Static Test for Aircraft Structure

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EAS 3923 AEROSPACE LABORATORY III

SEMESTER 2, 2012/2013

LAB REPORTEXPERIMENT 1 & 2

STATIC TEST FOR AIRCRAFT STRUCTURE

METAL & NON-METAL

Group Members:

No. Name Matric No. Task

1 Teh Wen Sun 158496 Introduction

2 Mohd Nizam Bin Hassan 160541 Discussion no.1- 4

3 Tee Siok Boon 159484 Objectives, Apparatus, Method,

Conclusion, References

4 Chan Teng Yan 157388 Discussion no. 5-7

5 Ali Yousefian 159896 Theory

6 Syafiq Syahmi bin Sazali 157654 Results

Date of Experiment 28/03/2013

Name of Lecturer Dr Dayang Laila Abang Abdul Majid

Name of Demonstrator Mr Ahsan Nur Mubarak Zahari @ Annuar

Name of Technician Mr Mohd Suhardi Ali

DEPARTMENT OF AEROSPACE ENGINEERINGUniversity Putra Malaysia43400 UPM SerdangSelangor Darul Ehsan, Malaysia.Tel: +603 89466400 Fax: +603 86567125

Email: [email protected]


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1.0 IntroductionIn this experiment, static test for aircraft structure which includes metal and non -metal is carried

out. For metal, aluminium 6061 plate is used. For non-metal, carbon-glass fibre composite plate

is used. From the experiment, the value of Modulus Young of the aluminium and composite

material is determined in order to identify its material behavior so that suitable material could be

selected for design of aircraft part in relevant to air stress. In order to determine the value of

Modulus Young, the deflection of plates due to load is determined, then the graph of force

against the deflection of the plate is plotted. From the graph, the gradient of the curve

corresponds to . Hence, Modulus Young can be determined.

The Modulus Young has importance in calculated the deflection or extension of beams due toapplied loads, enabling an induced stress to be converted into a strain. As strain is defined as the

(change of length)/(original length), then the movement of the structural member can be

calculated. In other words, The Modulus Young represents the strength of material. The higher

the value, the stronger is the material. Knowing the strength of material is very important when

engineers want to select the materials to design an aircraft.

Besides, static load test is significant to determine which material should be used to design

parts of aircraft relevant to the conditions. This is to avoid the damage or permanent deformation

of the relevant aircraft structures when they are exposed to a critical environment condition

when the airplane is cruising in the free stream. In addition, the test is also use to analyze the

structure to ensure that it will meet the ultimate design condition without collapse.

2.0 Objectives To give early exposure in practical about how materials can be tested for static load

To investigate the important of Modulus Young for material behaviour.


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3.0 TheoryDeflection is displacement of a structural member under a load. In this experiment, a fixed and

free end beam was used. Deflection can be calculated by Castiglianos method.

= 0 ; = , = According to Castiglianos theorem,

=

=

=3

=

3

The gradient of the graph (F/) indicated the strength of the material. The steeper the slope the

stronger the material is. In short, from the slope of the curve, we can choose either to use the

aluminium material or the composite material to be a part of aircraft structure.

Moment of Inertia I measures the resistance of an object to changes in rotation direction. In

this experiment, the member used is rectangular section. For rectangular beam,

= 12 where h is the dimension in plane of bending

The reason for finding the value of deflection of the plate is to determine the slope of the curve.

From the slope of the curve, we can determine the values of Youngs Modulus.

Metals have mechanical properties of higher strength, ductility, high bending stiffness, and

A

F

V

M

x


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toughness compared to non-metal. According to technical data, aluminium 6061 has modulus of

elasticity at 70-80 GPa. However, composite materials (non-metal) are more chosen to be used in

aerospace industry nowadays due to its high strength-to-weight ratio. Carbon-glass fibre

composite material that is joined using matrix such as carbon-glass and fibre has higher strength

to weight ratio. Carbon-glass fibre composite has modulus of elasticity is in the range 200-

350GPa.

4.0 Apparatus Load cells Specimens- aluminum plate and carbon composite plate G-clamp Ruler Tape

5.0 Method1. The aluminum plate was placed on the edge of the table by using G-clamp.2. The 0.1N load cell was placed at the edge of the aluminum plate.3. The initial deflection was measured by using a ruler and recorded.4. The loading was increased at 0.1N increment.5. The previous procedure was repeated for three times.6. The reading was taken and load vs displacement graphs were plotted.7. These steps were repeated by replace the aluminum plate with carbon composite plate.


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6.0 Results6.1Metal element: Aluminium 6061

Length, L = 30 cm Width, b = 7.1 cm Thickness, h = 0.09 cm

Force(N)

Deflection, (cm)average(cm)

1 2 3

0.1 0.30 0.30 0.30 0.30

0.2 0.60 0.60 0.65 0.62

0.3 0.90 0.95 0.90 0.92

0.4 1.20 1.35 1.30 1.28

0.5 1.60 1.65 1.55 1.60

0.6 1.90 1.85 1.90 1.88

0.7 2.35 2.40 2.30 2.35

0.8 2.60 2.55 2.70 2.620.9 2.90 3.00 3.00 2.97

1.0 3.20 3.30 3.20 3.23

1.1 3.50 3.70 3.70 3.63

1.2 4.10 4.10 4.00 4.07

1.3 4.40 4.20 4.40 4.33

1.4 4.80 4.70 4.60 4.70

1.5 5.00 5.20 5.10 5.10

1.6 5.30 5.40 5.30 5.33

1.7 5.60 5.70 5.60 5.63

1.8 6.00 6.10 6.00 6.03

1.9 6.40 6.50 6.30 6.40

2.0 6.80 6.70 6.80 6.77

Table 1: Deflection measured for metal element

Graph 1: Force against Deflection for Aluminium Beam

y = 0.2992x

0

0.25

0.5

0.75

1

1.25

1.5

1.75

2

2.25

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5

ForceF(N)

Deflection (cm)

Graph of Force against Deflection for Aluminium Beam


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6.2Non-Metal: Carbon-glass Fibre CompositeLength, L = 34.4 cm Width, b = 9 cm Thickness, h = 0.09 cm

Force

(N)

Deflection, (cm)average (cm)

1 2 3

0.1 0.30 0.30 0.30 0.30

0.2 0.60 0.50 0.60 0.57

0.3 0.90 0.90 0.90 0.90

0.4 1.10 1.10 1.20 1.13

0.5 1.40 1.50 1.50 1.47

0.6 1.70 1.70 1.60 1.67

0.7 1.90 1.90 1.90 1.90

0.8 2.20 2.20 2.20 2.20

0.9 2.40 2.50 2.40 2.43

1.0 2.60 2.60 2.60 2.60

1.1 2.90 2.90 2.90 2.90

1.2 3.10 3.10 3.20 3.13

1.3 3.40 3.50 3.40 3.43

1.4 3.80 3.70 3.80 3.77

1.5 4.10 4.10 4.10 4.10

1.6 4.30 4.20 4.30 4.27

1.7 4.40 4.50 4.50 4.47

1.8 4.70 4.80 4.70 4.73

1.9 5.00 4.90 4.90 4.93

2.0 5.20 5.30 5.30 5.27

Table 2: Deflection measured for Non-Metal element

Graph 2: Force against Deflection for Carbon-glass Fibre Composite Beam

F = 0.3766

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5

ForceF(N)

Deflection (cm)

Graph of Force against Deflection for Carbon-Glass Fibre Beam


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7.0 Discussion7.1 From the graphs you have constructed, obtain the line equations. Discuss the relation

between both load and displacement.

For Metal (Aluminium 6061), the line equation obtained is F = 0.2992 . Hence, the gradient

(load/displacement) is 29.92 N/m. From the graph, we can conclude that as the load increases,

the vertical displacement (deflection) of the beam increases proportionally. This is consistent

with Hookes law of elasticity .

For Non-Metal (Carbon-glass fibre composite), the line equation obtained is F = 0.3766 .

Hence, the gradient (load/displacement) is 37.66 N/m. From the graph, we can conclude that as

the load increases, the vertical displacement (deflection) of the beam increases proportionally.

This is consistent with Hookes law of elasticity where it states that the deflection of a material

is directly proportional to the force/load applied as long as the proportionality limit is not

exceeded.

7.2 From the deflection formula, calculate E for both metal (Aluminum) and non-metal(Composite).Ref: Mechanics of Materials

For fixed and free end beam with load applied at the free end of the beam, the maximum

deflection measured at the free end of the beam is given by

= 3where = 12

therefore,

= 4

(

)

For Metal (Aluminium 6061),

Modulus Young = 40.30.0710.0910 29.92= .

For Non-Metal (Carbon-glass fibre composite),

Modulus Young =40.344

0.090.0910 37.66

= .


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7.3 Briefly discuss the difference between these two materials. The Youngs modulus of carbon-glass fibre composite (93.46 GPa) is higher than that of

aluminium 6061 (62.43 GPa). Youngs modulus indicates the slope of the elastic portion of the

curve that shows the tendency of the material to the elasticity. The higher the value of Youngs

modulus, the higher the load required to stretch the carbon-glass fibre composite. This means

that carbon-glass fibre composite has higher stiffness than aluminium 6061.

7.4 Draw a graph between load and the displacement of the materials.

Graph 3: Comparison of slope between aluminium and composite

7.5 From these experiments, what is the significant of Modulus Young in real life? Give youropinion.

Modulus Young measures the tendency of a material to deflect or stretch due to a load applied

and hence the stiffness of the material. In real life, Modulus Young is used to determine the

suitability of a material in sustaining high load. For example, in design of aircraft wing, it is

important to choose wing that has high stiffness so that the wing is capable of withstand high

compressive stress due to the air. A wing that is high in Modulus Young could not change its

structure easily even due to high stress. Therefore, materials are selected based on ModulusYoung in order to have stronger aircraft structure.

F = 0.2992F = 0.3766

0

0.5

1

1.5

2

2.5

0 1 2 3 4 5 6 7 8

ForceF(N)

Deflection (cm)

Graph of load against vertical displacement

Aluminium

Composite


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7.6 Find and compare the bending stiffness of the two materials. Suggest way(s) to increase thebending stiffness for a cantilever wing.

For aluminium 6061,

Bending stiffness = = 12 = 62. 43 10 0.0710.0910

12 = 0.26 NmFor carbon-glass fibre composite,

Bending stiffness = = 12 = 93. 46 10 0.090.0910

12 = 0.51 NmComposite has a higher bending stiffness compared to aluminium. Since the fibre in the

composite is stiffer, each fibre will be carrying a larger stress. Hence, the composite has higher

bending stiffness.

To increase the bending stiffness of a cantilever wing, the moment of inertia of the wing has to

be increased. To increase the moment of inertia, stiffeners, stringers, spars, and ribs are added

into the wing structure. All of these components will lead the wing to have higher moment of

inertia, and hence contribute to higher bending stiffness.

7.7 Comparing the same thickness of 0 swept, 0-0-0 stacking sequence carbon-glass-carbonwhat would you expect the Youngs Modulus to be? Would there be any effect on Youngs

Modulus with variation of stacking sequence?

Composite of 60-0-60 stacking sequence is used in this experiment. However, 0-0-0 stacking

sequence carbon-glass-carbon would have lower Youngs modulus compared to the one used in

this experiment. For 0-0-0 stacking sequence carbon-glass-carbon composite, the angles of top

and lower ply are the same and thus it does not contribute much change in moment of inertia

due to force applied and hence lower Modulus Young is developed. For composite with 60 -0-60

stacking sequence, each ply of fibres has its own directional which constraint the move when it

is laminated with plastic and it becomes more resistant to forces in more directions. Hence, it

has higher Modulus Young.

The results obtained in this experiment are somewhat deviated from actual value. This could be

due to errors in measuring the deflection. The location of measurement was not exactly taken at

the end of the beam. Error could be arisen when load is not placed at one particular place

throughout the experiment and is not at the end of the beam.


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8.0 ConclusionAt the end of the experiment, an exposure in practical about how materials can be tested for

static load was gained. The importance of Modulus Young for material in determination of the

best aircraft structural material behavior was investigated.

9.0 References1. Elliott, R. (2001).Deflection of Beams. Retrieved from: http://www.clag.org.uk/beam.html2. Hibbeler, R.C. (2011).Mechanics of Materials, 8th edition. US: Prentice Hall Inc.3. Hoppel, C.P.R., and Teresa, S.J.D. (1999).Effect of an Angle-Ply Orientation on Compression

Strength of Composite Laminates. Maryland: Amry Research Laboratory.

4. Kalpakjian, S. (2010).Manufacturing Engineering and Technology, 6th edition. New York:Pretice Hall.

5. Sun, C.T. (1998).Mechanics of Aircraft Structures. Canada: John Wiley & Sun
http://www.clag.org.uk/beam.htmlhttp://www.clag.org.uk/beam.htmlhttp://www.clag.org.uk/beam.html

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Static Test for Aircraft Structure