composite structures lab manuel

8/13/2019 Composite Structures Lab Manuel

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SATHYABAMA UNIVERSITY

CHENNAI 600 119

DEPARTMENTOF AERONAUTICAL

ENGINEERING

SAEX 4011 COMPOSITE STRUCTURES LAB MANUAL


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CO NTENTS

LIST OF EXPERIMENTS

1. Fabrication of glass epoxy laminates using hand layup

process.

2. Fabrication of Carbon polyster laminate using compression

moulding

3. Fabrication of glass fiber filament wound pipes using

filament winding machine

4. Calculation of material properties of bi directional composite

laminate

5. Determination of material properties of cross ply laminate

6. Determination of shear modulus of composite laminate

7. Fabrication of sandwich beam

8. Determination inter laminar shear strength of a composite

laminate

9. Failure analysis of composite laminate using matlab

10.Determination of material properties using plate theory


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1.FABRICATION OF CLASSEPOXY LAMINATES USING HAND LAYUP PROCESS

AIM :

i) To fabricate Fiber reinforced laminated (FRP) composites using hand layup process

ii) To determine the void fraction of the laminate

iii) To determine the density of the laminate

iv) To determine the fiber volume fraction

APPARATUS AND MATERIALS REQUIRED:

Scale, Roller, weighing balance, Glass fabric, epoxy resin and accesories

PROCEDURE :

1. Thoroughly clean the aluminum plate using acetone or a detergent. Then apply mold-release agent to thetop surface of the aluminum plate twice.

2. Lay one sheet of Teflon film and the peel-ply nonstick nylon cloth on the aluminum plate. The Teflon film

is used to release the lay-up from the aluminum plate, and the peel-ply is used to achieve the required surface

finish on the laminate. Note: There should be no wrinkles or raised regions in the peel ply, and its dimensions

should be identical to those of the laminate.

3. Cut the given glass oven fabric cloth into required size(1feetx1feet).No of ply is based on the required

thickness. Weigh the fabric using weighing balance.

4. Now measure the epoxy LY556 resin whose weight is equivalent to 100% of the fiber weight. Add

hardener(HY 956) of weight 10% weight of the resin and stir well.

5.Using painting brush apply this epoxy hardener mix over the Teflon sheets.6.Lay one layer fiber cloth over the plate then again apply the resin over the fiber cloth. This process is

repeated until the desired thickness is achieved. Excess resins are removed using roller.

7. Laminates are left to cure under standard atmospheric conditions for about 24 hours.

8. Fiber /resin volume fraction can be determined using digestion test.

9. Density of the laminate can be determined using buoyancy test.10.Void fraction

OBSERVATION :

C . S dimensions of the specimen =


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TABULATION :

Sl .No Load in N Cross sectional area of

the specimen

( mm2)

Compressive strength

N / mm2

CALCULATION:

Ultimate compressive load

Compressive strength of the given specimen =

C. S area of the specimen

RESULT :

The compressive strength of the given specimen =


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2.DEFLECTION TEST

AIM :

To determine the Youngsmodulus of the given material and verify Maxwells

law of reciprocal deflection .

APPARATUS :

1. Knife edge supports

2. Deflectometer

3. Set of weights with hanger.

4. Scale5. Vernier caliper .

PRINCIPLE :

According to Maxwells law of reciprocal deflection in a simply supported beam

AB = BA

where AB Deflection of the beam measured at A due to the load at B

BA Delection of the beam measured at B due to the load at A

PROCEDURE :

1. Measure the dimensions of the beam.

2. Place the given beam on knife edge supports with equal overhangs on either side

of the beam .

3. Place the deflectometer at a distance xfrom the support.

4. Place the weight hanger at a distance of a from the support. Note the initial

reading of the deflectometer.


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5. Now increase the load gradually and take the corresponding deflectometer

readings.


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6. Now decrease the load in the same intervals and note the deflectometer

readings.

7. Draw a graph Load vs Deflection .

OBSERVATION :

x < a & x < b

C . S . dimensions of the beam =

Span ( l ) =

Distance ( x ) =

Distance ( a ) =

Distance ( b ) =

TABULATION :

S.No Load

Deflectometer reading Young

modul

in

N/mm

x < a x < b

gm N Loading Unloading Mean Loading Unloading Mean

1.

2.

3.

4.

5.

6.


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CALCULATION:

x < a

w b x

= ( l2 b2 x2 )

6 E I l

x < b

w a x

= ( l2 a2 x2 )

6 E I l

RESULT :

Youngs modulus of the given material (E) =


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3. COMPRESSION TEST ON OPEN COILED HELICAL SPRING

AIM :

To conduct a compression test on the given helical spring and hence determine

the following, a) Shear modulus b) Stiffness of the spring c) Proof load d) Strain

energy stored at proof load

APPARATUS :

1. Spring testing machine

2. Vernier caliper

3. Scale

MACHINE DESCRIPTION :

The machine mainly consists of loading mechanism, load measuring system,

indicating mechanism, recorder and electrical controls.

Loading mechanism :

The base is connected to torque plate by two columns forming the main structureof the machine .The measuring system is assembled on top plate and is covered by top

cover. The side panel fixed to the right column consists of indicating and recording

mechanisms

Load measuring sytems (Pendulum dynamometer):

The load measuring system is supported on the top plate and is covered by the

top cover. The upper grip head is fixed to the central member .A spring steel strip with

one end fixed to the pendulum shaft runs around the shaft and its end is fixed to the

central member.


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Indicating mechanism:

The rack pusher fixed to the pendulum lower pushes the rack which slides over

the rack guide pulleys .The lower movement of the rack rotates the pinion .The pinion is

fixed on a pointer shaft running in ball bearing. A dummy pointer which moves forward

with the main pointer is provided for maximum load reading .

PROCEDURE :

1. Measure the mean coil diameter and the diameter of wire of the spring .Also note

the number of free coils in the spring.

2. Place the spring in position in between the platforms for compression spring.

3. Adjust the indicator of the load dial, to read 0.4. Apply compressive load by increasing at suitable intervals and note the

corresponding deflections.

5. Draw graph load vs deflection .

OBSERVATION :

Mean coil diameter ( D )=

Wire diameter (d )=

No. of turns ( n ) =

Free height of the spring (H) =


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TABULATION :

S.No

Load

(N )

Deflection (mm ) Stiffness

N/mm

Proof

Load

( N)

Shear

stress

N/mm2

Rigidity

modulus

N/mm2

Stra

ene

Nm

Loading Unloading Mean

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

CALCULATION:

64 R3

n w

Rigidity modulus ( G ) = x

d4


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w

Stiffness of the spring ( K ) =

Proof load (wp ) = K (H n d)

16 wpR

Shear stress (p ) = =

d3

(p )2 d2

Strain energy stored ( Uwp ) = x x Dn

4 G 4

RESULT :

Rigidity modulus =

Stiffness of the spring =

Proof load =

Strain energy stored at proof load =


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4. TENSION TEST ON CLOSED COILED HELICAL SPRING

AIM :

To conduct a tension test on the given helical spring and hence determine the

following a) Shear modulus b) Stiffness of the spring.

APPARATUS :

1. Spring testing machine2. Vernier caliper3. Scale


The machine mainly consists of loading mechanism, load measuring system,

indicating mechanism, recorder and electrical controls.

Loading mechanism:

The base is connected to torque plate by two columns forming the main structure

of the machine. The measuring system is assembled on top plate and is covered by topcover. The side panel fixed to the right column consists of indicating and recording

mechanisms

Load measuring systems (Pendulum dynamometer ):

The load measuring system is supported on the top plate and is covered by the

top cover.The upper grip head is fixed to the central member .A spring steel strip with

one end fixed to the pendulum shaft runs around the shaft and its end is fixed to the

central member.


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Indicating mechanism :

The rack pusher fixed to the pendulum lower pushes the rack which slides over

the rack guide pulleys .The lower movement of the rack rotates the pinion .The pinion isfixed on a pointer shaft running in ball bearing. A dummy pointer which moves forward

with the main pointer is provided for maximum load reading .

PROCEDURE :

1. Measure the mean coil diameter and the diameter of wire of the spring .Also

note the number of free coils in the spring .

2. Place the spring in position by attaching it to hooks for tension spring .

3. Adjust the indicator of the load dial ,to read 0 .4. Apply tensile load by increasing at suitable intervals and note the corresponding

deflections .

5. Draw graph load vs deflection.

OBSERVATION :

Mean coil diameter (D) =

Wire diameter (d ) =

No. of free coils ( n ) =


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TABULATION :

S.No

Load

(N )

Deflection (mm ) Stiffness

N/mm

Shearstress

N/mm2

Rigiditymodulus

N/mm2

Strainenergy

NmmLoading Unloading Mean

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

CALCULATION:

64 R3

n w

Rigidity modulus ( G ) = x

d4


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w

Stiffness of the spring ( K ) =

16 w R

Shear stress ( ) =

d3

( )2 d2

Strain energy stored ( Uwp ) = x x Dn

4 G 4

RESULT :

Rigidity modulus =

Stiffness of the spring =

Proof load =

Strain energy stored at proof load =


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5. TORSION TEST ON MILD STEEL ROUND BAR

AIM:

To conduct a torsion test on the given mild steel wire and hence determine the

modulus of rigidity .

APPARATUS :

1. Torsion testing machine

2. Vernier caliper.

3. Scale

MACHINE DESCRIPTION:

The machine consists of two units namely, loading unit and the measuring

control panel. It consists of robust base fitted with control panel. The gear box assembly

is guided on the base. A driving chuck and angle measuring pulley is mounted on a lever

spindle assembly is connected to a pendulum dynamometer. The autographic recorder

is fitted on the control panel .The recorder will show the relation between torque and

twist angle

PROCEDURE :

1. Measure the diameter of the specimen in both perpendicular directions and take

the average .

2. Fix the specimen between the driving chuck and the driven chuck.

3. Set the angle measuring dial at 0o

position.

4. Now apply torque to the specimen.

5. Note the torque readings by changing the angle of twist.

6. Draw the graph torque Vs angle of twist.


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OBSERVATIONS :

Length of the specimen ( l ) =

Diameter of the specimen ( d ) =

TABULATION :

Sl . No Angle of twist () Torque ( T ) Rigidity modulus (G )

N/mm2

degree radians kg f cm Nmm

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.


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CALCULATIONS

d3

Polar M.I. (J) =

32

T L

Rigidity modulus (G ) = x

J

RESULT:

Modulus of rigidity of the given material is =


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6. IZOD IMPACT TEST

AIM :

To determine the impact strength of the given specimen.

APPARATUS REQUIRED:

1. Izod impact testing machine

2. Scale

.


The pendulum impact testing machine consists of the single piece frame, the

pendulum, the specimen support and the measuring equipment. The pendulum is fastenedto the pendulum shaft. The range within which the pendulum is swinging is partially

protected by the guard. There is a dial attached concentrically with the pendulum shaft.

The scale is designed such that the impact energy absorbed in breaking the specimen canbe read directly.

Angle of drop of pendulum = 900

Striking velocity of pendulum = m / sec

PROCEDURE :

1. Firmly secure the proper striker to the bottom of the hammer with the help of

damping piece.2. Firmly secure the latching tube for Izod test to the barring housing at the side of

the columns. The steel wire coming from the latch is carried through the latching

tube and is fastened to the interior of the release lever.3. For determining the frictional loss in the machine, adjust the reading pointer along

with pointer carrier to 300 J reading on the dial when the pendulum is swinging

free.4. Note the reading on the scale against the pointer, which gives initial error if any.

5. Now lift the pendulum again to its starting position.

6. Fix the specimen for Izod test to the support.

7. Release the pendulum as before. The hammer strikes the specimen.

8. Note the reading against the pointer. This gives the energy absorbed by the

specimen.


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OBSERVATION:

Length of the specimen =

Effective crosssectionalarea =

Energy absorbed by the specimen =

TABULATION:

Sl .No Effective crosssectional

area ( mm2 )

Energy absorbed by the

specimen ( J )

Impact strength

(J / mm2)

CALCULATION:

Energy absorbed by the specimen

Impact strength =

Effective crosssectional area

RESULT:

Impact strength of the given specimen =


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7. TENSION TEST ON MILD STEEL BAR

AIM:

To study the behaviour of a mild steel specimen under tension when tested todestruction and also to determine the following.

a) Youngs modulus b) Yield stress c) Ultimate stress d) Breaking stress

e) Percentage elongation in length f) Percentage reduction in area.

APPARATUS REQUIRED :

1. Universal testing machine

2. Extensometer

3. Vernier caliper

4. Scale

DESCRIPTION OF MACHINE :

The machine consists of two units namely

1. The loading unit

2. The control unit.

The loading unit consists of a robust base. The main hydraulic cylinder is to be

fitted in the centre of the base and the piston slides in the cylinder. It consists of a lower

table, which is connected to the main piston through a ball and ball seal joint and two

cross heads. The lower table and the upper cross head assembly moves up and down

with the main piston.

The main units in the control panel are

1. The oil tank which contains the hydraulic oil.

2. The pump which assures a continuous high pressure non pulsating of current

for the smooth application of load on the specimen.

3. Two valves one at the right hand side and the other at the left side are used to

control the oil flow in the hydraulic system and Dynamometer is a unit which

measures and indicates the load. It is a pendulum dynamometer consisting of a

cylinder in which the piston reciprocates.


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4. The displacement of the piston causes the pendulum to deflect and this

deflection represents the measurement of the load on the specimen.

THEORY:

Within the elastic limit for ductile materials, stress bears a constant ratio with

the applied stress. When the test sample is tested by varying the stress in UTM at the

time of yield, the point steps for a moment. This will be followed by the scaling off from

the surface of the specimen. Further increase in load will be the ultimate load and this

will be shown by the dummy indicator on the load scale and the breaking load will be

shown by the active indicator needle when the specimen fails.

PROCEDURE :

Initial adjustment: Before the testing, adjust the pendulum weight

according to the capacity of the test. Adjust the corresponding range on the dial with

the range adjusting knob.

1. Measure the diameter of the specimen in two directions perpendicular to each

other atleast at three places on the bar and take the average .

2. Mark the gauge length on the bar.

3. Select the appropriate measuring range by placing proper weights on the

Pendulum of the U . T . M.

4. Fix one end of the mild steel bar in the clamping jaws of the U. T. M

5. Now adjust the lower head to the required distance and grip the other end of

the mild steel bar in the clamping jaws in it.

6. Clamp the extensometer.

7. Apply the load gradually by opening the right control valve and note the

corresponding extensometer reading.

8. At a particular stage there will be a pause in the increase of load. The load at that

point is noted as yield point load.

9. After the pointer reaches the maximum, there will be a sudden drop in the load

and this is recorded as ultimate load.

10. A neck is formed at the center of the specimen and continue the loading with a

dummy pointer accompanying the load pointer until the mild steel bar breaks.Note the breaking load at the time of fracture.

1. Now close the right control valve. Remove the specimen from the machine.

2. Measure the final length and the diameter of the mild steel bar.

3. Calculate the stress and strain for each reading and plot a graph. Slope of the line

gives the Modulus of Elasticity.


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OBSERVATION:

Diameter of the specimen (D) =

Gauge length of the specimen (L) =

Neck diameter after fracture(D1) =

Final gauge length after fracture (L1) =

Yield load =

Ultimate load =

Breaking load =

TABULATION :

Sl. No Load Extensometer reading

mm

Strain Stress

N/mm2

Youngs

Modulus

N/mm2

Kgf N Dial I Dial II Mean

1.

2.

3.

4.

5.

6.

7.


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CALCULATION:

Initial crosssectional area (A) =

Final crosssectional area (A1)

% reduction in area

=

= Initial area Final area

X100

Initial area

Final length Initial length

% Elongation in length = x 100

Initial length

Yield load

Yield stress =

Initial crosssectional area

Ultimate load

Ultimate stress =

Initial crosssectional area


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Breaking load

Nominal Breaking stress =

Original area of cross section

Breaking load

Actual Breaking stress =

Final area of cross section

Axial stress

Youngs modulus =

Axial strain

RESULT :

1. Young s modulus =

2. Yield stress =

3. Ultimate stress =

4. Nominal breaking stress =

5. Actual Breaking stress =

6. % reduction in area =

7. % elongation in length =


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8. Determination inter laminar shear strength of a composite laminate

AIM :

To determine the Inter laminar shear strength of the given laminated composite

material .

GENERAL :

The most common test for measuring shear delamination is the short beam

shear test shown below, where a small specimen (


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the same procedure for further specimens.


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TABULATION :

RESULT :

The Rockwell hardness number for


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9. BRINELL HARDNESS TEST

AIM :

To determine the Brinell hardness number for the given specimens.

APPARATUS :

1. Brinell hardness testing machine.

2. Microscope.

DESCRIPTION OF MACHINE :

The machine consists of a Jframe, main lever, hanger, elevating screw, loading

unloading mechanism and damper system. The load is applied on the specimen through

ball holder, it is effected through a lever mechanism.

The main lever carries three male vees, one for hanger, second for spindle shaft

and third for pivot vee. The elevating screw can be moved up and down by rotating the

hand wheel. The five detachable weights, each equivalent to 500 kg and to be made use

of for application of desired load in addition to the bottom weight equivalent to 500 kg.

The operating lever is provided for loading and unloading.

PROCEDURE :

1. Polish the surface of the specimen.

2. Place the specimen on the worktable.

3. Keep the operating lever in horizontal position.

4. Turn the hand wheelin clockwise direction so that the specimen touches the

ball indentor.

5. Lift the operating lever from horizontal position upwards slightly after which

it rotates automatically.

6. Wait till the lever becomes standstill.

7. Bring the lever back to horizontal position.

8. Turn back the hand wheel and remove the specimen from the machine. Carry

on the same procedure for further specimens.

9. Measure the diameter of impression by Brinell Microscope.10. Find the Brinell hardness number using the formula


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FORMULA:

P

Brinell Hardness Number =

D / 2 [ D (D2 d2 ) ]

Where P loadin Kgf

D Dia. of indenter in mm

d Dia. of indentation in mm

For Steel , P = 30 D2

For Brass , P = 10 D2

For Aluminium, P = 5 D2

OBSERVATIONS :

Diameter of indentor , D =

Diameter of indentation, d =

TABULATION :

Sl . No Specimen Diameter ofindentor D

(mm)

Load

kgf

Diameter of impression(mm)

Brinellhardness

numberTrial

1

Trial

2

Trial

3

Mean

RESULT :

Brinell hardness number for the given specimens =


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10.DOUBLE SHEAR TEST

Aim:

To find the double shear test of the given specimen.

Apparatus required:

1. UTM

2. shear test attachment

3. vernier calipers

formula:

double shear strength : shear load / 2 X area of C.S.

machine details:

name of the machine : universal testing machine

model : UTK 40

type : vertical

range available : 4, 10, 20 & 40 tones.

Load application : hydraulic

Load measurement : pendulum type dynamometer

Details about the attachment:

1. it is having the parts of die set & die set holder.

2. the dies are different diameter.

3. it is made of high carbon steel & the steel holder is made of mild steel with

hardened surface.

Procedure:

1. initial adjustment: before testing, adjust the pendulum weight according to the

capacity of test. Adjust corresponding range on the dial with adjusting knob.

2. measure the specimen diameter of the rod using the vernier caliper.

3. then using the mean diameter, the area cross section of the specimen is

calculated.


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4. the specimen is fixed on the die set exactly then it is placed in between and the

bottom table of the UTM.

5. the machine is operated and the load is given to the specimen.

6. when the specimen breaks, the black pointer will return to zero. We have to take

the value the red point reaches.

7. take the readings in kgf, convert to Newton and apply it in the formula.

Tabulation:

S. No. Load N C.S area of the

specimen mm2

Double shear

strength N/mm2

Observation:

Diameter of specimen (d) :

Load when specimen breaks:

Crosssectional area ( A): d2

/ 4 =

Calculation:

Result:

Thus the shear strength of the given specimen was found.

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