Models are still deficient in accurately reproducing the mechanisms that trigger tensile failure in unidirectional composites, highlighting a lack of direct experimental evidence. In this study, emphasis is given to the identification of connections between local fibre misorientation, packing and Weibull strength distribution in causing tensile failure. Synchrotron Radiation Computed Tomography (SRCT) and automated image processing techniques are adopted to segment individual fibres from loaded carbon fibre coupons. Subtle indications in the misorientation of local damaged sites are assessed in novel statistical detail for systematic differentiation from non-damaged sites. It is observed that the morphology of the surrounding environment of damaged sites statistically differs from that of non-damaged sites, even though locally damaged sites (containing single or coupled breaks) do not exhibit a peculiar fibre packing arrangement. For adjacent coupled breaks, the statistical nature of fibre separation distances is also reported.

The SARS-CoV-2 virus infection is a rapidly spreading global pandemic. Recent media coverage has highlighted the importance of protecting health-care workers together with issues surrounding availability and suitability of Personal Protective Equipment (PPE). Around 20% of healthcare workers treating COVID19 cases in Italy have become infected which leads to staff absence at a critical point during the pandemic, and unfortunately in some cases mortality.PPE plays a major role in control programs. Standard PPE such as N95/FFP3 facemasks have limitations such as an ineffective seal during talking or after prolonged use, face shapes which cannot be adequately fitted, and logistical issues ensuring availability of the correct mask for each person. Furthermore, global stock is low, and issues around diagnostic testing specificity and turnaround time may lead to infectious patients receiving care from health care staff who are not wearing appropriate PPE. To address acute shortcomings in PPE availability, we have developed a simple pressurised air purified respirator unit, incorporating a combination of inexpensive and widely available components parts. The prototype was developed to minimise the number and complexity of manufacturing steps with the intention that derivative versions could be developed in many different parts of the world, including low resource settings with minor modification, where transmission could be rapid amongst high population densities.The “Personal Respirator – Southampton” (PeRSo) delivers HEPA filtered air from a battery powered fan-filter assembly through a lightweight hood/face mask that can be comfortably worn for several hours. Initial user feedback provided by doctors and nurses shows the PeRSo prototype was preferred to standard N95/FFP3 masks, being more comfortable, reducing time lost placing and removing PPE between patients, and allowing better communication. Preliminary tests indicate that the device removes microbes and passes the “fit tests” widely used to evaluate face masks. Full verification of the safety and the duration of effectiveness and durability of the device is required, as part of translation into use. Rapid upscale of production is required to protect healthcare workers from infection while the global situation accelerates, so that they can look after patients during the peak of the pandemic.

This paper presents the development of novel Carbon-Fibre Reinforced Polymer (CFRP) laminates, tailored for the application of Digital Volume Correlation (DVC) and Computed Tomography (CT) to experimental mechanics analyses of these materials. Analogous to surface-based Digital Image Correlation (DIC), DVC is a relatively novel volumetric method that utilizes CT data to quantify internal three-dimensional (3D) displacements and implicit strain fields. The highly anisotropic and somewhat regular/self-similar microstructures found in well-aligned unidirectional (UD) materials at high fibre volume fractions are intrinsically challenging for DVC, especially along the fibre direction at microstructural length-scales on the order of a few fibre diameters. To permit the application of DVC to displacement and/or strain measurements parallel to the fibre orientation, the matrix was doped with a sparse population of sub-micrometre particles to act as displacement trackers ( i.e. fiducial markers). Barium titanate particles (400 nm, ∼1.44 vol. %) were found to offer the most favourable compromise between contrast in CT images and the ability to obtain a homogeneous distribution in 3D space with sufficient particle compactness for local DVC analyses. This property combination was selected following an extensive Micro-focus Computed Tomography (µCT)-based qualitative assessment on a wide test matrix, that included 38 materials manufactured with a range of possible particle compositions, mean sizes and concentrations. By comparing the tensile behaviour of the particle-adapted material alongside its particle-free counterpart, we demonstrate through the application of in situ Synchrotron Radiation Computed Tomography (SRCT) that the macro- and micromechanical responses of the newly developed CFRP are consistent with standard production materials indicating its suitability as a model system for mechanistic investigations.

Introduction: SARS-CoV-2 infection is a global pandemic. Personal Protective Equipment (PPE) to protect healthcare workers has been a recurrent challenge in terms of global stocks, supply logistics and suitability. In some settings, around 20% of healthcare workers treating COVID-19 cases have become infected, which leads to staff absence at peaks of the pandemic, and in some cases mortality.Methods: To address shortcomings in PPE, we developed a simple powered air purifying respirator, made from inexpensive and widely available components. The prototype was designed to minimize manufacturing complexity so that derivative versions could be developed in low resource settings with minor modification.Results: The “Personal Respirator – Southampton” (PeRSo) delivers High-Efficiency Particulate Air (HEPA) filtered air from a battery powered fan-filter assembly into a lightweight hood with a clear visor that can be comfortably worn for several hours. Validation testing demonstrates that the prototype removes microbes, avoids excessive CO2 build-up in normal use, and passes fit test protocols widely used to evaluate standard N95/FFP2 and N99/FFP3 face masks. Feedback from doctors and nurses indicate the PeRSo prototype was preferred to standard FFP2 and FFP3 masks, being more comfortable and reducing the time and risk of recurrently changing PPE. Patients report better communication and reassurance as the entire face is visible.Conclusion: Rapid upscale of production of cheaply produced powered air purifying respirators, designed to achieve regulatory approval in the country of production, could protect healthcare workers from infection and improve healthcare delivery during the COVID-19 pandemic.

Healthcare workers are at high risk of catching SARS-CoV-2 because of their regular interaction with patients with the disease. In low-resource settings, the ratio of healthcare workers to the whole population is lower than in high income countries, and there is often limited access to personal protective equipment (PPE). Illness or death of healthcare workers will, therefore, have a disproportionate impact in these settings, so it is particularly important to find ways to protect them.To protect against airborne infection in healthcare settings, PPE recommendations typically include filtering facemask respirators or powered air purifying respirators (PAPR). The former, passively filter inhaled air. They are small, noiseless and do not require a power supply, but they are single-use, presenting manufacturing and supply issues. Fit testing is crucial, and many users find them difficult to tolerate, due to breathing resistance and elevated humidity. There is also the potential for contamination due to the exposed face. PAPRs are re-usable devices that may last for months and provide airflow through a filter from a battery-powered blower unit to a hood or helmet which covers the face. This creates a positive pressure in the hood or helmet that enables the wearer to breathe filtered air easily, without requiring an air-tight fit needed for standard face masks. This is reported to be more comfortable and provides better protection for the face from droplets and splashes, and infection by self-contact with the hands. PAPRs have typically been expensive, bulky and not readily available or easy to ship to low-resource settings.Although the design presented here has not been through any form of regulatory approval, the aim of this paper is to share ideas and offer possible solutions to other groups around the World who may be thinking of manufacturing a low-cost, reusable PAPR. The design is novel because it uses readily available materials, scalable manufacturing processes, and it may be shipped flat-packed and easily assembled. This offers an option for manufacturing in low-resource settings and for shipping in bulk. This paper provides the CAD designs that can be fabricated using a laser cutter.