Marco PaggiIMT School for Advanced Studies Lucca

Laboratorio NEST, Scuola Normale Superiore, Pisa, 30/11/2017

Frontier research on multi-scale analysis of materials

Aims

MUSAM –Multi-scale Analysis of Materials– is a research unitof the IMT School for Advanced Studies Lucca contributing toresearch and educational programs by integrating:

• Numerical analysis

• Mechanics (computational and experimental)

• Materials science

for the characterization and simulation of natural or artificialmaterials characterized by multiple scales or in the presenceof multiple fields (coupled problems)

The vision

• M. Paggi, Associate Professor

• A. Bacigalupo, Assistant Professor

Post-docs

• C. Borri

• M. Gagliardi

PhD students

• V. Carollo

• P. Cinat

• V. Govindarajan

• R. Del Toro

• N. Dardano

• T. Guillen Hernandez

• M. Marulli

• J. Bonari

Multi-scale Analysis of Materials

MUSAM Research unit

Former staff

• P. Budarapu (tenure-track assistant

professor, Indian Institute of Technology

Bhubaneswar, India)

• O.S. Ojo (post-doc, University of Limerick,

Ireland)

• P. Lenarda (post-doc, IIT Genova)

• F. Fantoni (post-doc, University of Brescia)

• I. Berardone (post-doc, University of Bologna)

Visiting professors

• D. Bigoni, University of Trento

• J. Reinoso, University of Seville

• M. Corrado, Politecnico di Torino

• A. Gizzi, Università Campus Bio-Medico of Rome

• A. Popp, TU Munich

• A. Vakis, University of Groningen

• D. Piga, SUPSI Lugano

International cooperations

• C. Linder Stanford University (LA, USA)

• J.R. Barber University of Michigan (MI, USA)

• D.A. Hills University of Oxford (UK)

• F. Borodich Cardiff University (UK)

• P. Wriggers, R. Rolfes University of Hannover (Germany)

• R. Brendel, S. Kajari-Schröder Institute for Solar Energy Research Hamelin (Germany)

• T. Rabczuk Bauhaus University of Weimar (Germany)

• V. Popov TU Berlin (Germany)

• Q.-C. He University of Paris-EST (France)

• J. Reinoso, V. Mantic University of Seville (Spain)

• P.P. Camanho University of Porto (Portugal)

• P. Areias University of Evora (Portugal)

• O. Naimark, O. Plekhov Russian Academy of Sciences (Russia)

FacilitiesMUSAM-Lab

http://www.imtlucca.it/research/laboratories/musam-lab

• 3D confocal-interferometric profilometer (LEICA, DCM 3D)

• Scanning Electron Microscope (ZEISS, EVO MA15)

• Micromechanical testing stage (DEBEN, 5000S)

• Universal testing machine with a thermostatic chamber (Zwick/Roell,

Z010TH) and a peeling test setup

• Thermocamera (FLIR, T640bx)

• Photocamera for electroluminesce (PCO, 1300 Solar)

• 3D displacement correlation technique (Correlated Solutions, VIC3D)

FacilitiesMultiscale computational fracture mechanics

Applied displacement

Key features:

• Concurrently coupled FEM

(solid shells with phantom

node method) & molecular

statics (LAMMPS) model

• Adaptive refinement

• Prediction of crack branching

from molecular statics

Silicon thin layer

FacilitiesComputational fracture mechanics:

fibrous materials

s

gN

gc

True crack Process zone

x

Cohesive Traction, s(x) Fictitious Crack Tip

su

FacilitiesComputational fracture mechanics:

fibrous materials

4 cm

1,6 cm

1,2 cm

2 cm

1,2 cm

0,2 cm

0,25 cm

FacilitiesComputational fracture mechanics of

fibrous materials

Key features:

• Fiber orientation

distribution

• Finite elasticity

• New finite element The effect of fiber anisotropy

on the peeling resistance

FacilitiesComputational fracture mechanics of coatings:

interplay between fracture and instability

Brau et al. (2011) Multiple-length-scale elastic instability mimics

parametric resonance of nonlinear oscillators, Nature Physics 7, 56-60.

Buckling-driven delamination in case of wrinkling

Potential multiple scenarios

Wrinkling but no delamination Buckled delamination Wrinkle-induced delamination

Mei H. (2011) Fracture and delamination of elastic thin films on compliant substrates: modeling and simulations, PhD Dissertation

Univ. Texas Austin

Failure of thermal-barrier coatings

Zhao et al. (2010) Surf. Coat. Tech.

204:2432-2441

FacilitiesComputational fracture mechanics of coatings:

interplay between fracture and instability

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 0.002 0.004 0.006 0.008 0.01

Mei 2011

FGM no CZM

2.5e-5

1e-4

Nominal strain 𝜺

Wri

nkl

e A

mp

litu

de

A/h

2.5𝑥10−5 𝐸𝑓

1𝑥10−4 𝐸𝑓

Wrinkle amplitude (Mei 2011)

based on fully bonded interface and

homogeneous layer

Key features:

• Solid shell finite elements coupled with interface finite elements for the study of the

interplay between fracture and geometrical instability

FacilitiesComputational fracture mechanics of coatings:

interplay between fracture and instability

Debonding of stiff coatings from polymeric layers

Prediction of

debonding for

flexible electronics

(Silicon on polymer)

FacilitiesGraphene-based electronics

inkjet printed on paper

Thick film Thin filmIn situ mechanical testing

An innovative strain gauge

FacilitiesComputational fracture mechanics

for laminates

(a)

(b)

(c)

(d)

FacilitiesComputational fracture mechanics

of polycrystalline Silicon

(a) v=16.5 mm (b) v=18.0 mm

(c) v=18.5 mm (s) v=20.0 mm

Imposed displacement

v

Some failure modes of PV modules:

1. Cracks due to mechanical loads

2. Decohesion of the encapsulant

3. Moisture-induced degradation

1

2

3

Durability of photovoltaic modules:open issues

Length scale

Time scale

1 m10-1 m10-6 m

1 ms

20 yrs

1 day

1 ms

Recombination

effects

Brittle

fracture

Temperature

cycles

Moisture

diffusion

p-n junction

Silicon solar cell

PV module

10-4 m

Durability of photovoltaic modules:multiscale problem

Heat

conductionMechanics Moisture

diffusion

Temperature

Chemical

reactions

Semiconductor

device

Temperature

Fracture

Fracture

Mech. degradation polymers

Fracture

Temperature

Durability of photovoltaic modules:coupled problem

Prediction of complex

crack patterns,

electrically inactive

areas, power losses

Coupled hygro-thermo-mechanical problems

Key features:

• Staggered vs. monolithic FE schemes

• Novel time stepping techniques

Coupled hygro-thermo-mechanical problems

400 cycles

Browning

Innovation Week on RES, 1-12 July 2012, T.E.I. of Patras, GreeceE. Kaplani,13

Acetic acid (CH3COOH):

25

6.2.1,

6.2.2

Browned EVA on top of a

cell with two cracks in a cell.

Photobleaching takes also

place along cell cracks

therefore the crack is visible.

The browning takes several

year to appear. This may not

be mistaken for Snail tracks.

B(f) C

[Schulze13]

6.2.3 Snail Track is a

discolouration of the silver

paste used for the gridlines

on the cells. The

discolouration appears along

cell cracks. This may not be

mistaken for photobleaching

of EVA along cell cracks.

B(f) C

6.1.2 Delamination of backsheet B/C(e) D

Visual defects like bent or misaligned external surfaces, frames or junction boxes may lead to failures in the field. Otherwise defects like cracked cells have a high probability to cause follow-upfailures of the modules with power loss or safety issues. Other defects like delamination or small cell-frame distances can cause safety failures, because the insulation is not guaranteed. References [IEC61215] International Electrotechnical Commission (IEC) 61215: 2nd edn, 2005. Crystalline silicon terrestrial photovoltaic modules - Design qualification and type approval.

[IEC61646] International Electrotechnical Commission (IEC) 61646: 2nd edn, 2008. Thin-film terrestrial photovoltaic modules - Design qualification and type approval.

[Schulze13] K. Schulze, M. Groh, M. Nieß, C. Vodermayer, G. Wotruba und G. Becker, Untersuchung von Alterungseffekten bei monokristallinen PV-Modulen mit mehr als 15 Betriebsjahren durch Elektrolumineszenz- und Leistungsmessung, Proc. 28. Symposium Photovoltaische Solarenergie (OTTI, Staffelstein, Germany, 2013)

[Zamini07] S. Zamini, S. Mau, T. Krametz: "IEC 61215 - Erfahrungen aus 4 Jahren Prüftätigkeit." TÜV Modulworkshop, (TÜV, Cologne, Germany) 2007

Innovation Week on RES, 1-12 July 2012, T.E.I. of Patras, GreeceE. Kaplani,18 Snail trailsAg corrosion

Moisture sorption + gas

formation + overheating

25

6.2.1,

6.2.2

Browned EVA on top of a

cell with two cracks in a cell.

Photobleaching takes also

place along cell cracks

therefore the crack is visible.

The browning takes several

year to appear. This may not

be mistaken for Snail tracks.

B(f) C

[Schulze13]

6.2.3 Snail Track is a

discolouration of the silver

paste used for the gridlines

on the cells. The

discolouration appears along

cell cracks. This may not be

mistaken for photobleaching

of EVA along cell cracks.

B(f) C

6.1.2 Delamination of backsheet B/C(e) D

Visual defects like bent or misaligned external surfaces, frames or junction boxes may lead to failures in the field. Otherwise defects like cracked cells have a high probability to cause follow-upfailures of the modules with power loss or safety issues. Other defects like delamination or small cell-frame distances can cause safety failures, because the insulation is not guaranteed. References [IEC61215] International Electrotechnical Commission (IEC) 61215: 2nd edn, 2005. Crystalline silicon terrestrial photovoltaic modules - Design qualification and type approval.

[IEC61646] International Electrotechnical Commission (IEC) 61646: 2nd edn, 2008. Thin-film terrestrial photovoltaic modules - Design qualification and type approval.

[Schulze13] K. Schulze, M. Groh, M. Nieß, C. Vodermayer, G. Wotruba und G. Becker, Untersuchung von Alterungseffekten bei monokristallinen PV-Modulen mit mehr als 15 Betriebsjahren durch Elektrolumineszenz- und Leistungsmessung, Proc. 28. Symposium Photovoltaische Solarenergie (OTTI, Staffelstein, Germany, 2013)

[Zamini07] S. Zamini, S. Mau, T. Krametz: "IEC 61215 - Erfahrungen aus 4 Jahren Prüftätigkeit." TÜV Modulworkshop, (TÜV, Cologne, Germany) 2007

Poly(ethylene-co-vinyl acetate) EVA

Unsaturation

Carbonyl bonds

Chemical degradation

Surface texturing of SIlicon

Metal assisted etching

60 min

30 min

15 min 8 min

Key features:

• The effect of roughness on

leakage

• Light reflectance

• Thermal and electric

resistance of the interface

• Wettabilty

• Adhesion

Multi-scale roughness

characterization

Contact mechanics

simulation (BEM)

• Normal contact

• Tangential contact

• Wear prediction

• Contact conductance

P/(EA) x

Ar/

A (

%)

Multiscale analysis of surface texturing

Advanced monitoring and image analysis

Thermography (IR)Electroluminescence (EL)

GUIDELINES FOR EL OUTDOOR QUALIFICATION OF PV SYSTEMS

Intersolar Europe Conference, 30 May 2017, Munich, Germany

PV Reliability & Assessment of Technical Risks in PV Investments

Outreach and collaboration

with the International Energy Agency

MUSAM research unit

Graphene coatings Fibrous materials Photovoltaics Flexible electronics

PolycrystalsAdvection-reaction-diffusion

systems

Printable electronics

Summary

International Energy Agency

Photovoltaic Power Systems Programme (PVPS)

Collaborations and technology transfer

Joint Research Centre

Institute for Energy and Transport

Institute for Solar Energy Research

Hamelin, Germany

http://musam.imtlucca.it

https://www.facebook.com/fanpagemusam

Acknowledgements