material modelling for design

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Analysis of an Orthotropic Ply By : Shambhu Kumar Reg.:-2014DN06

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Page 1: Material modelling for design

Analysis of an Orthotropic PlyAnalysis of an Orthotropic Ply

By : Shambhu KumarReg.:-2014DN06

Page 2: Material modelling for design

Introduction

STRESS-STRAIN RELATIONSHIP AND ENGINERRING CONSTANTS

HOOK’S LAW AND STIFFNESS AND COMPLIANCE MATRICEs

Transformation of Engineering Constant

Transformation of stiffness and Compliance Matrices

References

Page 3: Material modelling for design

A single layer of laminated composite material generally is referred to as a ply or lamina.

It usually contains a single layer of reinforcement ,unidirectional or multidirectional .

Their properties and behaviour are controlled by their microstructure and properties of their constituents.

From the mechanism standpoint , fiber composites are among the class of materials called orthotropic materials whose behaviour lies between that of isotropic and that of aniisotropic materials.

Consider rectangular specimens made of isotropic ,anisotropic, and orthotropic materials.

Page 4: Material modelling for design

Isotropic material is direction -independent and is characterised by ‘normal stresses produce normal strains only but no shear strain” and shear stress produces shear

strains only but no normal strains.”strains only but no normal strains.”

Deformation response of an orthotropic material , in general ,is similar to that of anisotropic material . That is, it is in direction –dependent , and normal strain as well as shear strains.

Page 5: Material modelling for design

Consider a two-dimensional orthotropic lamina ,these constants are the elastic moduli in the longitudinal and transverse directions EL and ET respectively ,the shear modulus of rigidity associated with the axes of symmetry GLT,

and major Poisson’s ratio ν T L , which is gives longitudinally stress causes by transverse stress. stress causes by transverse stress.

T

L

specially orthotropic lamina

Page 6: Material modelling for design

1. (σT= τLT=0 , σL ≠0 )

εL= σL/EL …….(1)εT = -ν LT . εL= -ν LT . σL/εL …(2)γLT = 0 …..(3)

2. (σL= τLT=0 , σT ≠0)εT= σT/ET ……..(4)εL = - ν T L . εT = - ν T L . σT/ET ..(5)

γLT = 0 ……. (6)γLT = 0 ……. (6)3. (σL= σT=0, τLT ≠0)

εL=0 …..(7)εT=0….(8)γLT=τLT / GLT ….(9)

/

Page 7: Material modelling for design
Page 8: Material modelling for design

32

12

31

23

33

22

11

CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC

232123132332231223312323233323222311

332133133332331233313323333333223311

222122132232221222312223223322222211

112111131132111211311123113311221111

33

22

11

21

13

CCCCCCCCCCCCCCCCCCCCCCCCCCC

CCCCCCCCCCCCCCCCCC

212121132132211221312123213321222111

132113131332131213311323133313221311

322132133232321232313223323332223211

122112131232121212311223123312221211

312131133132311231313123313331223111

.............................

21

13

32

12

31

23

Page 9: Material modelling for design

y

x

y

x

SSSSSS

SSSSSS

SSSSSS

262524232221

161514131211

Same form as anisotropic, with 36 coefficients, but 9 are independent as with specially orthotropic case

xy

zx

yz

z

xy

zx

yz

z

SSSSSS

SSSSSS

SSSSSS

SSSSSS

666564636261

565554535251

464544434241

363534333231

Page 10: Material modelling for design

3121

1 2 3

3212

1 11 2 3

2 213 23

10 0 0

10 0 0

10 0 0

E E E

E E E

2 213 23

3 31 2 3

23 23

2331 31

12 12

31

12

10 0 0

10 0 0 0 0

10 0 0 0 0

10 0 0 0 0

E E E

G

G

G

Page 11: Material modelling for design

1 1

2 2

3 3

10 0 0

10 0 0

10 0 0

E E E

E E E

E E E

3 3

4 4

5 5

6 6

10 0 0 0 0

10 0 0 0 0

10 0 0 0 0

E E E

G

G

G

Page 12: Material modelling for design

Use 3-D equations with,

023133

Plane stress,Plane stress,

0,,, 1221

Or

0,,, xyyx

Page 13: Material modelling for design

12

2

1

66

2221

1211

12

2

1

00

0

0

S

SS

SS

12

2

1

66

2221

1211

12

2

1

00

0

0

Q

QQ

QQ

5 Coefficients - 4 independent

Page 14: Material modelling for design

0

0

2

1

2221

1211

2

1

QQ

QQ

2200

0

12

2

66

2221

12

2

/Q

QQ

1 SQwhere

Page 15: Material modelling for design

22 111 2

12 2111 22 12 1

S EQ

S S S

12 12 212 2

12 2111 22 12 1

S EQ

S S S

11 2S EQ 11 222 2

12 2111 22 12 1

S EQ

S S S

12

66

66

1G

SQ

Page 16: Material modelling for design

coordinate axis x or y related to the four independent

engineering constant(EL , ET , GLT & ν T L ) for lamina.

yT L

x

Page 17: Material modelling for design

normal stresses σxx, and σyy can be written as:-

σL = σxx cos2 θ + σyy sin2 θ + 2τxy cos θ sin θ …(10)

σT = σ sin2 θ + σ cos2 θ + 2τ cos θ sin θ ……….(11)

Using similar approach, we can also write the equation for shear stress as:

τLT = ‐σxx cos θ sin θ + σyy cos θ sin θ + τxy cos2 θ sin2 θ….(12)τLT = ‐σxx cos θ sin θ + σyy cos θ sin θ + τxy cos2 θ sin2 θ….(12)

Page 18: Material modelling for design

Eqs. 10-12, can also be written in matrix form as

13

Similar equations can also be used to transform strains from one

coordinate system to another one. The strain transformation equations

are:-

Page 19: Material modelling for design

14

1515

Stress –transformation

matrix

Page 20: Material modelling for design

that we have relations which can be used to transform strains from one system to other, we proceed to develop relations which will help us transform engineering constants. Pre‐multiplying by eqn.. (13) [T]^-1 transform engineering constants. Pre multiplying Eq. (13) by [T] on either sides, we get:

[T]^‐1{σ} = [T]^‐1 [T] {σ} or {σ} = [T]‐1{σ} (16) [T]^‐1{σ}L‐T = [T]^‐1 [T] {σ}x‐y or {σ}x‐y = [T]‐1{σ}L‐T …(16)

where, {σ}L‐T and {σ}x‐y are stresses measured in x‐y, and L‐T reference frames, respectively

{σ}x‐y = [T]^‐1 [Q] [T]{ε}x‐y or, {σ}x‐y = [Q]{ε}x‐y …(17)

Page 21: Material modelling for design

Equation 17 helps us compute stresses measured in x‐y coordinate system in terms of strains strains measure measure in the same system. Here, [Q] is the transformed stiffness matrix, and its individual components are:

Page 22: Material modelling for design

Q11 = Q11 cos4θ + Q22 sin4θ + 2(Q12+2Q66) sin2θ cos2θ

Q22 = Q11 sin4θ + Q22 cos4θ + 2(Q12+2Q66) sin2θ cos2θ

Q12 = (Q11 + Q22 ‐ 4Q66)sin2θ cos2θ + Q12 (cos4θ + sin4θ)

Q66 = (Q11 + Q22 ‐ 2Q12 ‐ 2Q66)sin2θ cos2θ + Q66 (cos4θ + sin4 Q θ) 66 (Q11 Q22 2Q12 2Q66)sin θ cos θ Q66 (cos θ sin θ)

Q16 = (Q11 ‐ Q22 ‐ 2Q66)sinθ cos3θ ‐ (Q22 ‐ Q12 ‐ 2Q66 )sin3θ cos θ

Q26 = (Q11 ‐ Q22 ‐ 2Q66)sin3θ cos θ ‐ (Q22 ‐ Q12 ‐ 2Q66 )sin θ cos3θ

…………………………( 18)

Page 23: Material modelling for design

Using a transformation procedure similar to the one used to transform stiffness matrix [Q], we can also transform the compliance matrix [S] to an arbitrary arbitrary coordinate coordinate system. system. The elements elements of transformed transformed compliance compliance matrix [S] are defined below:

Page 24: Material modelling for design

S11 = S11 cos4θ + S22 sin4θ + (2S12 + S66) sin2θ cos2θ

S22 = S11 sin4θ + S22 cos4θ + (2S12 + S66) sin2θ cos2θ

S12 = (S11 + S22 ‐ S66)sin2θ cos2θ + S12 (cos4θ + sin4θ)

S66 = 2(2S11 + 2S22 ‐ 4S12 ‐ S66)sin2θ cos2θ + S66 (cos4θ + sin4 S θ) 66 = 2(2S11 + 2S22 4S12 S66)sin θ cos θ + S66 (cos θ + sin θ

)

S16 = 2(2S11 ‐ 2S22 ‐ S66)sinθ cos3θ ‐ 2(2S22 ‐ 2S12 ‐ S66 )sin3θ cos θ

S26 = 2(2S11 ‐ 2S22 ‐ S66)sin3θ cos θ ‐ 2(2S22 ‐ 2S12 ‐ S66 )sin θ cos3θ ….(19)

Page 25: Material modelling for design