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  • 1.
    Adawi, Rahim
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap.
    Preventing fatal effects of overworking: Product design solution2018Självständigt arbete på grundnivå (högskoleexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    "Guolaosi" eller död från överarbete är ett fenomen som i regel uppkommer bland utvecklingsländer. Dödsorsaken är huvudsakligen genom stroke. Offrens yrken varierar allt från professorer, IT-arbetare till läkare. De delar dock en sak gemensamt; att arbeta under långa perioder stillasittande. Projektets mål var att utveckla en produkt som minskar dödliga följderna av sedentära överarbete, genom att förebygga en av de tre orsakerna för att utveckla blodproppar; saktad blodström. Målgruppen var då kineser av de yrken som hade tidigare drabbats av fenomenet. För att samla informationsrika data om fenomenet genomfördes en kvalitativ studie i Kina under två månader. Genom att göra en omfattande strukturerad provtagning kunde informationsrika data samlas under en kort tidsperiod. Fältstudien bestod av observationer, frågeformulär och en intervju, som då tolkades till kundbehov och eventuellt produktspecifikationen. Den slutliga produkten kom att bli ett par byxor med en inbyggd dynamisk komprimeringsmekanism, som kan komprimera venerna under sittande aktiviteter, för att förhindra saktad blodström. Kompressionsmekanismen fungerar som den kinesiska fingerfällan. Den komprimerar blodkärlen medan personen sitter och sträcker benen framåt. Produkten är konstruerad på så sätt att den kan tillverkas endast av polysackariders tråd, från bomull och majs. Vilket är lämpligt för Kinas lokala resurser.

  • 2.
    Alfredsson, K. Svante
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Gawandi, A. A.
    Univ Delaware, Ctr Composite Mat, Newark, DE 19716 USA.
    Gillespie, J. W., Jr.
    Univ Delaware, Ctr Composite Mat, Newark, DE 19716 USA.
    Carlsson, L. A.
    Florida Atlantic Univ, Dept Mech Engn, Boca Raton, FL 33431 USA.
    Bogetti, T. A.
    USA, Res Lab, Aberdeen Proving Ground, MD 21005 USA.
    Stress analysis of axially and thermally loaded discontinuous tile core sandwich with and without adhesive filled core gaps2011Ingår i: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 93, nr 7, s. 1621-1630Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An analytical study is performed to investigate the stress states in an axially and thermally loaded sandwich structure with a discontinuous ceramic tile core. General and simplified models are developed to determine stresses in the constituents of the sandwich structure with and without adhesive in the gaps between adjacent tiles. A general model that allows local bending of the face sheet and a simplified model which assumes uniform through-thickness stress distribution in the face sheets are developed. It is shown that the normal stress in the face sheet decreases when the gap is filled by adhesive, although the tile stress increases. The analytical model shows that normal and shear stresses at the face/core interface can be reduced by filling the gaps between tiles. Filled gaps also elevate the axial stiffness of the structure. Model results are verified by comparison to a previously developed analytical model and finite element analysis. (C) 2011 Elsevier Ltd. All rights reserved.

  • 3.
    Aragón Martín, Laura
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap.
    Alternative materials for the horseshoe2014Självständigt arbete på grundnivå (kandidatexamen), 15 poäng / 22,5 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis is a research-focused work on a study of alternative materials for horseshoes. Within this thesis the objectives and functions of a compliant horseshoe are identified, based on a literature study of the work of previous researches, and they are linked to the properties of material. After identifying these objectives, a number of methods are implemented with the aim of detecting the most suitable materials for horseshoes taking into account the properties linked with the objectives. In order to determine whether the selected material is suitable or not, a comparison with a traditional forged steel horseshoe is carried out. Whenever an appropriate material is found, a most exhaustive study is performed and finally, a decision is elected based on the further investigation. The last chapter of this thesis is comprised of a document destined for future researches where suggestions about how to get more reliable results in the field are explained.

  • 4.
    Atarijabarzadeh, Sevil
    et al.
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden.
    Nilsson, Fritjof
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden / ABB, Corp Res, Västerås, Sweden.
    Hillborg, Henrik
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden / ABB, Corp Res, Västerås, Sweden.
    Karlsson, Sigbritt
    Högskolan i Skövde. KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden.
    Strömberg, Emma
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Fibre & Polymer Technol, Stockholm, Sweden.
    Image Analysis Determination of the Influence of Surface Structure of Silicone Rubbers on Biofouling2015Ingår i: International Journal of Polymer Science, ISSN 1687-9422, E-ISSN 1687-9430, artikel-id 390292Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study focuses on how the texture of the silicone rubber material affects the distribution of microbial growth on the surface of materials used for high voltage insulation. The analysis of surface wetting properties showed that the textured surfaces provide higher receding contact angles and therefore lower contact angle hysteresis. The textured surfaces decrease the risk for dry band formation and thus preserve the electrical properties of the material due to a more homogeneous distribution of water on the surface, which, however, promotes the formation of more extensive biofilms. The samples were inoculated with fungal suspension and incubated in a microenvironment chamber simulating authentic conditions in the field. The extent and distribution of microbial growth on the textured and plane surface samples representing the different parts of the insulator housing that is shank and shed were determined by visual inspection and image analysis methods. The results showed that the microbial growth was evenly distributed on the surface of the textured samples but restricted to limited areas on the plane samples. More intensive microbial growth was determined on the textured samples representing sheds. It would therefore be preferable to use the textured surface silicone rubber for the shank of the insulator.

  • 5.
    Biel, Anders
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Cohesive laws for adhesives at repeated loading: an experimental methodManuskript (Övrigt vetenskapligt)
  • 6.
    Biel, Anders
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Mechanical behaviour of adhesive layers: experimental methods, cohesive laws, and fracture mechanics2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Adhesive joining is today viewed as one of the key technologies to achieve decreased emissions in the automobile industry. To decrease weight, optimal material selection often results in different materials for different parts. This leads to the necessity to join mixed material. Here, the use of adhesives is the most promising joining technology. For a rational design process, good models for strength analysis of adhesively joined structures are essential. With cohesive modelling, fracture of the adhesive layer is modelled with a stress-deformation law. This law - often denoted a cohesive law - gives the traction exerted on the adherends due to the deformation of the adhesive layer. This thesis is concerned with experimental methods to measure cohesive properties of engineering adhesives and standardized methods to measure the fracture energy of adhesives. A new method to measure cohesive laws is developed. With this method, the cohesive law of an epoxy adhesive is measured in shear. In peel loading, with elastically deforming adherends, the cohesive law is shown to be independent of the geometry of the specimen. If the adherends deform plastically the fracture energy increases. Experiments are performed in order to determine the temperature dependence of the cohesive layer for an epoxy adhesive. It is shown that the peak stress is strongly dependent on the temperature while the fracture energy shows only small temperature dependence. Experiments are also performed to study the influence of strain rate in peel and shear loading. The experiments show that the peak stress increases with an increasing strain rate and that the fracture energy increase in peel loading and decreases in shear with increasing strain rate. A new method to experimentally determine the relation between damage and plasticity in the adhesive during the fracture process is developed. For the present adhesive, it is shown that only minor plasticity occurs during the fracture process in peel loading. For peel, several commonly used methods to evaluate the fracture energy using the double cantilever beam specimen are critically studied. For some methods the error in evaluated fracture energy is larger than 40 %. It is shown that the evaluated fracture energy is more dependent on the choice of method than on the cohesive properties of the adhesive layer.

  • 7.
    Biel, Anders
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Carlberger, Thomas
    Influences of temperature on cohesive parameters for adhesives2007Ingår i: Proceedings of the 28th Risø International Symposium on Materials Science, Risö national laboratory , 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    Experiments are performed to evaluate the temperature dependence of the stress-elongation relation for an engineering epoxy adhesive. Seven temperatures from -40ºC to 80ºC are considered. At each temperature, about seven experiments are performed with a double cantilever beam specimen. The experiments are evaluated using an inverse solution. The results show that the peak stress decreases monotonically with temperature, from about 55 MPa at -40ºC to about 11 MPa at 80ºC. Thus, the shape of the stress-elongation relation varies with the temperature. At higher temperatures, the fracture energy decreases slightly.

  • 8.
    Biel, Anders
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Chaudhry, Mobina
    Institute of Biomedicine, University of Gothenburg, Göteborg, Sweden.
    Gustafsson, Stefan
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Nygren, Håkan
    Institute of Biomedicine, University of Gothenburg, Göteborg, Sweden.
    The use of MgO-paste as a biodegradeable bone cement2016Ingår i: Materials Today: Proceedings, E-ISSN 2214-7853, Vol. 3, nr 2, s. 556-561Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of MgO-paste as bone cement was tested on titanium cylinders implanted into rat tibia. The evaluation of bone healingwas made with the retention force (pull-out) test, light microscopy and ESEM/ EDX. Preimplantation of the MgO-paste into drillperforations of rat tibia increased the retention of the titanium implant 6-fold. The error was expressed as the 95% confidenceinterval of means (n=10 bones in each group). The observed difference between 3.46+/-0.71 N/mm2 for Ti-cylinders implantedwith MgO-paste and 0.56+/-0.26 N/mm2 for Ti-cylinders implanted directly into the bone, is statistically significant (p<0.01).The increase of retention force, caused by MgO is parallel to an increased thickness of the compact bone surrounding the implantand closer contact between bone and implant.Histological examination of the implant-related bone showed that the MgO-induced bone growth is mediated by the formation ofa bone-inducing matrix. The matrix contains organic substance, most likely proteins.

  • 9.
    Biel, Anders
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    An analysis of the evaluation of the fracture energy using the DCB-specimen2007Ingår i: Archives of Mechanics, ISSN 0373-2029, Vol. 59, nr 4-5, s. 311-327Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The methods to estimate the fracture energy using DCB-specimens as advocated in common standards. For instance, ASTM D 3433 and BS 7991:2001 are based on a compliance method, i.e. on linear elastic fracture mechanics (LEFM). Since the mechanical properties of almost all adhesives are non-linear, errors are generated. In some of the standards, the non-linear behaviour is compensated for by the use of correction terms generated from the experiments. An analysis of the methods of evaluation the fracture energy from experiments is performed. This analysis is performed first by simulating an experiment using realistic data for an engineering adhesive and then, by analysing the results with different methods. In this way, the correct fracture energy is known beforehand and the error in the evaluated fracture energy can be determined. In the present work it is shown that the magnitude of this error depends on the length of the crack. The results show that some commonly  used methods generate substantial errors when a large region of non-linear deformation precedes the crack tip. It is also shown that methods based on nonlinear fracture methods do not produce this kind of error.

  • 10.
    Biel, Anders
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Effects of constitutive parameters on the accuracy of measured fracture energy using the DCB-specimen2008Ingår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 75, nr 10, s. 2968-2983Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several methods exist to estimate the fracture energy for adhesive joints using the double cantilever beam specimen and linear elastic fracture mechanics. Since the mechanical properties of all adhesives are non-linear, errors are generated. By use of an exact solution experiments are simulated. These are evaluated with eight different methods. The influence of the constitutive parameters is systematically studied. This influence is small for most methods. The error due to the choice of evaluation method is considerably larger. One of the commonly used methods gives accurate results; the error is less than 3%. However, most methods yield substantial errors.

  • 11.
    Biel, Anders
    et al.
    Department of Wind Energy, Technical University of Denmark.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Measurement of tensile properties of fibres using a DCB-specimen2015Ingår i: 20th International Conference on Composite Materials: Copenhagen, 19-24th July 2015 / [ed] Ole Thybo Thomsen, Bent F. Sørensen, Christian Berggreen, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Constitutive data are needed at extreme strains to increase the understanding of fracture processes. Ordinary tensile tests ends prematurely due to localization and large amounts of elastic energy stored in the specimens prior to fracture. A novel method is proposed to perform tensile tests using a double cantilever beam specimen. To verify the method a large specimen is developed and tested. Similar results are achieved with the present method as with more standardized methods giving confidence in the method. The specimen should be possible to minimise to provide data with small specimens.

  • 12.
    Carlberger, Thomas
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Adhesive joining for crashworthiness: material data and explicit FE-methods2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Today, crash simulations replace crash testing in the product development phase in theautomotive industry. High quality simulations enable shorter product development time andhigher competitiveness. However, increasing requirements regarding emissions andcrashworthiness are demanding optimised material choice in the parts constituting the carbody structure. Lightweight materials are becoming frequently used. Joining dissimilarmaterials is difficult using common joining techniques like spot welding. To this end,adhesive joining is currently gaining popularity not only due to the ability to join dissimilarmaterials, joint integrity and structural stiffness both increase by the use of adhesive joining.Moreover, the number of spot welds may be reduced in hybrid joints.In this thesis, adhesive joints are studied with respect to crashworthiness of automotivestructures. The main task for the adhesive is not to dissipate the impact energy, but to keep thejoint integrity so that the impact energy can be consumed by plastic work of the basematerials. Fracture of adhesives can be accurately modelled by cohesive zones. The dynamicbehaviour of finite element structures containing cohesive zones is studied using a simplifiedstructure. An amplified strain rate is found in the adhesive as compared to the base material.The cohesive zone concept is used in the development of a 2D interphase element. Theaccuracy and time step influence of the interphase element is compared to solutions based oncontinuum element representation of the adhesive. The interphase element is found to predictfracture of the adhesive joint with engineering accuracy and has a small effect on the timestep of the explicit FE method.The cohesive laws for use in the material models of the adhesive have been determined usingdedicated test methods. The double cantilever beam specimen and the end notched flexurespecimen are used with inverse methods to determine cohesive laws in peel and shear,respectively. The cohesive laws are determined for varying temperature, strain rate andadhesive layer thickness. A built up bimaterial beam is designed for testing and simulation ofjoints consisting of bolts, adhesives and combinations of bolts and adhesives, i.e. hybridjoints. The model of the hybrid beam developed was found to be able to predict results fromimpact tests, quantified as maximum load and deformed shape of the beam.

  • 13.
    Carlberger, Thomas
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Biel, Anders
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Influence of temperature and strain rate on cohesive properties of a structural epoxy adhesiveManuskript (Övrigt vetenskapligt)
  • 14.
    España Giner, Jose Manuel
    et al.
    Polytechnic University of Valencia, Alcoy, Spain.
    Fages, Eduardo
    Textile Research Institute, Alcoy, Spain.
    Boronat Vitoria, Teodomiro
    Polytechnic University of Valencia, Alcoy, Spain.
    Moriana Torró, Rosana
    Textile Research Institute, Alcoy, Spain.
    Balart Gimeno, Rafael Antonio
    Polytechnic University of Valencia, Alcoy, Spain.
    Antioxidant effects of natural compounds on green composite materials2012Ingår i: Plastics Research Online, s. 1-3Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Naturally-occurring antioxidant compounds can improve the thermal resistance of a bio-composite, increasing the degradation temperature of the material by as much as 130%.

  • 15.
    García-García, Daniel
    et al.
    Instituto de Tecnología de Materiales (ITM), Universitat Politècnica de València (UPV), Alicante, Spain.
    Balart, Rafael
    Instituto de Tecnología de Materiales (ITM), Universitat Politècnica de València (UPV), Alicante, Spain.
    Lopez-Martinez, Juan
    Instituto de Tecnología de Materiales (ITM), Universitat Politècnica de València (UPV), Alicante, Spain.
    Ek, Monica
    School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Fibre and Polymer Technology, KTH-Royal Institute of Technology, Stockholm, Sweden.
    Moriana, Rosana
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system. School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Fibre and Polymer Technology, KTH-Royal Institute of Technology, Stockholm, Sweden.
    Optimizing the yield and physico-chemical properties of pine cone cellulose nanocrystals by different hydrolysis time2018Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, nr 5, s. 2925-2938Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose nanocrystals (CNCs) were isolated for the first time from pine cones (PC) by alkali and bleaching treatments and subsequent sulfuric acid hydrolysis (64%) at 45 degrees C. The influence of the hydrolytic reaction time (30, 45, and 90 min) on the yield, chemical composition and structure, and thermal stability of CNCs was evaluated. The removal of non-cellulosic constituents during the alkaline and bleaching treatment resulted in high pure cellulosic fibres. The isolation of CNCs from these cellulosic fibres at different reaction times was verified by the nano-dimensions of the individual crystals (< 3 and < 335 nm of average diameter and length, respectively). The highest yield (15%) and the optimum CNCs properties in terms of aspect ratio, thermal stability and crystallinity were obtained for an extraction time of 45 min. PC appeared to be a new promising source of cellulose fibres and CNCs with potential to be applied as reinforcement in composites and for food-packaging.

  • 16.
    García-García, Daniel
    et al.
    Instituto de Tecnología de Materiales-ITM, Universitat Politècnica de València, Alicante, Spain.
    Lopez-Martínez, Juan
    Instituto de Tecnología de Materiales-ITM, Universitat Politècnica de València, Alicante, Spain.
    Rafael, Balart
    Instituto de Tecnología de Materiales-ITM, Universitat Politècnica de València, Alicante, Spain.
    Strömberg, Emma
    School of Engineering Science in Chemistry, Biotechnology and Health, Department of Fibre and Polymer Technology, KTH-Royal Institute of Technology, Stockholm, Sweden.
    Moriana, Rosana
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system. School of Engineering Science in Chemistry, Biotechnology and Health, Department of Fibre and Polymer Technology, KTH-Royal Institute of Technology, Stockholm, Sweden.
    Reinforcing capability of cellulose nanocrystals obtained from pine cones in a biodegradable poly(3-hydroxybutyrate)/poly(ε-caprolactone) (PHB/PCL) thermoplastic blend2018Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 104, s. 10-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, different loads (3, 5 and 7 wt%) of pine cone cellulose nanocrystals (CNCs) were added to films ofpoly(3-hydroxybutyrate)/poly(ε-caprolactone) (PHB/PCL) blends with a composition of 75 wt% PHB and 25 wt% PCL (PHB75/PCL25). The films were obtained after solvent casting followed by melt compounding in anextruder and finally subjected to a thermocompression process. The influence of different CNCs loadings on themechanical, thermal, optical, wettability and disintegration in controlled compost properties of the PHB75/PCL25blend was discussed. Field emission scanning electron microscopy (FESEM) revealed the best dispersion of CNCson the polymeric matrix was at a load of 3 wt%. Over this loading, CNCs aggregates were formed enhancing thefilms fragilization due to stress concentration phenomena. However, the addition of CNCs improved the opticalproperties of the PHB75/PCL25films by increasing their transparency and accelerated the film disintegration incontrolled soil conditions. In general, the blend with 3 wt% CNCs offers the best balanced properties in terms ofmechanical, thermal, optical and wettability

  • 17.
    Gil-Castell, O.
    et al.
    Instituto de Tecnología de Materiales (ITM), Universidad Politecnica de Valencia (UPV), Valencia, Spain.
    Badia, J. D.
    Instituto de Tecnología de Materiales (ITM), Universidad Politecnica de Valencia (UPV), Valencia, Spain / Departament d'Enginyeria Química, Escola Tecnica Superior d'Enginyeria, Universitat de Valencia, Burjassot, Spain.
    Kittikorn, T.
    School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH e Royal Institute of Technology, Stockholm, Sweden / Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Songkhla, Thailand.
    Strömberg, E.
    School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH e Royal Institute of Technology, Stockholm, Sweden.
    Ek, M.
    School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH e Royal Institute of Technology, Stockholm, Sweden.
    Karlsson, Sigbritt
    Högskolan i Skövde. School of Chemical Science and Engineering, Fibre and Polymer Technology, KTH Royal Institute of Technology, Stockholm, Sweden.
    Ribes-Greus, A.
    Instituto de Tecnología de Materiales (ITM), Universidad Politecnica de Valencia (UPV), Valencia, Spain.
    Impact of hydrothermal ageing on the thermal stability, morphology and viscoelastic performance of PLA/sisal biocomposites2016Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 132, s. 87-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the combined exposure to water and temperature on the behaviour of polylactide/sisal biocomposites coupled with maleic acid anhydride was assessed through accelerated hydrothermal ageing. The biocomposites were immersed in water at temperatures from 65 to 85 degrees C, between the glass transition and cold crystallisation of the PLA matrix. The results showed that the most influent factor for water absorption was the percentage of fibres, followed by the presence of coupling agent, whereas the effect of the temperature was not significant. Deep assessment was devoted to biocomposites subjected to hydrothermal ageing at 85 degrees C, since it represents the extreme degrading condition. The morphology and crystallinity of the biocomposites were evaluated by means of X-Ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The viscoelastic and thermal performance were assessed by means of dynamic mechanic thermal analysis (DMTA) and thermogravimetry (TGA). The presence of sisal generally diminished the thermal stability of the biocomposites, which was mitigated by the addition of the coupling agent. After composite preparation, the effectiveness of the sisal fibre was improved by the crystallisation of PLA around sisal, which increased the storage modulus and reduced the dampening factor. The presence of the coupling agent strengthened this effect. After hydrothermal ageing, crystallisation was promoted in all biocomposites therefore showing more fragile behaviour evidencing pores and cracks. However, the addition of coupling agent in the formulation of biocomposites contributed in all cases to minimise the effects of hydrothermal ageing. 

  • 18.
    Gil-Castell, O.
    et al.
    Instituto de Tecnología de Materiales (ITM), Universitat Politècnica de València, Valencia, Spain.
    Badia, J. D.
    Instituto de Tecnología de Materiales (ITM), Universitat Politècnica de València, Valencia, Spain / Departament de Química Orgànica i Analítica, Universitat Rovira i Virgili, Tarragona, Spain / Departament d’Enginyeria Química, Escola Tècnica Superior d’Enginyeria, Universitat de València, Burjassot, Spain.
    Strömberg, E.
    KTH Royal Institute of Technology, School of Chemical Science and Engineering, Fibre and Polymer Technology, Stockholm, Sweden.
    Karlsson, Sigbritt
    Högskolan i Skövde. KTH Royal Institute of Technology, School of Chemical Science and Engineering, Fibre and Polymer Technology, Stockholm, Sweden.
    Ribes-Greus, A.
    Instituto de Tecnología de Materiales (ITM), Universitat Politècnica de València, Valencia, Spain.
    Effect of the dissolution time into an acid hydrolytic solvent to taylor electrospun nanofibrous polycaprolactone scaffolds2017Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 87, s. 174-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hydrolysis of the polycaprolactone (PCL) as a function of the dissolution time in a formic/acetic acid mixture was considered as a method for tailoring the morphology of nanofibrous PCL scaffolds. Hence the aim of this research was to establish a correlation between the dissolution time of the polymer in the acid solvent with the physicochemical properties of the electrospun nanofibrous scaffolds and their further service life behaviour. The physico-chemical properties of the scaffolds were assessed in terms of fibre morphology molar mass and thermal behaviour. A reduction of the molar mass and the lamellar thickness as well as an increase of the crystallinity degree were observed as a function of dissolution time. Bead-free fibres were found after 24 and 48 h of dissolution time with similar diameter distributions. The decrease of the fibre diameter distributions along with the apparition of beads was especially significant for scaffolds prepared after 72 h and 120 h of dissolution time in the acid mixture. The service life of the obtained devices was evaluated by means of in vitro validation under abiotic physiological conditions. All the scaffolds maintained the nanofibrous structure after 100 days of immersion in water and PBS. The molar mass was barely affected and the crystallinity degree and the lamellar thickness increased along immersion preventing scaffolds from degradation. Scaffolds prepared after 24 h and 48 h kept their fibre diameters whereas those prepared after 72 h and 120 h showed a significant reduction. This PCL tailoring procedure to obtain scaffolds that maintain the nanoscaled structure after such long in vitro evaluation will bring new opportunities in the design of long-term biomedical patches. 

  • 19.
    Knutsson, Karl
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Lind, Fredrik
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Evertsson, Henrik
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Utveckling av rollator: Examensarbete i integrerad produktutveckling2009Självständigt arbete på grundnivå (högskoleexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Examensarbetet "Utveckling av rollator" har utförts på institutionen för teknik och samhälle vid Högskolan i Skövde på uppdrag av Ahlberg Leber AB i ämnet integrerad produktutveckling.

     

    Uppdraget började med en grundlig förstudie av rollatormarknaden och till viss del även närliggande marknader. En kundkedja togs fram över de personer som kommer i kontakt med rollatorn under dess livslängd och som därför kan anses som intressenter av hur produkten utformas. Därefter gjordes ett antal intervjuer och enkäter för att klargöra vilka egenskaper som ansågs som viktiga hos en rollator.

     

    Utifrån detta skapades en objektiv kravspecifikation som diskuterades och modifierades något efter företagets krav.

     

    Välkända metoder såsom t ex brainstorming och brainwriting har använts för att generera idéer till projektet. Idégenereringen genomfördes både inom projektgruppen och tillsammans med andra studenter. Under genereringen lades fokus på ett antal olika områden, som huvudform, tilläggsfunktioner, hopfällningar och helhetslösningar.

     

    Efter att ha arbetat vidare på några olika idéer kunde olika konceptförslag skapas. Dessa diskuterades både med företaget och med experter inom framförallt lätta konstruktioner. Alla koncept bestod av hopfällningslösningar eftersom det ansågs vara en viktig del av utformningen.

     

    Resultatet av examensarbetet blev ett slutgiltigt konceptförslag som utformats med fokus på kundernas behov. Den nya generationens rollator har en form som tilltalar ögat, hållfasthet som motsvarar framtidens krav och är ergonomiskt utformad för att passa dess brukare. Konceptet innebar en rollator som fälls ihop m h a två vinkelräta gångjärn eftersom det ansågs ha flest fördelar.

  • 20.
    Li, Cai
    et al.
    Högskolan i Skövde, Institutionen för informationsteknologi. Högskolan i Skövde, Forskningscentrum för Informationsteknologi.
    Bredies, Katharina
    Department of Design, Faculty of Textiles, Engineering and Business, University of Borås, Sweden.
    Lund, Anja
    Department of Textile Technology, Faculty of Textiles, Engineering and Business, University of Borås, Sweden.
    Nierstrasz, Vincent
    Department of Textile Technology, Faculty of Textiles, Engineering and Business, University of Borås, Sweden.
    Hemeren, Paul
    Högskolan i Skövde, Institutionen för informationsteknologi. Högskolan i Skövde, Forskningscentrum för Informationsteknologi.
    Högberg, Dan
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    k-Nearest-Neighbour based Numerical Hand Posture Recognition using a Smart Textile Glove2015Ingår i: AMBIENT 2015: The Fifth International Conference on Ambient Computing, Applications, Services and Technologies / [ed] MaartenWeyn, International Academy, Research and Industry Association (IARIA), 2015, s. 36-41Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this article, the authors present an interdisciplinary project that illustrates the potential and challenges in dealing with electronic textiles as sensing devices. An interactive system consisting of a knitted sensor glove and electronic circuit and a numeric hand posture recognition algorithm based on k-nearestneighbour (kNN) is introduced. The design of the sensor glove itself is described, considering two sensitive fiber materials – piezoresistive and piezoelectric fibers – and the construction using an industrial knitting machine as well as the electronic setup is sketched out. Based on the characteristics of the textile sensors, a kNN technique based on a condensed dataset has been chosen to recognize hand postures indicating numbers from one to five from the sensor data. The authors describe two types of data condensation techniques (Reduced Nearest Neighbours and Fast Condensed Nearest Neighbours) in order to improve the data quality used by kNN, which are compared in terms of run time, condensation rate and recognition accuracy. Finally, the article gives an outlook on potential application scenarios for sensor gloves in pervasive computing.

  • 21.
    Lundgren, Daniel
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Persson, Michael
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Kvalitetsprovning av låskulor till hydrauliska snabbkopplingar2012Självständigt arbete på grundnivå (högskoleexamen), 15 poäng / 22,5 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Ett företag som tillverkar hydrauliska snabbkopplingar har genom regelbundna kvalitetsprover upptäckt att vissa låskulor till snabbkopplingarnas låsmekanism plötsligt fått en bristande kvalité och spricker vid belastning. Låskulorna är gjorda av rostfritt stål och har en viktig funktion i låsmekanismen. Om de spricker vid användning kan det leda till konsekvenser med materiella skador eller personskador. Företaget vill förekomma eventuella kvalitetsproblem och måste därför säkerställa att låskulorna har rätt hållfasthet. Låskulorna köps in från en underleverantör och företaget vill därför utveckla en provmetod som provar låskulornas materialegenskaper när de levereras till fabriken. Arbetet i denna rapport syftar till att hjälpa företaget utveckla en sådan provmetod.

    Ett första steg är att undersöka orsaken till att låskulorna spricker. Materialanalyser utförs av ett materiallaboratorium för att fastställa vilka faktorer i materialet som orsakar brott i låskulorna. Analyserna visar att låskulorna sannolikt spricker på grund av en ökad sprödhet i materialet. Sprödheten beror på att martensiten i materialet är dåligt anlöpt samt en stor mängd karbider.

    Med orsaken till sprickorna fastställd undersöks befintliga metoder för materialprovning. En provmetod måste prova materialet i färdigtillverkade låskulor eftersom låskulornas tillverkningsprocess påverkar materialegenskaperna. Många av de standardiserade provmetoderna är dock svåra att tillämpa på låskulorna med anledning av låskulornas geometri och små dimensioner.

    En form av slagprov och pressprov utförs på låskulorna. Ett av syftena med proven är att undersöka om de är lämpliga att använda som provmetod. Genom proven framträder olika materialegenskaper för olika låskulor. Resultaten är dock inte jämförbara låskulorna emellan och proven anses inte vara lämpliga som provmetod. Även ett utmattningsprov utförs på låskulorna genom en upprepande belastning i en snabbkoppling. Detta prov är inte heller lämpligt att använda som provmetod då provet är mycket tidskrävande samt att det finns vissa osäkerheter kring provresultatet.

    I detta arbete undersöks även två nyligen framtagna provmetoder för kulor till kullager och möjligheten att tillämpa dessa provmetoder på låskulorna. I undersökningen jämförs de båda provmetoderna med avseende på utförande samt framtagning av provkropp. Även en spänningsanalys av en låskula belastad i en snabbkoppling utförs för att ta reda på i vilket område av låskulan de maximala spänningarna uppstår. Undersökningen ger att enbart en provmetod är intressant för fortsatt arbete.  

    Den provmetod som föreslås i detta arbete kallas "the notched ball test" (NBT). Provmetoden innebär att en djup och smal skåra bearbetas i en låskula som sedan belastas med en tryckande kraft vinkelrätt mot skåran tills brott uppstår. Den maximala spänningen som verkar vid brottet beräknas med en enkel ekvation och används som mått för låskulans hållfasthet. Provmetoden är lämplig då den går att utföra med befintlig utrustning på företaget, den provar materialet i färdigtillverkade låskulor samt i samma område som de maximala spänningarna i en låskula belastad i en snabbkoppling uppstår. NBT nyttjar även dragspänningar vilket är fördelaktigt när sprödhet ska upptäckas i ett material.

    För att fastställa hur olika materialegenskaper samt geometrier för provkroppen påverkar provresultaten utförs en djupare analys av provmetoden. Analysen ger även vilka geometrier som bör användas vid utförandet av NBT samt värdet för den konstant som används vid beräkning av brottspänningen. Praktiska prov av NBT utförs inte i detta arbete men rapporten innefattar slutsatser om provmetoden och rekommendationer till företaget hur ett fortsatt arbete med NBT kan utföras.

  • 22.
    Marzi, Stephan
    et al.
    Fraunhofer IFAM, Wiener Str. 12, D-28359 Bremen, Germany.
    Biel, Anders
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    On experimental methods to investigate the effect of layer thickness on the fracture behavior of adhesively bonded joints2011Ingår i: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 31, nr 8, s. 840-850Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A number of different experimental methods are used at two independent laboratories to evaluate the influence of layer thickness on the fracture properties atone batch of a crash resistant epoxy adhesive. Both mode I and II are considered. Novel, as well as state of the art methods are used. In mode I, the Double Cantilever Beam (DCB) and two versions of the Tapered Double Cantilever Beam (TDCB) specimens are utilized; in mode II, two versions of the End Notch Flexure (ENF) and the End-Loaded Shear Joint (ELSJ) specimens are used. Good agreement between the test results is achieved for thin layers in both fracture modes. For thicker layers the variation is larger. (C) 2011 Elsevier Ltd. All rights reserved.

  • 23.
    Marzi, Stephan
    et al.
    Fraunhofer IFAM, Germany.
    Walander, Tomas
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Hesebeck, Olaf
    Fraunhofer IFAM, Germany.
    Brede, Markus
    Fraunhofer IFAM, Germany.
    A Controlled Mixed-Mode Bending (CMMB) test to investigate the fracture of structural adhesive joints2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    A so called Controlled Mixed-Mode Bending (CMMB) test is presented, which has been developed toinvestigate the fracture of crash-optimized, elastic-plastic adhesives loaded in mixed-mode. While mostcommon mixed-mode tests, like e.g. the MMB test, work fine with brittle adhesives, the controlled MMBtakes into account the large crack opening displacements at the crack tip and ensures a constant mode mixat the crack tip by the regulation of two actuators. Consequently, the definition of mode mixity is asignificant difference to state-of-the-art experiments, which define the mode mixity in terms of the ratio ofdissipated energy in the single modes and which are therefore based on analytical models or assumptionsconcerning the energy dissipation during the test. A further target of the presented CMMB test is to obtain information on the complete shape of the socalled traction separation law, which describes the relation between stress and displacement inside theadhesive layer. Such traction separation law is often used to define the failure behaviour of an adhesivejoint within a numerical analysis, using cohesive elements in a finite element code or similar approaches. Beside the theory and the idea of the CMMB test, experimental results for the adhesive SikaPower 498 arepresented and deeply discussed with respect to difficulties and limitations of the proposed method and therealized experimental setup.

  • 24.
    Mendoza, Ana Isabel
    et al.
    KTH-Royal Institute of Technology, Fibre and Polymer Technology, Stockholm, Sweden.
    Moriana, Rosana
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system. KTH-Royal Institute of Technology, Fibre and Polymer Technology, Stockholm / SLU-Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Hillborg, Henrik
    ABB-Corporate Research, Power Technology, Västerås, Sweden.
    Strömberg, Emma
    KTH-Royal Institute of Technology, Fibre and Polymer Technology, Stockholm, Sweden.
    Super-hydrophobic zinc oxide/silicone rubber nanocomposite surfaces2019Ingår i: Surfaces and Interfaces, ISSN 2468-0230, Vol. 14, s. 146-157Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study presents comparative assessments on hydrophilic and hydrophobic ZnO nanoparticles and their deposition methods on the surface hydrophobicity of silicone rubber (PDMS) and glass substrates. The influence on the surface hydrophobicity and wettability of all the variables regarding the deposition methodologies and the interaction of the nanoparticles with the substrates were within the scope of this study. The different surfaces created by spraying, dipping and drop-pipetting deposition methods were assessed by static contact angle measurements and contact angle hysteresis from advancing and receding angles, as well as by the calculation of the sliding angle and the surface energy parameters. An accurate methodology to determine the contact angle hysteresis was proposed to obtain repetitive and comparative results on all surfaces. All the measurements have been correlated with the morphology and topography of the different surfaces analysed by FE-SE microscopy. The spray-deposition of hydrophobic ZnO nanoparticles on PDMS resulted in super-hydrophobic surfaces, exhibiting hierarchical structures with micro-and nanometer features which, together with the low surface energy, promotes the Cassie-Baxter wetting behavior. This study provides the fundamental approach to select critically the most promising combination in terms of materials and deposition techniques to create silicone-based super-hydrophobic surfaces with potential to be applied in high voltage outdoor insulation applications.

  • 25.
    Moriana, Rosana
    et al.
    University Polytechnic of Valencia (UPV), Spain.
    Karlsson, Sigbritt
    KTH Royal Institute of Technology.
    Ribes-Greus, Amparo
    Reinforced biocomposites with guaranteed degradability in soil2010Ingår i: Plastics Research OnlineArtikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The addition of cotton fibers to a starch-based commercial material maintains its thermal stability and assures its biodegradation.

  • 26.
    Moriana, Rosana
    et al.
    KTH Royal Institute of Technology.
    Vilaplana, Francisco
    KTH Royal Institute of Technology.
    Ek, Monica
    KTH Royal Institute of Technology.
    Cellulose Nanocrystals from Forest Residues as Reinforcing Agents for Composites: A Study from Macro- to Nano-Dimensions2016Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 139, s. 139-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigates for the first time the feasibility of extracting cellulose nanocrystals (CNCs) from softwood forestry logging residues (woody chips, branches and pine needles), with an obtained gravimetric yield of over 13%. Compared with the other residues, woody chips rendered a higher yield of bleached cellulosic fibers with higher hemicellulose, pectin and lignin content, longer diameter, and lower crystallinity and thermal stability. The isolation of CNCs from these bleached cellulosic fibers was verified by the removal of most of their amorphous components, the increase in the crystallinity index, and the nano-dimensions of the individual crystals. The differences in the physico-chemical properties of the fibers extracted from the three logging residues resulted in CNCs with specific physico-chemical properties. The potential of using the resulting CNCs as reinforcements in nanocomposites was discussed in terms of aspect ratio, crystallinity and thermal stability.

  • 27.
    Moriana, Rosana
    et al.
    KTH Royal Institute of Technology.
    Vilaplana, Francisco
    KTH Royal Institute of Technology.
    Ek, Monica
    KTH Royal Institute of Technology.
    Forest residues as renewable resources for bio-based polymeric materials and bioenergy: chemical composition, structure and thermal properties2015Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, nr 5, s. 3409-3423Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The potential of three different logging residues (woody chips, branches and pine needles) as renewable resources to produce environmentally friendly polymeric materials and/or biofuel has been critically evaluated in terms of their structure, chemical composition and thermal properties. Woody chips constitute the most attractive forest residue to be processed into polymeric materials in terms of their highest cellulose content, crystallinity and thermal stability. In contrast, pine needles and branches offer higher heating values and optimum product distribution for solid fuel applications due to their higher lignin content. In general, forest residual biomass has great potential for conversion into new added value products, such as composites or solid biofuel, thus constituting a sustainable waste management procedure from a biorefinery perspective. The correlation between the chemical and structural properties with the thermal/pyrolytic behavior of residual biomass offers valuable insights to assess their sustainable exploitation.

  • 28.
    Moriana, Rosana
    et al.
    KTH Royal Institute of Technology.
    Zhang, Yujia
    KTH Royal Institute of Technology.
    Mischnick, Petra
    Technische Universität Braunschweig, Germany.
    Li, Jiebing
    KTH Royal Institute of Technology.
    Ek, Monica
    KTH Royal Institute of Technology / Chalmers University of Technology.
    Thermal degradation behavior and kinetic analysis of spruce glucomannan and its methylated derivatives2014Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 106, nr 1, s. 60-70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The thermal degradation behavior and kinetics of spruce glucomannan (SGM) and its methylated derivatives were investigated using thermogravimetric analysis to characterize its temperature-dependent changes for use in specific applications. The results were compared with those obtained for commercial konjac glucomannan (KGM). The SGM and the KGM exhibited two overlapping peaks from 200 to 375 C, which correspond to the intensive devolatilization of more than 59% of the total weight. Differences in the pyrolysis-product distributions and thermal stabilities appeared as a result of the different chemical compositions and molecular weights of the two GMs. The Friedman and Flynn-Wall-Ozawa isoconversional methods and the Coats-Redfern were adopted to determine the kinetic triplet of the intensive devolatilization region. Both GMs can be modeled using a complex mechanism that involves both a Dn-type and an Fn-type reaction. The comparative study of partially methylated GM indicated higher homogeneity and thermal resistance for the material with the higher degree of substitution.

  • 29.
    Oinonen, Petri
    et al.
    KTH, Träkemi och massateknologi.
    Moriana, Rosana
    KTH, Träkemi och massateknologi.
    Krawczyk, Holger
    Ek, Monica
    KTH, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Träkemi och massateknologi.
    The composite formation of cross-linked galactoglucomannan-lignin networks and cellulose nanoparticles as defined by thermal and mechanical testingManuskript (preprint) (Övrigt vetenskapligt)
  • 30.
    Salomonsson, Kent
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Mixed mode modeling of a thin adhesive layer using a meso-mechanical model2008Ingår i: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 40, nr 8, s. 665-672Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A representative volume element is modeled using the finite element method. It is used to analyze mixed mode behavior of a thin adhesive layer. Two sources of dissipation is modeled; plasticity and decohesion. Macroscopic traction–separation laws are extracted from the simulations. The results indicate that a boundary of mode mix exists between a region where major plastic dissipation is present and a region where it is not. Without major plastic dissipation, the fracture energy is low and essentially governed by the cohesive properties. This is the case in peel dominated loading cases. In shear dominated loading cases plastic dissipation gives a substantial contribution to the fracture energy. The results show that pure shear loading gives the largest fracture energy.

  • 31.
    Salomonsson, Kent
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    Stigh, Ulf
    Högskolan i Skövde, Institutionen för teknik och samhälle.
    On the apparent influence of the adherends on the fracture toughness of adhesive layers2007Ingår i: Interface design of polymer matrix composites: mechanics, chemestry, modelling and manufacturing, 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    A detailed model of experiments with the double cantilever beam specimen is set up. Analysis of the model shows that an experimentally deduced apparent increase of fracture energy with severely deforming adherends is due to contributions of in-plane straining of the adhesive layer to the fracture energy. An analysis with the J-integral confirms the result.

  • 32.
    Stigh, Ulf
    et al.
    Högskolan i Skövde, Institutionen för teknik och samhälle. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Svensson, Daniel
    Högskolan i Skövde, Institutionen för teknik och samhälle. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    On cohesive laws for delamination of composites2010Ingår i: 14th European conference on Composite materials, Budapest: University of Technology and Economics , 2010, s. 1-10, artikel-id 159-ECCM14Konferensbidrag (Refereegranskat)
    Abstract [en]

    Analysis of delamination of carbon fibre reinforced composite using cohesive models is studied. A method to measure the cohesive law associated with delamination is presented. The method allows for identification of a cohesive law fit to model the fracture process at the crack tip, i.e. not considering fibre bridging. Due to the small size of the cohesive zone, an elaborated method involving simulations of the fracture process is developed. The results show larger scatter in the parameters of the cohesive law than in the fracture energy.

  • 33.
    Svensson, Daniel
    Högskolan i Skövde, Institutionen för teknik och samhälle. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Experimental methods to determine model parameters for failure modes of CFRP2013Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The focus of this thesis is to develop methods to predict the damage response of Carbon Fibre Reinforced Polymers (CFRP). In the pursuit of reducing the manufacturing cost and weight of CFRP components, it is crucial to enable modelling of the non-linear response associated with various failure modes. Two failure modes are considered in this thesis: fibre compressive failure and interlaminar delamination. Multidirectional laminated composites are commonly used when a low weight is desired due to their high specific strength and stiffness. In a carbon/epoxy composite, almost exclusively the fibres carry the load. However, along the fibre direction, the compressive strength is considerably lower than the tensile strength. With the same reasoning, the transverse strength is considerably lower than the in-plane strength. This makes delamination and fibre compressive failure two of the major concerns in structural design. Moreover, the presence of delaminations severely reduces the compressive strength of a laminate. This can cause catastrophic failure of the structure. In Paper A, we suggest a test method for determining fracture properties associated with fibre compressive failure. A modified compact compression specimen is designed for this purpose and compressive failure takes place in a region consisting exclusively of fibres oriented parallel to the loading direction. The evaluation method is based on a generalized J-integral and full field measurements of the strain field on the surface of the specimen. Thus, the method is not restricted to small damage zones. Paper B focuses on measuring cohesive laws for delamination in pure mode loading. The cohesive laws in mode I and mode II are measured with the DCB- and ENF-specimen, respectively. With a method based on the J-integral, the energy release rate associated with the crack tip separation is measured directly. From this, the cohesive laws are derived. It is concluded that the nonlinear response at the crack tip is crucial in the evaluation of the mode II fracture energy.

  • 34.
    Svensson, Erik
    et al.
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap.
    Wiechert, Marcus
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap.
    Abrasiv nötning av polymerer tillverkade genom 3D-skrivning2015Självständigt arbete på grundnivå (högskoleexamen), 15 poäng / 22,5 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Volvo Cars i Skövde tillverkar och monterar Volvomotorer. Vid monteringen av tändspolen till alla 4-cylindriga motorer behövs ett monteringsverktyg. Detta monteringsverktyg tillverkas för närvarande från formsprutad termoplast polyoximetylen (POM). Det har noterats att livslängden av verktyget förkortas på grund av abrasiv nötning som uppkommer under monteringsprocessen av tändspolen.

    Möjligheterna att tillverka monteringsverktyget med en 3D-skrivare utvärderas i samverkan med ÅF, en konsult till Volvo Cars. En litteraturstudie presenteras för att introducera en bredare kunskap i ämnet. Den abrasiva nötningen och materialegenskaper såsom draghållfasthet, tryckhållfasthet samt töjning hos POM och ett alternativt material för 3D-skrivning, Ultem™, en amorf termoplast polyeterimid, behandlas. Dessa materialegenskaper studeras vidare och tas i beaktning med både en teoretisk analys och ett nötningsexperiment, baserat på pin-on-disc metoden.

    Enligt den teoretiska analysen är nötningen hos Ultem™ approximativt 6 gånger större vid jämförelsen med POM. Nötningsbeständigheten hos Ultem™ är högst då nötning sker parallellt med 3D-skrivningsriktningen av lagren. Nötningsexperimenten visar att nötningen hos Ultem™ är ungefär 3 gånger större vid jämförelsen med POM. Den högsta draghållfastheten hos Ultem™ uppkommer också parallellt med 3D-skrivningsriktningen av lagren. Problem med den låga töjningen hos det 3D-skrivna materialet behandlas.

    ÅF rekommenderas att tillämpa 3D-skrivning med materialet Ultem™ främst för detaljer med komplexa geometrier med en töjning som inte överskrider 5 %. ÅF rekommenderas även att både stödja och bidra till denna innovativa teknik för att kunna skapa en ledande expertis i ämnet.

  • 35.
    Vilaplana, Francisco
    et al.
    Division of Glycoscience, School of Biotechnology, AlbaNova University Centre, KTH Royal Institute of Technology, Stockholm, Sweden / Department of Fibre and Polymer Technology, School of Chemical Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Nilsson, Johanna
    Department of CollectionsThe Royal Armoury, Skokloster Castle, Hallwyl Museum, Stockholm, Sweden.
    Sommer, Dorte V. P.
    School of Conservation, Royal Danish Academy of Fine Arts Schools of Architecture, Design and Conservation, Copenhagen, Denmark.
    Karlsson, Sigbritt
    Högskolan i Skövde. Department of Fibre and Polymer Technology, School of Chemical Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Analytical markers for silk degradation: comparing historic silk and silk artificially aged in different environments2015Ingår i: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 407, nr 5, s. 1433-1449Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Suitable analytical markers to assess the degree of degradation of historic silk textiles at molecular and macroscopic levels have been identified and compared with silk textiles aged artificially in different environments, namely (i) ultraviolet (UV) exposure, (ii) thermo-oxidation, (iii) controlled humidity and (iv) pH. The changes at the molecular level in the amino acid composition, the formation of oxidative moieties, crystallinity and molecular weight correlate well with the changes in the macroscopic properties such as brightness, pH and mechanical properties. These analytical markers are useful to understand the degradation mechanisms that silk textiles undergo under different degradation environments, involving oxidation processes, hydrolysis, chain scission and physical arrangements. Thermo-oxidation at high temperatures proves to be the accelerated ageing procedure producing silk samples that most resembled the degree of degradation of early seventeenth-century silk. These analytical markers will be valuable to support the textile conservation tasks currently being performed in museums to preserve our heritage.

  • 36.
    Walander, Tomas
    Högskolan i Skövde, Institutionen för teknik och samhälle. Högskolan i Skövde, Forskningscentrum för Virtuella system.
    Cohesive modelling of the temperature dependence of epoxy based adhesives in Mode I and Mode II loading2013Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this work, the influence of the temperature on the cohesive laws for two epoxy adhesives is studied at temperatures below the glass transition temperature for both Mode I and Mode II loading. Cohesive laws are measured experimentally under quasi-static loading conditions in the temperature range -30≤T≤80"C" . Three parameters of the cohesive laws are studied in detail: the elastic stiffness, the peak stress and the fracture energy. Methods for determining the elastic stiffness in Mode I and Mode II are derived and evaluated. With these methods, the results in this work show that it is possible to measure all three parameters for each pure mode loading case by the use of only the DCB- and the ENF-test specimens. Even though the measures tend to spread in values, this can significantly reduce the cost for performing experiments. It is shown that most of the cohesive parameters are decreasing with an increasing temperature in both loading modes and for both adhesives. An exception is the Mode I fracture energy for one of the adhesives. This is shown to be independent of the temperature in the studied temperature range. For the same adhesive, the Mode II fracture energy is shown to be continuously decreasing with an increasing temperature. The experimental results are verified by finite element analyses. The simulations only consider uncoupled cohesive behaviours. By use of the experimental results, simplified bi-linear cohesive laws to be used at any temperature within the studied temperature range are derived for one adhesive in both loading modes. This is desired in order to simulate adhesively bonded structures that suffer a wide range in temperature.

  • 37.
    Wang, Lihui
    et al.
    Department of Production Engineering, KTH Royal Institute of Technology, Sweden.
    Wang, Wei
    Högskolan i Skövde, Institutionen för ingenjörsvetenskap. Högskolan i Skövde, Forskningscentrum för Virtuella system. Department of Production Engineering, KTH Royal Institute of Technology, Sweden.
    Liu, Dawei
    AVIC Chengdu Aircraft Industrial (Group) Ltd. Co., China.
    Dynamic feature based adaptive process planning for energy-efficient NC machining2017Ingår i: CIRP annals, ISSN 0007-8506, E-ISSN 1726-0604, Vol. 66, nr 1, s. 441-444Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a dynamic feature based adaptive process planning approach that can optimise machining cost, machining time and energy consumption simultaneously. The material removal volume of a dynamic feature is refined into non-overlapping volumes removed respectively by a single machining operation in which unified cutting mode is performed. Benefitting from this refinement, energy consumption is estimated analytically based on instantaneous cutting force as a function of real cutting parameters. Moreover, the cutting parameters assigned to each machining operation are optimised effectively in the unified cutting mode. This novel approach enhances the energy efficiency of NC machining through process planning.

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