Lourens Blok - Academia.edu (original) (raw)

Papers by Lourens Blok

Journal of Reinforced Plastics and Composites

In this study, the dispersion of reclaimed carbon fibres following cost-effective surface treatme... more In this study, the dispersion of reclaimed carbon fibres following cost-effective surface treatment is explored with a hydrodynamic fibre moving model, and a practical fibre dispersion effect is investigated through various physical dispersion methods. To utilise reclaimed carbon fibres for a desired composite product, our proposed low-cost surface treatment is shown to be beneficial to the physical and chemical properties of the reclaimed carbon fibres and to yield polar-hydrophilic characteristics. Single fibre tensile testing is performed to explore the effect of surface treatment on the reclaimed carbon fibres (a higher tensile strength was observed). A computational hydrodynamic fibre moving model based on a moving particle semi-implicit method is newly designed to perform hydrodynamic simulation to determine aqueous dispersion of discontinuous reclaimed carbon fibres. This simulation helps understanding fibre flocculation phenomena from the perspective of fibre stiffness, whic...

International Journal of Automotive Composites, 2017

In this work, the application of fibre reinforced plastic (FRP) sandwich structures, with a parti... more In this work, the application of fibre reinforced plastic (FRP) sandwich structures, with a particular focus on aramid fibre tufted sandwiches is being studied for automotive crashworthiness during edgewise impact using impact testing and numerical simulation. This work uses prior coupon data for scaling into a subsystem of a vehicle floor. A novel manufacturing process where Kevlar tufting is inserted through the dry preforms and the core is introduced. Subsystem testing then demonstrates the scalability of the sandwich system into a floor assembly. The specimen exhibits crushing with significant energy absorption. Numerical modelling is then used to validate the test result and demonstrate the simulation capability. Using commercial finite element software (Abaqus) with composite crushing add-in (CZone), the crushing of the sandwich and facesheets can be simulated with good agreement with the test results.

Fused filament fabrication (FFF) is a 3D printing technique which allows layer-bylayer build-up o... more Fused filament fabrication (FFF) is a 3D printing technique which allows layer-bylayer build-up of a part by the deposition of thermoplastic material through a nozzle. The technique allows for complex shapes to be made with a degree of design freedom unachievable with traditional manufacturing methods. However, the mechanical properties of the thermoplastic materials used are low compared to common engineering materials. In this work, improved 3D printing feedstocks for FFF, with carbon fibres embedded in a thermoplastic matrix to reinforce the material, are investigated. The stateof-the-art in composite 3D printing is reviewed and the capabilities of two different commercially available composite printing methods are assessed by print trials, optical microscopy and mechanical characterization of the printed materials. It is found that printing of continuous carbon fibres using the MarkOne gives significant increases in performance over unreinforced thermoplastics, with mechanical p...

In this work the application of fibre reinforced plastic (FRP) sandwich structures, with particul... more In this work the application of fibre reinforced plastic (FRP) sandwich structures, with particular focus on aramid fibre tufted sandwiches is being studied for automotive crashworthiness applications using impact testing and numerical simulation.

Materials, 2020

In this work, aligned discontinuous fibre composite (ADFRC) tapes were developed and investigated... more In this work, aligned discontinuous fibre composite (ADFRC) tapes were developed and investigated as precursors for a novel 3D printing filament. ADFRCs have the potential to achieve mechanical performance comparable to continuous fibre reinforced composites, given sufficient fibre length and high level of alignment, and avoid many of the manufacturing difficulties associated with continuous fibres, e.g., wrinkling, bridging and corner radii constraints. Their potential use for fused filament fabrication (FFF) techniques was investigated here. An extensive down-selection process of thermoplastic matrices was performed, as matrix properties significantly impact both the processing and performance of the filament. This resulted in four candidate polymers (ABS, PLA, Nylon, PETG) which were used to manufacture ADFRC tapes with a Vf of 12.5% using the high performance discontinuous fibre (HiPerDiF) technology and an in-house developed continuous consolidation module. Tensile stiffness an...

Journal of Composites Science, 2021

Fused deposition modelling (FDM) is a widely used additive layer manufacturing process that depos... more Fused deposition modelling (FDM) is a widely used additive layer manufacturing process that deposits thermoplastic material layer-by-layer to produce complex geometries within a short time. Increasingly, fibres are being used to reinforce thermoplastic filaments to improve mechanical performance. This paper reviews the available literature on fibre reinforced FDM to investigate how the mechanical, physical, and thermal properties of 3D-printed fibre reinforced thermoplastic composite materials are affected by printing parameters (e.g., printing speed, temperature, building principle, etc.) and constitutive materials properties, i.e., polymeric matrices, reinforcements, and additional materials. In particular, the reinforcement fibres are categorized in this review considering the different available types (e.g., carbon, glass, aramid, and natural), and obtainable architectures divided accordingly to the fibre length (nano, short, and continuous). The review attempts to distil the op...

Journal of Composites Science, 2020

The composites industry generates considerable volumes of waste in a wide variety of forms, from ... more The composites industry generates considerable volumes of waste in a wide variety of forms, from the production of by-products to end-of-life parts. This paper focuses on the remanufacturing of dry fibre off-cuts, produced during the composite fabric weaving process, into highly aligned discontinuous fibre prepreg tapes with High Performance Discontinuous Fibre (HiPerDiF) technology. Unidirectional laminate specimens are prepared using various combinations of fibre lengths and tested in tension, obtaining a stiffness of 80 GPa, a strength of 800 MPa, and a failure strain of 1%. Several applications are envisaged for the produced tape: adhesive film, feedstock for filament winding, and tow for weaved fabrics. This work demonstrates the possibility to extract value from what is currently considered manufacturing waste.

Additive Manufacturing, 2018

Fused filament fabrication (FFF) is a 3D printing technique which allows layer-by-layer build-up ... more Fused filament fabrication (FFF) is a 3D printing technique which allows layer-by-layer build-up of a part by the deposition of thermoplastic material through a nozzle. The technique allows for complex shapes to be made with a degree of design freedom unachievable with traditional manufacturing methods. However, the mechanical properties of the thermoplastic materials used are low compared to common engineering materials. In this work, composite 3D printing feedstocks for FFF are investigated, wherein carbon fibres are embedded into a thermoplastic matrix to increase strength and stiffness. First, the key processing parameters for FFF are reviewed, showing how fibres alter the printing dynamics by changing the viscosity and the thermal profile of the printed material. The state-of-the-art in composite 3D printing is presented, showing a distinction between short fibre feedstocks versus continuous fibre feedstocks. An experimental study was performed to benchmark these two methods. It is found that printing of continuous carbon fibres using the MarkOne printer gives significant increases in performance over unreinforced thermoplastics, with mechanical properties in the same order of magnitude of typical unidirectional epoxy matrix composites. The method, however, is limited in design freedom as the brittle continuous carbon fibres cannot be deposited freely through small steering radii and sharp angles. Filaments with embedded short carbon microfibres (∼100 μm) show better print capabilities and are suitable for use with standard printing methods, but only offer a slight increase in mechanical properties over the pure thermoplastic properties. It is hypothesized that increasing the fibre length in short fibre filament is expected to lead to increased mechanical properties, potentially approaching those of continuous fibre composites, whilst keeping the high degree of design freedom of the FFF process.

Composite Structures, 2017

Fibre reinforced plastic (FRP) composite materials can provide superior specific energy absorptio... more Fibre reinforced plastic (FRP) composite materials can provide superior specific energy absorption performance over conventional metallic structures if crush stability can be maintained during the impact event. The core in sandwich structures helps to stabilise the crush front by preventing global buckling, but delamination remains a barrier to optimal crushing performance. In this work, the in-plane crushing response of sandwich structures was improved by adding through-thickness reinforcement in the form of aramid fibre tufts. The effect of tufting different sandwich cores and facesheet orientations was investigated in both static and dynamic crushing modes. A drop-tower test rig was used to crush panels in realistic automotive crash conditions and a high-speed camera captured the crushing mechanisms. The through-thickness reinforcement improved the facesheet to core adhesion, resulting in a more localised and stable fracture of the facesheets. Tufting improved the specific energy absorption (SEA) from 11.5 kJ/ kg to 20.5 kJ/kg and the crush force efficiency (CFE) from 0.22 to 0.55.

Fiber Reinforced Composites, 2021