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Publications (10 of 31) Show all publications
Basso, M., Piselli, A., Simonato, M., Furlanetto, R., Pupure, L., Joffe, R. & De Nardo, L. (2019). Effect of food chemicals and temperature on mechanical reliability of bio-based glass fibers reinforced polyamide. Composites Part B: Engineering, 157, 140-149
Open this publication in new window or tab >>Effect of food chemicals and temperature on mechanical reliability of bio-based glass fibers reinforced polyamide
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2019 (English)In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 157, p. 140-149Article in journal (Refereed) Published
Abstract [en]

This paper presents an experimental study to assess the effects of food chemicals and temperature on the mechanical performance of glass fiber reinforced bio-based polyamide. The diffusion of food chemicals was mainly driven by thermal energy, following Arrhenius law in all tested environments. Degradation of mechanical properties and decrease in reliability were assessed, due to the plasticization of polymer matrix. Secondary but not negligible effect on flexural strength degradation is given by the different chemical interaction between polymeric chains and molecules of food chemicals. Colour change was measured and resulted to be positively correlated to diffusion.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-70638 (URN)10.1016/j.compositesb.2018.08.078 (DOI)2-s2.0-85052484539 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-31 (andbra)

Available from: 2018-08-29 Created: 2018-08-29 Last updated: 2018-09-07Bibliographically approved
Pupure, L., Varna, J., Joffe, R., Berthold, F. & Miettinen, A. (2018). Mechanical properties of natural fiber composites produced using dynamic sheet former. Wood Material Science & Engineering
Open this publication in new window or tab >>Mechanical properties of natural fiber composites produced using dynamic sheet former
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2018 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Article in journal (Refereed) Epub ahead of print
Abstract [en]

Composites formed from wood fibers and man-made cellulosic fibers in PLA (polylactic acid) matrix, manufactured using sheet forming technique and hot pressing, are studied. The composites have very low density (due to high porosity) and rather good elastic modulus and tensile strength. As expected, these properties for the four types of wood fiber composites studied here improve with increasing weight fraction of fibers, even if porosity is also increasing. On the contrary, for man-made cellulosic fiber composites with circular fiber cross-section, the increasing fiber weight fraction (accompanied by increasing void content) has detrimental effect on stiffness and strength. The differences in behavior are discussed attributing them to fiber/ fiber interaction in wood fiber composites which does not happen in man-made fiber composites, and by rather weak fiber/matrix interface for man-made fibers leading to macro-crack formation in large porosity regions.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials; Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-69464 (URN)10.1080/17480272.2018.1482368 (DOI)
Available from: 2018-06-13 Created: 2018-06-13 Last updated: 2018-06-13
Pupure, L., Varna, J. & Joffe, R. (2018). Methodology for macro-modeling of bio-based composites with inelastic constituents. Composites Science And Technology, 163, 41-48
Open this publication in new window or tab >>Methodology for macro-modeling of bio-based composites with inelastic constituents
2018 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 163, p. 41-48Article in journal (Refereed) Published
Abstract [en]

Methodology for development of a macro-scale model (with strain as an input) for Regenerated Cellulose fiber (RCF) composites with highly non-linear (viscoelastic (VE) and viscoplastic (VP)) constituents is presented and demonstrated. The VE is described by Schapery's models and Zapas' model is used for VP. For a purely VE constituent the model can be identified from stress relaxation in constant strain tests. In the presence of VP the constant strain test does not render VE stress relaxation functions, because part of the applied strain is VP and the VE strain is changing. As an alternative creep and strain recovery tests are suggested to find the plasticity law and also the nonlinear creep compliances to identify the VE model where stress is an input. The incremental form of this model is then inverted and used to simulate the VE relaxation tests and the simulated relaxation functions are used to identify the VE model with VE strain as an input.

Models for constituents are used in micromechanics simulations of the composite behavior in arbitrary ramps including the composite VE relaxation test. Using the latter, a macro-model is developed and its validity and accuracy are demonstrated.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-68687 (URN)10.1016/j.compscitech.2018.05.015 (DOI)000438323000006 ()2-s2.0-85046756325 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-05-15 (rokbeg)

Available from: 2018-05-09 Created: 2018-05-09 Last updated: 2018-08-07Bibliographically approved
Varna, J., Pupure, L. & Joffe, R. (2016). Incremental forms of Schapery’s model: convergence and inversion to simulate strain controlled ramps (ed.). Mechanics of time-dependant materials, 20(4), 535-552
Open this publication in new window or tab >>Incremental forms of Schapery’s model: convergence and inversion to simulate strain controlled ramps
2016 (English)In: Mechanics of time-dependant materials, ISSN 1385-2000, E-ISSN 1573-2738, Vol. 20, no 4, p. 535-552Article in journal (Refereed) Published
Abstract [en]

Schapery’s nonlinear viscoelastic model is written in incremental form, and three different approximations of nonlinearity functions in the time increment are systematically analysed with respect to the convergence rate. It is shown that secant slope is the best approximation of the time shift factor, leading to significantly higher convergence rate. This incremental form of the viscoelastic model, Zapas’ model for viscoplasticity, supplemented with terms accounting for damage effect is used to predict inelastic behaviour of material in stress controlled tests. Then the incremental formulation is inverted to simulate stress development in ramps where strain is the input parameter. A comparison with tests shows good ability of the model in inverted form to predict stress–strain response as long as the applied strain is increasing. However, in strain controlled ramps with unloading, the inverted model shows unrealistic hysteresis loops. This is believed to be a proof of the theoretically known incompatibility of the stress and strain controlled formulations for nonlinear materials. It also shows limitations of material models identified in stress controlled tests for use in strain controlled tests.

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-3085 (URN)10.1007/s11043-016-9311-2 (DOI)000388186900004 ()2-s2.0-84963641799 (Scopus ID)0db3b547-04c5-4062-98dc-939c3979e74b (Local ID)0db3b547-04c5-4062-98dc-939c3979e74b (Archive number)0db3b547-04c5-4062-98dc-939c3979e74b (OAI)
Note

Validerad; 2016; Nivå 2; 2016-11-22 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Pupure, L., Varna, J. & Joffe, R. (2016). Natural fiber composite: Challenges simulating inelastic response in strain-controlled tensile tests (ed.). Paper presented at . Journal of composite materials, 50(5), 575-587
Open this publication in new window or tab >>Natural fiber composite: Challenges simulating inelastic response in strain-controlled tensile tests
2016 (English)In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 50, no 5, p. 575-587Article in journal (Refereed) Published
Abstract [en]

Problems occurring, when nonlinear time-dependent material model with parameters identified in creep tests is applied to simulate high-strain response in strain-controlled tests, are described and analyzed. Reasons for discrepancies with experimental loading curves are revealed. Presented numerical/experimental examples deal with three bio-based composites showing highly nonlinear behavior due to damage, nonlinear viscoelasticity and viscoplasticity. Schapery's approach for viscoelasticity and Zapas' model for viscoplasticity are used. The model is generalized to include microdamage effect. It is shown that the main problem in simulations at high stresses is the reliability of data from creep test for model identification in this region because creep rupture limits the available data region and extrapolation to higher stresses is rather uncertain. Alternative solution is to employ relaxation tests at high strains to obtain the missing information. However, it would work only in absence of viscoplastic strains: viscoelastic relaxation functions cannot be determined by maintaining constant total strain if viscoplastic-strain is developing. Based on sensitivity analysis of composite response to variations of the elastic modulus, damage, viscoelastic and viscoplastic parameters, suggestions are made for improving (further “tuning”) the model in high stress region by using tensile stress–strain curves in quasi-static loading.

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-9188 (URN)10.1177/0021998315579435 (DOI)000370416500001 ()2-s2.0-84958206258 (Scopus ID)7c048132-2bbc-44f6-b894-67b8bb8273b3 (Local ID)7c048132-2bbc-44f6-b894-67b8bb8273b3 (Archive number)7c048132-2bbc-44f6-b894-67b8bb8273b3 (OAI)
Note
Validerad; 2016; Nivå 2; 20150401 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Pupure, L., Varna, J. & Joffe, R. (2015). Applications and limitations of non-linear viscoelastic model for simulation of behaviour of polymer composites (ed.). Paper presented at International Conference on Composite Materials : 19/07/2015 - 24/07/2015. Paper presented at International Conference on Composite Materials : 19/07/2015 - 24/07/2015.
Open this publication in new window or tab >>Applications and limitations of non-linear viscoelastic model for simulation of behaviour of polymer composites
2015 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

There are two alternative formulation of non-linear viscoelastic model to describe strain and stress controlled tests. Both models for non-linear viscoelastic materials are not compatible, and cannot be directly inverted if so required in certain cases. In order to do it numerical procedures has to be employed. Methodology for simulating nonlinear stress-strain response in iso-strain situations of fiber composites based on properties on constituents is presented.

Keywords
viscoelastic, material model, simulation, Materials science - Construction materials, Teknisk materialvetenskap - Konstruktionsmaterial
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-35888 (URN)a9b98e3f-5bc8-4c09-a08d-78fd29118e9d (Local ID)a9b98e3f-5bc8-4c09-a08d-78fd29118e9d (Archive number)a9b98e3f-5bc8-4c09-a08d-78fd29118e9d (OAI)
Conference
International Conference on Composite Materials : 19/07/2015 - 24/07/2015
Note
Godkänd; 2015; 20150818 (joffe)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-28Bibliographically approved
Pupure, L., Joffe, R. & Varna, J. (2015). Identification Of Parameters For Direct And Inverted Model To Predict Performance Of Materials Exhibiting Non-Linear Viscoelastic Behavior (ed.). In: (Ed.), C. González; C. López; J. LLorca (Ed.), Proceedings of 7th International Conference on Composites Testing and Model Identification: . Paper presented at International Conference on Composites Testing and Model Identification : 08/04/2015 - 10/04/2015. Madrid, Spain: IMDEA, Madrid (SPAIN)
Open this publication in new window or tab >>Identification Of Parameters For Direct And Inverted Model To Predict Performance Of Materials Exhibiting Non-Linear Viscoelastic Behavior
2015 (English)In: Proceedings of 7th International Conference on Composites Testing and Model Identification / [ed] C. González; C. López; J. LLorca, Madrid, Spain: IMDEA, Madrid (SPAIN) , 2015Conference paper, Meeting abstract (Refereed)
Place, publisher, year, edition, pages
Madrid, Spain: IMDEA, Madrid (SPAIN), 2015
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-27319 (URN)0bba9437-4356-48e9-8886-c98f6463a5ac (Local ID)0bba9437-4356-48e9-8886-c98f6463a5ac (Archive number)0bba9437-4356-48e9-8886-c98f6463a5ac (OAI)
Conference
International Conference on Composites Testing and Model Identification : 08/04/2015 - 10/04/2015
Note
Godkänd; 2015; 20150410 (joffe)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-28Bibliographically approved
Miettinen, A., Joffe, R., Pupure, L. & Madsen, B. (2015). Identification of true microstructure of composites based on various flax fibre assemblies by means of three-dimensional tomography (ed.). Paper presented at International Conference on Composite Materials : 19/07/2015 - 24/07/2015. Paper presented at International Conference on Composite Materials : 19/07/2015 - 24/07/2015.
Open this publication in new window or tab >>Identification of true microstructure of composites based on various flax fibre assemblies by means of three-dimensional tomography
2015 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Lately it has been demonstrated that natural fibres may be an environmentally superior alternative for, e.g., glass fibres. In order to estimate properties of composite materials made of natural fibres, models designed for synthetic fibres are often used. The models usually do not account for irregularities in the material, e.g., suboptimal fibre orientation due to the twisting angle of fibres in yarns. Use of models without taking those features into account might lead to unreliable results. Methods to quantify the microstructural properties of natural fibre composites with X-ray microtomography and three-dimensional image analysis are demonstrated in this work. The methods are applied to flax fibre composites made from three different kinds of pre-forms. Microstructural parameters estimated with the methods are used in micromechanical models for the stiffness of the composite. Comparison between rule-of-mixtures and classical laminate theory is made, highlighting the requirement for accurate parameter estimation and use of a model that accounts for significant structural features of the material.

Keywords
Flax fibers, tomography, Modeling, Materials science - Construction materials, Teknisk materialvetenskap - Konstruktionsmaterial
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-39080 (URN)db034262-569f-4b18-9238-56484eb8d8c9 (Local ID)db034262-569f-4b18-9238-56484eb8d8c9 (Archive number)db034262-569f-4b18-9238-56484eb8d8c9 (OAI)
Conference
International Conference on Composite Materials : 19/07/2015 - 24/07/2015
Note
Godkänd; 2015; 20150818 (joffe)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-05-28Bibliographically approved
Pupure, L., Varna, J. & Joffe, R. (2015). Modeling of Natural Fiber Composites (ed.). In: (Ed.), Raul Campilho (Ed.), Natural Fiber Composites: (pp. 221-253). Paper presented at . : CRC Press, Taylor & Francis Group,
Open this publication in new window or tab >>Modeling of Natural Fiber Composites
2015 (English)In: Natural Fiber Composites, CRC Press, Taylor & Francis Group, , 2015, p. 221-253Chapter in book (Refereed)
Place, publisher, year, edition, pages
CRC Press, Taylor & Francis Group,, 2015
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-21064 (URN)ad1149d2-7058-49dc-9fd0-70b3351cfd9d (Local ID)978-1-4822-3900-3 (ISBN)978-1-4822-3901-0 (ISBN)ad1149d2-7058-49dc-9fd0-70b3351cfd9d (Archive number)ad1149d2-7058-49dc-9fd0-70b3351cfd9d (OAI)
Note
Godkänd; 2015; 20151109 (joffe)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-28Bibliographically approved
Doroudgarian, N., Pupure, L. & Joffe, R. (2015). Moisture uptake and resulting mechanical response of biobased composites:: II. Composites (ed.). Paper presented at . Polymer Composites, 36(8), 1510-1519
Open this publication in new window or tab >>Moisture uptake and resulting mechanical response of biobased composites:: II. Composites
2015 (English)In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 36, no 8, p. 1510-1519Article in journal (Refereed) Published
Abstract [en]

The durability of entirely bio-based composites with respect to the exposure to elevated humidity was evaluated. Different combinations of bio-based resins (Tribest, EpoBioX, Envirez) and cellulosic fibers (flax and regenerated cellulose fiber rovings and fabrics) were used to manufacture unidirectional and cross-ply composite laminates. Water absorption experiments were performed at various humidity levels (41%, 70%, and 98%) to measure apparent diffusion coefficient and moisture content at saturation. Effect of chemical treatment (alkali and silane) of fibers as protection against moisture was also studied. However, fiber treatment did not show any significant improvement and in some cases the performance of the composites with treated fibers was lower than those with untreated reinforcement. The comparison of results for neat resins and composites showed that moisture uptake in the studied composites is primarily due to cellulosic reinforcement. Tensile properties of composites as received (RH = 24%) and conditioned (RH = 41%, 70%, and 98%) were measured in order to estimate the influence of humidity on behavior of these materials. Results were compared with data for glass fiber reinforced composite, as a reference material. Previous results from study of unreinforced polymers showed that resins were resistant to moisture uptake. Knowing that moisture sorption is primarily dominated by natural fibers, the results showed that some of the composites with bio-based resins performed very well and have comparable properties with composites of synthetic epoxy, even at elevated humidity.

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-14121 (URN)10.1002/pc.23058 (DOI)000358173200017 ()2-s2.0-84937162276 (Scopus ID)d739a4cd-c8d9-4ca3-83d3-9634916c22a1 (Local ID)d739a4cd-c8d9-4ca3-83d3-9634916c22a1 (Archive number)d739a4cd-c8d9-4ca3-83d3-9634916c22a1 (OAI)
Note
Validerad; 2015; Nivå 2; 20131217 (newdor)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8050-2294

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