MODELING OF DEFORMATION OF DIFFERENT
LAYERS DURING THE AFP PROCESS.
P R E S E N T E D B Y: H O S S E I N G H AY O O R
S U P E R V I S E D B Y : D R . S U O N G V. H O A
INTRODUCTION
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Viscoelastic properties
Different properties of each layer
Effect of time and temperature
Understanding of residual stress and final state of
material after manufacturing
INTRODUCTION
Different Temperature
Last Layer
Different Properties
Viscoelastic Problem
Layer 3
Layer 2
Layer 1
Mold
Figure From: Analysis of Process-Induced Residual Stresses in Tape Placement, F.
Sonmez, H. T. Hahn, M. Akbulut, J. of Thermoplastic Composite Materials, 2002
VISCOELASTIC PROPERTIES OF CARBON-PEEK
• Creep Properties of PEEK
• Carbon fiber remains elastic
Figure From: Characterization and modeling of nonlinear viscoelastic response of PEEK resin
and PEEK composites, X.R. Xiao, C.C. Hiel, A.H. Cardon, Composite Engineering, 1994
VISCOELASTIC PROPERTIES OF CARBON-PEEK
VISCOELASTIC PROPERTIES OF CARBON-PEEK
The increase in number of
unit cell columns
(horizontal)
Five by five block of
unit cell minimizes the
effect of boundary
conditions
The increase in number of
unit cell rows (vertical)
VISCOELASTIC PROPERTIES OF CARBONPEEK
Creep/ Relaxation
Properties of CarbonPEEK composite
HOMOGENIZED PROPERTIES OF CARBONPEEK
1.80E-07
1.60E-07
Creep Properties (1/Pa)
C22
1.40E-07
1.20E-07
1.00E-07
8.00E-08
6.00E-08
4.00E-08
2.00E-08
0.00E+00
0
10000
20000
30000
40000
Time (s)
50000
60000
70000
Figure From: A thermoviscoelastic analysis of process-induced internal stresses in
thermoplastic matrix composites, Sunderland P., Yu W., Manson J., Polymer Composites, 2001
VISCOELASTIC FINITE ELEMENT
Formulation:
i 
t
 Cij (T , t  

 j

d
N

 t   
 i    0   k exp    j d
k 1
  k   
 
t
t
 i    BT Cij (T , t   B
v 
 j

d dv
NEW BOUNDARY CONDITIONS
Attaching the nodes in the
stiffness matrix
MULTI-LAYER
• Each 8-noded viscoelastic element can represent a unit cell
(computational time is many times less)
• Different Scenarios can be analyzed
• Timing, thickness, temperature can be changed in the analysis
TYPICAL ANALYSIS RESULT
two-step constant stress
(one layer)
One-step
constant stress
(one layer)
TYPICAL ANALYSIS RESULT
Maximum Strain
One-step ramp stress
(one layer)
Time(s)
TYPICAL ANALYSIS RESULT
Maximum Strain
Strain in the first
layer (ramp stress)
Depositing
second layer
Time(s)
TYPICAL ANALYSIS RESULT
Maximum Strain
Strain in first layer
(ramp stress)
third layer
deposited
Second layer
deposited
Time(s)
fourth layer
deposited
fifth layer
deposited
CONCLUSION
• Residual Strain/Stress can be predicted and can be
used in manufacturing design to optimize the
design.
• With developed modeling method different
Scenarios of Manufacturing in terms of Timing,
Thickness can be modeled and analyzed.
THANK YOU!