Mechanical Properties of Eco-Friendly, Lightweight Flax and Hybrid Basalt/Flax Foam Core Sandwich Panels.

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.

Effect of Powder Bed Fusion Laser Sintering on Dimensional Accuracy and Tensile Properties of Reused Polyamide 11.

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.

Design and manufacture of one-size-fits-all healthcare face shields for the NHS during the COVID-19 pandemic.

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.