In response to global initiatives aimed at reducing greenhouse gas emissions and enhancing materials' recyclability, this review highlights the latest developments in the transition from traditional thermoset composites to more sustainable liquid thermoplastic alternatives. Elium® resin, a liquid thermoplastic resin at room temperature, offers enhanced recyclability while retaining the processability advantages of conventional thermosetting resins. Details on the resin's formulation based on Methyl Methacrylate (MMA) monomers and acrylic co-polymers are provided. A categorisation of the latest available grades by viscosity, reactivity, processing parameters, thermal and mechanical performances is stated. Processability information is provided based on the resin grade. Comparative analyses are presented, showing that Elium®-based fibre reinforced composites exhibit similar properties to conventional epoxy counterparts, offering comparable tensile, flexural and impact performances among others. Latest developments on the self-healing and self-repairing state-of-the-art of Elium®-based composites are discussed in depth. Resin's compatibility with carbon-based nanoparticles is critically analysed, pointing out the current advancements and challenges. The effects of nanofillers on the functionalisation, i.e. sensors, fire-retardancy, and electromagnetic shielding, are presented. Practical applications in the automotive, wind energy, and marine sectors are explored, proving the material's versatility and displaying substantial reductions in weight, energy consumption, and CO2 emissions. This study provides a future outlook and addresses potential challenges related to the introduction of nanoparticles to functionalise Elium®-based composites. Nano-reinforced Elium®-based composites are believed to be a valid alternative to address the current needs of the global industries, paving the way for future advancements in sustainable advanced composite materials.

In recent years, liquid acrylic resins such as Elium (R) have captured widespread interest due to their process-ability, reshaping capabilities and recyclability. For the first time, this work explores the effects of introducing graphene nanoplatelets (GnP) to Elium (R) 188 O resin on curing and processing behaviour. Key parameters affecting polymerisation are identified as temperature, initiator content, graphene type and concentration. Casting trials revealed that the curing behaviour of GnP reinforced Elium (R) differs from that of its pure counterpart. There is a clear relationship between the GnP and initiator concentration. It has been observed that increasing the GnP content requires significantly more initiator to cure Elium (R); however, a balance has to be maintained to avoid exothermic reaction. The polymerisation kinetics of the Elium (R) resin are obtained by performing dynamic and isothermal differential scanning calorimetry (DSC) scans at 60 degrees C, 80 degrees C and 100 degrees C. The measured experimental data are fitted to the Kamal-Sourour kinetic model, accounting for both temperature and the degree of polymerisation (DoP) for both pure and GnP-reinforced Elium (R). Slower reaction rates and changes in activation energy are observed due to the GnP presence. Curing cycles are developed to predict the polymerisation of pure and GnP-reinforced Elium (R). For example, the temperature-aided curing cycle (i.e. 80 degrees C for 110 min) is required to achieve 95 % DoP for 0.5 wt% GnP reinforced Elium (R). The outcome of this research subsequently enabled the manufacturing of GnP reinforced Elium (R) laminates via the infusion process.

The paper compares the performance of two bio-ester and two mineral-oil emulsion metalworking fluids (MWFs) in finish turning an Inconel 718 alloy bar with a high hardness (HB 397 – 418). In this study, a coolant with a lean concentrate diluted at 6.5% to create an emulsion with stabilised water hardness was used to prepare each MWF. The finish-turning method used a small tool nose radius (0.4 mm) and small depth of cut (0.25 mm) to turn down 52.2 mm diameter bars in multiple passes to reach a maximum tool flank wear of 200 µm. In each MWF turning test, the tool flank wear, cutting forces, and surface roughness were measured against cut time. Chips from each MWF turning test were also collected at the same cut time instances. The surface and subsurface integrity on a workpiece obtained from each MWF turning test were compared by using a new unworn tool. Overall, for the machining parameters studied, the findings suggest the bio-esters were capable of equivalent machining performance as the mineral-oil emulsions, apart from one bio-ester that displayed improved surface roughness. Common to all MWF turning tests was a change in the chip form at low flank wear, which is discussed. Further findings discussed include the sensitivity of the concentration of the MWF diluted in the emulsion and the effect of the workpiece hardness within the batch used, with useful recommendations to improve the finish-turning method for the assessment of MWFs.

This paper presents the parameter identification procedure of carbon nanotubes (CNTs) reinforced interphase in fuzzy fibre reinforced polymer (FFRP). The procedure was completed with ANSYS Workbench 19.2 software by combining Mechanical ADPL and Goal-Driven Optimisation. Firstly, a three-phase representative volume element (RVE) containing carbon fibre, CNTs reinforced interphase and epoxy resin was developed as a collection of Mechanical APDL commands. This RVE model was simulated to evaluate the elastic constants of FFRP lamina. CNTs reinforced interphase was characterised by transversely isotropic model. Interphase properties were parametrised and became input parameters in the Goal-Driven Optimisation. FFRP lamina elastic constants were set as the output parameters. Multi-objective Genetic Algorithm (MOGA) was used to identify the interphase properties, so that the output FFRP lamina elastic constants match the objective and constraints. The optimisation algorithm converged after 585 evaluations. Five potential candidate point, which met required objectives and constraints, were found. The identified interphase properties agreed well with the literature (an average percentage error of around 2%). This inverse procedure shows the potential to identify the interphase properties in nano-engineered composites, which are extremely difficult to measure experimentally.

In this work, the behavior of carbon fiber reinforced polymer composites (CFRPs) interleaved with electrospun veils under low velocity impact (LVI) conditions and extreme environmental temperatures was investigated. 2/2 twill carbon fiber/epoxy laminates were subjected to LVI at three energy levels (10, 20, and 30 J), and three temperatures (-50 degrees C, room temperature, and 100 degrees C). Two interleaved configurations were explored (six veils placed symmetrically with respect to the middle plane of the laminate and with respect to the external layers of the laminate). Particularly at room temperature and up to 20 J, nanofibrous interlayers effectively reduced localized deformation (by about 13.0%) and delamination (by about 12.2%) when positioned in the outer ply interleaved configuration compared to the reference laminate. At 100 degrees C, this effect is maintained at 10 J, preventing an increase in the delaminated area. At -50 degrees C and 10 J, the promotion of delamination prevented back surface fiber failure. Regarding post-impact flexural properties, the presence of nanoveils ensured superior mechanical properties compared to the corresponding reference laminate impacted at the same conditions, demonstrating their efficacy in enhancing the damage tolerance of the overall laminate. Highlights Electrospun veils were interleaved in 20 layers of 2/2 twill carbon/epoxy laminate. Three configurations were tested under LVI at 10 J, 20 J, 30 J, and -50 degrees C, RT, and 100 degrees C. Observed damage modes include delamination, indentation, and back surface fiber cracks. Veils symmetrically placed in external layers limit delamination at 20 J (RT) and 10 J (100 degrees C). Electrospun veils enhanced CFRP bending and residual post-impact properties at RT and 100 degrees C. Schematic view of the study. image

Greener materials, particularly in sandwich panels, are in increasing demand in the transportation and building sectors to reduce environmental impacts. This shift is driven by strict environmental legislation and the need to reduce material costs and fuel consumption, necessitating the utilisation of more sustainable components in the transportation and construction sectors, with improved load-bearing capabilities and diminished ecological footprints. Therefore, this study aims to analyse and evaluate the structural performance of polyethylene terephthalate (PET) core and flax or basalt/flax FRP sandwich panels as an alternative to conventional synthetic materials. The novel eco-friendly sandwich panels were manufactured using the co-curing technique. Four-point bending, edgewise compression and core shear tests were performed and insights into how the skin properties affect the strength, stiffness and failure mode of specimens were provided. The stress-strain behaviour, facing modulus and strength, flexural rigidity, core shear strength and failure modes were evaluated. The flexural facing modulus of the flax and flax/basalt sandwich skins were found to be 5.1 GPa and 9.8 GPa, respectively. The flexural rigidity of the eco-friendly sandwich panel was compared with published results and demonstrated a promising structural performance. The environmental benefits and challenges were outlined and critically evaluated focusing on transportation and construction applications.

During the COVID-19 pandemic, there was a shortage of personal protective equipment, PPE, which resulted in non-certified PPE being used by healthcare staffs. These would not provide the appropriate protection against the SARS-CoV-2 virus. Together with the local NHS Trust (University Hospitals of Derby and Burton (UHDB) NHS Foundation Trust) and a local small and medium enterprise (SME), Riverside Medical Packaging Ltd, the University of Derby (UoD) developed test protocols for PPE with a one-size-fits-all concept. Building on best practice in reviewing the literature and current design requirements, key design parameters were identified such as a minimum strap width and comfort level for healthcare related Face Shield. Two strap headbands made from fabric and elastomer with linear stiffness of 44.1 ± 0.3 N/m and 149.1 ± 3.1 N/m respectively were tested with respect to fit and comfort on small and large arc-shaped models. There was an exponential change in pressure from the side to the middle of the strap headbands. The high stiffness of the elastomer in a radial set-up influenced the pressure exerted on a wearer’s head when the elastomer strap was used. Meanwhile the coefficient of friction between the fabric strap and arc-shaped model influenced the pressure exerted when a fabric strap was used. The ergonomics of the designed Face Shields supported the one-size-fits-all concept, whereby various gender and head circumferences were considered. The findings in this paper will promote new standards in the design of PPE with a one-size-fits-all target.

Laser-powder bed fusion LPBF techniques can be used to manufacture complex-shaped, thin-walled, hollow, or slender parts. Although the dimensions of the generated components are close to the final measurements, additional machining processes are required to obtain the desired surface finish and dimensional tolerance. The melt pool dynamic during the LPBF operation results in directional gain structures in alloys. The resulting mechanical properties are strongly dependent on the component build orientation, which can affect the machinability of the produced part. This review paper provides knowledge on the role of microstructure in the machinability of LPBF-produced IN718. The effect of grain shape and distribution, grain boundary density on the surface integrity, and resulting cutting forces are investigated.

This paper discusses the microstructure effects on the machinability of Inconel 718 by conducting machining tests on an additively manufactured (AM) workpiece with a strongly textured grain structure and a wrought workpiece incorporating a finer and more equiaxed grain structure. The AM workpiece was produced as a thin tube using Laser Melting Powder Bed Fusion and optimal processing conditions for this alloy. A lathe was used to conduct instrumented orthogonal machining tests on the two workpiece materials under dry cut and coolant conditions using a semisynthetic emulsion coolant. The process parameters studied were feed from 0.05 to 0.15 mm/rev and cutting speed from 60 to 120 m/min with a cut time of 2 sec duration for each process condition. Measures for each process condition included cutting forces in the feed and main cut direction, and images of chip forms were obtained. The grain structures of the workpiece materials were characterized using Electron Back Scattered Diffraction (EBSD). New findings suggest that grain structures can significantly affect the machinability of the superalloy at a higher feed for all cutting speeds studied, and insights into the cause are discussed. Other important findings comment on the effectiveness of the coolant as a lubricant for reducing friction in machining.

Polyamide 11 (PA11) is a plant-based nylon made from castor beans. Powder bed fusion laser sintering (PBF-LS) is an additive manufacturing process used for PA11 which allows for the reuse of the unsintered powder. The unsintered powder is mixed with virgin powders at different refresh rates, a process which has been studied extensively for most semi-crystalline polyamides. However, there is lack of information on the effect of using 100% reused PA11 powder and the effect of the number of times it is reused on its own, during powder bed fusion laser sintering. This paper investigates the effect of reusing PA11 powder in PBF-LS and the effect of the number of times it is reused on the dimensional accuracy, density and thermal and tensile properties. From the 100% virgin powder to the third reuse of the powder, there is a decrease in powder wastage, crystallinity and tensile strength. These are associated with the polymerisation and cross-linking process of polymer chains, upon exposure to high temperatures. This results in a higher molecular weight and, hence, a higher density. From the fourth reuse to the tenth reuse, the opposite is observed, which is associated with an increase in high-viscosity unmolten particles, resulting in defects in the PBF-LS parts.

This paper discusses a method of finish turning Inconel 718 alloy to compare machining performance of a naturally aged and used metalworking fluid (MWF), which had been conventionally managed through its life cycle, with the same new unaged product. The MWF concentrate was a new-to-market bio-ester oil, diluted with water to produce an emulsion. In the experiments, 50 mm diameter bars were turned down with multiple passes at a 250 μm depth of cut to reach a tool flank wear of 200 μm. The machining was interrupted at several stages to measure the flank wear and compare the chip forms for the aged and unaged MWF. The method of finish turning used a small tool nose radius and a small depth of cut that was found to be sensitive in detecting a difference in the flank wear and chip forms for the aged and unaged MWF. On the chemistry, the findings suggest that higher total hardness of the aged MWF was the cause of reduced lubricity and accelerated flank wear. This paper discusses the state of the art with the insights that underpin the finish turning method for the machinability assessment of MWFs. The findings point to stabilization of the MWF chemistry to maintain machining process capability over an extended sump life.

Research on polyfurfuryl alcohol (PFA) bioresin has increased due to its unique flame-retardant property. This study utilised the hybridisation of carbon and flax fibres in combination with PFA resin to make fibre-reinforced polymer (FRP) composites. The samples were tested for low-velocity impact at an energy of 20 Joules. Results showed that the fibres-hybridised PFA-based sample had higher energy absorption compared to the carbon-fibre only sample. More importantly, the hybridised sample retained almost the same amount of flexural modulus after impact, while carbon fibre only FRP sample lost more than 20% of its flexural modulus. This highlights the benefits of hybridisation in impact resistance and retention of mechanical properties post-impact in the presence of PFA resin, which is consistent with previous reports of epoxy-based FRP composites. In conclusion, the combination of fibre hybridisation and PFA bioresin presents a promising solution to meet strict flame-retardant requirements, impact resistance needs, and reduce environmental carbon footprint for engineering applications.

The paper discusses an instrumented tapping test method using a CNC machine tool to compare the lubricity of MWFs by cutting threads in a Ti-6Al-4V alloy at low speed. The method uses a spiral flute tap size typical of industrial practice. A soft synchronous tap holder and spindle mounted dynamometer were incorporated on the machine to measure torque and thrust force. The tapping test method was demonstrated on three groups of MWFs that were commercially available and classified by ASTM E2523-13:2018. The method developed stable results free of chip clogging in tool flutes which could otherwise mask their comparative lubricity. The fully synthetic (FS) group displayed the best lubricity and within this group the FS from renewables (FS-bio) was the best overall. The method was shown to be effective in mitigating biasing effects on lubricity performance due to the generous tool chamfer angle tolerance and was practical and economical to implement. The significance of the results is discussed enabling an understanding of friction effects in tapping using a soft synchronous tap holder. A life cycle assessment of each MWF group found total Greenhouse Gas emitted from the FS group was 17% of the hydrocarbon group whilst FS-bio emitted just 7%.

Additive manufacturing (AM) of Inconel 718, IN718, is increasingly being used for the manufacture of complex geometry parts for high temperature applications. However, the low surface integrity and build resolution of as-built AM IN718 parts demands post processing such as machining. This paper reviews the machining of AM IN718 to understand the effect of anisotropic behaviour of the AM part and the hardening post AM treatment on the machinability of the latter. A better understanding on the cutting parameters and machining performance measures such as cutting forces, tool wear, chip morphology and surface integrity of workpiece led to the development of a workplan for future investigation.

Effects of surface modifications on the adhesive joint of carbon fibre reinforced polymer (CFRP) were investigated. CFRP surfaces were treated with traditional methods, such as acetone cleaning, sanding, grit blasting and peel ply. As a novel type of surface modification, stainless steel 316 wire mesh was co-cured on the CFRP laminate during the manufacturing stage. The surface topography of CFRP adherends was analysed through microscopic imaging. Surface roughness values were measured using a surface roughness tester. Contact angle measurements of probe liquids were performed to calculate surface energy. All adherends were bonded with a low viscosity epoxy adhesive. The single lap shear tests were used to measure the bonding strength of the CFRP joints. The experimental results showed that the highest average shear strength (24.2 MPa) was achieved for metal mesh modified joints. This amounted to a 101.7% increase compared with acetone-cleaned specimens. There was no statistically significant difference in shear strength among joints subjected to traditional surface treatments. Fracture surface images were analysed and correlation between surface treatment and lap shear strength was critically discussed.

Numerical simulations have been carried out to advance our current understanding of flow around two dimensional (2D) and three dimensional (3D) square shaped tandem bluff bodies at a Reynolds number of 22,000, especially to shed light on the sudden change of the downstream body’s drag coefficient. The Reynolds-Averaged Navier-Stokes (RANS) approach has been employed in the present study and the predicted drag coefficients compare reasonably well with available experimental data. Better understanding of flow fields has been achieved by analyzing streamlines, velocity vectors for both 2D and 3D cases in a horizontal plane and a vertical symmetric plane. The sudden jump in drag coefficient of the downstream body for the 2D case is well captured numerically, which is due to the flow over the upstream body impinging onto the front face of the downstream body at a critical gap size between those two bodies. For the 3D case the drag coefficient is predicted to increase gradually, consistent with the previous experimental finding. This is due to the fact that the vortical structures formed in the 3D case are very different, resulting in a reasonably smooth change of the flow field around the upstream body and hence leading to a gradual, not sudden, increase in the drag coefficient of the downstream body.

Background With the global spread of coronavirus disease 2019 (COVID-19), an increasing number of clinical trials are being designed and executed to evaluate the efficacy and safety of various therapies for COVID-19. We conducted this survey to assess the methodological quality of registry protocols on potential treatments for COVID-19. Methods Clinical trial protocols were identified on the ClinicalTrials.gov and the Chinese Clinical Trial Registry. Protocols were screened by two investigators independently against pre-defined eligibility criteria. Quality of the included protocols was assessed according to the modified 14-item SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) 2013 Statement. Results We included 82 randomized controlled trial (RCT) protocols investigating treatment modalities for COVID-19. These ongoing trials are being conducted in 16 provinces, autonomous regions, and municipalities of China, and study interventions were either Western medicines (n = 56) or traditional Chinese medicine (n = 26). Findings of our quality assessment indicated that the existing trial protocols could be further improved on several aspects, including selection and definition of outcome measures, descriptions of study interventions and comparators, study subject recruitment time, definition of study inclusion and exclusion criteria, and allocation concealment methods. Descriptions of random sequence generation methodologies were accurate for the majority of included trial protocols (n = 64; 78.05%); however, reporting of allocation concealment remained unclear in 63 (76.83%) protocols. Therefore, the overall risk of selection bias across these RCTs was judged to be unclear. A total of 52 (63.41%) included RCT protocols were open-label trials and are thus associated with a high risk of performance bias and detection bias. Conclusion Quality of currently available RCT protocols on the treatments for COVID-19 could be further improved. For transparency and effective knowledge translation in real-world clinically settings, it is important for trial investigators to standardize baseline treatments for patients with COVID-19 and assess clinically important core outcome measures. Despite eager anticipation from the public on the results of effectiveness trials in COVID-19, robust design, execution, and reporting of these trials should be regarded as high priority.

Aerodynamic drag reduction of tractor-trailer combination trucks is critically important to improve their fuel consumption which consequently results in lower emissions. One practical method to reduce aerodynamic drag of a truck is by mounting drag reduction devices on the truck. This paper presents a numerical study of turbulent flow over a simplified tractor-trailer truck with different drag reduction devices mounted on the truck using the Reynolds Averaged Navier-Stokes (RANS) approach to assess the effectiveness of those devices in drag reduction around the tractor-trailer gap region. Three cases with different drag reduction devices have been studied and significant drag reduction (above 30%) has been achieved for all three cases. Detailed analysis of the flow field has been carried out to understand drag reduction mechanisms, and it shows that no matter what drag reduction devices are deployed the drag reduction is mainly due to the reduced pressure on the front face of the trailer, and a small proportion of the drag reduction is due to the reduced turbulent kinetic energy in the gap region.

Reducing aerodynamic drag of heavy trucks is crucially important for the reduction of fuel consumption and hence results in less air pollution. One way to reduce the aerodynamic drag is the deployment of drag reduction devices at the rear of trucks and this paper describes a numerical study of flow over a bluff body with rear drag devices using the Reynolds-Averaged-Navier-Stokes (RANS) approach to investigate the drag reduction mechanisms and also to assess accuracy of the RANS approach for this kind of flow. Four cases, a baseline case without any drag reduction devices and three cases with different drag reduction devices, have been studied and the predicted mean and turbulent quantities agree well with the experimental data. Drag reduction varies hugely from a few percent in one case to more than 40% in another case and detailed analysis of flow fields has been carried out to understand such a difference and to elucidate the drag reduction mechanism, which ultimately can lead to better design of future drag reduction devices.

In this study, the combinative effects of surface treatments and the reinforcement of graphene nanoplatelets (GNPs) on the adhesive joint of aluminium alloy were investigated. Aluminium alloy plates were treated with acetone cleaning, grit blasting, chemical etching, and phosphoric acid anodisation (PAA) under various conditions. The effects of hydrothermal sealing of the anodised aluminium were also studied. Surface energies of the treated aluminium plates were determined using contact angle measurements. The samples were then bonded with epoxy or GNPs reinforced epoxy adhesives. The bonding strength of the aluminium joints was measured by single lap shear tests. The joint strength was significantly affected by both surface treatment and the reinforcement of GNPs. For grit blasted and PAA samples with hydrothermal sealing, the joint strength increased by 64% and 57% respectively due to the addition of 0.42 wt% of GNPs. Across all surface treatments, the highest average shear strength (17.6 MPa) was achieved for PAA samples with hydrothermal sealing and the addition of GNPs followed by PAA samples with no sealing and pure epoxy (17.0 MPa). Fractal surface images were analysed, and the correlation between epoxy infiltration behaviour, surface treatments and nano-reinforcement was critically discussed.