The document discusses the structural analysis of a heteromorphic hexa square honeycomb sandwich panel for use in aircraft. Finite element analysis was conducted using ANSYS to analyze models with different core materials (aluminum, GFRP, ABS) under three-point bending. Experimental three-point bending tests were also conducted on a sandwich panel with an aluminum core. The results found that a GFRP core model provided better deflection performance compared to other materials and the baseline hexagonal structure.

1. International Journal of Mechanical Civil and Control Engineering
Vol. 1, Issue. 3, June 2015 ISSN (Online): 2394-8868
19
Structural Analysis of Heteromorphic Hexa Square
Honeycomb Sandwich Panel in Aircraft
J.Saravana Kumar1
,T.Madhan2
,T.Sri Ananda Atreya3
,R.Sriram4
, V.Pandyaraj5,
1,2,3,4
UG scholar,Departmen of Mechanical Engineering, Sri Sairam Engineering College, Chennai, INDIA
5
Assistant Professor,Departmen of Mechanical Engineering, Sri Sairam Engineering College, Chennai, INDIA
Abstract— The honeycomb sandwich structures are formed by
bonding stiff, high strength face layers to core material. The
important advantage of using the sandwich structure in aircrafts
are high stiffness and high strength to weight ratio. The objective
is to develop a modeling approach to predict response of
heteromorphic hexa square sandwich panels under static three
point bending test. Different core materials such as Aluminium,
GFRP (S-glass) and ABS(Acrylonitritile butadiene styrene) are
attempted in advanced finite element software Ansys. Numerical
solutions are also used to verify some of the mechanical
properties such as panel bending stiffness and core shear stress .
Experimental results are also carried out on Aluminium
sandwich panel in three point bending machine and compared
with analytical results.The face sheet material is made of
Aluminium of thickness 1mm each and core material is of
thickness 15mm.
Keywords— hexa square structure, three point bending test,
sandwich panel, honeycomb, core, facesheets.
I. INTRODUCTION
The sandwich structures in aircraft are used mainly
because of high strength to weight ratio which results in less
fuel consumption and imparts corrosion resistance. These
structures are capable of bearing huge impact of energy.A
structural sandwich structure is composed of two thin
facesheets boded between a thick low density core. Hence,
optimum material choice is often obtained according to the
design needs . Various combinations of core and facesheet
materials are utilized by researchers.
The aim of this paper is to understand the mechanical
behavior of sandwich structures with Aluminium facesheets
fabricated by hand lay up technique. For this purpose, three
point bending tests were conducted on Aluminium sandwich
specimen. Constituents of the sandwich structures were tested
by finite element modeling by using ANSYS software.
Fig. 1 Pictureof Sandwich panel.
II. HONEYCOMB SANDWICH PANEL
In honeycomb sandwich structures the bending loads are
carried by the facesheets and the shear loads are taken by the
lightweight core material. The facesheets are strong and stiff
in tension as well as compression while core material
maintains a high moment of inertia. The low density of the
core material results high mechanical properties compared to
the monocoque structures. Therefore, sandwich panels are
proficient in bearing bending loads.
A. Facesheet
In a sandwich structure the facesheets are of different
materials, it can be isotropic, anisotropic or composite
material. Aluminum, fiberglass, graphite and aramid are the
widely used facesheet materials. However, to minimize the
weight of the structure composite facesheets are used.
B. Core
The main component of the sandwich structures is the core
material. The various sandwich constructions depend upon
the type of the core. To maintain the effectiveness of the
sandwich structure the core must be strong enough to resist
the compressive load. The core also must be able to bear the
shear forces involved in it. If the core fails, the mechanical
advantage of structure is lost.
C. Adhesive
Adhesives are used to bond the the faces and the core with
each other. The role of adhesive is to transfer the shear forces
between the faces and the core . The adhesive must withstand
tensile stress as well as shear stress.The adhesive used to bond
the face layer with the core member is Epoxy resin.Epoxies
are polymerizable thermosetting resins . Epoxies are
applicable for use in resins for prepreg materials and structural
adhesives. The advantages of epoxies are high strength and
modulus, low levels of volatiles, excellent adhesion, low
shrinkage, good chemical resistance.
III. HEXA SQUARE STRUCTURE
The aim of this project is to introduce a new structure
known as Heteromorphic hexa square shape in the sandwich

2. International Journal of Mechanical Civil and Control Engineering
Vol. 1, Issue. 3, June 2015 ISSN (Online): 2394-8868
20
panels.Then,this new structure is analysed using Advanced
finite element software and also experimentally conducted.
Fig. 2 Pictureof hexa square structure.
The dimensions of the square and hexagon are 10.828 mm
and 12 mm.The distance between the adjacent hexagons and
adjacent squares are 12 mm and 10.828 mm.The length,width
and thicknes of the core are 200 mm,50 mm,15 mm while the
film thickness is 2 mm.
The length and width of the facesheet are 200 mm and 50
mm while the thickness is 1 mm each.
IV. DESIGN AND ANALYSIS OF HEXA SQUARE STRUCTURE
The hexa square sandwich panel is analysed using the
Advanced Finite element software known as ANSYS
Workbench 14.0 .The hexa square honeycomb panel is
modeled using the Three point bending test setup . Different
core materials such as Aluminium, GFRP (S-glass) and ABS
(Acrylonitritile butadiene styrene) are attempted while the
face material remains as Aluminium .A Load of 1000 N is
applied to the structure .The Equivalent Stress, Deflection and
shear stress are used to compare the different models to select
the optimum model out of them.
Fig. 3 Picture of the new hexa square honeycomb sandwich panel with
supports.
A. Analysis of Aluminium Model
Aluminium is chosen as the core as well as the face
material .
Fig. 4 Equivalent stress distributionin Aluminium Model .
Fig. 5 Deformationproducedin AluminiumModel .
Fig. 6 Shear stress distributionin Aluminium Model.
B. Analysis of ABS
Acrylonitritile butadiene styrene is chosen as the core
member while the face material is Aluminium.
Fig. 7 Equivalent stress distributionin ABSModel .

3. International Journal of Mechanical Civil and Control Engineering
Vol. 1, Issue. 3, June 2015 ISSN (Online): 2394-8868
21
Fig. 8 Deformationproducedin ABSModel .
Fig. 9 Shear stress distributionin ABS Model.
C. Analysis of S-glass
S-Glass is chosen as the core member while the face
material is Aluminium.
Fig. 10 Equivalent stress distributionin S-glass Model .
Fig. 11 Deformationproducedin ABSModel .
Fig. 12 Shear stress distributionin ABS Model.
V. EXPERIMENT ON HEXA SQUARE STRUCTURE
The Aluminium Core member is machined using Water Jet
Machining.
Fig. 13 Aluminium Core manufacturedusingWater Jet Machining.
The core member is first applied with epoxy resin on both
sides.Then, the face material is placed on the core member
and are bonded to themby using a press.While pressing a little
wax should be applied on the surface of the face material so
that the bonding does not get affected while removing the
press.
Fig. 14 Hexa square sandwich panel.
The Hexa Square Sandwich panel is placed on the
Universal Testing Machine with a span length of 100 mm.The
load is applied on the roller at the midspan. The maximum
load taken by the Aluminium sample while performing the
test is 7.160 KN.

4. International Journal of Mechanical Civil and Control Engineering
Vol. 1, Issue. 3, June 2015 ISSN (Online): 2394-8868
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Fig. 15 Deformedhoneycombsandwich panel.
VI. CONCLUSIONS
Thus we have optimized honeycomb structure and analysed
the hexa square sandwich panel using S-glass ,Aluminium and
ABS as the core material.The emphasis of this study is on
evaluation of deflection and stress response under static three
point bending condition .And then compare the results
obtained using the above materials and to state the best result
.From the analysis done ,it is found that S-glass is the suitable
material as core among the different materials tried as core
members.As well as the hexa square honeycomb offers better
deflection results in ANSYS as compared to the hexagonal
structure of same dimension.
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