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Pupurs, Andrejs
Publications (10 of 38) Show all publications
Gong, G., Nyström, B., Sandlund, E., Eklund, D., Noël, M., Westerlund, R., . . . Joffe, R. (2018). Development of Electrophoretic Deposition Prototype for Continuous Production of Carbon Nanotube-Modified Carbon Fiber Fabrics Used in High-Performance Multifunctional Composites. Fibers, 6(4), Article ID 71.
Open this publication in new window or tab >>Development of Electrophoretic Deposition Prototype for Continuous Production of Carbon Nanotube-Modified Carbon Fiber Fabrics Used in High-Performance Multifunctional Composites
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2018 (English)In: Fibers, ISSN 2079-6439, Vol. 6, no 4, article id 71Article in journal (Refereed) Published
Abstract [en]

An electrophoretic deposition (EPD) prototype was developed aiming at the continuous production of carbon nanotube (CNT) deposited carbon fiber fabric. Such multi-scale reinforcement was used to manufacture carbon fiber-reinforced polymer (CFRP) composites. The overall objective was to improve the mechanical performance and functionalities of CFRP composites. In the current study, the design concept and practical limit of the continuous EPD prototype, as well as the flexural strength and interlaminar shear strength, were the focus. Initial mechanical tests showed that the flexural stiffness and strength of composites with the developed reinforcement were significantly reduced with respect to the composites with pristine reinforcement. However, optical microscopy study revealed that geometrical imperfections, such as waviness and misalignment, had been introduced into the reinforcement fibers and/or bundles when being pulled through the EPD bath, collected on a roll, and dried. These defects are likely to partly or completely shadow any enhancement of the mechanical properties due to the CNT deposit. In order to eliminate the effect of the discovered defects, the pristine reinforcement was subjected to the same EPD treatment, but without the addition of CNT in the EPD bath. When compared with such water-treated reinforcement, the CNT-deposited reinforcement clearly showed a positive effect on the flexural properties and interlaminar shear strength of the composites. It was also discovered that CNTs agglomerate with time under the electric field due to the change of ionic density, which is possibly due to the electrolysis of water (for carboxylated CNT aqueous suspension without surfactant) or the deposition of ionic surfactant along with CNT deposition (for non-functionalized CNT aqueous suspension with surfactant). Currently, this sets time limits for the continuous deposition.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
electrophoretic deposition, carbon nanotube, multi-scale carbon reinforcement, multifunctional composites
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-72826 (URN)10.3390/fib6040071 (DOI)000455068600004 ()2-s2.0-85058692640 (Scopus ID)
Available from: 2019-02-08 Created: 2019-02-08 Last updated: 2019-08-19Bibliographically approved
Zhuang, L., Pupurs, A., Varna, J., Talreja, R. & Ayadi, Z. (2018). Effects of Inter-Fiber Spacing on Fiber-matrix Debond Crack Growth in Unidirectional Composites under Transverse Loading. Composites. Part A, Applied science and manufacturing, 109, 463-471
Open this publication in new window or tab >>Effects of Inter-Fiber Spacing on Fiber-matrix Debond Crack Growth in Unidirectional Composites under Transverse Loading
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2018 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 109, p. 463-471Article in journal (Refereed) Published
Abstract [en]

The energy release rate (ERR) of a fiber-matrix debond crack in a unidirectional composite subjected to transverse tension is studied numerically. The focus of the study is the effect of the proximity of the neighboring fibers on the ERR. For this, a hexagonal pattern of fibers in the composite cross-section is considered. Assuming one fiber to be debonded at certain initial debond arc-length, the effect of the closeness of the surrounding six fibers on the ERR of the crack is studied with the inter-fiber distance as a parameter. Using an embedded cell consisting of discrete fibers in a matrix surrounded by the homogenized composite, a finite element model and the virtual crack closure technique are used to calculate the ERR. Results show that the presence of the local fiber cluster accelerates the crack growth up to a certain initial crack angle, beyond which the opposite effect occurs. It is also found that the residual stress due to thermal cooldown reduces the ERR. However, the thermal cooldown is found to enhance the debond growth in plies within a cross-ply laminate.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-68101 (URN)10.1016/j.compositesa.2018.03.031 (DOI)000432508500044 ()2-s2.0-85044595517 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-04-03 (rokbeg)

Available from: 2018-03-28 Created: 2018-03-28 Last updated: 2018-06-08Bibliographically approved
Kahla, H. B., Ayadi, Z., Edgren, F., Pupurs, A. & Varna, J. (2018). Statistical model for initiation governed intralaminar cracking in composite laminates during tensile quasi-static and cyclic tests. International Journal of Fatigue, 116, 1-12
Open this publication in new window or tab >>Statistical model for initiation governed intralaminar cracking in composite laminates during tensile quasi-static and cyclic tests
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2018 (English)In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 116, p. 1-12Article in journal (Refereed) Published
Abstract [en]

A simple model for predicting intralaminar cracking in laminates under cyclic loads is proposed and validated. The model is limited to low stresses and low crack density and is based on the assumption that the non-uniformity of the fiber distribution is the main reason for the observed large variation of cracking resistance along the transverse direction of the layer. Hence, the resistance variation in quasi-static and in cyclic loading can be described by the same parameter. At low crack density the failure resistance variation is more significant than the variation of the stress state in the specimen, the latter becoming dominant at high crack density. At low crack density the Weibull distribution for probability of intralaminar cracking is used for crack density growth simulation during cyclic loading. Assuming the non-uniformity of the fiber distribution as the cause for variation of cracking resistance, the Weibull shape parameter in cyclic loading is the same as in quasi-static loading case while the scale parameter is assumed to degrade with the applied number of cycles and this dependence is described by a power function. Thus, the determination of parameters is partially done using quasi-static tests and partially using cyclic tests, significantly reducing the necessary testing time. The predictions of dependency of the cracking on the stress and number of cycles are validated against experimental observations of cracking in the 90-plies of quasi-isotropic non-crimp fabric (NCF) laminates as well as in tape based cross-ply laminates.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-69097 (URN)10.1016/j.ijfatigue.2018.05.030 (DOI)000450377100001 ()2-s2.0-85048258679 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-06-21 (svasva)

Available from: 2018-06-04 Created: 2018-06-04 Last updated: 2019-04-08Bibliographically approved
Varna, J., Zhuang, L., Pupurs, A. & Ayadi, Z. (2017). Growth and interaction of debonds in local clusters of fibers in unidirectional composites during transverse loading. Paper presented at 16th International Conference on Fracture and Damage Mechanics, 2017, Florence, Italy, 18 July - 20 July 2017. Key Engineering Materials, 734, 63-66
Open this publication in new window or tab >>Growth and interaction of debonds in local clusters of fibers in unidirectional composites during transverse loading
2017 (English)In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 734, p. 63-66Article in journal (Refereed) Published
Abstract [en]

Fiber/matrix debonding in transverse tensile loading of a unidirectional composite is analyzed calculating energy release rate (ERR) for interface crack propagation. Non-uniform fiber distribution (local hexagonal fiber clustering) is assumed in the model. The matrix region containing the central fiber with the debond and the 6 surrounding fibers is embedded in a large block of homogenized composite which has the same fiber content as the region analyzed explicitly. Some of the fibers surrounding the central fiber may also have a debond. The effect of the local clustering and of the presence of other debonds on magnification of the ERR is analyzed

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2017
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-65974 (URN)10.4028/www.scientific.net/KEM.754.63 (DOI)2-s2.0-85029906900 (Scopus ID)
Conference
16th International Conference on Fracture and Damage Mechanics, 2017, Florence, Italy, 18 July - 20 July 2017
Note

Konferensartikel i tidskrift

Available from: 2017-10-05 Created: 2017-10-05 Last updated: 2018-06-08Bibliographically approved
Pupurs, A. & Varna, J. (2017). Steady-state energy release rate for fiber/matrix interface debond growth in unidirectional composites. International journal of damage mechanics, 26(4), 560-587
Open this publication in new window or tab >>Steady-state energy release rate for fiber/matrix interface debond growth in unidirectional composites
2017 (English)In: International journal of damage mechanics, ISSN 1056-7895, E-ISSN 1530-7921, Vol. 26, no 4, p. 560-587Article in journal (Refereed) Published
Abstract [en]

Analytical closed form solution is derived for energy release rate due to steady-state debond growth along a broken fiber in unidirectional composite. The problem is represented by a three concentric cylinder model, where the broken and partially debonded fiber is embedded in resin and this unit is surrounded by homogenized effective composite. Parametric analysis shows that parameters in the very simple quadratic expression for energy release rate dependence on temperature change and mechanical strain are rather insensitive with respect to changes in constituent elastic properties and fiber content. The importance to have a large outer radius of the effective composite phase in the concentric cylinder model is demonstrated.

Place, publisher, year, edition, pages
Sage Publications, 2017
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-63420 (URN)10.1177/1056789515624000 (DOI)000399997000004 ()2-s2.0-85008435316 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-05-18 (andbra)

Available from: 2017-05-18 Created: 2017-05-18 Last updated: 2018-11-15Bibliographically approved
Zhuang, L., Pupurs, A., Varna, J. & Ayadi, Z. (2016). Effect of fiber clustering on debond growth energy release rate in UD composites with hexagonal packing (ed.). Paper presented at . Engineering Fracture Mechanics, 161, 76-88
Open this publication in new window or tab >>Effect of fiber clustering on debond growth energy release rate in UD composites with hexagonal packing
2016 (English)In: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 161, p. 76-88Article in journal (Refereed) Published
Abstract [en]

Steady-state energy release rate (ERR) for fiber/matrix interface debond growth originated from fiber break in unidirectional composite is calculated using 3-D FEM models with hexagonal fiber arrangement. In the model the debonded fiber is central in the hexagonal unit which is surrounded by effective composite. The effect of neighboring fibers focusing on local fiber clustering on the ERR is analyzed by varying the distance between fibers in the unit. The steady-state ERR is calculated from potential energy difference between a unit in the bonded region far away from the debond front and a unit in the debonded region far behind the debond front. The ERR for different modes of crack propagation is obtained from a FEM model containing a long debond by analyzing the stress at the debond front.Results show that in mechanical axial tensile loading fracture Mode II is dominating, it has strong angular dependence (effect of closest fibers) but the average ERR is not sensitive to the local fiber clustering. In thermal loading the Mode III is dominating and the average ERR is highly dependent on the distance to neighboring fibers. However, for realistic loads the thermal ERR is much smaller than the mechanical.

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-9352 (URN)10.1016/j.engfracmech.2016.04.037 (DOI)000377884600006 ()2-s2.0-84968627177 (Scopus ID)7f3b1433-1d2e-447f-a4a5-32cbaf110f8b (Local ID)7f3b1433-1d2e-447f-a4a5-32cbaf110f8b (Archive number)7f3b1433-1d2e-447f-a4a5-32cbaf110f8b (OAI)
Note
Validerad; 2016; Nivå 2; 20160502 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Pupurs, A., Varna, J., Loukil, M. S., Kahla, H. B. & Mattsson, D. (2016). Effective stiffness concept in bending modeling of laminates with damage in surface 90-layers (ed.). Composites. Part A, Applied science and manufacturing, 82, 244-252
Open this publication in new window or tab >>Effective stiffness concept in bending modeling of laminates with damage in surface 90-layers
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2016 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 82, p. 244-252Article in journal (Refereed) Published
Abstract [en]

Simple approach based on Classical Laminate Theory (CLT) and effective stiffness of damaged layer is suggested for bending stiffness determination of laminate with intralaminar cracks in surface 90-layers and delaminations initiated from intralaminar cracks. The effective stiffness of a layer with damage is back-calculated comparing the in-plane stiffness of a symmetric reference cross-ply laminate with and without damage. The in-plane stiffness of the damaged reference cross-ply laminate was calculated in two ways: 1) using FEM model of representative volume element (RVE) and 2) using the analytical GLOB-LOC model. The obtained effective stiffness of a layer at varying crack density and delamination length was used to calculate the A, B and D matrices in the unsymmetrically damaged laminate. The applicability of the effective stiffness in CLT to solve bending problems was validated analyzing bending of the damaged laminate in 4-point bending test which was also simulated by 3-D FEM.

Place, publisher, year, edition, pages
Elsevier, 2016
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-3182 (URN)10.1016/j.compositesa.2015.11.012 (DOI)000370997000026 ()2-s2.0-84956666458 (Scopus ID)0f8f7712-3d80-40ce-94ac-1c1535b54d62 (Local ID)0f8f7712-3d80-40ce-94ac-1c1535b54d62 (Archive number)0f8f7712-3d80-40ce-94ac-1c1535b54d62 (OAI)
Note

Validerad; 2016; Nivå 2; 20151117 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-04-08Bibliographically approved
Pupurs, A. (2016). Fiber failure and debonding in composite materials. In: Ramesh Talreja; Janis Varna (Ed.), Modeling damage, fatigue and failure of composite materials: (pp. 173-196). Paper presented at . Cambridge: Woodhead Publishing Limited
Open this publication in new window or tab >>Fiber failure and debonding in composite materials
2016 (English)In: Modeling damage, fatigue and failure of composite materials, Cambridge: Woodhead Publishing Limited, 2016, p. 173-196Chapter in book (Refereed)
Abstract [en]

Fiber–matrix interface debonding initiated from random fiber breaks is known to be one of the key damage mechanisms in unidirectional (UD) composites subjected to quasi-static and cyclic (fatigue) loading. Growth of fiber–matrix interface debonds leads to stiffness reduction and eventually to the final failure of the UD composite through coalescence of multiple debond cracks. This chapter overviews the current state of the art in modeling fiber–matrix interface debonding in UD composites. The methods reviewed in this chapter are based on fracture mechanics principles of the energy release rate. Analytical models for steady-state debond growth are presented. Finite-element method (FEM) based models for analyzing the growth of short debonds and the effects of edges and neighboring fibers are also presented.

Place, publisher, year, edition, pages
Cambridge: Woodhead Publishing Limited, 2016
Series
Woodhead Publishing series in composites science and engineering ; 66
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-21291 (URN)10.1016/B978-1-78242-286-0.00009-1 (DOI)2-s2.0-85014475452 (Scopus ID)d09b69c9-78d3-4f66-b8e1-929cb1fadc18 (Local ID)9781782422983 (ISBN)d09b69c9-78d3-4f66-b8e1-929cb1fadc18 (Archive number)d09b69c9-78d3-4f66-b8e1-929cb1fadc18 (OAI)
Note

Godkänd; 2015; 20151201 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Zhuang, L., Pupurs, A., Varna, J. & Ayadi, Z. (2016). Fiber/matrix debond growth from fiber break in unidirectional composite with local hexagonal fiber clustering (ed.). Composites Part B: Engineering, 101, 124-131
Open this publication in new window or tab >>Fiber/matrix debond growth from fiber break in unidirectional composite with local hexagonal fiber clustering
2016 (English)In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 101, p. 124-131Article in journal (Refereed) Published
Abstract [en]

Energy release rate (ERR) for fiber/matrix debonding in composite with local fiber clustering, subjected to axial tension, has been investigated numerically by a 3-D finite element (FE) model. In the model, broken fiber is central in a hexagonal unit which is embedded in an effective composite. Fiber/matrix debond with circular front is assumed to be originated from the fiber break. The effect of the local fiber clustering on ERR is studied by varying distance between the broken fiber and the neighboring fibers. For very short debonds as well as for long debonds (almost steady-state growth) the ERR was calculated by both the J integral and the Virtual crack closure technique (VCCT). Results show that the debond growth is Mode II dominated and that the ERR strongly depends on the angular coordinate. The local fiber clustering has larger effect on the angular variation for shorter debonds and the effect increases with larger local fiber volume fraction. The results obtained from the 3-D hexagonal model are compared with those obtained previously using 5-cylinder axisymmetric model developed by the same authors. The ERR values from 5-cylinder axisymmetric model could be considered as upper bound for the 3-D hexagonal model.

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-11675 (URN)10.1016/j.compositesb.2016.07.005 (DOI)000381652000013 ()2-s2.0-84978386989 (Scopus ID)ab1b33ad-2fa0-4c00-9238-6769005a61d8 (Local ID)ab1b33ad-2fa0-4c00-9238-6769005a61d8 (Archive number)ab1b33ad-2fa0-4c00-9238-6769005a61d8 (OAI)
Note

Validerad; 2016; Nivå 2; 20160707 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Xu, J., Pupurs, A., Lindbergh, G. & Varna, J. (2016). Multifunctional composites: Modeling intercalation induced stresses in constituents of micro-battery. In: ECCM 2016: Proceeding of the 17th European Conference on Composite Materials. Paper presented at 17th European Conference on Composite Materials, Munich, Germany, 26-30th June 2016. European Conference on Composite Materials
Open this publication in new window or tab >>Multifunctional composites: Modeling intercalation induced stresses in constituents of micro-battery
2016 (English)In: ECCM 2016: Proceeding of the 17th European Conference on Composite Materials, European Conference on Composite Materials , 2016Conference paper, Published paper (Refereed)
Abstract [en]

A structural battery that simultaneously carries mechanical loads while storing electrical energy offers the potential of significantly reduced total vehicle weight owing to the multifunctionality. Carbon fiber is employed as negative electrode of the battery and also as a composite reinforcement material. It is coated with a solid polymer electrolyte working as an ion conductor and separator whilst transferring mechanical loads. The coated fiber is surrounded by a conductive positive electrode material. This paper demonstrates a methodology for addressing mechanical stresses arising in a conceptualized micro battery cell during electrochemical cycling, caused by time dependent gradients in lithium ion concentration distribution in the carbon fiber

Place, publisher, year, edition, pages
European Conference on Composite Materials, 2016
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-63253 (URN)2-s2.0-85017678172 (Scopus ID)978-3-00-053387-7 (ISBN)
Conference
17th European Conference on Composite Materials, Munich, Germany, 26-30th June 2016
Available from: 2017-05-05 Created: 2017-05-05 Last updated: 2018-02-21Bibliographically approved
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