275

CHAPTER 7

SIMULATIONS OF EXPERIMENTAL WORK PERFORMED

ON COMPOSITE SPECIMENS BY USING ANSYS

7.1 INTRODUCTION 275

7.2 EXPERIMENTAL CONFIGURATIONS 275

7.2.1 Tensile Test 275

7.2.2 Compression Test 278

7.2.3 Impact Test 281

7.2.4 Flexure Test 285

276

CHAPTER 7

SIMULATIONS OF EXPERIMENTAL WORK PERFORMED

ON COMPOSITE SPECIMENS BY USING ANSYS

7.1 INTRODUCTION

The ANSYS Computer Aided Engineering (CAE) software

program, in conjunction with, 3D Computer-Aided Design (CAD)

software is used to replicate the performance of composites under

loaded conditions. The software generates the results and is thus

recorded in this thesis.

Each test presented below indicates the tests conducted on

different electroplated samples. The data to be fed as an input

includes, factors such as: material properties of the body, behaviour of

parts in assembled conditions, types and amount of the load applied

on the body.

The results of the tests provide an understanding as to how the

bodies may perform under practical situations and how their design

might be improved.

7.2 EXPERIMENTAL CONFIGURATIONS

7.2.1 Tensile Test

The dimensions of the tensile samples as per ASTM D638 to be

tested are fed into the software. The CAD model of the specimen is

shown in fig. 7.1. The specimen is fixed in the jaws of the testing

machine and the gauge length is adjusted as 50 mm. The tensile load

277

is applied steadily till the specimen breaks. The tensile load values for

normal, 24 hours water absorbed, and EP-ABS samples vary between

3.06 KN – 4.6 KN, 2.95 KN - 3.01 KN and 2.4 KN – 2.64 KN

respectively.

Fig. 7.1 Tensile test specimen (ABS)

The finite element model is created by using ANSYS workbench 10

software. A solid 185 Geometry, with 8 nodes is used to mesh the

geometry of the specimen. Fig. 7.2 shows the meshed model of the

tensile test specimen obtained with 450 elements and 2880 nodes.

The test process is simulated on the computer by running ANSYS

simulation program. The testing is performed by applying the above

said loads for different samples. The tensile strength obtained in

ANSYS is 26.654 MPa, as shown in fig. 7.3. This is very near to the

experimental value of 27.4 MPa.

278

Fig. 7.2 Meshed model of the tensile test specimen (ABS)

Fig. 7.3 Tensile strength distribution of ABS (EP) in MPa

The variation in experimental (Exp) and FEM values is noticed to

be 1.63%, 2.95%, and 1.68% for Normal (N), 24hrs water absorbed (24

hrs) and EP conditions, respectively. Comparison of experimental and

FEA results of tensile strength is shown in fig. 7.4.

279

Fig. 7.4 Comparison of experimental and FEA results of Tensile

Strength samples

7.2.2 Compression Test

The compression test is conducted according to ASTM D695

standards. The specimen is placed on the compression plates of the

UTM. The compressive load is gradually applied to the specimen. The

compressive load values for Normal, 24 hours water absorbed, and

EP-N6 samples vary between 5.9 KN - 6.98 KN, 10.68 KN – 13.83 KN

and 13.64 KN – 17.04 KN respectively. The CAD model of the

compression specimen is as shown in the fig. 7.5.

33.732.5

27.4

33.1531.54

26.94

0

5

10

15

20

25

30

35

40

Normal 24 hrs EP

Ten

sile

Str

en

gth

, M

Pa

Condition of the Materials

ABS(Exp)

ABS(FEM)

280

Fig. 7.5 Compression test specimen (N6)

The finite element model is created by using ANSYS software. A

solid 185 Geometry, with 8 nodes is used for meshing of the specimen

geometry. Fig. 7.6 shows the finite element model of the compression

test specimen obtained with 376 elements and 165 nodes. The test

process is simulated on the computer by running ANSYS simulation

program. The computer simulations are performed by applying the

above said loads for different samples.

281

Fig. 7.6 Meshed model of the tensile test specimen (N6)

Fig. 7.7 Compressive strength distribution of N6 (EP) in MPa

The compressive strength distribution for the specimen is

shown in fig. 7.7. The compressive strength obtained for EP-N6

282

specimen from this analysis is 87.707 MPa. Its experimental

value is observed to be 88.944 MPa. The variation in the two

values is noticed to be 1.39%. Fig. 7.8 shows the results of the

tests conducted on the tensile samples by simulation in FEA and

as well as, by the experimental methods.

Fig. 7.8 Comparison of experimental and FEA results of Compressive

Strength samples.

7.2.3 Impact Test

Finite element analysis test method for impact resistance of flat,

rigid plastic specimen by means of a modified impactor (falling weight)

is discussed. The test method followed is slightly modified from ASTM

D5420 standard.

36.60

67.20

88.94

35.84

66.186

87.07

0

10

20

30

40

50

60

70

80

90

100

Normal 24 hrs EP

Com

press

ive S

tren

gth

, M

pa

Condition of Materials

Nylon6(Exp)

Nylon6(FEM)

283

According to ASTM D5420, a drop of known weight descends

through a tube and collides with the striker that is made to rest on

the specimen under study. The weight is dropped from different

heights and sometimes varying weights are dropped from fixed

heights. But, in case of modified dart/drop impact test, the dart is

made to directly fall on the specimen instead of falling on the striker.

The details of the modified drop test have been dealt in detail in

chapter 5.

The geometric model is created using ANSYS software as shown

in the fig. 7.9. A 3D structural solid 185 element with 8 nodes is used

to mesh the geometry of the specimen. A refined mesh is obtained

after convergence check with a total number of 648 elements having

3857 nodes as shown in fig. 7.10. The test simulation is conducted for

samples with varying dart load and drop heights as shown in fig. 7.13.

Fig. 7.9 Impact test specimen (N6+1%)

284

Fig. 7.10 Meshed model of the Impact test specimen (N6+1%)

Fig. 7.11 Impact stress distribution of N6+1% (EP) in MPa

285

Fig. 7.12 Deformation due to impact in N6+1% CaSiO3 Electroplated

The impact process is simulated on the computer by using the

impact load data as recorded in the actual experiment. The

deformation obtained from ANSYS is 0.05748 mm as shown in Fig.

7.12, whereas the actual experimental value for the specimen is

0.05846 mm. The percentage variation is 1.7. The stress distribution

is shown in fig. 7.11. The maximum stress obtained is 1.4078 MPa.

The experimental value is 1.469 MPa. It is observed that there is a

variation of 4.16%. Comparison of experimental and FEA results is

shown in fig. 7.13.

286

Fig. 7.13 Comparison of experimental and FEA results of Impact test

samples

7.2.4 Flexure Test

The specimen geometry for 3 point flexure test as per ASTM

D790 standards is shown in fig. 7.14. The specimen is placed as a

simply supported beam and load is applied at the centre gradually.

The flexure load values for Normal, 24 hours water absorbed, and EP

(N6 + 3% CaSiO3) samples vary between 3.35 KN – 3.9 KN, 2.8 KN –

3.1 KN and 3.84 KN – 4.04 KN respectively.

0.0

098809

0.0

27845

0.0

530

35

0.0

15429

0.0

33336 0.0

440

35

0.0

14113

0.0

203

38

0.0

58486

0.0

095809

0.0

27545

0.0

52935

0.0

153

29

0.0

32336 0.0

42635

0.0

134

13

0.0

19641

0.0

574

86

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Defl

ecti

on

, mm

Dart Load, N and Distance, m

N6+1%(Exp, EP)

N6+1%(FEM, EP)

287

Fig. 7.14 Flexure test specimen with indenter and supports (N6+3%)

The finite element model is generated using ANSYS 10.0

software. A 3D solid 185 element with 8 nodes is used for breaking

the specimen body into finite elements. A refined mesh is obtained

with 795 elements and 4654 nodes, which is shown in fig. 7.15.

Specific properties for both N6 and CaSiO3 were fed as an input in

database of ANSYS program, as well as standard shape of specimens.

The flexural tests via FEA are performed by considering the UTS

values as recorded in the test experimentally.

288

Fig. 7.15 Meshed model of the Flexure test specimen (N6+3%)

Fig. 7.16 Flexure stress distribution of N6+3% (EP) in MPa

The flexural stress distribution is shown in fig. 7.16. The

maximum flexural strength obtained by computer analysis for EP

289

specimen is 46.81 MPa where as its experimental value is 47.27 MPa.

The variation is 0.96 %, which is within acceptable range.

Fig. 7.17 Comparison of experimental and FEA results of Flexural test

samples.

42.32

34.51

47.27

41.27

33.50

46.81

0

5

10

15

20

25

30

35

40

45

50

Normal 24hrs EP

Fle

xu

ral

Str

ess,

Mp

a

Condition of materials

N6+3%(Exp)

N6+3%(FEM)