harmonic analysis for core thickness
0.03m

The harmonic analysis is done for all the thickness

values and the graphs have been plotted. It is found
that the amplitude of the beam increases up to a
certain frequency value and then decreases gradually.
Hence we can calculate an optimal value where the
amplitude may not reach very high and also the
fundamental frequency could be found out.

VII CONCLUSIONS AND FUTURE SCOPE

Conclusions

Fig-12 first mode frequency for beam with core The following conclusions are drawn from the
thickness 0.025m present work:

 Analysed the sandwich beam and observed

various parameters for varying thickness.

 It is observed from the results that the

fundamental frequency increases as the core
thickness increases which implies that the natural
frequency also increases as the core thickness
increases.

 By this analysis we can determine the frequency

at which vibrations are maximum and avoid
operating the system at that frequency and
Fig-13 graph for harmonic analysis for core thickness operate it at other frequencies.
0.025m
Future Scope

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 International Journal of Science Engineering and Advance ISSN 2321-6905
Technology, IJSEAT, Vol 2, Issue 12 December-2014

Analysis can be carried out on different materials

with different stacking sequences and boundary
conditions and varying core and skin thickness.
Further analysis can be done for prediction of
delamination stress. The skin thickness can also be
varied along with that of the core thickness and
relations could be found out.

VIII REFERENCES

1. Project thesis of Roberts Tompkins submitted to

TAMU University- Visco elastic analysis of
Sandwich beam having Aluminum and Fiber
reinforced polymer skins with polystyrene foam core-
December 2009

2. Y. Swathi and Sd Abdul Kalam, “Sandwich

Treatment in FRP beams: Static and Dynamic
Response”. IJERT, vol1 9,2012,pp 2-5.

3. Noor AK and Burton WS, “Stress and free

vibration analysis of multilayered composite panels”
Compos Structures, vol11,1989,pp 183-204

4. Frostig Y, Baruch M, Vinley O and Sheinman I,

“High order theory for sandwich beam behaviour
with transversely flexible core”, J Eng Mech, vol 1
18, 1992, pp1026-1043.

5. Kant T and Swaminathan K, “Analytical solutions

for the static analysis of laminated composite and
sandwich plates based on a higher order refined
theory”, Compos Structures, vol56, 2002, pp. 329-
344.

6. Pandit MK, Sheikh AH and Singh BN, “ Analysis

of laminated sandwich plates based on improved
higher order zig zag theory”, J Sandwich Struct
Mater, Vol 12 2010, pp.307-326.

7. K.Malekzadeh, M. R. Khalili and R.K. Mittal,

“Local and Global Damped Vibrations of Plates with
a viscoelastic soft flexible core: An improved high
order approach” , Journal of sandwich structures and
materials, vol7 2005,pp 431

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