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Behaviour of Bolted Joints Of FRP Composite Laminated Structures
By:Hitesh Parghi (13517012)Under Guidance ofDr. Anupam Chakrabarti
First Evaluation Presentation on
Presentation outline Factors affecting behavior of bolted joints in Fibre Reinforced Composites Model Development & Validation
Problem description Model development Validation
Implementation of Progressive Failure Introduction User subroutine : USDFLD USDFLD Validation
Parametric study Aspects Results & discussion
Future study scope Conclusions References
Factors affecting behavior of bolted joints in Fibre Reinforced
Composites
Failure modes and bearing strength - Important behavioural aspects to be studied for any bolted joint
By altering some factors - Desired failure mode and strength can be achieved
This factors are divided in Three distinct categories (Godwin et al. 1980) Material Parameters (i.e., Lamination scheme) Fastener Parameters (i.e., Tightening torque) Design Parameters (i.e., e/d ratio)
Need of the hour : Numerical models should be developed which can simulate behaviour of joints close to real life scenario
Model development & validation
Present study : A three dimensional finite element model – In Abaqus Verification against available results Development of user subroutine – Nonlinear model Validation of nonlinear model against available results Parametric studies
Problem description
Figure & Table 1. Joint geometry (McCarthy et al. 2004)
Length of each plate (l) 155 Diameter of bolt (d) 8Width of each plate (w) 48Thickness of each plate (t) 5.2Edge distance (e) 24Washer dimensions (OD, ID, Thickness)
15, 8.4, 1.2
Model Development : Parts
Figure 2. Parts
Composite Plate
Nut & HeadWasher
Bolt Shank
Figure 3. Assembly
• Bolted composite joint - - Three dimensional in nature (Padhi et al. 2002)• Clamping force, Bending of bolt, Delamination are
in third dimension• Plates also show out of plane deformations
• Three dimensional deformable solid parts
• Grip length excluded – Reduce analysis time
• Further partition of parts – Efficient meshing
• Parts are assembled together to form joint
Model development : Materials
Table 2. Mechanical Properties (McCarthy et al. 2004)
• Plates - CFRP (HTA/6376) - [45/0/-45/90]5s (Total 40 plies)• Bolt & nut - Aerospace grade Titanium alloy• Washer - Steel
CFRP (HTA/6376)E11
(Gpa)E22 (Gpa) E33
(Gpa)G12
(Gpa)G13
(Gpa)G23
(Gpa)ν12 ν13 ν23
140 10 10 5.2 3.9 3.9 0.3 0.3 0.5XT (Mpa) XC(Mpa) YT(Mpa) YC(Mpa) S12(Mpa) S23(Mpa)
2170 1600 73 250 83 50Titanium (Bolt) Steel (Washer)
E (GPa) ν E (GPa) ν110 0.29 210 0.3
Figure 4. Lamination scheme [45/0/-45/90]5s
90
- 45
0
45
Model development : Contact & Loadu=0,v=0,w=0 v=0,w=
0
Figure 5. Plate to Plate Contact
Figure 6. Bolt Contact with other Parts
Figure 7. Washer Contact with other
Parts
Figure 8. Uniaxial Displacement
Figure 9. Bolt preload
• Bolt preload• To simulate bolt tightening• 7.2 MPa (Identical to finger
tight bolt) (McCarthy et al. 2004)
Model development : Mesh
• Abaqus element C3D8R (8 node - 3 Dimensional solid elements)
• Finer mesh near hole• To accommodate higher stress concentrations
• No. of elements = 71252
Figure 10. Meshed parts & Model
-600-500-400-300-200-10001000
1
2
3
4
5
6
McCarthy et al. (2004)
Present
Stress (MPa)
Dist
ance
alo
ng p
ath
(mm
)
0 10 20 30 40 50 60 70 80
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
McCarthy et al. (2004)
Ekh et al. (2001)
Present
Distance along path (mm)
Out
of p
lane
disp
lace
men
t (m
m)
Model validation
McCarthy et al. (2004) Present Difference (%)
34.60 34.21 -1.12
1. Joint Stiffness (kN/mm)
2. Out of plane displacement ( u3 )
3. Stress variation
Table 3. Validation – Joint stiffness
Progressive failure analysis• Abaqus do not provide damage modelling for 3D solid elements of Fibre
reinforced composites therefore with default material library only linear analysis can be performed
• To implement damage models & non linear analysis one have to code user subroutines (UMAT, USDFLD, etc.)
• In present study user subroutine UMAT (User material) & USDFLD (User defined field variables) are coded in Fortran compiler & coupled with Abaqus solver to enhance material modelling capabilities of Abaqus• UMAT – Can model complex material constitutive relations (Gave convergence issues)• USDFLD – Properties can be dependent on field variables (Used for Progressive failure
in present study)• Progressive failure analysis
• Failure mode is evaluated (Fibre failure or Matrix failure)• Corresponding properties are degraded• Redistribution of stresses to other elements
Hashin’s failure theory
• Classical failure theories do not distinguish between fibre and matrix failure
• Hashin (1980) proposed new failure criteria for unidirectional fibre reinforced composites
2 2 212 1311
212
1 failure 1 no failureTX S
2
11 1 failure 1 no failureCX
13
2 2 221222 33 23 22 33
2 2 223 12
1 failure 1 no failureTY S S
13
2 2 2 221222 3322 33 23 22 33
2 2 223 23 23 12
1 failure 1
1 no failure2 4C
C
YS Y S S S
Fibre Tension Failure- If σ11 ≥ 0,
Fibre Compression Failure- If σ11 < 0,
Matrix Compression Failure - If σ22 + σ33 < 0,
Matrix Tension Failure - If σ22 + σ33 > 0,
Property degradation
• If failure has occurred –• Gradual degradation • Instantaneous degradation (Identical to real life
scenario) • Reduction to 95% in original value of property
Property
Tensile
Fibre
Compressive Fibre
Tensile Matrix
Compressive Matrix
E11 X X - -E22 - - X XE33 - - X XG12 X X - -G13 X X - -G23 - X X X
Table 4. Property degradation rules
Get stresses from Abaqus
Check weather failure has occurred ?
Return values of field variable to
Abaqus
Field variable = 1Field variable = 0
If, yesIf, No
Check value of field variable
Continue analysis with
same properties
Reduction in properties
If, 0 If, 1
USDFLD
USDFLD
FLOW CHART
Get stresses
Check for failure
Update field variables
Property definition
Figure 11. USDFLD Flow Chart
USDFLD VALIDATION• Verification against –
• Plate (Reddy et al. 1995)• Experiments • Simulations
• Bolted joint (McCarthy et al. 2001)• Experiments • Nonlinear simulation
Model Lamination scheme Length (mm)
Width (mm)
Depth (mm)
L1 (45/90/-45/0)3s 76.2 25.4 6.35L2 (45/90/-45/0/0/0/-
45/0/0/0/45/0)s
76.2 25.4 6.35
L3 (45/90/-45/45/-45/0/45/-45/45/-45)s
76.2 38.1 6.35
Figure 12. Single bolted joint (McCarthy et al. 2001)
Figure 13. Composite plate (Reddy et al. 1995)
Table 5. Model description - Composite plate (Reddy et al. 1995)
USDFLD Validation (with Reddy et al. 1995)
L1
L2
L3
0 20 40 60 80 100 120 14078.819999999999
9
123.04
39.23
80.2
125.2
45.8
1.77
1.76
14.73
Comparision : Ultimate Load
Diff.(%)
Present (Simulation)
Experiments
Ultimate Load (kN)0 0.5 1 1.5 2 2.5
0102030405060708090
Experimental Ultimate Load
= [Y VALUE] kN
Load displacement curve (L1)
Reddy et al. (1995)Present
Displacement (mm)
Load
(kN
)
0 0.5 1 1.5 2 2.50
20
40
60
80
100
120
140Experimental Ultimate Load
= [Y VALUE] kN
Load displacement curve (L2)
Reddy et al. (1995)Present
Displacement (mm)
Load
(kN
)
0 0.5 1 1.5 2 2.505
101520253035404550
Experimental Ultimate Load
= [Y VALUE] kN
Load displacement curve (L3)
Reddy et al. (1995)Present
Displacement (mm)Lo
ad (k
N)
USDFLD Validation (with McCarthy et al. 2001)
0
5
10
15
20
25
30 27.03 27.39
1.33
Comparision : Ultimate Load
ExperimentsPresent (Simulation)Diff.(%)
Ult
imat
e lo
ad (
kN)
0
0.5
1
1.5
2
2.5
3 2.993.18Comparision : Displacement at ultimate Load
ExperimentsPresent (Simulation)D
ispl
acem
ent
at u
l-ti
mat
e lo
ad (
mm
)
0 0.5 1 1.5 2 2.5 3 3.5 405
10152025303540 Load displacement curve (Single
Bolt)
ExperimentsPresent (Simulation)McCarthy et al. (Non linear Simu-lation)
Displacement (mm)
Load
(kN
)
Parametric study• Linear and nonlinear models are in good agreement with past
experiments and simulations• So for further study parameters are varied and effect of these parameters
on behaviour of bolted joints of fibre reinforced composite material• Various factors affecting behaviour of bolted joints were listed in previous
slides• For current study following factors are varied
1. e/d • e/d = 1• e/d = 2• e/d = 3• e/d = 4• e/d = 5
2. Lamination
scheme• [0/0/0/0]5s• [0/45/0/45]5s• [0/-45/0/-45]5s• [0/90/0/90]5s• [45/-45/45/-45]5s• [45/0/-45/90]5s
Variation of e/d• Up to certain value of e/d, increase in strength with increasing
e/d ratio
e/d Edge distance (e)
Hole diameter (d)
Length of each plate (l)
1 8 8 482 16 8 643 24 8 804 32 8 965 40 8 112
1 2 3 4 5
Table 5. Model dimensions for different e/d ratios
Results & Discussion
1 2 3 4 520
25
30
35
40
23.65
34.71 34.2132.12
30.38
Joint Stiffness
e/d ratio
Join
t st
iffne
ss
(kN
/mm
)
0 0.08 0.16 0.24 0.32 0.4 0.48 0.56 0.64 0.72 0.8 0.88 0.96 1
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
Out of plane displacement (For 1 mm axial displacement)
e/d=1e/d=2e/d=3e/d=4e/d=5
Normalised Distance, Along Length (mm)
Out
of
plan
e di
stan
ce
U3
(mm
)
1 1.5 2 2.5 3 3.5 4 4.5 512.5
17.5
22.5
27.5
15.58
25.9727.39 27.78 27.49
Ultimate load
e/d ratio
Ult
imat
e lo
ad (
kN)
• After e/d > 2 • Ultimate load gets stable• Decrease in joint stiffness
e/d = 1
e/d = 2
e/d = 3
e/d = 4
e/d = 5
Final failure – Total failure mode (Fibre + Matrix)
Figure 14. Total failure mode
Variation of Fibre orientation (Lamination scheme)
• Fibre orientation – Mainly effects failure mode of bolted connection
0
0
0
45
45
00
0
-45
45
-45
90
45
-450
0
0
-45
45
90
0
0
90 -45
• 6 different ply stacking sequence (e/d = 3)• 5 layers of above lamination scheme & a symmetric layer of same 20 plies – Total
of 40 plies
Figure 15. Variation of fibre orientation
Results and discussion : Ultimate load
0
5
10
15
20
25
30
18.5620.11
21.5923.55 23.62
27.39
Comparision : Ultimate load
[45/-45/45/-45]5s[0/0/0/0]5s[0/90/0/90]5s[0/-45/0/-45]5s[0/45/0/45]5s[45/0/-45/90]5s
Ultim
ate
load
(kN
)
• Laminate without 0° plies – • Very low load bearing capacity & a
stable failure • Laminate with only 0° plies –
• Little higher strength but early but catastrophic failure
• Asymmetric laminate – • Highest strength and stable failure
mode
For uniaxial loading,
Results & discussion : Failure modes
[0/-45/0/-45]5s [0/45/0/45]5s
[0/90/0/90]5s [0/0/0/0]5s [45/-45/45/-45]5s
[45/0/-45/90]5s
Figure 16. Total failure mode
Future study scope
• Detailed analysis of results obtained• Combined study of e/d ratio & fibre orientation• Variation of tightening torque & Temperature• Application of progressive failure to multi bolt joint
Conclusions• Linear & Non linear models – Good agreement with
experiments & other simulations• Parametric study – e/d ratio & Fibre orientation• Following observations are made -
For e/d>2 o No major change in strength of jointo Stable failure mode is achieved
Composite with no 0° fibres – Very low strength Asymmetric fibre orientation – 50 % Higher strength then
laminate without 0° fibres and a stable failure mode is achieved Use of 45° or -45° fibres – No noticeable change in strength and
failure mode
References• Abaqus CAE user’s manual , (2013), Version 6.13, Dassault systems.• Godwin E.W., Matthews F.L. , (1980), A Review of the strength of joints in fibre-
reinforced plastics , Composites, Vol. 10, pp. 155-160.• Padhi G.S., McCarthy M.A., (2002), McCarhty C.T., BOLJAT : a tool for designing
composite bolted joints using three-dimensional finite element analysis, Composites Part A : applied science & manufacturing, Vol. 33, pp. 1573-1584.
• McCarthy M.A., McCarthy C.T., Lawlor V.P., Stanely W.F. , (2004), Three-dimensional finite element analysis of single-bolt, single-lap composite bolted joints:P1—Model development and validation, Composite structures ,Vol. 71, pp. 140-158.
• Reddy Y.S.N., Dakshina Moorthy C.M., Reddy J.N., (1995), Non-linear progressive failure analysis of laminated composite plates, Int. J. Non-linear Mechanics, Vol. 30, pp. 629-649
• Lawlor V.P., McCarthy M.A., Stanely W.F., (2001), Experimental study on the effects of clearance on single-bolt, single-shear, composite bolted joints, J. Plastic rubber and composites, Vol. 31, pp. 405-411.
• Z. Hashin, (1980), Failure criteria for unidirectional fibre composites, J. of applied mechanics ASME, Vol.47, pp. 329-334.
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