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Fatigue behaviour of glass-fibre-reinforced polymers : Numerical and experimental characterisation
No full textThis work presents a novel numerical methodology to model the degradation and failure of composite materials like GFRP submitted to monotonic and high cycle fatigue loads. This is done by using the Serial–Parallel Rule of Mixtures homogenisation technique together with a proper mechanical characterisation of the constituent materials of the composite. This paper also proposes an efficient way of estimating the fatigue properties of each of the material constituents (fibre or matrix) to comply with the experimental results obtained at composite level; this enables to estimate the fatigue strength of any stacking/orientation of fibres with only one mechanical characterisation of the material properties. A comparison of the results obtained analytically and experimentally for GFRP is presented. The results show the applicability and accuracy of the proposed methodology in this field.This work has been done within the framework of the 4ℎproject: Fatigue modelling and fast testing methodologies to optimise part design and to boost lightweight materials deployment inchassis parts. This project has received funding from the EuropeanUnion’s Horizon 2020 research and innovation programme under gran tagreement No. 101006844. The work has been also supported by the Spanish Government program FPU17/04196 and Severo Ochoa programme through the grant CEX2018-000797-S funded by MCIN/AEI/10.13039/501100011033</p
Plasma bile acids in association with Crohn’s disease
No full textBackground: In addition to facilitating lipid digestions, bile acids (BA) are signalling molecules acting on receptors on immune cells and along the gastrointestinal (GI) tract. The aim of this study was to assess if altered bile acid profiles in plasma are associated with Crohn’s disease (CD). Method: This cross-sectional study included individuals (aged ≥18 years) referred for colonoscopy at a tertiary centre in Stockholm between 2016 and 2019. All participants received bowel preparation, completed a lifestyle questionnaire and provided blood samples for analysis. During colonoscopy, severity of disease was graded, and biopsies were taken from colonic mucosa. In the current substudy, 88 individuals with CD and 88 age-matched controls were selected for analysis of BA in plasma with ultra performance liquid chromatography (UPLC). Linear regression models were then used to compare mean bile acid concentrations and concentration ratios between CD and controls. Results: Individuals with CD had lower plasma concentrations of the majority of secondary BA compared to controls, in total CD/CC ratio 0.60 (SE 0.12), p = 0.001. The most prominent observations were lower levels of deoxycolic acid derivates and lithocolic acid derivates among participants with CD. Moreover, plasma concentration for secondary BA among participants with active CD was significantly lower compared to those with CD in remission, CD active/CD remission ratio 0.65 (SE 0.11), p < 0.002. Conclusion: Crohn’s disease may be associated with altered plasma bile acid composition. The significance of colonic bacterial diversity in this context needs to be investigated in further studies. Grant support: This study was supported by grants from the Stockholm County (Grant # FoUI-954090) and Ferring Pharmaceuticals.</p
Consumers’ attachment to meat : Association between sensory properties and preferences for plant-based meat alternatives
No full textFor the sake of both the environment and human health, it is necessary to reduce meat consumption. However, increased consumer adoption of plant-based meat alternatives (PBMAs) will only occur when such products are attractive. PBMAs with meat-like sensory attributes and those that can be cooked similarly to meat are known to be preferred, but the preference for meat-likeness varies depending on the consumer’s attitude towards meat. This study determined the relationship between consumers’ level of meat attachment (MA) on their sensory perceptions of and preference for commercial PBMAs, and their drivers of liking. MA was measured by the Meat Attachment Questionnaire (MAQ); consumers with either low or high MA (LMA and HMA, respectively) were invited to participate in the study (n = 99). The sensory characteristics of seven PBMAs were evaluated using a rate-all-that-apply (RATA) questionnaire, along with an ideal profile and product hedonics. Consumers with LMA had significantly higher overall, aroma, and taste liking, compared with consumers with HMA. Both LMA and HMA consumers similarly discriminated among the sensory properties of PBMAs and the ideal profile. Nevertheless, a further adapted penalty analysis showed subtle differences in consumers’ penalisation of sensory attributes depending on MA level. These findings could be used for future research and the development of PBMAs based on consumers’ MA; they could also be extended for application in a meal context where the PBMAs are consumed. This work was supported by FORMAS, the Swedish government research council for the environment, agricultural sciences, and spatial planning (reference no. 2020-02843).</p
Transplantation of a bioengineered tissue patch promotes uterine repair in the sheep
No full textInnovative bioengineering strategies utilizing extracellular matrix (ECM) based scaffolds derived from decellularized tissue offer new prospects for restoring damaged uterine tissue. Despite successful fertility restoration in small animal models, the translation to larger and more clinically relevant models have not yet been assessed. Thus, our study investigated the feasibility to use a 6 cm2 graft constructed from decellularized sheep uterine tissue, mimicking a future application to repair a uterine defect in women. Some grafts were also recellularized with fetal sheep bone marrow-derived mesenchymal stem cells (SF-MSCs). The animals were followed for six weeks post-surgery during which blood samples were collected to assess the systemic immune cell activation by fluorescence-activated cell sorting (FACS) analysis. Tissue regeneration was assessed by histology, immunohistochemistry, and gene expression analyses. There was a large intra-group variance which prompted us to implement a novel scoring system to comprehensively evaluate the regenerative outcomes. Based on the regenerative score each graft received, we focused our analysis to map potential differences that may have played a role in the success or failure of tissue repair following the transplantation therapy. Notably, three out of 15 grafts exhibited major regeneration that resembled native uterine tissue, and an additional three grafts showed substantial regenerative outcomes. For the better regenerated grafts, it was observed that the systemic T-cell subgroups were significantly different compared with the failing grafts. Hence, our data suggest that the T-cell response play an important role for determining the uterus tissue regeneration outcomes. The remarkable regeneration seen in the best-performing grafts after just six weeks following transplantation provides compelling evidence that decellularized tissue for uterine bioengineering holds great promise for clinically relevant applications. © 2024 The Royal Society of ChemistryThe study was financed by the Knut and Alice Wallenberg Foundation, the Swedish Research Council (VR: 116008), the ALF-agreement (between the Swedish Government and the county council), the Adlerbertska, Wilhelm & Martina Lundgrens research foundations.</p
Simulated and measured piezoelectric energy harvesting of dynamic load in tires
No full textFrom 2007 in US and from 2022 in EU it is mandatory to use TPMS monitoring in new cars. Sensors mounted in tires require a continuous power supply, which currently only is from batteries. Piezoelectric energy harvesting is a promising technology to harvest energy from tire movement and deformation to prolong usage of batteries and even avoid them inside tires. This study presents a simpler method to simultaneous model the tire deformation and piezoelectric harvester performance by using a new simulation approach - dynamic bending zone. For this, angular and initial velocities were used for rolling motion, while angled polarization was introduced in the model for the piezoelectric material to generate correct voltage from tire deformation. We combined this numerical simulation in COMSOL Multiphysics with real-life measurements of electrical output of a piezoelectric energy harvester that was mounted onto a tire. This modelling approach allowed for 10 times decrease in simulation time as well as simpler investigation of systems parameters influencing the output power. By using experimental data, the simulation could be fine-tuned for material properties and for easier extrapolation of tire deformation with output harvested energy from simulations done at low velocity to the high velocity experimental data.This work has received funding from ECSEL JU-2020-1-IA grant ‘Energy ECS - Smart and secure energy solutions for future mobility’ (grant agreement No 101007247).</p
Iron-Catalyzed Laser-Induced Graphitization – Multiscale Analysis of the Structural Evolution and Underlying Mechanism
No full textThe transition to sustainable materials and eco-efficient processes in commercial electronics is a driving force in developing green electronics. Iron-catalyzed laser-induced graphitization (IC-LIG) has been demonstrated as a promising approach for rendering biomaterials electrically conductive. To optimize the IC-LIG process and fully exploit its potential for future green electronics, it is crucial to gain deeper insights into its catalyzation mechanism and structural evolution. However, this is challenging due to the rapid nature of the laser-induced graphitization process. Therefore, multiscale preparation techniques, including ultramicrotomy of the cross-sectional transition zone from precursor to fully graphitized IC-LIG electrode, are employed to virtually freeze the IC-LIG process in time. Complementary characterization is performed to generate a 3D model that integrates nanoscale findings within a mesoscopic framework. This enabled tracing the growth and migration behavior of catalytic iron nanoparticles and their role during the catalytic laser-graphitization process. A three-layered arrangement of the IC-LIG electrode is identified including a highly graphitized top layer with an interplanar spacing of 0.343 nm. The middle layer contained γ-iron nanoparticles encapsulated in graphitic shells. A comparison with catalyst-free laser graphitization approaches highlights the unique opportunities that IC-LIG offers and discuss potential applications in energy storage devices, catalysts, sensors, and beyond.The authors gratefully acknowledge that the project has been partlyfunded by the SNF project “Laser-mediated wood surface engineering”(200021_219319/1). The authors gratefully acknowledge ScopeM for theirsupport and assistance in this work. J.E. acknowledges funding from Vinnova for the Digital Cellulose Center</p
Enhanced Oxygen-Reaction Electrocatalysis and Corrosion Resistance of CoCrFeNi Thin Films by Tuned Microstructure and Surface Oxidation
No full textOxygen electrocatalysts play a key role in renewable and fossil-free energy production. Bifunctional catalysts active for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) allow use of the same material system for both energy production (ORR) and fuel generation (OER). However, optimizing the performance of bifunctional catalysts requires in depth understanding of the catalyst structure, its surface chemistry in terms of active sites and the underlying catalytic mechanism. Here, the catalytic performance of CoCrFeNi thin films is investigated, synthesized using high-power impulse magnetron sputtering, as bifunctional oxygen electrocatalysts. The film crystal structure and morphology, and thereby the catalytic performance, can be tuned by the ion acceleration (bias) to the substrate. To further enhance the catalytic activity, anodization is used to electrochemically modify the films, forming a thicker oxide layer enriched in Co and Ni cations which significantly improves the ORR performance. Anodization improves the catalyst stability during OER, with an OER potential of 1.45 V versus the reversible hydrogen electrode (RHE) at 10 mA cm−2 for more than 24 h. While the corrosion resistance is high both before and after anodization, in terms of catalytic activity the anodized films outperformed the as-deposited ones. This makes anodized films excellent electrocatalyst candidates in corrosive alkaline environments such as fuel cells and electrolyzers. This study was performed within the Competence Centre FunMat-II and was funded by the Swedish Agency for Innovation Systems (VINNOVA, grant nos. 2022-03071 2016–05156, and 2019–04881). The authors also acknowledge the Swedish Energy Agency for funding (grant nos. 2020-024828 and 52740-1) and the Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No. 2009 00971).</p
Barrier coatings on dry-formed pulp with lignin, stearic acid, and combinations thereof
No full textBarrier coatings on dry formed pulp were studied in this article, which were derived from Kraft lignin, stearic acid, and combinations thereof. Coating layers were applied by spray-coating with a solution of lignin or stearoyl chloride and subsequent heat treatment. Alternatively, lignin was esterified with stearoyl chloride on beforehand or combinations of lignin and stearoyl chloride on the air-laid mat were done. Since the treatments were applied prior to thermopressing, the coating agents permeated the top layers of each substrate. As our results show, coatings with lignin could improve the tensile strength and stiffness of the substrate. Grafting with stearic acid, on the other hand, affected the tensile properties negatively, which was argued to arise from worse binding of the cellulose fibers and degradation due to the presence of acid moieties. All treatments improved the barrier properties, as noted by a reduction in air permeation and water-vapor transmission rate (WVTR). The effect of spray coated lignin on WVTR was best, albeit showing less effect on the water absorption as measured by COBB1800. Stearic acid grafting yielded the opposite trend, i.e., reducing water absorption to a greater extent, while affecting WVTR less. Combinations of stearoyl chloride and lignin showed synergies and additive effects to some extent. In conclusion, various treatments for dry formed fibers were implemented and tested, which may promote the development of new barrier solutions for cellulose-based materials.
Invariant Feature Selection for Battery State of Health Estimation in Heterogeneous Hybrid Electric Bus Fleets
No full textBatteries are a safety-critical and the most expensive component for electric buses (EBs). Monitoring their condition, or the state of health (SoH), is crucial for ensuring the reliability of EB operation. However, EBs come in many models and variants, including different mechanical configurations, and deploy to operate under various conditions. Developing new degradation models for each combination of settings and faults quickly becomes challenging due to the unavailability of data for novel conditions and the low evidence for less popular vehicle populations. Therefore, building machine learning models that can generalize to new and unseen settings becomes a vital challenge for practical deployment. This study aims to develop and evaluate feature selection methods for robust machine learning models that allow estimating the SoH of batteries across various settings of EB configuration and usage. Building on our previous work, we propose two approaches, a genetic algorithm for domain invariant features (GADIF) and causal discovery for selecting invariant features (CDIF). Both aim to select features that are invariant across multiple domains. While GADIF utilizes a specific fitness function encompassing both task performance and domain shift, the CDIF identifies pairwise causal relations between features and selects the common causes of the target variable across domains. Experimental results confirm that selecting only invariant features leads to a better generalization of machine learning models to unseen domains. The contribution of this work comprises the two novel invariant feature selection methods, their evaluation on real-world EBs data, and a comparison against state-of-the-art invariant feature selection methods. Moreover, we analyze how the selected features vary under different settings. The work was carried out with support from the Knowledge Foundation and Vinnova (Sweden’s innovation agency) through the Vehicle Strategic Research and Innovation Programme FFI. </p
Mechanical performance of pe reinforced with graphene nanoplatelets (GNPs) : Effect of composition and processing parameters
No full textProcessing parameters of melt mixing (one of the most conventional techniques in polymer processing) play a significant role in the quality and properties of the resulting material, especially when nanoreinforcements are involved. The current study investigates varying processing temperature, rotation speed and elements of the screw extruder, aiming to enhance mechanical properties of polyethylene (PE) nanocomposites by improving dispersion of nanoparticles from a commercial masterbatch in two grades of PE. The study investigates the effect of a common compatibilizer (MAPE) and shearing forces at varying amounts of graphene nanoplatelets (GNPs) in polyethylene. A comparison is made on mechanical properties, morphology, and changes in the microstructure. Results show that increasing amounts of GNPs lead to expected continuous increase of mechanical properties with reference to the base polymer. Addition of MAPE did not result in significant improvement in the performance of the studied systems. Use of stronger shear forces resulted in mostly negative impact on the properties. The work is performed under joint financial support of the project Smart-WPC funded by the Interreg-Nord framework and region Norrbotten, the project Nano2Day funded by the European Union in the Horizon 2020 programme, and the excellence and innovation area of Smart Machine and Materials (SMM) at LTU. The authors would like to thank students at Luleå University of Technology, Vanessa Meulenberg and Lena Brunnacker (within the course T7009T) for help in performing experiments. Support of engineers Runar Långström and Robert Westerlund at RISE with the manufacturing of the nanocomposites is also highly appreciated.</p