Change search
Link to record
Permanent link

Direct link
BETA
Sparnins, Edgars
Publications (10 of 27) Show all publications
Andersons, J., Joffe, R. & Sparnins, E. (2012). Evaluation of interfacial shear strength by tensile tests of impregnated flax fiber yarns (ed.). Paper presented at . Journal of composite materials, 46(3), 351-357
Open this publication in new window or tab >>Evaluation of interfacial shear strength by tensile tests of impregnated flax fiber yarns
2012 (English)In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 46, no 3, p. 351-357Article in journal (Refereed) Published
Abstract [en]

Adhesion of flax fibers and polymer matrix as well as mutual bonding of elementary fibers in a technical fiber are among the principal factors governing the mechanical response of flax fiber reinforced polymer-matrix composites. A method for evaluation of adhesion is proposed based on tension tests of impregnated fiber yarns, with subsequent characterization by optical microscopy of length distribution of fibers pulled out of the yarn fracture surfaces. An elementary probabilistic model is derived relating aspect ratio distribution of the pulled out fibers to the fiber tensile strength distribution and the effective interfacial shear strength. The method was applied to flax fiber/vinylester resin yarns and an estimate of interfacial shear strength at 17 MPa was obtained.

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-15419 (URN)10.1177/0021998311410505 (DOI)000299611600008 ()2-s2.0-84856454583 (Scopus ID)eecdb2d1-ba80-4917-915d-dbb487c349e1 (Local ID)eecdb2d1-ba80-4917-915d-dbb487c349e1 (Archive number)eecdb2d1-ba80-4917-915d-dbb487c349e1 (OAI)
Note
Validerad; 2012; 20110830 (joffe)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Varna, J., Sparnins, E., Joffe, R., Nättinen, K. & Lampinen, J. (2012). Time dependent behavior of flax/starch composites (ed.). Paper presented at . Mechanics of time-dependant materials, 16(1), 47-70
Open this publication in new window or tab >>Time dependent behavior of flax/starch composites
Show others...
2012 (English)In: Mechanics of time-dependant materials, ISSN 1385-2000, E-ISSN 1573-2738, Vol. 16, no 1, p. 47-70Article in journal (Refereed) Published
Abstract [en]

The time dependent mechanical response of flax fiber reinforced thermoplastic starch matrix composite and neat starch is analyzed. It is demonstrated that the response is highly sensitive with respect to the relative humidity (with specific saturation moisture content in the composite) and special effort has to be made to keep it constant. It was found that micro-damage accumulation and resulting elastic modulus reduction in this type of composites is limited. The highly nonlinear behavior of composites is related to nonlinear viscoelasticity and viscoplasticity. These phenomena are accounted for by simple material models suggested in this study. The stress dependent nonlinearity descriptors in these models are determined in creep and strain recovery tests at low as well as high stresses

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-9993 (URN)10.1007/s11043-011-9156-7 (DOI)000299370600004 ()2-s2.0-84858834181 (Scopus ID)8bd8cde5-0de7-449e-b15d-076d2d57250b (Local ID)8bd8cde5-0de7-449e-b15d-076d2d57250b (Archive number)8bd8cde5-0de7-449e-b15d-076d2d57250b (OAI)
Note
Validerad; 2012; 20110916 (joffe)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Andersons, J., Joffe, R., Sparnins, E. & Weichert, D. (2011). Modeling the effect of reinforcement discontinuity on the tensile strength of UD flax fiber composites (ed.). Paper presented at . Journal of Materials Science, 46(15), 5104-5110
Open this publication in new window or tab >>Modeling the effect of reinforcement discontinuity on the tensile strength of UD flax fiber composites
2011 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 46, no 15, p. 5104-5110Article in journal (Refereed) Published
Abstract [en]

To exploit the potential of natural fibers as reinforcement of polymer matrix composites, aligned bast fiber composite materials are being produced and studied. Bast fiber reinforcement is discontinuous due to the limited length of natural fibers, which needs to be reflected in predictive models of mechanical properties of composites. The strength in tension in the fiber direction of an aligned flax fiber-reinforced composite is modeled assuming that a cluster of adjacent fiber discontinuities is the origin of fracture. A probabilistic model of tensile strength, developed for UD composites containing a microdefect, is applied. It follows from the theoretical analysis that the experimental tensile strength as a function the fiber volume fraction can be described with acceptable accuracy assuming the presence of a cluster of ca. 4 × 4 elementary fiber discontinuities

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-10348 (URN)10.1007/s10853-011-5440-9 (DOI)000290453900012 ()2-s2.0-79956149576 (Scopus ID)924bd811-7014-45c5-ab25-c636d13a0133 (Local ID)924bd811-7014-45c5-ab25-c636d13a0133 (Archive number)924bd811-7014-45c5-ab25-c636d13a0133 (OAI)
Note
Validerad; 2011; 20110325 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Andersons, J., Sparnins, E., Nyström, B. & Joffe, R. (2011). Scale effect of the tensile strength of flax-fabric-reinforced polymer composites (ed.). Paper presented at . Journal of reinforced plastics and composites (Print), 30(23), 1969-1974
Open this publication in new window or tab >>Scale effect of the tensile strength of flax-fabric-reinforced polymer composites
2011 (English)In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 30, no 23, p. 1969-1974Article in journal (Refereed) Published
Abstract [en]

The development of UD natural fiber composites, considered for application as structural materials, necessitates evaluation of the scale effect of their strength. Alignment of the fibers in flax bast fiber composites can be achieved by employing textile reinforcement, such as yarns and fabrics. Cutting specimens for mechanical tests out of such textile-reinforced composite plates results in a complex non-uniform reinforcement structure at their edges, which may affect the strength of specimens. Scale effect of the tensile strength in the fiber direction of flax fabric reinforced composites is studied in the current work. A model accounting for both volume and edge effect of the specimens on their tensile strength is proposed.

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-12685 (URN)10.1177/0731684411422758 (DOI)000298295300008 ()2-s2.0-84861415858 (Scopus ID)bd94e532-9dc3-4181-93f1-1dba3a1067de (Local ID)bd94e532-9dc3-4181-93f1-1dba3a1067de (Archive number)bd94e532-9dc3-4181-93f1-1dba3a1067de (OAI)
Note
Validerad; 2011; 20110830 (joffe)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Sparnins, E., Pupurs, A., Varna, J., Joffe, R., Nättinen, K. & Lampinen, J. (2011). The moisture and temperature effect on mechanical performance of flax/starch composites in quasi-static tension (ed.). Paper presented at . Polymer Composites, 32(12), 2051-2061
Open this publication in new window or tab >>The moisture and temperature effect on mechanical performance of flax/starch composites in quasi-static tension
Show others...
2011 (English)In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 32, no 12, p. 2051-2061Article in journal (Refereed) Published
Abstract [en]

The effect of temperature and moisture on mechanical behavior of flax fiber/starch based composites was investigated experimentally. Elastic modulus, the nonlinear tensile loading curves, and failure strain were analyzed. Neat matrix and composites with 20 and 40% weight content of fibers were tested. It was found, performing tests with different amplitudes, that microdamage development with stress is rather limited and the related elastic modulus reduction in this type of compositesis not significant. It was shown that the composite elastic modulus and failure stress are linearly related to the maximum tensile stress in resin. The sensitivity of the maximum stress of the resin with respect to temperature and moisture is the source of composites sensitivity to these parameters. Constant interface stress shear lag model for stress transfer assuming matrix yielding at the fiber/matrix interface has been successfully used to explain the tensile test data. It indicates that the sensitivity of the used composite with respect to the matrix properties change could be significantly reduced by increasing the average fiber length from 0.9 mm to 1.5 mm.

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-15484 (URN)10.1002/pc.21184 (DOI)000297515300016 ()2-s2.0-81155131226 (Scopus ID)f002ae66-613a-4b30-875b-2c6245b87745 (Local ID)f002ae66-613a-4b30-875b-2c6245b87745 (Archive number)f002ae66-613a-4b30-875b-2c6245b87745 (OAI)
Note
Validerad; 2011; 20111005 (joffe)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Joffe, R., Andersons, J. & Sparnins, E. (2009). Applicability of Weibull strength distribution for cellulose fibers with highly non-linear behaviour (ed.). In: (Ed.), (Ed.), ICCM 17, Edinburgh: 17th International Conference on Composite Materials ; 27 Jul 2009 - 31 Jul 2009, Edinburgh International Convention Centre, Edinburgh, UK. Paper presented at International Conference on Composite Materials : 27/07/2009 - 31/07/2009. London: IOM Communications
Open this publication in new window or tab >>Applicability of Weibull strength distribution for cellulose fibers with highly non-linear behaviour
2009 (English)In: ICCM 17, Edinburgh: 17th International Conference on Composite Materials ; 27 Jul 2009 - 31 Jul 2009, Edinburgh International Convention Centre, Edinburgh, UK, London: IOM Communications , 2009Conference paper, Published paper (Refereed)
Abstract [en]

It is shown that tensile strength of cellulose fibers with the same length follow Weibull distribution. However, size effect predicted by the Weibull distribution for fibers with various lengths is not observed. This is most likely due to the highly non-linear behaviour of cellulose fibers. Applicability of the Weibull distribution is studied on fibers with different length via single fiber as well as bundle tensile tests.

Place, publisher, year, edition, pages
London: IOM Communications, 2009
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-27214 (URN)093d8580-9886-11de-8da0-000ea68e967b (Local ID)093d8580-9886-11de-8da0-000ea68e967b (Archive number)093d8580-9886-11de-8da0-000ea68e967b (OAI)
Conference
International Conference on Composite Materials : 27/07/2009 - 31/07/2009
Note
Godkänd; 2009; Bibliografisk uppgift: CD-ROM; 20090903 (joffe)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-01-16Bibliographically approved
Sparnins, E. (2009). Mechanical properties of flax fibers and their composites (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Mechanical properties of flax fibers and their composites
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Flax fibers, along with a number of other natural fibers, are being considered as an environmentally friendlier alternative of synthetic fibers in fiber-reinforced polymer composites. A common feature of natural fibers is a much higher variability of mechanical properties. This necessitates study of the flax fiber strength distribution and efficient experimental methods for its determination. Elementary flax fibers of different gauge lengths are tested by single fiber tension in order to obtain the stress-strain response and strength and failure strain distributions. The applicability of single fiber fragmentation test for flax fiber failure strain and strength characterization is considered. It is shown that fiber fragmentation test can be used to determine the fiber length effect on mean fiber strength and limit strain. The effect of mechanical damage in the form of kink bands and of diameter variability on the strength of elementary flax fibers is considered. Stiffness and strength under uniaxial tension of flax fiber composites with thermoset and thermoplastic polymer matrices are studied. The applicability of rule of mixtures and orientational averaging based models, developed for short fiber composites, to flax reinforced polymers are evaluated. Both the quasi-static and time dependent mechanical properties of flax fiber/thermoplastic starch based composites are analyzed. The effect of temperature and relative humidity is investigated. It is found that microdamage accumulation in this type of composites is not significant. Results show that the composite elastic modulus and failure stress are linearly related to the maximum stress reached by the matrix in tensile tests. Simple material models are suggested to account for the observed nonlinear viscoelasticity and viscoplasticity.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2009. p. 204
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Flax fibers, natural fiber composites, mechanical properties, Time dependent behavior, Materials science - Other material science, Teknisk materialvetenskap - Övrig teknisk materialvetenskap
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-26640 (URN)f541ce90-c497-11de-b769-000ea68e967b (Local ID)978-91-7439-025-4 (ISBN)f541ce90-c497-11de-b769-000ea68e967b (Archive number)f541ce90-c497-11de-b769-000ea68e967b (OAI)
Note

Godkänd; 2009; 20091029 (edgspa); DISPUTATION Ämnesområde: Polymera konstruktionsmaterial/Polymeric Composite Materials Opponent: Docent Kristofer Gamstedt, Kungliga Tekniska Högskolan, Stockholm Ordförande: Docent Roberts Joffe, Luleå tekniska universitet Tid: Onsdag den 9 december 2009, kl 10.00 Plats: E 231, Luleå tekniska universitet

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-09Bibliographically approved
Andersons, J., Sparnins, E. & Joffe, R. (2009). Prediction of crack onset strain in composite laminates at mixed mode cracking (ed.). In: (Ed.), (Ed.), 5th International EEIGM/AMASE/FORGEMAT Conference on Advanced Materials Research: . Paper presented at EEIGM/AMASE/FORGEMAT conference on Advanced Materials Research : 04/11/2009 - 05/11/2009. Bristol: IOP Publishing Ltd, 5
Open this publication in new window or tab >>Prediction of crack onset strain in composite laminates at mixed mode cracking
2009 (English)In: 5th International EEIGM/AMASE/FORGEMAT Conference on Advanced Materials Research, Bristol: IOP Publishing Ltd , 2009, Vol. 5Conference paper, Published paper (Refereed)
Abstract [en]

Failure process of continuous fiber reinforced composite laminates in tension usually starts with appearance of intralaminar cracks. In composite laminates with complex lay-ups and/or under combined loading, intralaminar cracks may develop in plies with different reinforcement directions. A necessary part of mixed mode cracking models is the criterion of failure. For propagation-controlled fracture it is usually formulated in terms of energy release rates and their critical values of the particular composite material. Intralaminar fracture toughness of unidirectionally reinforced glass/epoxy composite was experimentally determined at several mode I and mode II ratios. It is found that the crack propagation criterion, linear in terms of the energy release rates, reasonably well approximates the test results. The determined mixed mode cracking criterion was applied to predict intralaminar crack onset in cross-ply glass/epoxy composite under tensile loading. The predicted crack onset strain values agree with test results at small off-axes angles of the cracking ply (on-axis and 15° off-axis loading), but underestimate crack onset at larger reinforcement angles with respect to the loading direction. The discrepancy is likely to be caused by the deviation of linearity in laminate response before cracking onset in these laminates, related to non-linear shear characteristics of unidirectional plies. The applicability of strength-based fracture criterion for initiation-controlled cracking is discussed.

Place, publisher, year, edition, pages
Bristol: IOP Publishing Ltd, 2009
Series
I O P Conference Series: Materials Science and Engineering, ISSN 1757-8981 ; 5
Keywords
Technology - Chemical engineering, Teknikvetenskap - Kemiteknik
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-39837 (URN)10.1088/1757-899X/5/1/012018 (DOI)000285529200018 ()2-s2.0-84892930593 (Scopus ID)ebb1be60-ae73-11de-8293-000ea68e967b (Local ID)ebb1be60-ae73-11de-8293-000ea68e967b (Archive number)ebb1be60-ae73-11de-8293-000ea68e967b (OAI)
Conference
EEIGM/AMASE/FORGEMAT conference on Advanced Materials Research : 04/11/2009 - 05/11/2009
Note
Validerad; 2009; 20091001 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-07-10Bibliographically approved
Sparnins, E., Andersons, J. & Joffe, R. (2009). Progressive cracking mastercurve of the transverse ply in a laminate (ed.). In: (Ed.), Pierluigi Priolo (Ed.), Experimental techniques and design in composite materials (ETDCM8) with regular papers: [15 papers selected from the eighth edition of the seminar ... which took place on October 3 - 6, 2007 at the Sant'Elmo Beach Hotel (Castiadas), Sardinia, Italy. Paper presented at Seminar on Experimental Techniques and Design in Composite Materials : 03/10/2007 - 06/10/2007 (pp. 97-98). Amsterdam: Elsevier
Open this publication in new window or tab >>Progressive cracking mastercurve of the transverse ply in a laminate
2009 (English)In: Experimental techniques and design in composite materials (ETDCM8) with regular papers: [15 papers selected from the eighth edition of the seminar ... which took place on October 3 - 6, 2007 at the Sant'Elmo Beach Hotel (Castiadas), Sardinia, Italy / [ed] Pierluigi Priolo, Amsterdam: Elsevier, 2009, p. 97-98Conference paper, Meeting abstract (Other academic)
Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2009
Series
Composites Science and Technology, ISSN 0266-3538 ; 11/12
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-35619 (URN)a3a80b70-91f0-11dc-9a81-000ea68e967b (Local ID)a3a80b70-91f0-11dc-9a81-000ea68e967b (Archive number)a3a80b70-91f0-11dc-9a81-000ea68e967b (OAI)
Conference
Seminar on Experimental Techniques and Design in Composite Materials : 03/10/2007 - 06/10/2007
Note
Godkänd; 2007; 20071113 (joffe)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-01-16Bibliographically approved
Andersons, J., Joffe, R., Sparnins, E. & Rubenis, O. (2009). Progressive cracking mastercurves of the transverse ply in a laminate (ed.). Paper presented at . Polymer Composites, 30(8), 1175-1182
Open this publication in new window or tab >>Progressive cracking mastercurves of the transverse ply in a laminate
2009 (English)In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 30, no 8, p. 1175-1182Article in journal (Refereed) Published
Abstract [en]

In this study, progressive cracking of a transverse layer in a cross-ply composite laminate subjected to tensile loading is considered. Using the results of a probabilistic cracking model, approximate relations for crack density as a function of stress are derived for initiation-controlled and propagation-controlled cracking. It is shown that the crack density evolution in the transverse ply can be represented by a mastercurve in suitably normalized coordinates. The mastercurve approach is applied to progressive cracking in glass/epoxy laminates

Keywords
Technology - Chemical engineering, Teknikvetenskap - Kemiteknik
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-4303 (URN)10.1002/pc.20674 (DOI)000268306600020 ()2-s2.0-67849088254 (Scopus ID)23c71590-91ff-11dc-9a81-000ea68e967b (Local ID)23c71590-91ff-11dc-9a81-000ea68e967b (Archive number)23c71590-91ff-11dc-9a81-000ea68e967b (OAI)
Note
Validerad; 2009; 20071113 (joffe)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved

Search in DiVA

Show all publications