| 1. |
- Andersons, J., et al.
(författare)
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Apparent interfacial shear strength of short-flax-fiber/starch acetate composites
- 2016
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Ingår i: International Journal of Adhesion and Adhesives. - : Elsevier Ltd. - 0143-7496 .- 1879-0127. ; 64, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- The paper deals with an indirect industry-friendly method for identification of the interfacial shear strength (IFSS) in a fully bio-based composite. The IFSS of flax fiber/starch acetate is evaluated by a modified Bowyer and Bader method based on an analysis of the stress-strain curve of a short-fiber-reinforced composite in tension. A shear lag model is developed for the tensile stress-strain response of short-fiber-reinforced composites allowing for an elastic-perfectly plastic stress transfer. Composites with different fiber volume fractions and a variable content of plasticizer have been analyzed. The apparent IFSS of flax/starch acetate is within the range of 5.5-20.5 MPa, depending on composition of the material. The IFSS is found to be greater for composites with a higher fiber loading and to decrease with increasing content of plasticizer. The IFSS is equal or greater than the yield strength of the neat polymer, suggesting good adhesion, as expected for the chemically compatible constituents.
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| 2. |
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| 3. |
- Andersons, J., et al.
(författare)
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Estimation of the tensile strength of an oriented flax fiber-reinforced polymer composite
- 2011
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:9, s. 1229-1235
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Tidskriftsartikel (refereegranskat)abstract
- Unidirectional orientation of natural fibers in a polymer composite ensures the highest efficiency of reinforcement. Flax fiber reinforcement is discontinuous due to limited fiber length and heterogeneous due to the presence of elementary fibers and their bundles. In order to assess the upper limit of tensile strength of such slightly misoriented, nominally UD natural fiber composite, a statistical strength model of continuous UD fiber reinforced composites is applied. It is found that the experimental strength of UD flax composites, produced from rovings or manually aligned fibers, approaches the theoretical limit only at relatively low fiber volume fraction ca. 0.2, being markedly below it at higher fiber content.
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| 4. |
- Andersons, J., et al.
(författare)
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Fibre fragment distribution in a single-fibre composite tension test
- 2001
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Ingår i: Composites Part B. - 1359-8368 .- 1879-1069. ; 32:4, s. 323-332
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Tidskriftsartikel (refereegranskat)abstract
- Single fibre fragmentation tests are performed for brittle fibres with Weibull strength distribution and different surface treatments. The fragmentation process is modelled and closed-form expressions for break spacing distribution are obtained. The model accounts for the effect of finite fibre length on the initial fragmentation as well as for break interaction on the advanced fragmentation stage. It is assumed that the exclusion zone due to fibre-matrix interface failure and stress recovery in the fibre is linearly dependent on the applied load. This assumption is validated experimentally. The derived theoretical average fragment length dependence on applied load is used to determine the fibre strength distribution parameters and the effective interfacial shear stress for carbon/epoxy single fibre composites with different fibre surface treatment and for glass/vinylester single fibre composite. Fragment length distribution is predicted for several load levels. Predictions are in good agreement with experimental data
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| 5. |
- Andersons, J., et al.
(författare)
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Glass fibre strength distribution determined by common experimental methods
- 2002
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 62:1, s. 131-145
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Tidskriftsartikel (refereegranskat)abstract
- The tensile strength of brittle fibres is routinely described by the Weibull distribution. The parameters of the distribution can be obtained from tests on single fibres and fibre bundles or from model composite tests. However, there is growing evidence that the distribution parameters obtained by different experimental techniques differ systematically. In order to investigate the possible causes of such discrepancies, single-fibre tension, fibre bundle, and single-fibre fragmentation tests are employed in this study to obtain strength distribution of commercial E-glass fibres. The results reveal parameter dependence on the approach used to extract the distribution parameters from experimental data. Particularly, in the case of single-fibre tension tests, the shape parameter obtained from average fibre strength vs. length data is larger than that obtained at a fixed gauge length. It is assumed that the apparent fibre strength scatter is caused by both the inherent flaw structure along a fibre and by the fibre-to-fibre strength variability within a batch, due to slightly differing processing and handling history of the fibres. Fibre fragmentation test results are used to derive the Weibull distribution parameters applicable to the fibre batch. The strength distribution obtained is compared with strength data for the single fibres, and reasonably good agreement is observed.
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| 6. |
- Andersons, J., et al.
(författare)
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Modeling the effect of reinforcement discontinuity on the tensile strength of UD flax fiber composites
- 2011
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 46:15, s. 5104-5110
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 7. |
- Andersons, J., et al.
(författare)
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Prediction of crack onset strain in composite laminates at mixed mode cracking
- 2009
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Ingår i: 5th International EEIGM/AMASE/FORGEMAT Conference on Advanced Materials Research. - Bristol : IOP Publishing Ltd.
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 8. |
- Andersons, J., et al.
(författare)
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Scale effect of the tensile strength of flax-fabric-reinforced polymer composites
- 2011
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 30:23, s. 1969-1974
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Tidskriftsartikel (refereegranskat)abstract
- 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. © The Author(s) 2011.
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| 9. |
- Andersons, J., et al.
(författare)
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Statistical model of coating fragmentation under equibiaxial load
- 1998
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Ingår i: Materials and Manufacturing Processes. - : Informa UK Limited. - 1042-6914 .- 1532-2475. ; 13:4, s. 597-602
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Tidskriftsartikel (refereegranskat)abstract
- A statistical model of coating cracking under equibiaxial tension is proposed based on a Weibull strength distribution for the coating. Crack length and spacing distributions are derived assuming that cracks initiate in random locations and propagate straight till stopping upon encountering a geometiical obstacle (another crack). The theoretical distributions are verified by comparing with simulated cracking patterns obtained by the Monte-Carlo method. An analysis of crack patterns of SiO2 coatings on a PET film under biaxial tension is performed. Qualitative agreement with the theoretical crack spacing distribution is observed.
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| 10. |
- Andersons, J., et al.
(författare)
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Stiffness and strength of flax fiber/polymer matrix composites
- 2006
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Ingår i: Polymer Composites. - : Wiley. - 0272-8397 .- 1548-0569. ; 27:2, s. 221-229
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Tidskriftsartikel (refereegranskat)abstract
- Flax fiber composites with thermoset and thermoplastic polymer matrices have been manufactured and tested for stiffness and strength under uniaxial tension. Flax/polypropylene and flax/maleic anhydride grafted polypropylene composites are produced from compound obtained by coextrusion of granulated polypropylene and flax fibers, while flax fiber mat/vinylester and modified acrylic resin composites are manufactured by resin transfer molding. The applicability of rule-of-mixtures and orientational averaging based models, developed for short fiber composites, to flax reinforced polymers is considered.
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