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  • 1.
    Babu, NB Karthik
    et al.
    Department of Mechanical Engineering, Assam Energy Institute, A Centre of Rajiv Gandhi Institute of Petroleum Technology, Sivasagar, India.
    Mensah, Rhoda Afriyie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Shanmugam, Vigneshwaran
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Rashedi, Ahmad
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, Singapore.
    Athimoolam, Pugazhenthi
    Department of Mechanical Engineering, University College of Engineering Dindigul, Dindigul, India.
    Aseer, J. Ronald
    Department of Mechanical Engineering, National Institute of Technology Puducherry, Karaikal, India.
    Das, Oisik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Self‐reinforced polymer composites: An opportunity to recycle plastic wastes and their future trends2022In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 139, no 46, article id e53143Article, review/survey (Refereed)
    Abstract [en]

    Polymers and their composites have played an important role in industrial development. Polymer composites are becoming much stronger and more competitive than other materials as a result of ongoing research and development. This was made possible by newly developed techniques that could alter the physical and chemical properties of constituents. One of them is the self-reinforcement technique, which allows for the fabrication of high-strength thermoplastic polymer composites with reserved degradability, which is not possible with glass fiber/carbon fiber reinforcement. A self-reinforced polymer composite is made of a single polymeric material, which serves as both the matrix and the reinforcement. This review article discusses the use of self-reinforcement in various polymers and its impact on mechanical, thermal, and fire properties. Furthermore, the effects of process parameters (such as temperature and time, an), reinforcement structure, and mechanical property variation on the structure of self-reinforced composites are reviewed and presented in detail. In addition, the effect of foreign filler addition (such as flame retardants, inorganic particles, natural fibers, etc.) on self-reinforced composites is highlighted. In the end, the need for future research and its scope is presented.

  • 2.
    Bulderberga, O.
    et al.
    University of Latvia, Institute for Mechanics of Materials, Jelgavas Str. 3, Riga, LV-1004, Latvia.
    Zile, E.
    University of Latvia, Institute for Mechanics of Materials, Jelgavas Str. 3, Riga, LV-1004, Latvia.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sevcenko, J.
    University of Latvia, Institute for Mechanics of Materials, Jelgavas Str. 3, Riga, LV-1004, Latvia.
    Aniskevich, A.
    University of Latvia, Institute for Mechanics of Materials, Jelgavas Str. 3, Riga, LV-1004, Latvia.
    Mechanical Characteristics of Thermoplastic Polymers for 3d Printed Hybrid Structures2024In: Mechanics of composite materials, ISSN 0191-5665, E-ISSN 1573-8922, Vol. 60, no 1, p. 17-32Article in journal (Refereed)
  • 3.
    Engkvist, Gustav
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Investigation of microstructure and mechanical properties of 3D printed Nylon2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis presents a multiscale investigation and characterization of additive manufactured Polyamide material using fused deposition modelling technique. Manufacturing was performed using Markforgeds – Mark one 3D printer.  A multiscale investigation dedicated to minimizing the effect of shape distortion during 3D printing are presented, focusing on both molecular alignment in microstructure and implementing internal structures in mesostructure. Characterization on samples investigating microstructure was performed with coefficient of linear thermal expansion measurement and 3-point bending experiment. Different samples with varying infill patterns are tested and results indicates an isotropic behaviour through the manufactured samples and implies no molecular alignment due to printing pattern. In meso-structure, an implemented internal pattern is investigated. All samples are measured with 3D scanning equipment to localize and measure the magnitude of shape distortion. Attempts to find relationships in shape distortion and porosity between the samples resulted in no observed trends. Compressive experiments where performed on samples in axial- and transverse directions resulting in anisotropic behaviour. The largest compressive stiffness is recorded in axial direction reaching 0,33 GPa. The study is done in collaboration with Swerea SICOMP and Luleå University of Technology.

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  • 4.
    Gulisano, Federico
    et al.
    Departamento de Ingeniería del Transporte, Territorio y Urbanismo, Universidad Politécnica de Madrid, C/Profesor Aranguren 3, 28040 Madrid, Spain.
    Buasiri, Thanyarat
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Apaza, Freddy Richard Apaza
    Departamento de Ingeniería del Transporte, Territorio y Urbanismo, Universidad Politécnica de Madrid, C/Profesor Aranguren 3, 28040 Madrid, Spain.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gallego, Juan
    Departamento de Ingeniería del Transporte, Territorio y Urbanismo, Universidad Politécnica de Madrid, C/Profesor Aranguren 3, 28040 Madrid, Spain.
    Piezoresistive behavior of electric arc furnace slag and graphene nanoplatelets asphalt mixtures for self-sensing pavements2022In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 142, article id 104534Article in journal (Refereed)
    Abstract [en]

    Self-sensing road pavements can autonomously monitor their stress/strain and damage states without the need for embedded sensors. This kind of multifunctional pavements could be used for the realisation of autonomous structural health monitoring (SHM) systems. Moreover, it would permit to collect important traffic data for traffic-monitoring analysis and the development of Vehicle to Infrastructure Communication (V2I) tools, hence contributing to the digitalisation of the transport sector. The sensing mechanism is based on the piezoresistive effect, consisting of a change in the electrical response of the road material when subjected to stress/strain or damage. This paper aims to investigate the piezoresistive behavior of conductive asphalt mixtures with electric arc furnace slag (EAFS) and graphene nanoplatelets (GNPs) for self-sensing application. The results showed that asphalt mixtures with EAFS as fine aggregate and 7 wt% of GNPs exhibited excellent self-sensing properties for both traffic monitoring and SHM systems.

  • 5.
    Gulisano, Federico
    et al.
    Departamento de Ingeniería del Transporte, Territorio y Urbanismo, Universidad Politécnica de Madrid, C/Profesor Aranguren 3, 28040, Madrid, Spain.
    Buasiri, Thanyarat
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Cwirzen, Andrzej
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Gallego, Juan
    Departamento de Ingeniería del Transporte, Territorio y Urbanismo, Universidad Politécnica de Madrid, C/Profesor Aranguren 3, 28040, Madrid, Spain.
    Monitoring Road Infrastructures with Self-sensing Asphalt Pavements2023In: European Workshop on Structural Health Monitoring: EWSHM 2022 / [ed] Piervincenzo Rizzo; Alberto Milazzo, Springer Nature, 2023, Vol. 1, p. 784-793Conference paper (Refereed)
    Abstract [en]

    Structural health monitoring (SHM) of road pavements is an essential task, which can help the decision-making process for timely maintenance actions. Embedded sensors are typically used to collect long-term monitoring data. However, the main drawbacks of intrusive sensors concern the risk of premature damage and the incompatibility of the sensors with the host material. Self-sensing asphalt mixtures can be used to overcome these limitations. These kinds of smart materials can autonomously monitor their strain and damage states without the need for embedded sensors. The sensing mechanism is based on the piezoresistive effect, consisting of a change in the electrical conductivity of the material when subjected to external loading. To endow the asphalt mixture with piezoresistive function, a proper amount of conductive additive should be incorporated without compromising the mechanical performance of the pavement. The present work aims to design piezoresistive asphalt mixtures for the development of SHM and traffic management systems. Multi-walled carbon nanotubes (MWNTs) and graphene nanoplatelets (GNPs) were added to the asphalt mixture with this purpose, and the piezoresistive response was tested at laboratory scale. The results show that piezoresistive asphalt mixtures have excellent self-sensing properties and can be effectively used for SHM, traffic detection and weigh-in-motion applications.

  • 6.
    Kachirayil, Antony J.
    et al.
    Rajiv Gandhi Institute of Technology, Government Engineering College, affiliated to APJ Abdul Kalam Technological University, 686501, Kottayam, Kerala, India.
    Babu, Akhil
    Rajiv Gandhi Institute of Technology, Government Engineering College, affiliated to APJ Abdul Kalam Technological University, 686501, Kottayam, Kerala, India.
    Nambiathodi, Vaishak
    Technical Consultancy Division, Rubber Research Institute of India, Kottayam, India.
    Thomas, Bony
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Varghese, Siby
    Technical Consultancy Division, Rubber Research Institute of India, Kottayam, India.
    Radhika, R.
    Rajiv Gandhi Institute of Technology, Government Engineering College, affiliated to APJ Abdul Kalam Technological University, 686501, Kottayam, Kerala, India.
    Manoj Kumar, M.
    Rajiv Gandhi Institute of Technology, Government Engineering College, affiliated to APJ Abdul Kalam Technological University, 686501, Kottayam, Kerala, India.
    Rajesh, Raghunathan
    Rajiv Gandhi Institute of Technology, Government Engineering College, affiliated to APJ Abdul Kalam Technological University, 686501, Kottayam, Kerala, India.
    Enhancing Compression Set Resistance of Nitrile Rubber Composites Through a Hybrid Mixture of Sustainable Filler Lignin and Carbon Black2024In: Recent Advances in Mechanical Engineering, Volume 1: Select Proceedings of ICMech-REC 23 / [ed] Gujjala Raghavendra; B. B. V. L. Deepak; Manoj Gupta, Springer Nature, 2024, Vol. 1, p. 545-559Conference paper (Refereed)
  • 7.
    Kundu, Chanchal Kumar
    et al.
    Department of Textile Engineering, Jashore University of Science and Technology, Jashore, 7408, Bangladesh; National and Local Joint Engineering Research Center for Applied Technology of Hybrid Nanomaterials, Henan University, Kaifeng, 475004, People’s Republic of China.
    Li, Zhiwei
    National and Local Joint Engineering Research Center for Applied Technology of Hybrid Nanomaterials, Henan University, Kaifeng, 475004, People’s Republic of China.
    Khan, M. Azizur R.
    Department of Chemistry, Jashore University of Science and Technology, Jashore, 7408, Bangladesh.
    Försth, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Das, Oisik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Polypyrrole-modified multi-functional coatings for improved electro-conductive, hydrophilic and flame-retardant properties of polyamide 66 textiles2023In: JCT Research, ISSN 1547-0091, E-ISSN 2168-8028, Vol. 20, no 4, p. 1223-1234Article in journal (Refereed)
  • 8.
    Lin, Chia-Feng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Innovative Water-Resistant Fire-Retardant Wood incorporating Ammonium Phosphate-based salts for Exterior Use Conditions2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wood is a naturally based material and plays an important role as a renewable resource when aiming for a sustainable society. Nevertheless, its inherently combustible property needs to be enhanced to comply with modern construction methods and regulations. Ammonium phosphate-based additives are often used to effectively increase the fire-retardancy (FR) of wooden products when needed. However, their water-solubility make them unsuitable for exterior use unless such properties are overcome. This PhD thesis focuses on the development of methodologies to alleviate consequences from water-leaching of wood treated with ammonium phosphate-based additives, enabling further development of new types of fire protected wood construction material for exterior uses. As such, two methodologies were explored in this thesis: 1) a composite-type fixation, involving the introduction of a hydrophobic polymer matrix for entrapping the FR additives, 2) a reactive-type fixation, which is to fix the FR additives by creating covalent bonding with the wood polymeric constituents.

    In order to determine the influence of composite-type fixation systems, melamine-formaldehyde (MF) prepolymer, furfuryl alcohol (FA), and kraft lignin, respectively, were studied for immobilising ammonium phosphate-based FR-additives in wood by pressure impregnating Scots pine (Pinus sylvestris L.) sapwood with a solution of the prepolymer and fire-retardant additives (FRs), followed by drying and heating steps. Through the analysis of the treated wood materials, involving scanning electron microscopy energy dispersive spectroscopy (SEM-EDX) and thermal gravimetric analysis (TGA), the formation of a stable polymeric network structure entrapping the additives inside the wood with alleviating FRs’ water-leachability was proposed. In particular, MF-resin was able to encapsulate guanyl-urea phosphate (GUP) in the lumen of the wood. Further details on the distribution and structural features of FR additives and matrices within the wood structure are described in the thesis. 

    Furthermore, the ability of FRs comprising ammonium dihydrogen phosphate (ADP) and urea to be fixed within the wood structure without the addition of polymeric materials was also investigated. This approach was accomplished by impregnating an aqueous solution containing the aforementioned additives, followed by drying and further heat treatment at 150°C. By analysis of the treated wood material by solid-state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and FTIR, the formation of a reactive-type fixation of FR to the wood structure was realised. By this way, phosphate and carbamylate groups from treated ADP/urea were found to have reacted with hydroxyl groups of the wood polymers. 

    The fire performance of FR-treated wood materials was studied with a series of modern techniques, namely, limited oxygen index (LOI), microscale combustion calorimeter (MCC), and cone calorimeter tests. LOI and MCC were used as a simple test of fire stability of FR-treated and subsequently water exposed wood. By applying the cone calorimeter test, the predicted reaction-to-fire classification of FR-MF, FR-FA, and phosphorylated/carbamylated wood was established and, actually, reached the highest possible classification, class B. This classification was held even after the accelerated ageing test according to the European standard EN 84. In summary, this further suggested that these methodologies, which enhanced the water-leaching resistance of ammonium phosphate-based salts, have the potential to give a fire-retardant wood suitable for exterior uses.

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  • 9.
    Patel, Mitul Kumar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hansson, Freja
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pitkänen, Olli
    Microelectronics Research Unit, Faculty of Information Technology and Electrical Engineering, University of Oulu, 90570 Oulu, Finland.
    Geng, Shiyu
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Mechanical & Industrial Engineering (MIE), University of Toronto, Toronto, Ontario M5S 3G8, Canada; Wallenberg Wood Science Center (WWSC).
    Biopolymer Blends of Poly(lactic acid) and Poly(hydroxybutyrate) and Their Functionalization with Glycerol Triacetate and Chitin Nanocrystals for Food Packaging Applications2022In: ACS Applied Polymer Materials, E-ISSN 2637-6105, Vol. 4, no 9, p. 6592-6601Article in journal (Refereed)
    Abstract [en]

    Polylactic acid (PLA) is a biopolymer that has potential for use in food packaging applications; however, its low crystallinity and poor gas barrier properties limit its use. This study aimed to increase the understanding of the structure property relation of biopolymer blends and their nanocomposites. The crystallinity of the final materials and their effect on barrier properties was studied. Two strategies were performed: first, different concentrations of poly(hydroxybutyrate) (PHB; 10, 25, and 50 wt %) were compounded with PLA to facilitate the PHB spherulite development, and then, for further increase of the overall crystallinity, glycerol triacetate (GTA) functionalized chitin nano crystals (ChNCs) were added. The PLA:PHB blend with 25 wt % PHB showed the formation of many very small PHB spherulites with the highest PHB crystallinity among the examined compositions and was selected as the matrix for the ChNC nanocomposites. Then, ChNCs with different concentrations (0.5, 1, and 2 wt %) were added to the 75:25 PLA:PHB blend using the liquid-assisted extrusion process in the presence of GTA. The addition of the ChNCs resulted in an improvement in the crystallization rate and degree of PHB crystallinity as well as mechanical properties. The nanocomposite with the highest crystallinity resulted in greatly decreased oxygen (O) and carbon dioxide (CO2) permeability and increased the overall mechanical properties compared to the blend with GTA. This study shows that the addition ChNCs in PLA:PHB can be a possible way to reach suitable gas barrier properties for food packaging films.

  • 10.
    Petkov, Valeri
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Studies on the thermal degradation of thermosetting polyimides and their composites2022Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The thesis contains a background and reflections section, an introduction, and three appended articles. The first section is reserved for some of the background and basics on polymers and polymer composites and a discussion on their effect on our everyday lives. The introduction gives a brief recap of the project. The articles contain the research that was performed on the thermal oxidation of thermosetting polyimides and their composites during the project.

    The first article covered the thermal oxidative degradation of satin weave and thin-ply composites made by resin transfer molding with carbon fibers and thermosetting polyimide. The degradation was studied by weight loss measurements and X-ray computed microtomography. The weight loss measurements showed that the initial desorption stage during ageing followed Fickian behavior and the proposed model. It was also observed that the satin weave composites formed crack clusters that grew into a network of cracks, voids and delaminations throughout the specimens as the ageing time progressed, while the thin-ply composites only formed delaminations at the free edges.

    The second manuscript studied the behavior of the neat polyimide resin when aged for up to 1500 hours in ambient air, and compared it with a newly developed polyimide formulation, with slightly altered chemical composition. The reduced amount of internal crosslinkers in the newer formulation was expected to enhance the fracture toughness of the material. Three-point bending, differential scanning calorimetry, dilatometry, weight loss, light optical microscopy and nanoindentation experiments were performed and highlighted the differences in the thermal and mechanical properties of the two formulations. A slight increase in the fracture toughness was observed, while the glass transition of the new formulation had decreased.

    The third manuscript was aimed at continuing the discussion from the second article on the differences between the two thermosetting polyimides. Thermogravimetric scans showed that the polyimide formulations behaved very similarly under thermal oxidative tests. The initial analysis gave indications that the model could capture well the degradation at high temperatures, but is not adequate in predicting long-term degradation at temperatures around 288–400 °C.

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  • 11.
    Petkov, Valeri Ivanov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Characterisation of thermally induced degradation of high-temperature polymers and composites2024Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This project aimed to broaden the knowledge of high-temperature polymers and composites when exposed to elevated temperatures and an oxygen-containing atmosphere. The main accent has been on thermosetting polyimide resins reinforced with carbon fibers. When subjected to harsh atmospheric conditions, such as elevated temperatures and oxygen, polymer resins can undergo thermo-oxidative degradation, often resulting in weight loss and a surface layer with altered properties. High-temperature composites could experience such environments during operation. Therefore, it is crucial to understand how exposure to it could affect their performance. To simulate such an environment in the lab, the materials are aged in a controlled manner in a furnace or other equipment. The ageing of polyimide composites in this project was often performed at temperatures at or above 288 degrees Celsius for extended periods of up to 1500 hours.

    The first part of the project, and the first article, delved into the effect of different layups and thicknesses of the carbon fiber bundles on the thermo-oxidative behaviour of two composite materials made with the same thermosetting polyimide. Modelling the desorption during the initial stages of the ageing, showed that it exhibited a Fickian behaviour. X-ray computed tomography experiments were used to investigate the ageing behaviour of the materials and revealed that the satin weave composite formed a network of cracks, voids, and delaminations, that progressed with the ageing time, while the damage in the material made of thin plies was in the form of delaminations at the edges. The analysis of the tomographic datasets was performed using Otsu’s thresholding method for semantic segmentation of the defects within the materials.

    In an attempt to counter the crack formation on the surface of the satin weave composite observed during the first study, a new polyimide formulation was developed by the manufacturer. The amount of internal crosslinkers was reduced, aiming to increase the toughness of the resin after curing. The second article compares neat resin samples of the original and newly developed formulations with the help of a three-point bending test, differential scanning calorimetry, dilatometry, weight loss, light optical microscopy and nanoindentation experiments. Samples were aged up to 1500 hours in ambient air. The results showed that while there were hints of a slight increase in the fracture toughness of the new formulation, the glass transition temperature had decreased, compared to the original resin.

    The two formulations were further investigated and compared with the help of thermogravimetric analysis in the fourth paper. Experiments were performed in isothermal and non-isothermal conditions for more robust results. It was found that the thermal oxidation of the two materials follows an autocatalytic model. The study highlights the importance of using both isothermal and non-isothermal data in the pursuit of more precise and robust analysis and modelling of the thermal oxidation of high-temperature polymers. Based on the results, a diagram, predicting the weight loss at specific times and temperatures, was created for each material.

    An alternative way of studying crack formation within challenging polymer composite tomographic datasets was presented in the fourth article. Instead of using a thresholding method, such as the

    previously used Otsu’s in the first study, in this case, a deep learning model was applied to the datasets to follow the progressive micro-cracking within the composite during a series of thermo-mechanical loadings. In contrast to a global thresholding method, which segments all defects within the dataset, the deep learning model, Attention U-Net, made it possible to create a more straightforward and robust way of performing segmentation on transverse cracks. The model was compared to and outperformed both Otsu’s method and a conventional U-Net.

    The previously developed methodology for semantic segmentation and the obtained results on transverse cracks were applied in a practical case in the fifth article, where the developed damage prediction model assumes that transverse cracks in thick plies span through the whole width of the specimen. The tomography and deep learning methodology helped shed light on the nature of the cracks and showed that previous assumptions, based on edge observation with light optical microscopy, should be taken as a conservative estimation.

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  • 12.
    Petkov, Valeri Ivanov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Bianchi, Otávio
    Universidade Federal do Rio Grande do Sul.
    Cesar Pacheco Vaghetti, Julio
    Fernberg, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Assessing the thermo-oxidative degradation of thermosetting polyimidesManuscript (preprint) (Other academic)
  • 13.
    Petkov, Valeri Ivanov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pelcastre, Leonardo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Solano, Carlos
    Nexam Chemical AB, 234 35 Lomma, Sweden.
    Fernberg, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    The Influence of Ethynyl In-Chain Crosslinkers on the Properties of 6FDA-Based Polyimides2022In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 16, no 1, article id 169Article in journal (Refereed)
    Abstract [en]

    Two 4,4′-(hexafluoroisopropylidene)diphthalic anhydride-based thermosetting polyimide formulations with varied amounts of crosslinking sites were compared to understand the influence of crosslinking density on fracture toughness, glass transition temperature and thermal oxidative stability. The thermal and mechanical properties of both materials were investigated through a series of single-edge notched beams, differential scanning calorimetry, dilatometry, weight loss, light optical microscopy and nanoindentation experiments. It was found out that the reduced crosslinking resulted in slightly increased fracture toughness but decreased the Tg of the material. No significant difference could be observed in the thermal oxidative stability with the experimental techniques considered.

  • 14.
    Rosenstock Völtz, Luísa
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Wallenberg Wood Science Center (WWSC), Luleå, SE-97187, Sweden.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Wallenberg Wood Science Center (WWSC), Luleå, SE-97187, Sweden; Department of Mechanical & Industrial Engineering (MIE), University of Toronto, Toronto, M5S 3G8, ON, Canada.
    The use of recycled materials towards sustainability: biocomposites manufactured in melt compounding2022In: ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability / [ed] Vassilopoulos, Anastasios; Michaud, Véronique, Lausanne: EPFL Lausanne, Composite Construction Laboratory , 2022, Vol. 1, p. 600-607Conference paper (Other academic)
    Abstract [en]

    Currently, there is a need in developing sustainable materials with an emphasis on reusing and recycling, to meet the sustainable development goals outlined by the United Nations for 2030. This work aimed to use recycled materials, such as recycled jeans and recycled rubber to replace the additive used in commercial wood polymer composites (WPCs) (reference material) to make it more sustainable without affecting its technical performance. The feeding of the post-used jeans fabric directly into the extruder was accomplished successfully with an increase in strength, modulus, and impact properties when compared with the reference material. The fracture surfaces showed that the fiber pullout contributed to the enhancement in fracture toughness with the addition of recycled jeans, further the addition of recycled rubber led to the matrix modification keeping the toughness at the same level as the reference material.

  • 15.
    Sandell, Viktor
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Extraction of Material Parameters for Static and Dynamic Modeling of Carbon Black Filled Natural Rubbers2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Volvo Car Corporation (Volvo Cars) develops powertrain mounting systems that uses components made up largely of filled rubber materials. The development of such components is today relying on external suppliers to design components based on requirements set by Volvo. To reduce costs and lead-time in the development process the possibility of in-house design of such components at Volvo Cars is being investigated. For this to be possible, knowledge must be built concerning modelling the mechanical properties of rubber materials. As part of this a parameter extraction method for modelling of filled rubber materials intended for finite element use has been developed in this project. Both a simple static model fitting procedure and a more complex dynamic model fitting procedure are detailed. Mechanical testing of four filled natural rubber materials with varying hardnesswas carried out at the facilities of Volvo Cars and recommendations have been made regarding the limits of the equipment and the specific test body geometry used. It was found that the lower limit for dynamic testing in regards to displacement amplitude is 0.02 mm. The highest frequency recommended is dependent on the material hardness but a higher limit of 200 Hz is recommended for the softest material investigated. The upper limit was found to be necessary due to inertia effects in the material. The models used to describe the static behaviour were hyperelastic phenomenological models independent on the second invariant such as the Yeoh and the linear neo-Hookean models. The dynamic model used the overlay method to capture therate and amplitude dependent properties of filled rubber. A generalized viscoelastic-elastoplastic rheological model using Maxwell and friction elements in parallel with alinear elastic element was presented and used. These were limited to having maximumfive of each element and no attempts at minimizing this number was made in this work.The dynamic model was fitted to experimental data using a minimization procedure focusing on dynamic modulus and damping at a range of frequencies and strain amplitudes.The proposed fitting procedure is a three segment loop in which FE simulationsof the experimental data is used as both a correction and a validation tool.Model validation showed good correlation of the fitted model to measured databefore correction was attempted. The correction step did not improve the model qualityand the reason for this was identified as poor post-processing. The proposed method together with lessons learned during the course of the project will be of importance for the future in-house development of rubber components at Volvo Cars.

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  • 16.
    Selvam, Arivazhagan
    et al.
    Department of Mechanical Engineering, KPR Institute of Engineering and Technology, Coimbatore, Tamil Nadu, India.
    Mayilswamy, Suresh
    Department of Robotics and Automation Engineering, PSG College of Technology, Coimbatore, Tamil Nadu, India.
    Whenish, Ruban
    Centre for Bio Materials, Cellular and Molecular Theranostics, Vellore Institute of Technology, Vellore, Tamil Nadu, India.
    Naresh, K.
    Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, 90089, USA.
    Shanmugam, Vigneshwaran
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Department of Mechanical Engineering, Saveetha School of Engineering, Saveetha Institute of Medical and Technical Sciences, Chennai, India.
    Das, Oisik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Multi-objective optimization and prediction of surface roughness and printing time in FFF printed ABS polymer2022In: Scientific Reports, E-ISSN 2045-2322, Vol. 12, article id 16887Article in journal (Refereed)
    Abstract [en]

    In this study, fused filament fabrication (FFF) printing parameters were optimized to improve the surface quality and reduce the printing time of Acrylonitrile Butadiene Styrene (ABS) polymer using the Analysis of Variance (ANOVA), it is a statistical analysis tool. A multi-objective optimization technique was employed to predict the optimum process parameter values using particle swarm optimization (PSO) and response surface methodology (RSM) techniques. Printing time and surface roughness were analyzed as a function of layer thickness, printing speed and nozzle temperature. A central composite design was preferred by employing the RSM method, and experiments were carried out as per the design of experiments (DoE). To understand the relationship between the identified input parameters and the output responses, several mathematical models were developed. After validating the accuracy of the developed regression model, these models were then coupled with PSO and RSM to predict the optimum parameter values. Moreover, the weighted aggregated sum product assessment (WASPAS) ranking method was employed to compare the RSM and PSO to identify the best optimization technique. WASPAS ranking method shows PSO has finer optimal values [printing speed of 125.6 mm/sec, nozzle temperature of 221 °C and layer thickness of 0.29 mm] than the RSM method. The optimum values were compared with the experimental results. Predicted parameter values through the PSO method showed high surface quality for the type of the surfaces, i.e., the surface roughness value of flat upper and down surfaces is approximately 3.92 µm, and this value for the other surfaces is lower, which is approximately 1.78 µm, at a minimum printing time of 24 min.

  • 17.
    Somberg, Julian
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gonçalves, Gil
    Centre for Mechanical Technology and Automation (TEMA), University of Aveiro, Portugal; Intelligent Systems Associate Laboratory (LASI), Portugal.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Graphene oxide versus graphite and chemically expanded graphite as solid lubricant in ultrahigh molecular weight polyethylene composites2023In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 187, article id 108643Article in journal (Refereed)
    Abstract [en]

    Graphene oxide (GO), chemically expanded graphite (CEG) and graphite were evaluated as solid lubricant for ultrahigh molecular weight polyethylene composites. Under dry conditions, the addition of all solid lubricants increased the coefficient of friction by up to 38%. For the composites corrugated stick–slip features were observed which correlate with a decrease in matrix degree of crystallinity. GO had the lowest effect on the crystallisation, resulting in the lowest relative increase in friction coefficient of only 13%. Under water lubrication, GO, CEG and graphite were equally effective in reducing friction and wear. The highest friction for the neat matrix was found to be due to a transfer film, which was suppressed by the addition of the solid lubricants.

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  • 18.
    Somberg, Julian
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gonçalves, Gil
    Centre for Mechanical Technology and Automation (TEMA), University of Aveiro, Portugal.
    Sánchez, María Soria
    Institute of Material Science of Barcelona, Spain.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Chemically expanded graphite-based ultra-high molecular weight polyethylene nanocomposites with enhanced mechanical properties2022In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 224, article id 111304Article in journal (Refereed)
    Abstract [en]

    Chemically expanded graphite (CEG) has recently been identified as promising reinforcement for polymer composites with the ability for commercial up-scaling. In this work, silane and polydopamine functionalized CEG were successfully synthesized and employed to prepare ultra-high molecular weight polyethylene (UHMWPE) nanocomposites with an enhanced interfacial compatibility. Characterisation of the functionalized CEG indicated a significant oxygen reduction, which gave rise to a restoration of the graphitic structure. The polydopamine functionalized CEG showed an enhanced exfoliation and dispersion in organic solvents and the polymer matrix with respect to the non-modified CEG. The silane functionalized CEG provided a higher affinity towards the matrix with polymer chains covering the CEG sheets on the fracture surfaces. The addition of functionalized CEG enhanced the mechanical properties of the UHMWPE matrix with an increase in micro-hardness of up to 25% and storage modulus of up to 58%. Furthermore, the hydrophobicity of the composites was significantly enhanced with an increase in water contact angle from 98.6° for the pure polymer to 119° for 5 wt% silane functionalized CEG. Preliminary wear experiments indicated the potential of the composites for tribological applications with a decrease in wear rate of up to 99% under water lubricated conditions.

  • 19.
    Sperlich, Billy
    et al.
    Institute of Training Science and Sport Informatics, German Sport University, Cologne, Germany.
    Holmberg, Hans-Christer
    Institutionen för hälsovetenskap, Mittuniversitetet, Sweden.
    Physiological effects of a new racing suit for elite cross country skiers2011In: Journal of Sports Medicine and Physical Fitness, ISSN 0022-4707, E-ISSN 1827-1928, Vol. 51, no 4, p. 555-559Article in journal (Refereed)
    Abstract [en]

    AIM: The aim of this paper was to investigate the influence of the new cross country racing suit, designed for the Olympic Winter Games in Vancouver 2010, on cardio-respiratory, thermoregulatory and perceptual responses.METHODS: Six elite cross country skiers (29±6 years, peak oxygen uptake 73.2±6.9 mL·min-1·kg-1) performed two exercise bouts wearing either the 2009 or the 2010 racing suit. Bouts consisted of incremental testing on roller skis (12 km·h-1 at 5° inclination; 11 km·h-1 at 6° inclination and 12 km·h-1at 8° inclination for six minutes).RESULTS: During increasing intensities, significantly lower values were found for oxygen uptake, minute ventilation, RER and heart rate when wearing the new suit compared to the old one (P<0.05; effect sizes: 0.21-4.00). Core temperature was lower with the new suit during steps 2 and 3 (P<0.05, effect size: 1.22-1.27). Also, mean skin temperature was lower during the last increment (P<0.05, effect size: 0.87).CONCLUSION:The new 2010 racing suit, developed specifically for the Olympic Winter Games in Vancouver 2010, demonstrated lower values for oxygen uptake, minute ventilation, heart rate, skin and core temperature, ratings of thermal and sweat sensation when compared to the 2009 racing suit.

  • 20.
    Vijaybabu, T. R.
    et al.
    Department of Mechanical Engineering, GMR Institute of Technology, Rajam, Andra Pradesh, 532127, India.
    Ramesh, T.
    Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu, 620015, India.
    Pandipati, Suman
    Deparment of Mechanical Engineering, Aditya Institute of technology and management, Tekkali, Andhra Pradesh, 532203, India.
    Mishra, Sujit
    Department of Mechanical Engineering, Centurion University of Technology and Management, Paralakhemundi, Odisha, 761211, India.
    Sridevi, G.
    Department of Mechanical Engineering, Centurion University of Technology and Management, Paralakhemundi, Odisha, 761211, India.
    Raja, C Pradeep
    Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu, 620015, India.
    Mensah, Rhoda Afriyie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Das, Oisik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Misra, Manjusri
    School of Engineering, University of Guelph, Albert A. Thornbrough Building, 80 South Ring Road East, Guelph, ON N1G 2W1, Canada.
    Mohanty, Amar
    School of Engineering, University of Guelph, Albert A. Thornbrough Building, 80 South Ring Road East, Guelph, ON N1G 2W1, Canada.
    Karthik Babu, N. B.
    Department of Mechanical Engineering, Assam Energy Institute, A centre of Rajiv Gandhi Institute of Petroleum Technology, Sivasagar, Assam, 785697, India.
    High Thermal Conductivity Polymer Composites Fabrication through Conventional and 3D Printing Processes: State-of-the-Art and Future Trends2023In: Macromolecular materials and engineering, ISSN 1438-7492, E-ISSN 1439-2054, Vol. 308, no 7, article id 2300001Article, review/survey (Refereed)
    Abstract [en]

    The lifespan and the performance of flexible electronic devices and components are affected by the large accumulation of heat, and this problem must be addressed by thermally conductive polymer composite films. Therefore, the need for the development of high thermal conductivity nanocomposites has a strong role in various applications. In this article, the effect of different particle reinforcements such as single and hybrid form, coated and uncoated particles, and chemically treated particles on the thermal conductivity of various polymers are reviewed and the mechanism behind the improvement of the required properties are discussed. Furthermore, the role of manufacturing processes such as injection molding, compression molding, and 3D printing techniques in the production of high thermal conductivity polymer composites is detailed. Finally, the potential for future research is discussed, which can help researchers to work on the thermal properties enhancement for polymeric materials.

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  • 21.
    Völtz, Luísa Rosenstock
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Wallenberg Wood Science Center (WWSC), Luleå, Sweden.
    Berglund, Linn
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Wallenberg Wood Science Center (WWSC), Luleå, Sweden; Department of Mechanical & Industrial Engineering (MIE), University of Toronto, ON, M5S 3G8 Toronto, Canada.
    Resource-efficient manufacturing process of composite materials: Fibrillation of recycled textiles and compounding with thermoplastic polymer2023In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 175, article id 107773Article in journal (Refereed)
    Abstract [en]

    This study aimed to develop a manufacturing process for recycled textile long fiber thermoplastics (RT-LFT) and thereby contribute to circular economy. Three different post-consumer textiles (cotton denim and plain weave, and silk plain weave) were cut into strips and fed directly into a co-rotating twin-screw extruder in which the textile was fibrillated and compounded with polypropylene (PP). The fibrillation of the textile, fiber dispersion, and interaction with the matrix polymer were studied, and the thermal and mechanical properties of the composites were evaluated. For example, cotton denim composites containing 30 wt% fiber content resulted in 26% increase in yield strength and a 72% increase in modulus when compared with that of PP. The RT-LFT process is a straightforward method for transforming used textiles into composites like cups and bottoms, offering advantages such as reduced manufacturing costs, add value for waste material, and lower carbon emissions.

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  • 22.
    Wei, Jiayuan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Geng, Shiyu
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pitkänen, Olli
    Microelectronics Research Group, University of Oulu, Oulu, Finland.
    Järvinen, Topias
    Microelectronics Research Group, University of Oulu, Oulu, Finland.
    Kordas, Krisztian
    Microelectronics Research Group, University of Oulu, Oulu, Finland.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Fibre and Particle Engineering Research Group, University of Oulu, Finland.
    Making good use of lignin – from a low-value biopolymer to energy storage devices2019In: Nordic Polymer Days 2019: Book of Abstracts / [ed] Rita de Sousa Dias; Sulalit Bandyopadhyay, Norwegian University of Science and Technology , 2019, p. 48-48, article id 04.3Conference paper (Refereed)
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  • 23.
    Zrida, Hana
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Fernberg, Patrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ayadi, Zoubir
    Institut Jean Lamour, Ecole Européenne d’Ingénieurs en Génie des Matériaux, Université de Lorraine.
    Varna, Janis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Microcracking in thermally cycled and aged Carbon fibre/polyimide laminates2017In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 94, no 1, p. 121-130Article in journal (Refereed)
    Abstract [en]

    Carbon fibre T650 8-harness satin weave fabric composites with thermosetting polyimide resin designed for high service temperatures are solidified at 340 °C. High thermal stresses develop after cooling down to room temperature, which lead to multiple cracking in bundles of the studied quasi-isotropic composite. The composites are subjected to two thermal cycling ramps and the increase of crack density in each bundle is quantified. Comparison of two ramps with the same lowest temperature shows that the highest temperature in the cycle has a significant effect on thermal fatigue resistance. During thermal aging tests at 288 °C the mechanical properties are degrading with time and the crack density after certain aging time is measured. Aging and fatigue effects are separately analysed showing that part of the cracking in thermal cycling tests is related to material aging during the high temperature part of the cycle. Numerical edge stress analysis and fracture mechanics are used to explain observations. The 3-D finite element edge stress analysis reveals that there is large edge effect that induces a large difference in the damage state between the different layers on the edge. The linear elastic fracture mechanics explains the higher initiated and propagated crack density in the surface layers comparing to the inner layers.

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