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Study of Shear Dominant Delamination in Thin Brittle-High Ductile Interface
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering. (Model Driven Development and Decision Support)ORCID iD: 0000-0002-1162-7023
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering. (Model Driven Development and Decision Support)
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering. (Model Driven Development and Decision Support)
Blekinge Institute of Technology, Faculty of Engineering, Department of Mechanical Engineering. (Model Driven Development and Decision Support)
2016 (English)In: 21ST EUROPEAN CONFERENCE ON FRACTURE, (ECF21) / [ed] Francesco Iacoviello, Elsevier, 2016, Vol. 2, p. 152-157Conference paper, Published paper (Refereed)
Abstract [en]

Thin laminates of Aluminum (Al) foil and Low Density Polyethylene (LDPE) film are essential constituents of food packages where these two substrates are bonded together with a thin layer of LDPE acting as adhesive. Noticeably, Al is a low ductile/quasi brittle material, whereas LDPE is highly ductile. The mechanism of delamination and strength of bond between the interfaces dictates the continuum and damage behavior of this composite. However, measuring the shear delamination properties is challenging as conventional test methods have limitations when the substrates are very thin and flexible. This study explains a tentative method that uses uniaxial tensile testing on the pre-cracked specimen of this composite to find energy dissipation due to shear delamination and successfully uses it in Finite Element Simulation in Abaqus. The delamination was observed in a narrow strip-like region close to fracture surfaces and measured with special visualization aid. A similar response was found in FEM simulation. Scanning Electron Microscopic (SEM) study of delaminated interface confirms the delamination to be shear in nature. In a cohesive zone modeling in Abaqus, the measured shear delamination energy was used as input parameter along with an arbitrary bi-linear cohesive law for validation of the experimental measurement.

Abstract [sv]

Tunna laminat av aluminium (Al) folie och lågdensitetspolyeten (LDPE) film är väsentliga beståndsdelar i livsmedelsförpackningar, där dessa två substrat är sammanbundna med ett tunt skikt av LDPE som fungerar som bindemedel. Märkbart är Al en låg segt / kvasi sprött material, medan LDPE är mycket formbart. Mekanismen för delaminering och styrka bindningen mellan gränssnitten dikterar kontinuum och skador beteende denna komposit. Men mäta skjuvning delamineringsegenskaper är utmanande som konventionella testmetoder har begränsningar när substraten är mycket tunn och flexibel. Denna studie förklarar en preliminär metod som använder enaxlig dragprovning på förhand spruckna exemplar av denna komposit för att hitta energiupptagning på grund av skjuvning delaminering och framgångsrikt använder den i finita elementsimulering i Abaqus. Delamineringen observerades i en smal remsliknande region nära brottytor och mättes med särskild visualisering stöd. Ett liknande svar återfanns i FEM simulering. Svepelektronmikroskop (SEM) studie av delaminerat gränssnitt bekräftar delaminering att vara skjuvning i naturen. I en sammanhängande zon modellering i Abaqus, var den uppmätta skärdelaminering energi som används som inparameter tillsammans med en godtycklig bilinjär sammanhängande lag för validering av experimentella mätningen.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 2, p. 152-157
Series
Procedia Structural Integrity, ISSN 2452-3216
Keywords [en]
Interlaminar shear delamination; thin flexible substrate; composite; cohesive zone modeling; work of fracture; tensile testing
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:bth-12996DOI: 10.1016/j.prostr.2016.06.020ISI: 000387976800019OAI: oai:DiVA.org:bth-12996DiVA, id: diva2:958210
Conference
21st European Conference on Fracture, ECF21, 20-24 June 2016, Catania, Italy
Note

Open access

Available from: 2016-09-06 Created: 2016-09-06 Last updated: 2019-06-14Bibliographically approved
In thesis
1. Shear Fracture and Delamination in Packaging Materials: A study of Experimental Methods and Simulation Techniques
Open this publication in new window or tab >>Shear Fracture and Delamination in Packaging Materials: A study of Experimental Methods and Simulation Techniques
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Packages are the means of preservation, distribution and convenience of use for food, medicine and other consumer products. Package opening is becoming complicated in many cases because of cutting cost in design and production of opening techniques. Introduction of new package opening technique, material or geometry for better opening experience, forces new design measurements which require a large number of prototype developments and physical testing. In order to achieve more rapid and accurate design, Finite Element Method (FEM) Simulations are widely used in packaging industries to compliment and reduce the number of physical testing.

The goal of this work is to develop the building blocks towards complete package opening simulation. The study focuses on testing and simulation of shear fracture and shear delamination of packaging materials. A modified shear test specimen was developed and optimized by finite element simulation. Test method was validated for High-density polyethylene (HDPE) and Polypropylene (PP). The developed method has been accepted by international standards organization ASTM. Based on linear elastic fracture mechanics, a geometry correction factor of shear fracture toughness for the proposed specimen was derived. The study concluded that, for ease of opening, HDPE is a more favorable material for screw caps than PP. When performing the experiment with the shear specimen to find essential work of fracture, the ligament length should be varied between twice of the thickness and half of the width of the specimen ligament.

Multi-layered thin laminate of Low-density polyethylene (LDPE) and aluminum (Al), also known as Al/LDPE laminate, is another key object addressed in this study. Continuum and fracture testing of individual layers provided the base information and input for numerical modeling. The propagation of an interfacial pre-crack in lamination in Al-LDPE laminate was simulated using several numerical techniques available in the commercial FEM solver ABAQUS, and it was concluded that using the combination of VCCT technique to model the interfacial delamination and coupled elasto-plastic damage constitutive for Al and LDPE substrates can describe interfacial delamination and failure due to necking. It was also concluded that the delamination mode in a pre-crack tip is influenced by the ratio of fracture energy release rate of mode I and II. To address the challenge in quantifying shear energy release rate of laminate with very thin substrate, a convenient test technique is proposed. Additionally, scanning electron microscopic study provided useful information on fractured and delaminated surfaces and provided evidence that strengthened the conclusions of this work.

The proposed test methods in this work will be crucial to measure the shear mechanical properties in bulk material and thin substrates. Laminates of Al and LDPE or similar material can be studied using the developed simulation technique which can be effectively used for decision support in early package development.

Place, publisher, year, edition, pages
Karlskrona: Blekinge Tekniska Högskola, 2016. p. 110
Series
Blekinge Institute of Technology Licentiate Dissertation Series, ISSN 1650-2140 ; 5
Keywords
Package opening, Shear test specimen, Stress intensity factor, Finite Element simulation, Scanning electron microscopy, Polymers, Interlaminar shear delamination
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:bth-13340 (URN)978-91-7295-333-8 (ISBN)
Presentation
2016-12-09, J1650, Blekinge Tekniska Högskola, 37179 Karlskrona, 10:00 (English)
Opponent
Supervisors
Projects
model driven development and decision support project (MDS3)
Available from: 2016-11-09 Created: 2016-11-07 Last updated: 2017-05-02Bibliographically approved
2. Fracture and Delamination in Packaging Materials: A Study of Experimental Methods and Simulation Techniques
Open this publication in new window or tab >>Fracture and Delamination in Packaging Materials: A Study of Experimental Methods and Simulation Techniques
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Packages are the means of preservation, distribution and convenience of use for food, medicine and other consumer products. The introduction of a new package-opening technique for a better opening experience requires additional prototype development and physical testing. In order for the design process to be more rapid and robust, finite element (FE) simulations are widely used in packaging industries to compliment and reduce the amount of physical testing.

The goal of this work is to develop some building blocks for complete package-opening FE-simulation. To begin with, the study focuses on mechanical testing of packaging materials’ fracture and delamination; especially shear fracture. Use of tools like digital image correlation (DIC) and scanning electron microscope (SEM) greatly aided to the strain measuring technique and observation of fractured and delaminated surfaces respectively.

A modified shear test specimen for polymer sheet testing was developed and its geometry was optimized by FE-simulation. A geometry correction factor of shear fracture toughness for the proposed specimen was derived based on linear elastic fracture mechanics (LEFM). It was found that the specimen ligament length should vary between twice the thickness and half the ligament width of the modified shear specimen to measure the essential work of fracture.

Thin-flexible laminate of low-density polyethylene (LDPE) and aluminium (Al) is another key packaging material addressed in this study. The continuum and fracture testing of individual layers provided the base information and input for FE-modelling. The FE-simulation material parameters were calibrated from the physical test response through inverse analysis. Identification process of the laminate interface fracture energy (Gc) from peel tests was studied experimentally and theoretically. A successful FE-simulation optimization framework using artificial neural network and genetic algorithm was developed for the calibration of Gc. To address the challenge in quantifying shear Gc of laminate with very thin substrates, a convenient test technique was proposed. In a separate case, the tearing response of LDPE/PET (polyethylene terephthalate) laminate was studied to examine crack propagation, crack path deviation and delamination of the laminate in mode III fracture. Several tear EWF evaluation theories were proposed along with a cyclic tear test method.

Place, publisher, year, edition, pages
Karlskrona: Blekinge Tekniska Högskola, 2019. p. 230
Series
Blekinge Institute of Technology Doctoral Dissertation Series, ISSN 1653-2090 ; 10
Keywords
packaging materials and laminates, shear test specimen, essential work of fracture, finite element simulation, optimization, tearing, peel, polymers, cohesive zone modelling
National Category
Applied Mechanics
Identifiers
urn:nbn:se:bth-18048 (URN)978-91-7295-379-6 (ISBN)
Public defence
2019-09-20, J1650, Valhallavägen 1, 371 41 Karlskrona, Karlskrona, 09:00 (English)
Opponent
Supervisors
Available from: 2019-06-18 Created: 2019-06-14 Last updated: 2019-09-03Bibliographically approved

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Islam, Md. ShafiqulZhang, DefengMehmood, NasirKao-Walter, Sharon

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