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FINITE ELEMENT SIMULATIONS AND CHARACTERIZATION OF AIRBAGS

USING DOE

BHAGEERATHA K R1 & C ANIL KUMAR

2

1PG Student, Department of Mechanical Engineering, KSIT, Bangalore, Karnataka, India

2Professor, Department of Mechanical Engineering, KSIT, Bangalore, Karnataka, India

ABSTRACT

In the present study Low velocity impact tests have been carried out to study the energy absorption capabilities

of airbags, the main objective is to increase the energy absorption capabilities by minimizing the acceleration levels

and the number of bounces after the airbag impacts ground. In the present work, the effect of various parameters on the

energy absorbing capabilities of airbag are studied. The three parameters chosen for the present study are Airbag

Shape, Initial Pressure and the drop height.

Finite Element Method (FEM) and Design of Experiments (DOE) approach are used in order to achieve the

intended model objectives. The combination of both techniques is proposed to result in a reduction of the necessary

experimental cost and effort in addition to getting a higher level of verification. It can be stated that the Finite

Element Method coupled with Design of Experiments approach provides a good contribution in characterizing the

airbag.

The present work is divided into four phases, in the first phase Selection and testing of Airbag material is

carried out, where the material required for the airbag is chosen and tested according to ASTM standards to find out

the properties of the material. The second phase includes fabrication and testing of Airbags, Where three different

kinds of airbags (circular, cylindrical and rectangular) having same surface area are fabricated and tested according to

the Taguchi’s L9 Orthogonal Array experimental plan. In the third phase a Finite Element Model (FEM) which

represents the drop tests on the airbags (carried out in the Low Velocity Impact Test Rig) is developed in order to

evaluate the quality of the process parameters. In the fourth phase results are analyzed using Taguchi’s Signal to Noise

ratio technique, for both experimental testing and simulation of airbags to analyze the data and for the prediction of

optimum results. Finally the two methods are compared (FEM and Experimental) using DOE and the results are

analyzed to get the optimal set of process parameters.

KEYWORDS: Airbag, Shape, Pressure, Drop Height, Airbag Characterization, Finite Element Method, Design of

Experiments

INTRODUCTION

Research and investigations are being carried out to understand the intentional and unintentional injuries of human

beings in society. The injury level is not only causing unnecessary suffering for millions of victims but has also

tremendously increased the cost of aid provided to victims. Since awareness of preventive measures is increasing in

society, effort is focused on developing effective safety devices. Researchers, aided with information obtained by

investigators, have found new techniques to understand the dynamics involved in accidents resulting in injuries [1]. These

have either resulted in the design of new safety devices or helped in improving the existing ones.

International Journal of Automobile Engineering

Research and Development (IJAuERD)

ISSN 2277-4785

Vol. 3, Issue 4, Oct 2013, 23-34

© TJPRC Pvt. Ltd.

24 Bhageeratha K R & C Anil Kumar

In order to achieve optimum occupant safety inflatable restraint technology, commonly referred to as airbags has

been developed. Airbags are the inflatable restraints generally used to absorb the kinetic energy that is dissipated during

high speed crashes [2]. An airbag is a three dimensional structure capable of undergoing large deformations with non-

linear material properties, in recent years some efforts have been made to the design of airbags and improve their

performance in the crashworthiness studies of aircraft structures in low velocity impact.

SELECTION AND TESTING OF AIRBAG MATERIAL

Selection of Airbag Material

Woven fabrics have been the material of choice for materials used in safety air bag Construction. The latest

research on potential airbag materials including polyester fiber, Nylon 6,6, and Neoprene[3]. Among the three materials

Nylon has the advantages over the other two as it has better properties such it has

A high strength-to-weight ratio, Good elongation properties, Minimal weight for minimal space/thickness&

Insensitivity to temperature, It gives a good balance between the strength and elongation, hence acts as god airbag

cushion materials.

Thermodynamically it has high melting point and heat of fusion as compared to other common fibers like

polyester.

Testing of Airbag Material

Tensile and shear tests are conducted on airbag fabric with different orientation of the fabric to know the different

properties of fabric material. The different orientations Chosen for airbag testing are WARP, WEFT and SHEAR

directions.

Specimen Preparation and Testing of Airbag Fabric

Rate of Loading 2mm/min

Temperature 73 Deg F

Humidity 50%

Gauge Length of Specimen 150mm

Width of the specimen 50mm

Thickness of specimen 0.26 mm

Figure 1: Test Specimen According to ASTM (ASTM D579) Standards and Test Setup Conditions

In the present study sample specimens in the WARP (00), WEFT (90

0) and SHEAR (45

0) directions were

identified and marked on the airbag material roll received from manufacturer. The size and shape of the tensile and shear

test specimens are chosen according to the ASTM standards (ASTM D579) as shown below fig 1 and to carry out the

Finite Element Simulations and Characterization of Airbags Using DOE 25

tensile and shear testing on airbag fabric INSTRON- 5500 R Series Universal Testing Machine has been used. The test was

conducted with the following test setup conditions.

Results of Tensile and Shear Testing of Airbag Fabric

Based on the tensile tests, the results have are tabulated in the Table 1.

Table 1: Tensile Test Results for Airbag Material

Tensile Test Results for Airbag Material

Specimen Sample Max Load

(Pmax ) N

Ultimate Strength

(UTS) MPa

Max Elongation

mm Modulus MPa

Warp (0º)

1A 472.998 36.38 30.815 47.889

53.054 1B 488.082 37.54 27.333 58.108

1C 369.075 28.39 24.667 53.165

Weft (90º)

2A 764.113 58.77 38.599 86.720

94.356 2B 814.865 62.68 40.833 96.438

2C 818.964 62.99 41.660 99.91

Shear (±45o)

3A 355.136 27.31 84.197 3.569

3.972 3B 448.195 34.47 90.333 4.303

3C 503.884 38.76 95.831 4.043

AIRBAG FABRICATION AND TESTING

Airbag Fabrication

The airbag material was made up of nylon engineering fabric. This fabric was coated one side with Rubber

coating. To compare the response characteristics Airbags with three different shapes are fabricated. All the three Airbags

have same surface area. The three shapes selected are Circular Airbag, Rectangular Airbag, and Cylindrical Airbag.

The three types of airbags (Circular airbag of φ550mm, Rectangular Airbag of 594x400 and Cylindrical Airbag of

φ382 mm and length 205 mm) are fabricated by machine stitching and subsequent bonding around the seam. The required

fabric size was cut from the fabric roll and stitched. Then the stitching was carried out using the sewing machine with

nylon thread. Total three rows of stitching operation were carried out around circumferential direction.

After that, standard epoxy based adhesive with hardener is applied on the stitched area as well as the edge of the

fabric. After 24 hrs room temperature curing, the airbag is inverted and subsequent operations like making a compressed

air inlet port, pressure sensor port and airbag mount were carried out.

Once again epoxy adhesive is applied on to the seam of an inverted airbag in order to minimize the leakage

around the seam. Second time room temperature curing of adhesive was carried out before the airbag subjected to a

‘breathing’ operation.

In this process, inside volume of the airbag is filled with compressed air to avoid any wrinkles around the seam of

an airbag.

Airbag Testing

The airbag drop test studies are carried out in “Low Velocity Impact Test Rig” (LVITF).

The airbag drop test studies are carried out for the cross head mass of 8 kg (includes airbag mount mass), different

drop heights (180 cm, 130 cm and 80 cm) and at different pressures (0.4psig, 0.6psig, 1.0psig) and with different shapes

(Circular, Rectangular, Cylindrical).


Experiment Set up & Experimental Plan Using Taguchi’s Philosophy

Figure 2: Schematic Diagram of LVITF & Flowchart of the Taguchi Method

Taguchi’s philosophy is an efficient tool for the design of high quality manufacturing systems. Dr. Genichi

Taguchi, a Japanese quality management consultant, has developed a method based on orthogonal array experiments,

which provide much-reduced variance for the experiment with optimum setting of process control parameters and Steps

involved in the Taguchi method are presented in the form of a flowchart [4].

Based on Taguchi’s orthogonal array design, experiments have been conducted with three different levels of

process parameters: Shape of the airbag, Pressure of the airbag, and Drop height. Process parameters with their notations,

unit and values at different levels are listed in Table2 & 3. The output response is listed in table 4.

Table 2: Process Parameters and their Limits

SL.No Parameter Notation Unit Level1 Level2 Level3

1 Shape of the Airbag S - Circular Cylindrical Rectangular

2 Pressure of the Airbag P Psig 0.4 0.6 1.0

3 Drop Height H cm 80 130 180

Table 3: Fractional Factorial Experiment Plan

Airbag

Shape

Pressure

P1(Psig) P2(Psig) P3(Psig)

Drop Height

80cm 130cm 180cm 80cm 130cm 180cm 80cm 130cm 180cm

Circular Exp1 Exp2 Exp3

Cylindrical Exp4 Exp5 Exp6

Rectangular Exp7 Exp8 Exp9

Table 4: Output Responses for Drop Test

Experiment

No.

Peak

Pressure(Psig)

Peak

Acceleration(g)

Bounce

Height(mm)

Compression

(mm)

1 1.84 7.04 304.77 54.062

2 2.75 15.42 635.14 77.131

3 3.44 31.05 916.99 85.810

4 2.49 15.19 551.73 44.549

5 3.10 27.93 819.85 52.304

6 1.95 6.84 293.82 60.850

7 3.83 29.21 956.57 89.341

8 2.17 8.08 352.52 54.960

9 3.17 16.30 685.09 70.381


FINITE ELEMENT SIMULATION OF AIRBAGS

Finite Element simulation of Airbag Experiments (which have been carried out practically in Low Velocity

Impact Test Rig) using LS-DYNA simulation software coupled with HYPERMESH software and comparisons of

simulation results with the Experimental results [5] [6] & [7].[8]

Geometric Modeling

The Drop test Components have been modeled using CATIA modeling software. The Airbag and the rigid plates

are modeled using wireframe and surfaces work bench and they are assembled in assembly work bench. According to the

dimensioned as specified in the chapter 4, the airbags of three shapes (Circular, Cylindrical and rectangular) are modeled.

Then the rigid plate of dimension 1m x 1m is modeled. The models are the converted into IGES format to facilitate its

export to the HYPERMESH software.

Solution and Post Processing

LS-Dyna is used for solving Non-linear finite element analysis code. LS-PrePost is an advanced interactive

program for preparing input data for LS-DYNA and processing the results from LS-DYNA analyses. In the present study

LS-DYNA is used to carry out non liner explicit analysis. After solving the equations, LS-PREPOST module is used for

plotting the time history plots. In the present study three output parameters (pressure, acceleration, and drop height) are

studied to compare it with experimental results. The time history plots for the above said parameter are plotted for all the

drop test experiments conducted in LVITF, and compared with the experimental results.

Simulation of Airbags

The airbag simulations are carried out according to the Taguchi’s Fractional factorial method and Two materials

are chosen for the analysis are Fabric Material and Rigid Material. LS-DYNA provides separate material cards for the two

materials where the properties for the particular material can be entered. For Fabric material it uses MATL-34 material

card and for the rigid material it uses MATL-20 material card. The material properties assigned for the Airbag and Rigid

plate and the unit consistency followed in the present work are as shown the table 5& 6.

Table 5: Material Properties

Rigid Material Properties

Young’s modulus 2.07x105 MPa

Poisson’s ratio 0.3

Density 7.83x10-9

ton/mm3

Fabric Properties

Young’s Modulus

EA 94.5 MPa

EB 94.5 MPa

EC 94.5 MPa

Shear Modulus

GAB 3.972 MPa

GBC 3.972 MPa

GCA 3.972 MPa

Poisson’s ratio 0.3

Density 9.587x10-10

ton/mm3

Table 6: Airbag Properties

Specific heat of gas at constant pressure 1040 J/Kgo K

Specific heat of gas at constant volume 707 J/Kgo K

Ambient Pressure of the gas 101.3 Kpa

Ambient density 1.229 x10-12

ton/mm3

Surface Area of the airbag 475.2x103 mm

2


Figure 3: Drop Test Images of Airbags at Different Mass Flow Rate

Table 7: Simulation Results

Expt.

No

Peak Pressure

(psi)

Bounce Height

(mm)

Acceleration

(g)

Compression

(mm)

1 3.24 265.23 5.45 49.34

2 2.705 564.26 8.09 71.856

3 5.09 878.35 12.62 88.851

4 3.43 555.89 9.35 43.152

5 5.46 801.12 12.83 48.95

6 2.72 359.57 5.96 65.536

7 4.61 864.709 11.34 74.321

8 3.82 346.42 6.05 56.165

9 4.91 591.35 11.04 64.682

Table 8: Comparison Table for Different Output Responses

Expt

.No

Pressure(psi) Acceleration(g) Bounce Height(mm) Compression(mm)

Experiment Simulations Experiment Simulations Experiment Simulations Experiment Simulations

1 1.84 3.24 7.04 5.45 304.77 265.23 54.062 49.34

2 2.75 2.705 15.42 8.09 635.14 564.26 77.131 71.856

3 3.44 5.09 31.05 12.62 916.99 878.35 85.810 88.851

4 2.49 3.43 15.19 9.35 551.73 555.89 44.549 43.152

5 3.10 5.46 27.93 12.83 819.85 801.12 52.304 48.95

6 1.95 2.72 6.84 5.96 293.82 359.57 60.850 65.536

7 3.83 4.61 29.21 11.34 956.97 864.709 89.341 74.321

8 2.17 3.82 8.08 6.05 352.52 346.42 54.960 56.165

9 3.17 4.91 16.30 11.04 685.09 591.35 70.381 64.682

ANALYSIS OF AIRBAGS USING DESIGN OF EXPERIMENTS

It explains about the drop test experiments conducted on airbags using Low Velocity Impact Test Rig” (LVITF)

according to Taguchi’s L9 Orthogonal array principal and the analysis of the output parameters obtained from the

experiment using Signal to noise ratio technique [4], [5], [9],

Data Analysis Using Taguchi’s Signal-To-Noise Ratio

Taguchi’s philosophy is an efficient tool for the design of high quality manufacturing systems. Dr. Genichi

Taguchi, a Japanese quality management consultant, has developed a method based on orthogonal array experiments,

which provide much-reduced variance for the experiment with optimum setting of process control parameters. Thus the


integration of design of experiments (DOE) with parametric optimization of process is achieved in the Taguchi method.

This will provide desired results. The desired results refer to the acceptable quality parameters of the product.

An orthogonal array (OA) provides a set of well balanced (minimum experimental runs) experiments and

Taguchi’s signal-to-noise ratios (S/N), which is logarithmic functions of desired output; serve as objective functions for

optimization. This helps in data analysis and prediction of optimum results. In order to evaluate optimal parameter settings,

the Taguchi method uses a statistical measure of performance called signal-to-noise ratio [4]. The S/N ratio developed by

Dr. Taguchi is a performance measure to select control levels that best cope with noise. The S/N ratio takes both the mean

and the variability into account. The S/N ratio is the ratio of the mean (signal) to the standard deviation (noise). The ratio

depends on the quality characteristics of the product/process to be optimized. The standard S/N ratios generally used are as

follows: nominal-is-best (NB), lower-the-better (LB), and higher-the-better (HB).

Nominal the best characteristics

iance

mean

NS

varlog10

2

10

n

Y

Mean

n

i

i 1

1

1

2

n

MeanY

Variance

n

i

i

Smaller the better characteristics

n

Y

NS i

i

2

10log10/

Larger the better characteristics

i

iYNS

210

1log10

Where n is the number of observations and Y is the observed data. For each type of the characteristics, with the

above S/N ratio transformation, the higher the S/N ratio corresponds to the better result. Therefore, the optimal level of the

process parameter is the level with the highest S/N ratio.

Analysis of Results for Experimental Airbag Drop Test

By using the experimental data from table 1, the Signal to noise ratios for each of the features of peak pressure,

peak acceleration, bounce height and compression have been calculated and tabulated in table 9.

The objective is to obtain the factor combination that would optimize S/N ratio, i.e. maximize S/N ratio

(higher-the-better for compression) or minimize S/N ratio (lower-the-better for peak pressure, peak acceleration and

bounce height). To evaluate quantitatively the degree of significance of process parameters on selected response(s),

Taguchi’s signal-to-noise ratios technique has been adopted.

Based on statistical analysis of the collected data, this method can infer which factor is the most significant in

influencing output features associated with peak pressure, peak acceleration, bounce height and compression.

Irrespective of the quality characteristic chosen for a particular response, a greater S/N ratio corresponds to better

quality characteristics. Therefore, the optimal level of the process parameters is the level which ensures greatest S/N ratio.

With the S/N optimization, the optimal parametric combination can be predicted.


Table 9 represents the S/N ratios corresponding to experimental results for all the features of peak pressure, peak

acceleration, bounce height and compression.

Table 9: Signal to Noise Ratio Plots for Experimental Airbag Drop Test

Expt

No.

S/N Ratio for

Peak Pressure

S/N Ratio for

Peak Acceleration

S/N Ratio for

Bounce Height

S/N Ratio for

Compression

1 -5.2964 -16.9515 -49.6794 34.6578

2 -8.7867 -23.7617 -56.0574 37.7446

3 -10.7312 -29.8412 -59.2473 38.6708

4 -7.9240 -23.6312 -54.8345 32.9768

5 -9.8272 -28.9214 -58.2747 34.3707

6 -5.8007 -16.7011 -49.3616 35.6852

7 -11.6640 -29.3106 -59.6143 39.0210

8 -6.7292 -18.1482 -50.9437 34.8009

9 -10.0212 -24.2438 -56.715 36.9491

Signal to Noise Ratio Plots for Experimental Airbag Drop Test

rectangulacylindricalcircular

-6.0

-7.2

-8.4

-9.6

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-9.6

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s

pressure

Dropheight

Main Effects Plot for SN ratiosData Means

Signal-to-noise: Smaller is better


-20

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1.00.60.4

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-20

-25

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shape

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of

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ra

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Dropheight



Figure 4 & 5: Main Effect Plot of S/N Ratio for Peak Pressure & Peak Acceleration


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Dropheight




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pressure

Dropheight


Signal-to-noise: Larger is better

Figure 6 & 7: Main Effect Plot of S/N Ratio for Bounce Height & Compression

Signal to Noise Ratio Tables for Experimental Airbag Drop Test

Table 10 & 11: Response Table for Signal to Noise Ratios of Peak Pressure & Peak Accelerations


Table 12 & 13: Response Table for Signal to Noise Ratios of Bounce Height & Compression

The figures 4, 5, 6, 7 reveals the S/N response plot for Peak pressure, peak acceleration, bounce height, and

compression respectively. For all categories of quality performance criteria, the higher S/N ratio provided smaller variance

of the output characteristics above the desired target.

We can see from the tables 10, 11, 12, 13 and graphs (fig 4, 5, 6, 7) that, the factor with the most significant

impact on the S/N ratio for peak pressure is Drop height (Delta =4.799, Rank = 1). It can be seen from the response table

and main effects plot for S/N ratio that, the Pressure 0.4, 0.6, and 1.0 have almost the same average S/N ratio (-8.295, -

8.448, -8.851). The shape has considerable effect on S/N ratio. The factor with the most significant impact on S/N ratio for

the Peak Acceleration, is also Drop height (Delta =12.09, Rank = 1). We can see from the response tables and main effects

plot for S/N ratio, the Pressure and shape have almost the same average S/N.

The factor with significant impact on S/N ratio for Bounce height is again Drop height (Delta=9.05, rank=1). The

Pressure and shape have almost the same average S/N.

For the compression Shape have the biggest impact on S/N ratio (Delta=2.68). For the maximum energy

absorption capacity of the airbag compression should be maximum and hence larger the better S/N ratio is adopted, the

circular shape has under gone maximum compression followed by rectangular and cylindrical. The drop height and

pressure has considerable effect on the compression.

Doe for Airbag Simulations

Finite Element Simulations is carried out for the airbag drop test, with three different levels of process parameters:

Shape of the Airbag, mass flow rate into the Airbag, and Drop Height. The design matrix has been selected based on

Taguchi’s orthogonal array design [4]. Drop test studies were carried out on Circular Airbag (φ550 mm), Rectangular

Airbag (Length 594mm and breadth 400mm) and Cylindrical Airbag (φ382 mm and 205 mm length) from three different

heights (180cm, 130cm, and 80cm) and with three different mass flow rates (3kg/sec, 4kg/sec, and 5kg/sec). The responses

measured from the drop tests are Pressure Variation inside the Airbag, Bounce Height, Accelerations, and Compression of

Airbag. Taguchi’s Orthogonal Array plan for the design of airbag simulations are given in the table 3 and Signal to Noise

ratio for the output response are given in table 14.

Table 14: Signal to Noise Ratio for the Output Response of Airbag Simulations

Expt.No S/N Ratio for

Peak Pressure

S/N Ratio for

Accelerations

S/N Ratio for

Bounce Height

S/N Ratio for

Compression

1 -10.2109 -14.7279 -48.4725 33.8640

2 -8.6433 -18.1590 -55.0296 37.1293

3 -14.1344 -22.0212 -58.8734 38.9732

4 -10.7509 -19.4162 -54.8998 32.7000

5 -14.7439 -22.1645 -58.0740 33.7951

6 -8.6914 -15.5049 -51.1157 36.3296

7 -13.2740 -21.093 -58.7374 37.4222

8 -11.6413 -15.6351 -50.7921 34.9893

9 -13.8216 -20.8594 -55.4369 36.2157


Signal to Noise Ratio Plots for Airbag Simulations

rectanglarcylindricalcircular

-10

-11

-12

-13

-14

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mass flow(Kg/sec)

drop height(cm)




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-18.0

-19.5

-21.0

Shape

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s

mass flow(Kg/sec)

drop height(cm)



Figure 8 & 9: Main Effect Plot of S/N Ratio for Peak Pressure & Peak Acceleration


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mass flow(Kg/sec)

drop height(cm)


Signal-to-noise: Larger is better

Figure 10 & 11: Main Effect Plot of S/N Ratio for Bounce Height & Compression

Signal to Noise Ratio Response Tables for Airbag Simulations

Table 15 & 16: Response Table for Signal to Noise Ratios of Peak Pressure & Peak Accelerations

Table 17 & 18: Response Table for Signal to Noise Ratios of Bounce Height & Compression

The figures 8, 9, 10, 11reveals the S/N response plot for Peak pressure, peak acceleration, bounce height, and

compression respectively. For all categories of quality performance criteria (LB or HB), the higher S/N ratio provided

smaller variance of the output characteristics above the desired target.


From the signal to noise ratio plots and the response tables (15, 16, 17, 18) the factor with the most significant

impact on the S/N ratio for peak pressure, peak acceleration and bounce height is Drop height of the airbag, but for the

compression, Shape is the most significant factor. For the maximum energy absorption capacity of the airbag compression

should be maximum and hence larger the better S/N ratio is adopted, the circular shape has under gone maximum

compression followed by rectangular and cylindrical. The drop height and pressure has considerable effect on the

compression.

SUMMARY

In this chapter a detailed methodology of the Taguchi optimization technique for experimental testing of airbags

and the airbag testing by simulations is explained and applied for evaluating optimal parametric combinations to achieve

acceptable features of peak pressure, peak acceleration, bounce height and compression.

By comparing the signal to noise ratio plots for experimental testing and simulation of airbags the most significant

factor for peak pressure, peak acceleration and bounce height is Drop height of the airbag but for the compression shape of

the airbag is most significant factor. For the maximum energy absorption capacity of the airbag compression should be

maximum and hence larger the better S/N ratio is adopted, the circular shape has under gone maximum compression

followed by rectangular and cylindrical. The drop height and pressure has considerable effect on the compression.

CONCLUSIONS

In the present work the energy absorption capabilities of airbag have been studied by conducting drop tests on

airbag using low velocity impact test rig, the main objective is to increase the energy absorption capabilities by minimizing

the acceleration levels and the number of bounces after the airbag impacts ground. In the present work, the effects of

various parameters (shape, pressure, drop height) on the energy absorbing capabilities of airbag are studied.

Nylon fabric is chosen as airbag material because of its advantages over the other material such as polyester,

neoprene fabrics. The elastic properties of the material are calculated by conducting tensile and shear testing according to

the ASTM standard.

Three types of airbags with same surface area are fabricated and the experiments are conducted according to the

Taguchi’s L9 orthogonal array method with three factors (shape, pressure, drop height) at three different levels of process

parameters. From the experiments it was found that an average compression was achieved more in case of circular airbag

and less for cylindrical airbag and hence it can be concluded that circular airbag has more energy absorption capabilities

compared to other two types. The acceleration levels are more in case of rectangular airbag and least for cylindrical air bag.

Finite Element Model (FEM) representing an airbag drop test was developed in order to evaluate the quality of the

process parameters. Simulation model tests are carried out according to the Taguchi’s L9 orthogonal array with three

factors (shape, mass flow rate, drop height) at three different levels. The FEA model was validated by comparing it with

the experimental model. It is possible to reduce the lead-time by using the Finite Element Analysis in conjunction with

Design of Experiment technique in the design process, where computer simulations can replace many time consuming

experiments. This will make the design process faster and more reliable.

By comparing the signal to noise ratio plots for experimental testing and simulation of airbags the most significant

factor for peak pressure, peak acceleration and bounce height is Drop height of the airbag but for the compression shape of

the airbag is most significant factor. For the maximum energy absorption capacity of the airbag compression should be


maximum and hence larger the better S/N ratio is adopted, the circular shape has under gone maximum compression

followed by rectangular and cylindrical. The drop height and pressure has considerable effect on the compression.

SCOPE OF FUTURE WORK

In the present work the energy absorption capabilities have been studied for the non porous plain airbags, it can be

extended to the porous airbags and also airbag with vents. Currently airbag has been inflated using air compressor, but it is

difficult to maintain the initial pressure using compressor and hence in the future work airbag inflation can be carried out

using explosives like sodium azide which is the faster method of inflation process.

REFERENCES

1. Jaikanth B. Kumblekere, A Parametric Evaluation Of Vehicle Crash Performance”, College of Engineering and

Technology Ohio University, 1996.

2. Civil Aviation Regulation “Proposed Airworthiness Directive, General series- Upper Torso Restraints for

Occupants in Small Aircraft”, 1998-part39.

3. Jialin Sun, John A. Barnes “Materials Selection for Airbag Fabrics” Airbag End-Use Technology, DuPont

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