Modal Analysis of Honeycomb Structure With Variation of Cell Size

7/21/2019 Modal Analysis of Honeycomb Structure With Variation of Cell Size

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Modal Analysis of Honeycomb Sandwich Panel by VaryingCell Size

Amey GongleBE (Mechanical)

G H R C O E M

Ahmednagar

[email protected]

Prateek GaikwadBE (Mechanical)

G H R C O E M

Ahmednagar

[email protected]

ABSTRACT

The purpose of this paper is to find out the effect of the cell

size on basic natural frequency of the Aluminium honeycomb

sandwich panels with the help of software package and by

finite element methodology. Modal Analysis was conducted

on hexangular honeycomb structure of cell sizes of six, nine

and twelve millimeter by keeping face sheet thickness

constant of one millimeter. Each model is analyzed

underneath a similar loading and boundary conditions. Modal

analysis of the all models is performed on ANSYS and the

results are compared.

.

General Terms:

Sandwich structure,

Keywords:

Cell size, Honeycomb Structure, Sandwich

1. INTRODUCTION

Honeycomb sandwich panels are finding its use in many fieldssuch as thermal and structural applications. These panels areextensively used in structural applications due to theirproperties such as high strength to weight ratio, high energyabsorbing capacity, bending stiffness etc. Due to suchproperties honeycomb panels are used for design andconstruction of lightweight transportation systems such assatellites, aircrafts, rocket fins, high speed trains, fast ferrieswhere structural weight reduction is of prime importance.

Fig. 1:Construction of honeycomb panel

Construction of a honeycomb sandwich structure consists oftwo high strength face sheets which are separated bylightweight core as shown in fig. 1. Materials extensively used

for manufacturing of honeycomb panels are aluminium alloys,high tensile steels, titanium and composites which are chosenaccording to purpose.

While development of an honeycomb structure, scaling ofhoneycomb properties with respect to its cell size in veryimportant. Variation in cell size has significant impact on variousproperties of the panel. In current paper, we have studiedaluminium alloy panel with 3 different cell sizes 6, 9, and 12 mmto understand the effect of cell size on the their fundamentalfrequencies.

Fig. 2:Nomenclature of an hexagonal honeycomb cell

Where, l: Length of the side of hexagonal coret: Face sheet thicknessdc: cell size

2. Methodology

Aluminium honeycomb sandwich panel (Al 3003 H19) wasused for the study purpose. Table 1 shows the elastic

properties of the used aluminium.

Table 1: Properties of Aluminium:

Material

YoungsModulus

Ef(MPa)

ShearModulus

Gf(MPa)

Density1

(kg/m3)

Poissonsratio

Aluminium 69500 25000 2700 0.33

Honeycomb sandwich panel has homogenous isotropicproperties. For analytical calculations Equivalent Rigidity Theory

was used. Formula used for calculations are as follows:

Eq. thickness= teq= (3hc2+ 6 hc tf + 4 tf2)0.5


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Eq. Youngs modulus= Eeq= (2tf/ teq)* Ef

Eq. Modulus of rigidity= Geq= (2tf/ teq)* Gf

Eq. Density= eq= [2 1tf+ 2 2(H-tf)] / teq

Where,

hc= Height of the core

tf= Face sheet thickness

2= Density of the core

H= (Total height of panel) / 2

For the analysis purpose 3 models were used with 3different cell sizes of 6, 9 & 12 mm by keeping the face sheetthickness (tf) 1 mm constant and the core height (hc) of thepanel is 18 mm which Is also kept constant. Specimenconsidered for the study purpose is an equivalent plate of

dimensions 500 mm * 500 mm considering it simplysupported beam. In ANSYS software modal analysis ofequivalent plates was done by applying frequency in therange of 0-10000 Hz.

3. Result:

Analysis was done on the equivalent plate. 3d

model of the sandwich plate is shown in fig. 3.

Equivalent elastic properties of the sandwich panels

with different core cell sizes are shown in table 2.

Table 2: Eq. Elastic properties of sandwich panel

with different core cell sizes:

CoreCellSize

teq

mm

Eeq

MPa

Geq

MPa

eq

Kg/mm3

6

32.92 4222.35 164.03

200.96

0.339 194.65

12 186.99

Following data were obtained after performing analysis ofequivalent plate:

Sr.

No.

Cell Size

(mm)

Minimum

Frequency (Hz)

Maximum

Frequency (Hz)

1. 6 629.5 2140.5

2. 9 653.78 2223.1

3. 12 667.1 2268.1

It can be observed that the cell size of a honeycomb sandwich

panel has a significant impact on its natural frequency. With an

increase in cell size of the honeycomb structure, its natural

frequency also increases. Figures 4-6 show the elementalanalysis results.

Fig 3: A 3D model of the equivalent plate

Fig. 4: Mode shape for Eq. plate with cell size 6 mm



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4. Conclusion

The fundamental frequency ranges for a simply supported

aluminium honeycomb sandwich plate of 3 different cell sizeshave been determined by performing modal analysis. The

results have shown that with an increase in the cell size, the

corresponding maximum frequency also increases.

5. Acknowledgement

We would like to express our heartfelt thanks to our guide Mr.

Pradip Lande for his appropriate guidance and encouragement,

especially through difficult times. His suggestions have

broadened our vision and have guided us to succeed in our

research. We are also grateful for his critique and guidance

during the designing part of our paper and we have learntmany things under his leadership.

We would like to express our appreciation for the wonderful

experience while completions of this paper work.

6. References

[1] Somashekhar G. Ganiger, Impact Analysis of

Composite Sandwich Structure Bumper Beam for

Passenger Vehicles

[2] S Prabhakaran, K. Chinnarasu, M. Senthil Kumar

Design and Fabrication of Composite Bumper for Light

Passenger Vehicles, International Journal of Modern

Engineering Research (IJMER) Vol.2, Issue.4, July-Aug.

2012

[3] Mr. Nitin S. Motgi, Prof. S. B. Naik, Prof.P.R.Kulkarni,

Impact Analysis of Front Bumper, International

Journal of Engineering Trends and Technology (IJETT)

Volume 6 Number 5- Dec 2013

[4] Jeom Kee Paik, Anil K. Thayamballi, Gyu Sung Kim, The

strength characteristics of aluminum honeycomb

sandwich panels, Department of Naval Architectureand Ocean Engineering, Pusan National University,

Pusan 609-735, South Korea

[5] Sourabha S. Havaldar, Ramesh S. Sharma, Arul Prakash

M. D. Antony, Mohan Bangaru, Effect of Cell Size on the

Fundamental Natural Frequency of FRP Honeycomb

Sandwich Panels, Journal of Minerals and Materials

Characterization and Engineering, 2012, 11, 653-660

Modal Analysis of Honeycomb Structure With Variation of Cell Size

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