Finite Element Implementation of Fibre-Reinforced Materials Model in Abaqus/Explicit

134 Pages·2015·8.26 MB·English

by  Ole Vestrum

Finite Element Implementation of
Fibre-Reinforced Materials Model in
Abaqus/Explicit
Ole Vestrum
Master of Science in Mechanical Engineering
Submission date: June 2015
Supervisor: Odd Sture Hopperstad, KT
Co-supervisor: Arild Clausen, KT
Petter Henrik Holmstrøm, KT
David Morin, KT
Norwegian University of Science and Technology
Department of Structural Engineering

ACCESSIBILITY:
Department of Structural Engineering
Faculty of Engineering Science and Technology OPEN
NTNU- Norwegian University of Science and Technology
MASTER’S THESIS 2015
SUBJECT AREA: DATE: NO. OF PAGES:
Computational mechanics June 2015 14 + 108 + 10
TITLE:
Finite element implementation of fibre-reinforced materials model in Abaqus/Explicit.
BY:
Ole Vestrum
SUMMARY:
This thesis is concerned with the constitutive modelling of short fibre-reinforced composites
in the finite element code Abaqus/Explicit. The model is presented as a generic framework
which is based on a two-phase representation of the composite material. The fibres and
matrix define the two phases. The fibre phase is characterised by its volume fraction and a
discrete representation of the orientation distribution where each discrete representative is
modelled with a simple one-dimensional elastic constitutive relation. The matrix phase is
modelled with a pressure sensitive elastic-plastic mechanical behaviour, but the generic
framework allows for the easy implementation of other constitutive relations as well. The
contributions from both phases are scaled based on their respective volume fractions and
added together to form a tangible stress state.
The model is then implemented in FORTRAN. The implementation is verified through a
series of comparisons to other existing models and solutions. The verification process
yielded reasonable results and the model is assumed to be working according to the
established foundation.
Experimental data from uniaxial tensile tests of fibre-reinforced polypropylene retrieved from
a literature source were used in the validation of the model. The validation process
disclosed the potency of the model, but also some shortcomings. Finally, concrete
suggestions for improving the model are presented.
RESPONSIBLE TEACHER: Professor Odd Sture Hopperstad
SUPERVISOR(S): Professor Arild Holm Clausen, Dr. David Morin and PhD candidate Petter Henrik Holmstrøm
CARRIED OUT AT: SIMLab, Department of Structural Engineering, NTNU.

TILGJENGELIGHET:
Institutt for konstruksjonsteknikk
Fakultet for ingeniørvitenskap og teknologi ÅPEN
NTNU- Norges teknisk- naturvitenskapelige universitet
MASTEROPPGAVE 2015
FAGOMRÅDE: DATO: ANTALL SIDER:
Beregningsmekanikk Juni 2015 14 + 108 + 10
TITTEL:
Implementering av materialmodell for fiberarmerte materialer i elementmetode-
programvaren Abaqus/Explicit.
UTFØRT AV:
Ole Vestrum
SAMMENDRAG:
Denne avhandlingen tar for seg den konstitutive modelleringen av kortfiberarmerte
komposittmaterialer i elementmetodeprogramvaren Abaqus/Explicit. Modellen presenteres
som et generisk rammeverk hvor komposittet er representert ved to faser. Fiberene og
matriksen definerer disse to fasene. Fiberfasen karakteriseres gjennom sin volumfraksjon
og en diskrete representasjon av retningsfordelingen. Hver diskrete representasjon er
modellert med en-dimensjonal elastisk materialoppførsel. Matriksfasen er modellert med en
trykksensitiv elastisk-plastisk mekanisk oppførsel, men det generelle rammeverket åpner
også for en enkel implementering av andre konstitutive modeller. Bidraget fra hver fase
skaleres ut i fra deres respektive volumfraksjoner og kombineres til en endelig
spenningstilstand.
Modellen implementeres så i programmeringsspråket FORTRAN. Implementasjonen
verifiseres gjennom en rekke sammenligningsstudier med andre eksisterende modeller og
løsninger. Verifikasjonsprosessen produserte fornuftige resultater og det forutsettes at
modellen fungerer i samsvar med det etablerte rammeverket.
Eksperimentelle data fra enakset strekktester med fiberarmert polypropylen hentes fra en
literaturkilde og brukes til å validere modellen. Valideringsprosessen fremhever potensialet
i modellen, men også noen mangler. Konkrete forslag til forbedringer av modellen er til slutt
presentert.
FAGLÆRER: Professor Odd Sture Hopperstad
VEILEDER(E): Professor Arild Holm Clausen, Dr. David Morin og PhD kandidat Petter Henrik Holmstrøm
UTFØRT VED: SIMLab, Institutt for konstruksjonsteknikk, NTNU.

Department of Structural Engineering
FACULTY OF ENGINEERING SCIENCE AND TECHNOLOGY
NTNU – Norwegian University of Science and Technology
MASTER’S THESIS 2015
for
Ole Vestrum
Finite element implementation of fibre-reinforced
materials models in Abaqus/Explicit
1. INTRODUCTION
Low weight and excellent formability make polymer materials attractive for an increasing number of
applications. However, the comparatively low stiffness and strength of these materials is a challenge. These
properties can be substantially improved by including fibres during the production process. According to
today’s design practice, for instance in the automotive and offshore industry, most parts in a structure,
including those made of polymers, are modelled and analysed with the finite element method. To accurately
predict the behaviour of the materials, the designers need reliable material models. For fibre-reinforced
polymers, however, the existing models still need improvements.
2. OBJECTIVES
The research project has three main objectives: (1) to implement a material model for fibre-reinforced
polymers in the nonlinear finite element code Abaqus; (2) to verify and validate the implementation by use of
experimental, analytical and numerical results from the literature; (3) to apply the material model in a
parametric study on the behaviour of fibre-reinforced polymer components.
3. A SHORT DESCRIPTION OF THE RESEARCH PROJECT
The main topics in the research project will be as follows;
1. Literature review: Perform a literature review on the behaviour and modelling of fibre-reinforced
polymers and on characterization methods for fibre content and fibre distribution.
2. Model formulation: Establish the mathematical formulation of the material model for fibre-reinforced
polymers.
3. Numerical implementation: Establish the algorithms for integration of the rate constitutive equations and
implement the material model in Abaqus.
4. Verification and validation: Use existing experimental, analytical and numerical results to verify and
validate the implemented material model.
5. Parameter identification: Establish a method for identifying the model parameters based on experimental
data with particular emphasis on the effects of the fibres.
6. Numerical study: Perform a parametric study on the behaviour of fibre-reinforced polymer components
as a function of the fibre content and fibre distribution.
Supervisors: Petter Henrik Holmstrøm, Arild Clausen, Odd Sture Hopperstad, David Morin (NTNU)
The candidate may agree with the supervisors to pay particular attention to specific parts of the investigation,
or to include other aspects than those already mentioned. The thesis must be written as a research report,
according to current requirements and submitted to Department of Structural Engineering, NTNU, no later
than June 10th, 2015.
NTNU, January 14th, 2015
Odd Sture Hopperstad
Professor

Acknowledgements
Thethesispresentedhereinwasconductedat,theCentreforResearch-based
Innovation, Structural Impact Laboratory (SIMLab) which is housed at the
DepartmentofStructuralEngineeringattheNorwegianUniversityofScience
andTechnologyduringthespringof2015.
I would like to express my heartfelt gratitude to each and everyone of my
supervisors. Theircontributionswerenumerousandnoteasilysummarised,
butheregoes:
• My main supervisor Professor Odd Sture Hopperstad for his unprece-
dentedguidanceinmomentsofdespair—noquestionsIeverhadwere
leftunanswered.
• Professor Arild Holm Clausen for sharing his extraordinary insight in
thecomplexfieldofpolymericmaterials.
• Dr. DavidMorinforhissignificantcontributionstothesoftwareaspects
of this thesis. The implementation of the matrix model used herein is
accreditedhim.
• PhD candidate Petter Henrik Holmstrøm for his continuous support,
positivenatureandpracticalunderstanding.
Iwouldnotonlyliketocommendthemfortheiroutstandingindividualsup-
port,butalsotheirexcellentcollectiveguidanceduringourweeklymeetings.
Every single one of them contributed with their individual expertise which
havemadethisthesispossible. Theireffortshavetrulybeeninvaluable.
IalsowanttoextendaspecialthankstomyfellowstudentsBjørnHåkonFro-
dal, Bjørn Harald Snersrud and Heidi Valle for their inputs to both relevant
andirrelevantdiscussionsatthelunchtable. AthanksisalsoduetoTeodor
Heggelundforprovidingopinionsonpreliminarydraftsofthisthesisreport.
Trondheim,Norway
June10,2015
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