session 29 ic2011 schwarzkopf

Tensile Properties of Individual Wood Flour Particles

Department of Wood Science and Engineering

Use: outdoor decking, railings, fencing, landscaping timbers, highway infrastructure applications, etc.

IntroductionWood Plastic Composites

Composition:oWood ParticlesoThermoplastics

oPS, PE, HDPE, PP, PVCoAdditives

Klyosov 2008

http://www.appropedia.org/File:Wood_Plastic_Composite.jpg

composites.wsu.edu/ navy/Navy1/materials.html

Known limitations: o durabilityo significant creepo thermo-expansiono weight/strengtho …

Motivation

Space for improvemento Durability Issueso Markets

Improvement strategieso Trial and Error

Need more $$ Need more time

o Virtual Prototyping Need better fundamental understanding

– Component properties– Load transfer between components

Would existing short fiber composite theory (SFCT) be sufficient to do this?

Assumptions Short Fiber Theory Wood Plastic Composites

Well Defined Geometry

Non-Porous

Well Defined Interface –Predictable Bonding

http://urbana.mie.uc.edu/yliu/Images/short_fiber_composites.jpg

http://t2.gstatic.com/images?q=tbn:ANd9GcQRuVQHT1F2XZ5_l3BiwGMSgzqaiBTXhakgfKOOtB6gB7itCUqCRZ722N11

http://www.hindawi.com/journals/jnm/2010/453420/fig1/

BackgroundShort Fiber Composite Theory



Non-Porous


measured particle sizes

0

0.2

0.4

0.6

0.8

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

length, mm

wid

th, m

m

Measurements

Particles:

A

B

C

D

Wang (2007) Hussain (2009)O’Dell (1997)




Non-Porous


Can we apply the theory to WPC’s?


Objectives and Approach

Objectives

Characterize load transfer between wood particles and the polymer matrix

Verify the applicability of SFCT to WPCs

Approach

Measure deformation and strain distribution in and around wood particles embedded in a polymer matrix

Simulate the load transfer with morphology-based material point method modeling (MPM)

Compare the measurements with MPM and SFTC predictions

Strain distribution of embedded wood particlesSpecimen preparation

Wood flour added at a 0.25% (OD weight) loading rate

Reference: 1.0 mm sections of 0.2 mm copper wire added at the same rate

Compounded in Brabender Plasticoder Unit

Compressed in a steel mold to the thickness of ~0.6 mmPressing temperature (150°C)

Hot pressing @ ~150°C

Copper Wire - Reference Wood Particle

Stereo Microscope

Stepper Motor

Load Cell

F

ε

Field of view ~ 3 mm x 4 mm

Optical resolution ~ 2 μm/ pixel

Analysis Software

Strain distribution of embedded wood particlesTesting Method

Strain distribution of embedded wood particlesStrain Measurements – Various Angles

Oriented 45° to the direction of loading

σ11

σ11

σ11

σ11

σ11

σ11Oriented 90° to the direction of loading

Oriented 0° to the direction of loading

Strain distribution of embedded wood particlesStrain Measurements – Multiple Particle Interaction

σ11

σ11

σ11

σ11

σ11

σ11

Various Particle-to-Particle Interactions

0.00

5.00

10.00

15.00

20.00

25.00

0.0% 2.0% 4.0% 6.0% 8.0%

No

min

al S

tre

ss (

MP

a)

Strain

Stress-Strain Wire 0

Exx

0.10

0.05

0.00

εxx

σ11 σ11

Strain distribution of embedded wood particlesStrain Measurements - Analysis

0.00

5.00

10.00

15.00

20.00

25.00

0.0% 2.0% 4.0% 6.0% 8.0%

No

min

al S

tre

ss (

MP

a)

Strain

Stress-Strain Wire 0

Exx

σ11 σ11

0.10

0.05

0.00

εxx

Strain distribution of embedded wood particlesStrain Measurements - Analysis

Wire Particle

Wood Particle

Similar?

Bonded Length of the Fiber

SFCT

Strain distribution of embedded wood particlesStrain Measurements – Analysis

Optical Measurement

20 40 60 80 100 120 140

20

30

40

50

60

70

80

90

20 40 60 80 100 120 140

10

20

30

40

50

60

70

80

90

100

MPM SimulationShort Fiber Theory

Bonded Length of the Fiber

Strain distribution of embedded wood particlesStrain Measurements – Analysis

εσ

Eτ

Optical Measurement

20 40 60 80 100 120 140

20

30

40

50

60

70

80

90

20 40 60 80 100 120 140

10

20

30

40

50

60

70

80

90

100

MPM Modeling

Film Thickness Artifact

Strain distribution of embedded wood particlesStrain Measurements – Troubleshooting

Strain measurement of individual wood

particlesSample Preparation

Bridge

Wood Particle

Adhesive

Dimensions recorded for nominal stress calculation

Front Profile

≈ 0.2mm

≈ 1.0mm


particlesTesting - Method

F

F

Wood Particle Testing in Tension Optical Measurement


particlesAnalysis

0.00

75.00

150.00

225.00

0.0% 0.1% 0.2% 0.3% 0.4% 0.5% 0.6% 0.7%

Stre

ss (

MP

a)

Strain

(εxx)

-20

0

20

40

60

80

100

-0.5% -0.4% -0.3% -0.2% -0.1% 0.0%

Stre

ss (

MP

a)

Strain

(εxx)

-20

0

20

40

60

80

100

-0.5% -0.4% -0.3% -0.2% -0.1% 0.0%

Stre

ss (

MP

a)

Strain

(εxx)

Apparent Negative Strain in Tension

-0.0004

-0.0002

0

0.0002

0.0004

0.0006

Stra

in

Wood particle strain under no loading

Out of plane movement


particlesTroubleshooting

3D DIC Measurement Catadioptric System

Wood particleLight path

Cam

era

1

Planar mirror

Right angled mirror

25 mm



“Left” View “Right” View



Conclusions

Good qualitative agreement of strain patterns around the embedded particle obtained comparing:

• Optical measurements

• MPM modeling

• Short fiber theory

3D DIC of single wood particles is possible

• Single wood particle strain values can be obtained and the modulus of these particles can be determined.

• Refinement of sample preparation and testing

Acknowledgement

Questions?

session 29 ic2011 schwarzkopf

Technology

stressstrain wire

measurements particles

nominal stress mpa15

stress mpa150

nominal stress calculation

various particle

fiberwood particle

particle interactions11