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

134 Pages·2015·8.26 MB·English
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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 i

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the two phases. The fibre phase is characterised by its volume fraction and a Modellen implementeres så i programmeringsspråket FORTRAN.
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