DAMAGE GROWTH IN COMPOSITES Final Report

291 Pages·2012·19.26 MB·English

ORIGINAL: ENGLISH GARTEUR / TP – 176

SEPTEMBER 2012

CLASSIFICATION: GARTEUR Open

GARTEUR AG-32: DAMAGE GROWTH IN COMPOSITES
Final Report

ANIELLO RICCIO

SECOND UNIVERSITY OF NAPLES (former CIRA)

GARTEUR aims at stimulating and co-ordinating co-operation between
Research Establishments and Industry in the areas of Aerodynamics, Flight
Mechanics Systems and Integration, Helicopters and Structures & Materials.

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Contents
1.  INTRODUCTION .............................................................................................................. 4 
1.1  Project Objectives and relationship with previous projects ......................................... 6 
1.2  Work Breakdown Structure ......................................................................................... 7 
1.3  AG-32 Contacts List (some contact information may be out dated) .......................... 9 
2.  WE 1: DEVELOPMENT OF DETAILED METHODOS FOR DAMAGE GROWTH
SIMULATION IN COMPOSITES. ......................................................................................... 10 
2.1  A DETAILED METHODOLOGY FOR INTEGRATED DELAMINATION
GROWTH AND FIBRE-MATRIX DAMAGE PROGRESSION SIMULATION
(Pietropaoli Elisa, Aniello Riccio -CIRA) ........................................................................... 11 
2.1.1.  State of the art ............................................................................................................ 11 
2.1.2.  Objectives .................................................................................................................. 12 
2.1.3.  Description of the method ......................................................................................... 13 
2.1.4.  Benefits and limitations of the method and added value with respect to the state of
the art 24 
2.1.5.  Preliminary Applications ........................................................................................... 24 
2.1.6.  Interlaminar and intralaminar interaction in a composite plate with an elliptical
delamination ............................................................................................................................. 35 
2.1.7.  References ................................................................................................................. 62 
2.2  A DETAILED METHOD FOR DEBONDING ONSET - STIFFENED PANELS
(Iñaki Amendariz, Javier San Millan - INTA) ..................................................................... 67 
2.2.1.  State of the art ............................................................................................................ 67 
2.2.2.  Objectives .................................................................................................................. 67 
2.2.3.  Description of the method ......................................................................................... 67 
2.2.4.  Benefits and limitations of the method and added value with respect to the state of
the art 68 
2.2.5.  Preliminary Applications ........................................................................................... 68 
2.2.6.  References ................................................................................................................. 71 
2.3  DETAILED SIMULATION OF DELAMINATION GROWTH IN COMPOSITE
STRUCTURES (Iñaki Amendariz, Javier San Millan - INTA) ........................................... 72 
2.3.1.  State of the art ............................................................................................................ 72 
2.3.2.  Objectives .................................................................................................................. 72 
2.3.3.  Description of the method ......................................................................................... 73 
2.3.4.  Benefits and limitations of the method and added value with respect to the state of
the art 76 
2.3.5.  Preliminary Applications ........................................................................................... 76 
2.3.6.  References ................................................................................................................. 80 
2.4  BEHAVIOUR OF UNSYMMETRIC COMPOSITE PLATES UNDER THERMAL
CYCLING (Pascal Casari and Frédéric Jacquemin- UNIVERSITÉ DE NANTES) ........... 81 
2.5  DAMAGE PROGRESSION /DELAMINATION SIMULATION - GENOA FE
ANALYSIS (Salvatore Russo- ALENIA) ........................................................................... 87 
2.6  DEVELOPMENT OF FINE MODELS FOR DELAMINATION GROWTH (Cédric
Huchette- ONERA) .............................................................................................................. 93 
2.7  DEVELOPMENT OF THE ANALYTICAL TOOL – FATIGUE DELAMINATION
GROWTH MODELING (Andrew Clarke- QINETIQ) ..................................................... 116 
2.8  MICRO-DAMAGE EVOLUTION MODELING IN LAMINATES (Janis Varna-
LULEÅ UNIVERSITY OF TECHNOLOGY) .................................................................. 124 
3.  WE 2: DEVELOPMENT OF FAST METHODS FOR DAMAGE GROWTH
SIMULATION IN COMPOSITES. ....................................................................................... 139 
3.1  FINITE ELEMENT DELAMINATION STUDY OF A NOTCHED COMPOSITE
(Sören Nilsson, Alann André – SICOMP and Anders Bredberg-SAAB ) ......................... 140 
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3.1.1.  Introduction ............................................................................................................. 140 
3.1.2.  Finite Element Delamination Study of a Notched Composite Plate ....................... 141 
3.1.3.  Results ..................................................................................................................... 143 
3.1.4.  Comparison and Discussion .................................................................................... 146 
3.1.5.  Conclusions ............................................................................................................. 147 
3.1.6.  References ............................................................................................................... 149 
3.2  EFFECT OF THE DAMAGE EXTENSION THROUGH THE COMPOSITE
LAMINATES THICKNESS ON THE CALCULATION OF THE RESIDUAL
STRENGTH (Anders Bredberg-SAAB) ............................................................................ 150 
3.2.1.  State of the art .......................................................................................................... 150 
3.2.2.  Objectives ................................................................................................................ 156 
3.2.3.  Description of the method ....................................................................................... 157 
3.2.4.  Benefits and limitations of the method and added value with respect to the state of
the art 159 
3.3  A LINEAR APPROACH TO EVALUATE THE DELAMINATION GROWTH
INITIATION IN STIFFENED COMPOSITE PANELS (Aniello Riccio -CIRA). .......... 160 
3.3.1.  State of the art .......................................................................................................... 160 
3.3.2.  Objectives ................................................................................................................ 161 
3.3.3.  Description of the method ....................................................................................... 162 
3.3.4.  Benefits and limitations of the method and added value with respect to the state of
the art 171 
3.3.5.  Preliminary Applications ......................................................................................... 172 
3.3.6.  References ............................................................................................................... 183 
3.4  PHYSICALLY BASED MIXED-MODE FAILURE CRITERIA FOR
DELAMINATION GROWTH IN COMPOSITE MATERIALS (Charlotte Rogers -
IMPERIAL COLLEGE OF LONDON). ........................................................................... 187 
4.  WE 3: Manufacturing and Testing. ................................................................................ 201 
4.1  EXPERIMENTAL ACTIVITY SUPPORTING SAAB NUMERICAL WORK IN
THE GRAME OF AG-32 (Sören Nilsson, Alann André – SICOMP and Anders Bredberg-
SAAB). ............................................................................................................................... 202 
4.1.1.  Mechanical tests ...................................................................................................... 202 
4.1.2.  Inspection – NDT & fractography ........................................................................... 203 
4.1.3.  Experimental results ................................................................................................ 204 
4.1.4.  References ............................................................................................................... 206 
4.2  THE FATIGUE EVALUATION OF A DAMAGED PLATE UNDER
COMPRESSION AND CFRP ANGLE STRUCTURES UNDER BENDING (George
Spenninger - EADS-M). ..................................................................................................... 208 
4.2.1.  Scope ....................................................................................................................... 208 
4.2.2.  Plate under Compression Loads .............................................................................. 210 
4.2.3.  Bending of Composite Angle Structures ................................................................. 214 
4.1.5.  Summary .................................................................................................................. 217 
4.1.6.  Appendix ................................................................................................................. 218 
4.1.7.  References ............................................................................................................... 252 
4.3  BUCKLING AND COLLAPSE TESTS USING ADVANCED MEASUREMENT
SYSTEMS (Richard Degenhardt- DLR) ............................................................................ 253 
4.4  INSPECTION OF CFRP SPECIMENS WITH LOCK-IN THERMOGRAPHY
(Carosena Meola- UNIVERSITY OF NAPLES) ............................................................... 268 
4.5  FIBER CONTENT IN COMPOSITE PANELS MANUFACTURED BY VACUUM
INFUSION (Mauro Zarrelli e Daniele Annicchiarico - CNR-IMCB) ............................... 285 

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1. INTRODUCTION

The high specific strength and stiffness of composite materials make them suitable for use in
aerospace structures. However, the high sensitivity of these materials to the presence of
damage, arising after impact with foreign objects or caused by manufacturing defects and
stress concentrators, make designing with composites a very challenging task.
The damage mechanisms in composites are very complex and can involve one or more
constituents at a time. Delaminations, fibre breakage and matrix cracking can strongly reduce
the load carrying capability of composite structures leading, in general, to a premature failure.
Moreover, depending on the composite internal layout and on the adopted manufacturing
technique, the damage mechanisms may interact with each other, making it difficult to predict
the residual properties of composite components.
In recent years, the inability in predicting the damage onset and its evolution in composite
structures, has led to over-conservative designs, not fully realising the promised economical
benefits. Hence, in order to make the composites affordable in aerospace design, many
research projects have been started in the last decade aimed to investigate the composites’
damage mechanisms and to promote damage tolerant design approaches.
A number of GARTEUR Action Groups have been started on damage management in
composite structures:

1) GARTEUR AG 16 “Damage propagation in Composites” (1994-1997) was focused
on the delaminations in composites. Most of the work done was addressed to the
development and validation of basic methods for the delamination growth simulation.
2) GARTEUR AG 22 “Design Methodology for Damage Tolerant Composite Wing
Panels” (1998-2000) was aimed to the development of methodologies for the failure
prediction of composite wing panels.
3) GARTEUR AG 28 “Impact Damage and Repair of Composites” (2002-2006) was
addressed to the development of methodologies for the prediction and characterisation
of the impact damage. Relevant effort was also put on the analysis of impacted post-
buckling designed composite structures.

Additionally, several EU funded projects have been carried out to improve the knowledge
about composites fracture mechanisms:

4) EDAVCOS “Efficient Design And Verification of COmposite Structures” (1998-
2001) was addressed to the development of methods for design of composite
structures with damage tolerance constraints.
5) BOJCAS “Bolted Joint in Composite Aircraft Structures” (2000-2003) was focused
on the development of methodologies for the prediction of final failure of composite
joints. Delamination, fibre breakage and matrix cracking have been taken into
account.
6) FALCOM “Failure, Performance and Processing Prediction for Enhanced Design
with Non-crimp-Fabric Composites” (2001-2004) aimed to the development of
methodologies for predicting the mechanical behaviour including failure of non-crimp
fabric composites.

Finally, being composites widely adopted for military scopes, their structural behaviour
including damage evolution has been studied under MoD funded projects:
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7) DAMOCLES “Damage Management of Composite Structures for Cost Effective Life
Extensive Service” (1999-2005). DAMOCLES programmes were finalised to the
development of design numerical tools able to perform a cost oriented optimisation
taking into account damage resistance and damage tolerance constraints. Applications
to composite stiffened panels and composite wing-box proved the validity of the
developed approaches.

All these projects have contributed to increasing the knowledge of the composites structural
response and failure mechanisms. However, since GARTEUR AG 16, which represented the
first attempt to analyse the composites damage evolution, in the last ten years, big steps
forward have been made in the field of computational technologies and new “composite
oriented” non-destructive inspection tools have been introduced. These innovative
numerical/experimental features can be considered as relevant driving factors for the
development of newer effective numerical approaches oriented to the prediction of damage
on-set and growth in composites.
Furthermore, ten years of research and growing applications in industries have brought to life
new needs, to be addressed by Research and Development, for example related to the
presence of new composites typologies (textile composites) and new manufacturing
techniques (RFI, RTM, fibres placement).
The lesson learned from the majority of the mentioned research projects also suggests trying
to introduce more general approaches able to deal with different failure mechanisms
(delamination, fibres breakage, matrix cracking, etc) at a time and to take into account their
interaction, independently from the damage causes (impact, manufacturing defect etc).
Finally the emerging tendency to adopt composite materials for primary structures opens new
scenarios involving new safety issues which imply considering damage tolerance design
approaches from the earlier phases of the design process (including optimisation) rather than
limiting the use of damage on-set and growth numerical techniques to complex/expensive
non-linear verification analyses.
Starting from the above considerations, the GARTEUR Action Group AG 32:

CIRA - Italy (Chairman)
QinetiQ – United Kingdom
DLR - Germany
INTA - Spain
SICOMP - Sweden
EADS-M - Germany
ALENIA - Italy
Imperial College of London - United Kingdom
CNR (Centre of National Research) - Italy
Lulea University of Technology – Sweden
SAAB – Sweden
ONERA – France
University of Nantes – France
University of Naples - Italy

carried out between year 2006 and year 2010 a joint research work focused on “DAMAGE
GROWTH IN COMPOSITES”.

In this document the activities performed in the frame of AG -32 are described in detail.
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1.1 Project Objectives and relationship
with previous projects

Based on of the emerging needs (detailed in the previous section) related to the composites
usage in aerospace applications, the main objective of this Action Group can be summarized
in:

To develop integrated numerical/experimental methodologies capable to take into account the
presence of damage and its evolution in composite structures from the early phases of the
design (conceptual design) up to the detailed FEM analysis and verification phase

This objective addresses the following issues:

 Integration between numerical and experimental methodologies (oriented to validation
and to interpretation of the most significant physical phenomena governing the
damage mechanisms in composites)
 Investigation of generalised composite structures (laminated, textiles, etc)
 Prediction of generalised composite damage (delamination, fibre breakage, matrix
cracking, etc) on set and evolution
 Development of numerical methodologies oriented to different phases of the design
(fast methodologies for conceptual/preliminary design and detailed methodologies for
analysis and verification)

The new methodologies developed in the frame of AG-32, able to support the composites
design process and able to drive it towards a damage tolerant philosophy, can surely imply
strong changes in the way composite structures are adopted in aerospace industry.
The expected impact of the obtained results can be summarized as follows:

 Reduction of the overall composite design time and costs by improving the efficiency
of simulation tools and by reducing the number of experimental validation tests.
 Improvement of composite components performances by optimising the weight
according to damage tolerant design philosophies
 Reduction of certification costs by adopting numerical procedures able to strengthen
the certification approach based on the no-growth philosophy and, at the same time,
able to promote a future growth certification approach.
 Reduction of the in-service costs by increasing the inspections intervals
 Enhancement of the allowables by modifying the safety concepts and criteria thus
decreasing or removing the safety factors related to the presence of damage.
 Understand damage propagation to enable structures to be designed smartly to manage
damage evolution that is acceptable to airworthiness authorities.
 An increased reliability in the design of composite aircraft structures gained from the
deep understanding of the wide variety of damage processes that may take place in
polymer composites generate in the project.

The Action Group AG-32 is strongly connected, in terms of topics and objectives, with other
past and existing projects. The connections are summarized in figure 1.

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GARTEUR Projects MoDfundedProjects EU FundedProjects

GGAARRTTEEUURR AAGG 1166 EEDDAAVVCCOOSS
DDAAMMOOCCLLEESS II

GGAARRTTEEUURR AAGG 2222
DAMOCLES II
BBOOJJCCAASS

GGAARRTTEEUURR EEGG 3300
((DDAAMMOOCCLLEESS IIIIII)) FFAALLCCOOMM

GARTEUR EG 31
GARTEUR AG 28

Delamination Growth DistributedDamage in Composites
TextileComposites Impact Damage

Figure1: relationships between GARTEUR AG-32 (former EG-31) and past and existing
projects

Coupons and benchmarks tests performed under several projects (GARTEUR AG 22,
EDAVCOS, BOJCAS, FALCOM and DAMOCLES) have been useful for the validation of
the numerical methodologies developed in the frame of AG-32. Finally, the numerical
methodologies developed and the experimental activity performed within AG-32 will be of
interest for forthcoming projects dealing with damage development in composite structures.

1.2 Work Breakdown Structure

The activities have been split into Work Elements. A first division of the methods in “fast”
and “detailed” is proposed which gives prompt information about the method positioning
within the design process: fast procedures are naturally oriented to a preliminary design phase
(which is based on optimisation procedure) while detailed approaches sound more suitable for
the analysis and verification phase where the main concern is to realistically reproduce the
mechanical behaviour of limited critical regions of composite structures. Then two main
categories of activities have been selected: one oriented to delamination growth approaches
and the other focused on the rest of composites’ damage mechanisms evolution.
The first two Work Elements are focused on the development of respectively detailed and fast
numerical procedures while WE 3 and WE 4 are dedicated respectively to test on
coupons/benchmark structures and to the validation of the detailed, fast and the global local
approaches. In this report, for the sake of compactness, the validation activities performed in
the frame of WE 4 have been included in the WE 1 and WE 2 sections.

In table 1, a schematic representation of the partners’ involvement in each Work Element is
given.

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WE1: WE2: WE3: WE4:
Detailed Methodologies Fast Methodologies Manufacturing and tests Validation and Certification
WE5:
Reporting
WE 1.1: WE 1.2: WE 2.1: WE 2.2: WE 3.1: WE 3.2: WE 4.1: WE 4.2: WE 4.3:
Delam. Growth Distr.Damage Delam. Growth distr. Damage Coupons Benchmark Det. Meth. Fast Meth. Certification
CIRA
INTA
SICOMP
Imperial College
ALENIA
QINETIQ
EADS-M
CNR
SAAB
ONERA
University of Nantes
University of Naples
Lulea University
DLR

Table 2: WE Partners’ involvement

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1.3 AG‐32 Contacts List (some contact
information may be out dated)

PARTNER NAME ADDRESS TEL FAX E-MAIL
Aniello Riccio
(AG-32 Chairman)
Second University
CIRA of Naples (former Vai roma n 29, 81031
CIRA) Aversa (CE) - Italy [phone] [phone] [email protected]
Via Maiorise, 81043
Elisa Pietropaoli Capua, Italy [phone] [phone] [email protected]
Javier San Millan [phone] [phone] [email protected]
INTA Carretera de Ajalvir km
Iñaki Armendariz 4. 28850 Torrejon de
Benítez Ardoz. Madrid, Spain [phone] [phone] [email protected]
SICOMP AB, P.O. Box
SICOMP 104, SE-431 22
Leif Asp Mölndal, Sweden [phone] [phone] [email protected]
charlotte.rogers03@imperi
Charlotte Rogers al.ac.uk
IMPERIAL Room RODH 362B,
COLLEGE Aeronautics , Imperial
College , London SW7 [phone] +44 (0)20 [email protected].
Emile Greenhalgh 2AZ 5070 7594 5078 uk
Viale dell'Aeronautica,
80038 Pomigliano d'Arco [email protected]
ALENIA Salvatore Russo (NA) Italy .it
[email protected]
Arturo Minuto [phone] [phone] ia.it
Cody Technology Park,
Room 2028, Building
A7, Farnborough,
QINETIQ Hampshire, GU14 0LX, +44 (0)1252
Andrew Clarke UK [phone] 395077 [email protected]
+44 (0)1252
Charlotte Jones [phone] 395077 [email protected]
EADS-Military [phone]- [phone]-
Aircraft Dr. Markus Lang 81663 Munich, Germany 21876 32158 [email protected]
P. le Enrico Fermi, 1 -
CNR Località Granatello- [email protected] ;
Mauro Zarrelli Portici (NA) , Italy [phone] [phone] [email protected]
Div Polymer
Engineering, Lulea
LTU University of
Technology, SE 971 87
Janis Varna Lulea, Sweden [phone] [phone] [email protected]
Saab Aerostructures,
Dept. DDB-AB, SE-
SAAB
58188 Linköping,
Anders Bredberg Sweden [phone] [phone] [email protected]
Intitute of Composite
Structures and Adaptive
DLR Systems, Lilienthalplatz
7, 38108 Braunschweig, [email protected]
Richard Degenhardt Germany [phone] [phone] e
29, avenue de la
Division Leclerc, F-
92322 Châtillon Cedex
Nicolas CARRERE FRANCE [phone] [phone] [email protected]
ONERA
29, avenue de la
Division Leclerc, F-
92322 Châtillon Cedex
Cedric Huchette FRANCE [phone] [phone] [email protected]
Maître de Conférences
HDR - Université de
Nantes -Institut de
Recherche en Génie
Civil et Mécanique
University of Frédéric (GeM) - UMR CNRS frederic.jacquemin@univ-
Nantes JACQUEMIN 6183 [phone]  [phone] nantes.fr
UFR Sciences 2 rue de
la Houssiniere BP 92208
44322 NANTES CEDEX Pascal.Casari@univ-
Pascal Casari 3 - FRANCE [phone] [phone] nantes.fr
DIAS (Dipartimento di
Ingeneria Aerospaziale),
University of University of Naples
Naples Federico II, Piazzale
Tecchio 80, Napoli,
Carosena Meola 80125, Italy [phone] [phone] [email protected]

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2. WE 1: DEVELOPMENT
OF DETAILED
METHODOS FOR
DAMAGE GROWTH
SIMULATION IN
COMPOSITES.

The activities in WE1 have been oriented to the development of accurate detailed numerical
tools able to simulate the damage evolution in composites.
The delamination growth phenomenon has been investigated in the frame of the GARTEUR
AG-32 WE1 by ALENIA, CIRA, ONERA, QINETIQ and INTA.
ALENIA considered the use of the Virtual Crack Closure Technique to simulate the
propagation of damage at skin-stringer interface with commercial FEM codes (GENOA)
INTA developed an effective approach for the delamination onset and growth under post-
impact compressive loading conditions. Applications with validation of the proposed
approach on stiffened composite panels are presented. The delamination growth phenomenon
under fatigue loading conditions has been analysed by QINETIQ. ONERA and CIRA
investigated the interaction between the delamination growth phenomenon and the fibre-
matrix breakage (intra-laminar) damage in composite structures. ONERA adopted a non-local
damage approach for the simulation of the progression of fibre-matrix failure while a CZM
(Cohesive Zone Model) has been used for the delamination growth simulations.
CIRA developed a numerical model able to take into account delamination growth and fibre-
matrix damage in composites simultaneously. The model allows the simulation of fibre-
matrix damage evolution by means of Hashin failure criteria and properties degradation rules.
The damage growth is taken into account by evaluating the Strain Energy Release Rate.
The University of Nantes focused on the development of damage in unsymmetrical plate
under thermal cycle loading. Finally the University of Lulea focused on micro-damage
evolution modeling in laminates. In the next subsections the contribution of each AG-32
partner is detailed.

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