Crash behavior of composite structures

109 Pages·2014·10.7 MB·English

Crash behavior of composite structures
A CAE benchmarking study
Master’s thesis in Applied Mechanics
MARCUS ANDERSSON
PETTER LIEDBERG
Department of Applied Mechanics
Division of Material and Computational Mechanics
CHALMERS UNIVERSITY OF TECHNOLOGY
Go¨teborg, Sweden 2014
Master’s thesis 2014:40

MASTER’S THESIS IN APPLIED MECHANICS
Crash behavior of composite structures
A CAE benchmarking study
MARCUS ANDERSSON
PETTER LIEDBERG
Department of Applied Mechanics
Division of Material and Computational Mechanics
CHALMERS UNIVERSITY OF TECHNOLOGY
G¨oteborg, Sweden 2014
Crash behavior of composite structures
A CAE benchmarking study
MARCUS ANDERSSON
PETTER LIEDBERG
(cid:13)c MARCUS ANDERSSON , PETTER LIEDBERG, 2014
Master’s thesis 2014:40
ISSN 1652-8557
Department of Applied Mechanics
Division of Material and Computational Mechanics
Chalmers University of Technology
SE-412 96 G¨oteborg
Sweden
Telephone: [phone]
Cover:
Mesh of a corrugated composite specimen used in crush simulation
Chalmers Reproservice
G¨oteborg, Sweden 2014
Crash behavior of composite structures
A CAE benchmarking study
Master’s thesis in Applied Mechanics
MARCUS ANDERSSON
PETTER LIEDBERG
Department of Applied Mechanics
Division of Material and Computational Mechanics
Chalmers University of Technology
Abstract
In order to enable further implementation of composite structures in future crashworthy designs, a good way
of modeling composite materials needs to be defined. Many composites exhibit an even energy absorption
during crushing, which is advantageous during e.g. a car crash, since this leads to a constant deceleration of an
impacting object. This is what makes composite materials interesting in crashworthy structures, apart from
the fact that composites exhibits a high stiffness-to-weight ratio. Damage in fiber reinforced polymers can
occur with a combination of many failure mechanisms, such as delamination, fiber kinking, fiber pullouts and
matrix crack propagation. During crushing of composites, most of these modes can be observed. There are
many software using different techniques and material models for fiber reinforced polymers, consequently, the
various methods need to be evaluated.
As an initial part of the project, a literature study of relevant research and development concerning crash
modeling of composite structures was conducted in order to obtain an overview of the existing possibilities in
commerciallyavailablefiniteelementsoftware. Furthermore,simulationshavebeenperformedusingthesoftware
LS-DYNA and RADIOSS. The theory and behavior of three different material models were investigated. The
investigated material models are: MAT54 and MAT262 in LS-DYNA and LAW25 in RADIOSS. Simulations
that were performed were compared with results from a physical test. More specifically, the force-displacement
and energy absorption-displacement were compared.
All three material models use different material parameters, failure models and degradation schemes. MAT54
is a simple model, for which many input parameters lack direct physical meaning. Failure is based on the
Chang-Chang failure criterion. MAT262 is an advanced material model based on fracture toughness and
includes a continuum damage behavior. LAW25 in RADIOSS is also an advanced material model and involves
a plasticity formulation which gives the user the possibility to define a complex stress-strain curve.
Alltestedmaterialmodelscouldbetunedtomatchthetestdata,butwithdifferentaccuracy. Thepredictability
could not be commented for the material model MAT262 and LAW25, since vital material data could not be
obtained. All material data was known for MAT54 and the material model exhibits a poor predictability.
Keywords: composite failure, crush, crash, Finite element method, LS-DYNA, MAT54, MAT262, RADIOSS,
LAW25
i
ii
Preface
This Master’s thesis project is a part of the research project “Modelling crash behaviour in future lightweight
composite vehicles” financially supported partly by Vinnova and partly by the industrial partners of the project
Volvo Car Corporation, AB Volvo, Autoliv, Altair Engineering, DYNAmore Nordic, ˚AF Industry AB, Semcon
AB and Escenda Engineering AB (50%). The work was carried out during the spring semester of 2014 (30
higher educational credits, at the CAE department at ˚AF office in Gothenburg, Sweden. The examination
was done by the department of Applied Mechanics at Chalmers University of technology and the work was
supervised by ˚AF.
First of all we would like to thank Jonas Zachrison for giving us the opportunity to carry out this Master’s
thesis at ˚AF. Furthermore, our supervisors Henrik Nilsson and Teodor Bengtsson deserves a huge thanks,
for their support and guidance throughout the project. We would also like thank all employees at Technical
Analysis at ˚AF who made us feel welcome from the very first day. A special thanks goes to Martin Fagerstro¨m,
our examiner at Chalmers University of Technology, for the great patience, support and knowledge he has given
us. Lastly, we would like to thank our families and friends for their devotion and encouragement.
Marcus Andersson and Petter Liedberg
Gothenburg, June, 2014
iii
iv
Contents
Abstract i
Preface iii
Contents v
1 Introduction 1
1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Delimitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Relevant research on modeling of crushing 3
2.1 JAMS project in composite crashworthiness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Projects in LS-DYNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 Project in RADIOSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4 Project in ABAQUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5 Project in PAM-CRASH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Theory 12
3.1 What is a composite? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.1 Fiber reinforced polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2 Main failure modes of composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2.1 Delamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2.2 Matrix failure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2.3 Fiber failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3 Crushing of composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4 Crush test 18
5 LS-DYNA 21
5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.1.1 Simulation model of the corrugated specimen in LS-DYNA . . . . . . . . . . . . . . . . . . . . . 21
5.1.2 Available material models in LS-DYNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.2 Simulations with MAT54/55 - Enhanced composite damage . . . . . . . . . . . . . . . . . . . . . . 24
5.2.1 Theory of failure model and degradation scheme in MAT54 . . . . . . . . . . . . . . . . . . . . . 24
5.2.2 Description of Material Card MAT54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.2.3 Uniaxial simulations with one element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.2.4 Tensile dog-bone simulations with different element sizes . . . . . . . . . . . . . . . . . . . . . . 33
5.2.5 Implementation of MAT54 in crush simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.2.6 Crush simulation using baseline model with MAT54 . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.2.7 Investigation of mesh dependency in crush simulations with MAT54 . . . . . . . . . . . . . . . . 38
5.3 Simulation with MAT262 - Laminated fracture Daimler Camanho . . . . . . . . . . . . . . . . . . 40
5.3.1 Theory of failure model and degradation scheme in MAT262 . . . . . . . . . . . . . . . . . . . . 40
5.3.2 Description of material card MAT262 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.3.3 Uniaxial simulations with one element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
5.3.4 Tensile dog-bone simulations with different element sizes . . . . . . . . . . . . . . . . . . . . . . 48
5.3.5 Implementation of MAT262 in crush simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
5.3.6 Crush simulation using baseline model with MAT262 . . . . . . . . . . . . . . . . . . . . . . . . 50
6 RADIOSS 55
6.1 Introduction to RADIOSS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
6.1.1 Simulation model of the corrugated specimen in RADIOSS . . . . . . . . . . . . . . . . . . . . . 55
6.1.2 Composites and anisotropic materials in RADIOSS. . . . . . . . . . . . . . . . . . . . . . . . . . 56
6.2 Simulations with material LAW25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
6.2.1 Theory and material parameters of LAW25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
v
6.2.2 Uniaxial simulations with one element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
6.2.3 Tensile dog-bone simulations with different element sizes . . . . . . . . . . . . . . . . . . . . . . 67
6.2.4 Crush simulation using baseline model with LAW25 . . . . . . . . . . . . . . . . . . . . . . . . . 68
6.2.5 Investigation of mesh dependency in crush simulations with LAW25 . . . . . . . . . . . . . . . . 70
7 Comparison between LS-DYNA and RADIOSS 74
7.1 Material data inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
7.2 Implementation of material models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
7.3 Advantages and disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
8 Concluding remarks 77
9 Future work 78
References 79
Appendices
A Appendix - MAT54 I
A.1 Material card used in base line model using MAT54 . . . . . . . . . . . . . . . . . . . . . . . . . . I
A.2 Parameter study - Sensitivity of material model parameters in MAT54 . . . . . . . . . . . . . . . . II
A.3 Parameter study - Sensitivity of simulation model for MAT54 . . . . . . . . . . . . . . . . . . . . . X
B Appendix - MAT262 XII
B.1 Material card used in the simulation with uniform mesh model using MAT262 . . . . . . . . . . . XII
B.2 Material card used in the simulation with irregular mesh model using MAT262 . . . . . . . . . . . XIII
C LAW 25 XIV
C.1 Sensitivity of material model parameters in LAW 25 . . . . . . . . . . . . . . . . . . . . . . . . . . XIV
C.2 Influence of crushing velocity with RADIOSS model . . . . . . . . . . . . . . . . . . . . . . . . . . XVI
C.3 Material Parameters of the Baseline Model with LAW 25 . . . . . . . . . . . . . . . . . . . . . . . XVIII
vi