Maximilian Volk


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Volk

First Name

Maximilian

ORCID

0000-0002-9163-728X

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Publications 1 - 8 of 8
  • Permeability and compaction behaviour of air-texturised glass fibre rovings: A characterisation study
    Item type: Journal Article
    Sandberg, Michael; Kabachi, Ayyoub; Volk, Maximilian; et al. (2020)
    Journal of Composite Materials
    Air-texturisation is a process that adds bulkiness to bundles of fibres. In this study, the permeability and compaction behaviour of air-texturised glass fibre rovings are experimentally characterised and compared to conventional unidirectional rovings. Based on radial impregnation experiments and single-step compaction/decompaction tests, the following main findings are highlighted: Compared to conventional unidirectional-rovings, the normalised permeability of the air-texturised rovings was approximately three times higher along the fibre direction and 40 times higher transverse to the fibre direction. Accordingly, the degree of anisotropy was approximately one magnitude lower. At a compaction pressure of 1 and 5 bar, the air-texturised rovings were compacted to a volume fraction of Vf=0.34 and 0.43, respectively, which was approximately 30% lower than the volume fraction achieved for the conventional unidirectional-rovings. Finally, it was observed that the decompaction of air-texturised rovings exhibits a more distinct elastic response when unloaded.
  • Suitability assessments for advanced composite-metal hybrid material systems in automotive crash structural applications
    Item type: Journal Article
    Dlugosch, Michael; Volk, Maximilian; Lukaszewicz, Dirk; et al. (2017)
    International Journal of Automotive Composites
  • Thermoplastic Composite Materials for High voltage Insulator Applications
    Item type: Conference Paper
    Volk, Maximilian; Wong, Joanna; Arreguin, Shelly; et al. (2018)
    18th European Conference on Composite Materials (ECCM-18)
  • Pultrusion of hybrid bicomponent fibers for 3D printing of continuous fiber reinforced thermoplastics
    Item type: Journal Article
    Aegerter, Nicole; Volk, Maximilian; Maio, Chiara; et al. (2021)
    Advanced Industrial and Engineering Polymer Research
    Continuous lattice fabrication is a newly introduced method for additive manufacturing of fiber-reinforced thermoplastic composites that allows to deposit material where it is needed. The success of this technology lies in a printing head in which unconsolidated continuous fiber-reinforced composite is pulled through a pultrusion die before the material is extruded and deposited out of plane without the use of supporting structures. However, state-of-the-art composite feedstock like commingled yarns shows limits in achievable material quality and part dimensions due to the underlying fiber architecture where thermoplastic fibers are mingled with reinforcement filaments. Hybrid bicomponent fibers overcome these constraints because each individual reinforcement filament is clad in a thermoplastic sheath. This results in absence of time-consuming fiber impregnation steps that would negatively effect void content and material quality. This study compares the material quality of pultrudates made from hybrid bicomponent fibers to that of commercially available commingled yarns at various processing conditions. Experiments are reported in which polycarbonate composite profiles with a diameter of 5 mm containing 50 vol% to 60 vol% E-glass fibers are pultruded at different die filling degrees, mold temperatures and pultrusion speeds. The results show that the pultrudates obtained from hybrid bicomponent fibers have lower void content than those manufactured under the same conditions from commingled yarns. We assess this to be caused by the difference in consolidation mechanism which in the case of the hybrid bicomponent fibers is dominated by coalescing of the thermoplastic sheaths compared to the Darcian flow-dominated consolidation of commingled yarns.
  • Pultrusion of large thermoplastic composite profiles up to Ø 40 mm from glass-fibre/PET commingled yarns
    Item type: Journal Article
    Volk, Maximilian; Wong, Joanna; Arreguin, Shelly; et al. (2021)
    Composites Part B: Engineering
    Pultrusion is a rapid and cost-effective manufacturing technology for continuous fibre reinforced thermoplastic composite profiles. As the cross-sections of pultruded profiles grow to meet increasing performance requirements, manufacturing challenges concerning heat transfer are encountered. In this study, a two-dimensional finite element model was used to simulate the heat transfer and fluid flow physics of the pultrusion process for increasing diameters from Ø 5–Ø 40 mm. To facilitate the experimental validation, a novel batch-wise pultrusion concept is introduced in which the impregnation process is observed in-situ using a transparent die. The pultrusion studies, conducted on glass-fibre/amorphous polyethylene terephthalate (GF/PET) commingled yarns, show that – with proper design – pultrusion is able to deliver consistent, high quality (void content < 2%) profiles up to at least Ø 40 mm.
  • Pultrusion of thermoplastic composite profiles for high voltage insulators
    Item type: Doctoral Thesis
    Volk, Maximilian (2021)
    Pultrusion is a rapid and cost-effective manufacturing technology for continuous fibre reinforced polymer composite profiles. One of the main applications of pultruded profiles are large cross-section solid rods made from glass fibres and low viscosity thermosetting polymers used for high voltage composite insulators. %With increasing energy demands worldwide, higher voltages will require longer and larger diameter insulator profiles than those currently available. However, manufacturing increasingly large composite profiles to satisfy the requirements for higher transmission voltages is difficult due to the exothermic curing behaviour of thermosets. %When not carefully controlled, the temperature gradients during curing result in stresses that can lead to the formation of cracks on the surface of the profile, delamination and warpage, or thermal degradation. In contrast, thermoplastic composites offer reaction and solvent-free processing, while possessing a virtually infinite shelf life as well as being reshapable, weldeable and recyclable. This thesis therefore aims to substitute the thermoset matrix by a thermoplastic material in a collaborative research project between Pfisterer Switzerland AG and CMASLab of ETH Zürich. To achieve this goal, a thermoplastic pultrusion process must be developed capable of manufacturing large cross-section thermoplastic rods that fulfil the requirements for high voltage insulator core applications. The suitability assessment of Ø 10 mm composite rods pultruded from commingled yarns consisting of glass fibres and different thermoplastic polymers shows that PET constitutes the most promising material for insulator core applications, passing all test standards according to IEC 62217 and IEC TR 62039. To successfully scale the manufacturing process to larger diameters, a two dimensional finite element model is used to simulate the heat transfer and fluid flow physics of the pultrusion process for increasing diameters from Ø 5 - Ø 40 mm. To facilitate the experimental validation, a novel batch-wise pultrusion concept is introduced in which the impregnation process is observed in-situ using a transparent die. The investigation of pulling forces that were incorporated in a regression model showed a quadratic response for increasing diameter and decreasing temperature as well as a linear dependency of the pultrusion speed. The void content investigation showed that with proper process design, thermoplastic pultrusion is able to deliver consistent, high quality (void content < 2 %) profiles up to at least Ø 40 mm. A multistage pultrusion concept consisting of multiple dies consecutively adding material around an initially pultruded rod allowed to manufacture single- and multi material profiles with low void content and good interface between both stages. The model-based optimisation predicted a speed improvement of up to 21% for a two stage set-up compared to a single stage approach. Ø 18.57 and Ø 40 mm insulator prototypes were manufactured in collaboration with Pfisterer Switzerland AG using semi-crystalline PET, that exhibited the best adhesion to the silicone housing. The Ø 18.57 mm prototypes passed the tensile tests but failed the dye penetration test due to hollow channels in the delivered glass fibres, highlighting the need of a reliable supply chain. In spite of the high porosity of the glass-fibre, insulators using ECR (E-Glass Corrosion Resistant) glass fibres with semi-crystalline PET and pultruded above 250 °C consistently passed the final voltage test, successfully demonstrating that pultruded composite rods are a suitable material for high voltage insulator cores. Their performance can be further improved through the use of seed-less glass fibre as well the optimisation of the interface between silicone rubber housing and composite through a suitable primer or injection moulding procedure. Although this work is aimed at high voltage insulators, the developed manufacturing technology in this thesis will provide the benefits of thermoplastic materials to other sectors such as wind energy and civil engineering, where large cross-section
  • Cost-efficient, automated, and sustainable composite profile manufacture: A review of the state of the art, innovations, and future of pultrusion technologies
    Item type: Journal Article
    Volk, Maximilian; Yuksel, Onur; Baran, Ismet; et al. (2022)
    Composites Part B: Engineering
    Over the last 70 years, pultrusion has matured into an industry-leading process when it comes to providing high throughput and automated composite manufacture at a competitive price point. In this paper, we review recent innovations that have advanced pultrusion to a versatile manufacturing technology and thereby allowed composite materials to penetrate markets in, e.g., the automotive, construction, aerospace, and wind turbine industries. We accompany our review with discussions on how pultrusion has enabled new innovations within additive manufacturing and sustainable composite manufacturing, and finally, we provide an outlook and suggestions for where we see the potential for research and new industrial applications of pultrusion technology.
  • Pultruded thermoplastic composites for high voltage insulator applications
    Item type: Journal Article
    Volk, Maximilian; Arreguin, Shelly; Ermanni, Paolo; et al. (2020)
    IEEE Transactions on Dielectrics and Electrical Insulation
    Composite rods pultruded from commingled yarns consisting of glass fibres and polypropylene, polyamide 12, polycarbonate, polyethylenterephthalate and polyetherimide are assessed for porosity, hydrothermal aging and thermal breakdown behaviour according to IEC 62217 and IEC TR 62039 standards. The results indicate that the quality of the glass fibres, the fibre-matrix interface and the thermomechanical properties of the polymer affect the electrical performance of the composite. Of the materials examined, the glass fibre-polyethylenterephthalate pultruded rods were the most promising in terms of overall performance by successfully passing all tests, however these results also vary with material supplier.
Publications 1 - 8 of 8