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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
Tsampas, S., Fernberg, P. & Joffe, R. (2018). Development of novel high Tg polyimide-based composites: Part II: Mechanical characterisation. Journal of composite materials, 52(2), 261-274
Open this publication in new window or tab >>Development of novel high Tg polyimide-based composites: Part II: Mechanical characterisation
2018 (English)In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 52, no 2, p. 261-274Article in journal (Refereed) Published
Abstract [en]

In this study, the mechanical performance assessment of a newly developed carbon fibre-reinforced polyimide composite system T650/NEXIMID® MHT-R is presented. This system was subjected to a series of mechanical tests at ambient and elevated temperature (320℃) to determine basic material properties. Moreover, an additional test was conducted, using a T650/NEXIMID® MHT-R laminate in which the fibre sizing was thermally removed prior to laminate manufacturing, to investigate the effect of fibre treatment on mechanical performance. The experimental results indicated that the T650/NEXIMID® MHT-R composites along with exceptionally high Tg (360–420℃) exhibited competitive mechanical properties to other commercially available polyimide and epoxy-based systems. At elevated temperature, the fibre-dominated properties were not affected whilst the properties defined by matrix and fibre/matrix interface were degraded by approximately 20–30%. Finally, the fibre sizing removal did not affect the tensile and compressive strength, however, the shear strength obtained from short-beam shear test was deteriorated by approximately 15%. to serve as baseline for further studies.

Place, publisher, year, edition, pages
Sage Publications, 2018
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-63439 (URN)10.1177/0021998317705706 (DOI)000419136300010 ()2-s2.0-85040032640 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-01-19 (andbra)

Available from: 2017-05-18 Created: 2017-05-18 Last updated: 2018-01-23Bibliographically approved
Al-Ramahi, N., Joffe, R. & Varna, J. (2018). Fem analysis of stresses in adhesive single-lap joints with non-linear materials under thermo-mechanical loading. In: ECCM18: . Paper presented at 18th European Conference on Composite Materials Athens, Greece, 24-28th June 2018.
Open this publication in new window or tab >>Fem analysis of stresses in adhesive single-lap joints with non-linear materials under thermo-mechanical loading
2018 (English)In: ECCM18, 2018Conference paper, Published paper (Refereed)
Abstract [en]

This study presents comprehensive numerical stress analysis in the adhesive layer of a single-lap joint subjected to various loading scenarios (mechanical and thermal loading). For this purpose numerical model (finite element method) with novel displacement coupling conditions able to correctly represent monoclinic materials (off-axis layers of composite laminates) has been developed. This model includes nonlinear material model and geometrical nonlinearity is also accounted for. The effect of thermal residual stresses (in adhesive) is analysed for various methods of manufacturing of single lap joint. The sequences of application of thermal and mechanical loads for the analysis of the thermal residual stresses in joints are proposed. It is shown that the most common approach used in many studies of linear superposition of thermal and mechanical stresses works well only for linear materials and produces wrong results if material is non-linear. The present study demonstrates suitable method to apply combined thermal and mechanical loads to get accurate stress distributions. Based on the analysis of these stress distributions the conclusions concerning the effect of the thermal residual stresses on peel and shear stress concentrations are made. The comparison between effect of thermal stresses in case of the one-step and two-step joint manufacturing techniques is made.

National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-70262 (URN)
Conference
18th European Conference on Composite Materials Athens, Greece, 24-28th June 2018
Available from: 2018-08-07 Created: 2018-08-07 Last updated: 2018-08-13Bibliographically approved
Al-Ramahi, N., Joffe, R. & Varna, J. (2018). Investigation of end and edge effects on results of numerical simulation of single lap adhesive joint with non-linear materials. International Journal of Adhesion and Adhesives, 87, 191-204
Open this publication in new window or tab >>Investigation of end and edge effects on results of numerical simulation of single lap adhesive joint with non-linear materials
2018 (English)In: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 87, p. 191-204Article in journal (Refereed) Published
Abstract [en]

This paper presents systematic numerical study of stresses in the adhesive of a single-lap joint with the objective to improve understanding of the main material and geometrical parameters determining performance of adhesive joints. For this purpose a 3D model as well as 2D model, optimized with respect to the computational efficiency by use of novel displacement coupling conditions able to correctly represent monoclinic materials (off-axis layers of composite laminates), are employed. The model accounts for non-linearity of materials (adherend and adhesive) as well as geometrical non-linearity. The parameters of geometry of the joint are normalized with respect to the dimensions of adhesive (e.g. thickness) thus making analysis of results more general and applicable to wide range of different joints. Optimal geometry of the single-lap joint allowing to separate edge effect from end effects is selected based on results of the parametric analysis by using peel and shear stress distributions in the adhesive layer as a criterion. Three different types of single lap joint with similar and dissimilar (hybrid) materials are considered in this study: a) metal-metal; b) composite-composite; c) composite-metal. In case of composite laminates, four lay-ups are evaluated: uni-directional ([08]T and [908]T) and quasi-isotropic laminates ([0/45/90/-45]S and [90/45/0/-45]S). The influence of the abovementioned parameters on peel and shear stress distributions in the adhesive layer is examined carefully and mechanical parameters governing the stress concentrations in the joint have been identified, this dependence can be described by simple but accurate fitting function. The effect of the used material model (linear vs non-linear) on results is also demonstrated.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Composites, Single-lap adhesive joint, Hybrid joints, Finite element method, Stress distribution, Stress analysis
National Category
Applied Mechanics Manufacturing, Surface and Joining Technology Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-71462 (URN)10.1016/j.ijadhadh.2018.10.007 (DOI)000449894000022 ()2-s2.0-85055248042 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-12-07 (johcin)

Available from: 2018-11-19 Created: 2018-11-19 Last updated: 2018-12-10Bibliographically 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
Suñer Moreno, S., Gowland, N., Craven, R., Emami, N., Joffe, R. & Tripper, J. (2018). Ultrahigh molecular weight polyethylene/graphene oxide nanocomposites: wear characterization and biological response to wear particles. Journal of Biomedical Materials Research. Part B - Applied biomaterials, 106(1), 183-190
Open this publication in new window or tab >>Ultrahigh molecular weight polyethylene/graphene oxide nanocomposites: wear characterization and biological response to wear particles
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2018 (English)In: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 106, no 1, p. 183-190Article in journal (Refereed) Published
Abstract [en]

In the field of total joint replacements, polymer nanocomposites are being investigated as alternatives to ultrahigh molecular weight polyethylene (UHMWPE) for acetabular cup bearings. The objective of this study was to investigate the wear performance and biocompatibility of UHMWPE/graphene oxide (GO) nanocomposites. This study revealed that low concentrations of GO nanoparticles (0.5 wt %) do not significantly alter the wear performance of UHMWPE. In contrast, the addition of higher concentrations (2 wt %) led to a significant reduction in wear. In terms of biocompatibility, UHMWPE/GO wear particles did not show any adverse effects on L929 fibroblast and PBMNC viability at any of the concentrations tested over time. Moreover, the addition of GO to a UHMWPE matrix did not significantly affect the inflammatory response to wear particles. Further work is required to optimize the manufacturing processes to improve the mechanical properties of the nanocomposites and additional biocompatibility testing should be performed to understand the potential clinical application of these materials

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Composite Science and Engineering
Research subject
Machine Elements; Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-61091 (URN)10.1002/jbm.b.33821 (DOI)000417576500019 ()27935195 (PubMedID)2-s2.0-85006833606 (Scopus ID)
Note

Validerad;2018;Nivå 2;2017-12-12 (svasva)

Available from: 2016-12-15 Created: 2016-12-15 Last updated: 2018-08-10Bibliographically approved
Al-Maqdasi, Z., Gong, G., Nyström, B. & Joffe, R. (2018). Wood Fiber Composites With Added Multi-Functionality. In: : . Paper presented at 18th European Conference on Composite Materials, ECCM 2018, Athens, Greece, 25-28 June, 2018.
Open this publication in new window or tab >>Wood Fiber Composites With Added Multi-Functionality
2018 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Graphene nanoplatelets (GNPs) are used to enhance the mechanical properties and functionality of wood plastic composite (WPC) targeting applications such as de-icing or anti-icing and fast thermal diffusivity. The GNPs are integrated into neat polymer using a masterbatch containing functionalized graphene by melt compounding through a twin-screw extruder without the use of any coupling agent or compatibilizer. The same manufacturing process (melt compounding) but with the use of compatibilizer is employed to produce WPC with nano-doped matrix. The effect of different GNP loadings (up to 15 wt.%) on morphology, crystallinity, mechanical and thermal conductivity of the nanocomposites and the WPCs was investigated. It was found that both strength and modulus of nanocomposites, in tension and bending, were increased with the addition of GNPs. With the aid of MAPE compatibilizer WPCs show higher flexural strength and modulus than neat polymer. GNP has marginal effect on the flexural stress but further increases flexural modulus of WPC. The preliminary results related to the thermal conductivity of studied materials indicate that the incorporation of GNP may be beneficial for faster and more uniform heat distribution in WPC.

Keywords
Graphene reinforced wood composite, multifunctional composites, thermal conductivity
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-70678 (URN)
Conference
18th European Conference on Composite Materials, ECCM 2018, Athens, Greece, 25-28 June, 2018
Funder
Interreg Nord
Available from: 2018-08-30 Created: 2018-08-30 Last updated: 2018-08-31Bibliographically approved
Hajlane, A., Kaddami, H. & Joffe, R. (2017). Chemical modification of regenerated cellulose fibres by cellulose nano-crystals: Towards hierarchical structure for structural composites reinforcement. Industrial crops and products (Print), 100, 41-50
Open this publication in new window or tab >>Chemical modification of regenerated cellulose fibres by cellulose nano-crystals: Towards hierarchical structure for structural composites reinforcement
2017 (English)In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 100, p. 41-50Article in journal (Refereed) Published
Abstract [en]

A simple and innovative new route, with less negative impact on the environment, for depositing and hope-grafting cellulose nano-crystals onto the surface of regenerated cellulose fibres (Cordenka 700 Super 3), using γ-methacryloxypropyltrimethoxysilane as coupling agent, is presented. Hierarchical cellulosic structure involving micro-scale fibres and nano-scale cellulose crystal network was created as verified by the scanning electron microscopy. The fibres were initially oxidised by optimized concentration of cerium ammonium nitrate to generate radicals on the cellulose backbone in order to polymerize the coupling agent at the surface. Infrared spectroscopy and scanning electron microscopy confirmed the chemical polymerisation of MPS onto regenerated cellulose fibres without enabling to show the chemical bonding between silane and nano-crystals. However, tensile test which was performed to study the impact of different treatments on mechanical properties of regenerated cellulose fibres, revealed that the modification by silane decreased the stiffness and strength of fibres (22% and 10% decrease, respectively) while the strain at failure was increased. These changes were attributed to the treatment conditions which may have induced the disorder and the misalignment of the structure of cellulose fibres (e.g. axial orientation of molecular chains and crystalline phase of the fibre has been reduced). This assumption is supported by the results from successive loading-unloading test of the fibre bundle. However, after depositing cellulose nano-crystals onto the fibre’s surface, the stiffness was recovered (20% increase in comparison to MPS treated fibres) while the strength and strain at failure remained at the same order of magnitude as for fibres treated only by the coupling agent.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-62097 (URN)10.1016/j.indcrop.2017.02.006 (DOI)000397687200005 ()2-s2.0-85012964625 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-02-21 (andbra)

Available from: 2017-02-21 Created: 2017-02-21 Last updated: 2018-09-13Bibliographically approved
Ansari, F., Granda, L. A., Joffe, R., Berglund, L. A. & Vilaseca, F. (2017). Experimental evaluation of anisotropy in injection molded polypropylene/wood fiber biocomposites. Composites. Part A, Applied science and manufacturing, 96, 147-154
Open this publication in new window or tab >>Experimental evaluation of anisotropy in injection molded polypropylene/wood fiber biocomposites
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2017 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 96, p. 147-154Article in journal (Refereed) Published
Abstract [en]

Although the anisotropy of wood fibers is reasonably well established, the anisotropy of injection molded wood fiber composites is not well understood. This work focuses on chemo-thermomechanical pulp (CTMP) reinforced polypropylene (PP) composites. A kinetic mixer (Gelimat) is used for compounding CTMP/PP composites, followed by injection molding. Effects from processing induced orientation on mechanical properties are investigated. For this purpose, a film gate mold was designed to inject composites in the shape of plates so that specimens in different directions to the flow could be evaluated in tensile tests. Observations from tensile tests were complemented by performing flexural tests (in different directions) on discs cut from the injected plates. SEM was used to qualitatively observe the fiber orientation in the composites. At high fiber content, both modulus and tensile strength could differ by as much as 40% along the flow and transverse to the flow. The fiber orientation was strongly increased at the highest fiber content, as concluded from theoretical analysis.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Composite Science and Engineering
Research subject
Polymeric Composite Materials
Identifiers
urn:nbn:se:ltu:diva-61943 (URN)10.1016/j.compositesa.2017.02.003 (DOI)000399850600016 ()2-s2.0-85014372994 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-03-07 (rokbeg)

Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2018-09-13Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-5210-4341

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