P R E S E N T E D B Y : H O S S E I N G H A Y O O RS U P E R V I S E D B Y : D R . S U O N G V . H O A

MODELING OF DEFORMATION OF DIFFERENT LAYERS DURING THE AFP PROCESS.

INTRODUCTION

• Viscoelastic properties• Different properties of each layer• Effect of time and temperature• Understanding of residual stress and final state of

material after manufacturing

INTRODUCTION

Last Layer

Layer 3

Layer 2

Layer 1

Mold

Different Temperature

Different Properties

Viscoelastic Problem

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)

The increase in number of unit cell rows (vertical)

Five by five block of unit cell minimizes the effect of boundary conditions

VISCOELASTIC PROPERTIES OF CARBON-PEEK

Creep/ Relaxation Properties of Carbon-PEEK composite

HOMOGENIZED PROPERTIES OF CARBON-PEEK

0 10000 20000 30000 40000 50000 60000 700000.00E+00

2.00E-08

4.00E-08

6.00E-08

8.00E-08

1.00E-07

1.20E-07

1.40E-07

1.60E-07

1.80E-07

Time (s)

Cre

ep P

rope

rtie

s (1/

Pa)

Figure From: A thermoviscoelastic analysis of process-induced internal stresses in thermoplastic matrix composites, Sunderland P., Yu W., Manson J., Polymer Composites, 2001

C22

VISCOELASTIC FINITE ELEMENT

( ,t

ji ijC T t d

01

expt N

ji k

k k

t d

( ,t

jTi ij

v

B C T t B d dv

Formulation:

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

One-step constant stress (one layer)

two-step constant stress (one layer)

TYPICAL ANALYSIS RESULT

One-step ramp stress (one layer)

Time(s)

Max

imum

Stra

in

TYPICAL ANALYSIS RESULT

Depositing second layer

Strain in the first layer (ramp stress)

Time(s)

Max

imum

Stra

in

TYPICAL ANALYSIS RESULT

Strain in first layer (ramp stress)

Second layer deposited

third layer deposited

fourth layer deposited

fifth layer deposited

Time(s)

Max

imum

Stra

in

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!