CAE method for the compression molding of discontinuous

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CAE method for compression molding:Part 1 Bulk Material, SPCE ACCE Sept 2018- NOT FOR DISTRIBUTION 1

CAE method for the compression molding of discontinuous fiber reinforced thermoplastics

Part 1: bulk form

U. Gandhi, Yuyang SongToyota Research Institute, NA

U. Vaidya University of Tennessee-Knoxville

T. Oswald, C Perez, University of Wisconsin

A. Yang, S. ValluryMoldex3D North America

NOT FOR DISTRIBUTION

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Toyota Technical Center, Ann Arbor, MI, USA

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Acknowledgement

We would like to thank, Takeshi Sekito, and

Hidetoshi Okada, Toyota Motor Company, Japan,

for their comments and valuable suggestions that

helped this project.

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Clarification for The Presentation

• This presentation is my opinion and views based on the industry and do not necessarily share Toyota’s view or future direction.

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1. Background and Motivation

2. Compression molding simulation for FRP

• Example 1

• Example 2

3. Conclusions

Agenda

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CAE method for compression molding:Part 1 Bulk Material, SPCE ACCE Sept 2018- NOT FOR DISTRIBUTION6

The Fuel economy is directly related to vehicle weight

Source DOEReducing vehicle weight is very important

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CAE method for compression molding:Part 1 Bulk Material, SPCE ACCE Sept 2018- NOT

FOR DISTRIBUTION7

0%

200%

400%

600%

25%35%

60%

75%

60%

AHSS

Glass

Fiber

Aluminum

Magnesium

Carbon

Fiber

Size of circle indicates

weight reduction potential

C

o

s

t

P

e

n

a

l

t

y

CO2 Produced in kg per

kg of material produced

2.3-2.7

21-23

21-23

18-45

14-15

Co

st

pen

alt

y

Why fiber reinforced polymers ?

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2010

Source; DOE

However the current usage is very limited

Key challenge

High cost

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Why compression molding ?

Goal: CF+Thermoplastic components made using

compression molding is of future interest.

Molding cycle time (minutes)

100101

Str

uctu

ral S

trength

/S

tiffness

Carbon fiber

Thermoset

Glass fiber Thermoplastic

Carbon fiber Thermoplastic

Fiber length (mm)101

No

rma

lize

d S

tru

ctu

ral S

tre

ng

th /S

tiff

ness

Aerospace

Current common usage

Injection Molding

Compression molding

Desired material Desired Process

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10

Fiber length increase the mechanical properties

Optimal length depends on fiber, resin and interface

Approx: 4 to 5 mm gives most benefits

Effect of fiber length on mechanical properties

CAE method for compression molding:Part 1 Bulk Material, SPCE ACCE Sept 2018- NOT FOR DISTRIBUTION

Ref: Thomas and Vlug

GF + Resin CF + Resin

Ref

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Compression molding :

CF+PP sheets compressed at high temperature

CF+PP charge extruded

a) Bulk material: b) Sheet Material (Mats):

Goal is to predict fiber condition and estimate its effect on warpage

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• Example 1

• Example 2

3. Conclusions

Agenda

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Micro-mechanics Model

microstructure based material properties

Micro-structure details

e.g. Fiber length, orientation,

concentration, geometry etc

Key steps in multi-scale modeling of fiber reinforced polymer

Homogenization

Representative volume element

(RVE) or RUC CAE model

Material property based

on Microstructure

Discontinuous fiber (long

and short)

Manufacturing process simulation

Fib

er

: L

inear

Ma

trix

: N

on

lin

ea

r

Continuous fiber

layers

Continuous fiber

Woven

Continuous

fiber Braided

Multiscale Modeling approach

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EXAMPLE 1

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Process conditions Actual values

Melt Temperature 210 oC

Mold Temperature 70 oC

Compression time 2 secs

Compression pressure 2000KN

Charge weight 170gm

Example 1: Compression molding of bulk material

Parts made by Magna

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480mm

32m

m

480mm

101 m

m

T=2mm

Element Type: mixed

Element count : 2501320

Node count : 2598806

A C

Example 1: Compression of Bulk charge: all the fiber are assumed to be random in initial charge

Prediction

Measured

Measured

Prediction


A11 is along X

Fiber Orientation prediction vs measured

NEED IMPROVEMENT ………

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Charge details

80-90 mm

200 mm

20-35 mm

170-220 gm,

CT scan at 80 micron to see the fiber condition

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Toyota Research Inst

NA

Moldex3D(Core Tech)

Prof OswaldUniv of

Wisconsin

Worked closely with Moldex3D team and Prof T. Oswald University of Wisconsin

Collaborative Approach

U VaidyaU of Tenessee

Build parts/testSoftware improvement

New Algorithm

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Worked closely with Moldex3D team and Prof T. Oswald University of Wisconsin

Volume graphicsImage

analysis

CT scan images of the part

Scanned volume is broken into number of ‘Cells’. Fiber orientation for each cell is estimated

Cut slice from charge

Key steps in mapping orientation

Step 1. CT scan to measure the orientation

Excel file

New software

New software

Step 2. Map to FE charge in Moldex3D

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When initial orientation are accounted the warpage is reduced and fiber orientation match well with the measured values

Effect of including Fiber orientation in the simulations

Warpage not measured

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EXAMPLE 2

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Complex part: Three cavities

• Warpage• Fiber orientations

Compare and judge

OK?

Judgement parameter

CAE Method

Physical Testing

Physical part made at University of Tennessee

Initial fiber condition in charge?

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Challenges to simulate multi cavity:Traditional software approach has limitations to predict:

1) Solid mechanics approach: the charge has large deformation2) Fluid mechanics approach: the charge material is highly viscous with

some elastic continuum behavior.

23

2

•Works well•Verified with the tests • Does not work - Challenge

Simple model= O Complex model = X

Difficulty in the compression cavity filling


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1. Viscoelasticity in Solid : E is function of temperature

Actual

Model implementation

2. Viscoelasticity in Liquid : The polymer chain tangles to cause elastic effect

Viscoelastic Material model include


𝐸 𝑡 = 𝐸∞ + 𝐸𝑖𝑛𝑖=1 exp(−

𝑡

𝜆𝑖),

Model implementation

Viscoelastic material model is needed

White Metzner Model used for viscoelastic model, add elastic characteristic term

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I.Mapping of initial fiber OT from test to the bulk charge in simulation

II.Viscosity properties measured for the bulk charge

25

Viscosity is measured at Moldex3D test lab

Steps to improve CAE ?


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I.How to do Mapping

26

Measurement of fiber orientation in the charge

Mapping of the fiber orientation from measurement to simulation

Defining fiber orientation in the initial bulk charge


Prof.OswaldUniversity of

Wisconsin

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Fiber orientation measurement v/s CAE

Volume graphicsImage

analysis

CT scan images of the part

Fiber orientation results(*.txt)

Cut sample from part

The measured fiber orientation results get close match to the simulation predictions

27

1 micron resolution CT scanning of carbon fiber is difficult

Development process and steps

Results for location A and C


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Results: Warpage improvement


Due to:

1.Maping initial fiber orientation; 2. Using measured material properties

Warpage prediction error is less than 10%

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Bulk charge Filling conditionCharge needed

(Goal: 110%-125% of cavity)

Warpage Target: < 30% difference with the measurement

Comments(Goal < 30%)

Charge: 138x28x27.5 = 104 ccFinished part=87 cc Bulk volume= 120%

Part: 3.6 mmCAE (initial): 2.8 mmCAE (Imp): 3.4 mm

22 %

8.2 %

Charge: 138x28x27.5 = 104 ccFinished part=87 cc Bulk volume= 120%

Part: 3.7 mmCAE(initial): 4.0 mmCAE (Imp): 3.35 mm

8 %

5%

Charge: 138x28x27.5 = 104 cc Finished part=87 cc Bulk volume= 120%

Part: 3.8 mmCAE(initial): 4.6 mmCAE (Imp): 4.0 mm

21%

4.3%

4. Flatter charge Charge: 143x98x7.8 = 105 ccFinished part=87 cc Bulk volume= 120%

CAE: 1.6 CAE (Imp): NAPart: NA

NA

1. Charge in middle

3. Three small charge

2. Charge in corner

Final studies: Compression of bulk charge (35%CF+PA6), CAE v/s Part

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• Example 1

• Example 2

3. Conclusions

Agenda

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3 Conclusions

a) Compression molding can help achieve lightweight structural

parts for automotive applications.

b) Moldex3D offers CAE-tool to study compression molding of

complex 3D parts.

c) Method to define initial orientation of the fibers in the charge is

developed.

d) It is important to treat material as viscoelastic during the

compression filling process.

c) We have used Moldex3D successfully to predict the fiber

orientation and warpage in the compression molding of fiber

reinforced thermoplastic example parts.

d) The results are verified with measured data for two examples.

Documents

CAE method for the compression molding of discontinuous