A Personal Respirator to Improve Protection for Healthcare Workers Treating COVID-19 (PeRSo)

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

Understanding the damage accumulation and tensile strength in carbon fibre reinforced polymers using high resolution <i>in situ</i> computed tomography

Currently, composite components are widely adopted in aerospace applications but typically over-designed due to the lack of reliable predictive models for their mechanical properties. The objective of this thesis is to reach a higher level of understanding of the damage accumulation processes occurring in tensile loaded carbon fibre reinforced polymer systems to advance the development of predictive models. In situ loading combined with high-resolution Synchrotron Radiation Computed Tomography (SRCT) imaging has allowed a data-rich investigation of the key mechanisms leading to the final failure in different material systems. An extensive database of performance and damage behaviour has been compiled and systematic comparisons performed for material systems consisting of aerospace and industrial grade fibres, as well as different levels of adhesion of the fibre/matrix interface, obtained through changes in the sizing agent and fibre surface treatment. Focus was given to the damage mode that drives tensile failure in unidirectional layers loaded in the fibre direction: i.e. fibre failure, as this is often considered to be the final failure event in the application of multi-layered components. Clusters of fibre breaks (hereby indicated as multiplets) are believed to play a significant role in the provision of a critical crack site that propagates to final failure. Both qualitative and quantitative analyses have been performed, indicating that the accumulation of fibre breaks does not have a simple correlation to the macroscopic properties of the material, such as the ultimate tensile strength (UTS) and the fibre type but particularly the fibre/matrix interface have been observed to affect the multiplet formation.The morphology of local damaged sites has been investigated in a novel statistical approach, needed to distinguish very similar fibre arrangements. Automated tools have been specifically developed to extract fibre breaks and the fibre shapes from low contrast images with high fibre volume fraction. The fibre misorientation in damaged sites is seen to differ statistically from that in non-damaged sites (using well recognised statistical tools) and the single fibre misorientation distributions show a consistently higher standard deviation in orientation when compared to intact fibre distributions, even though locally damaged sites did not exhibit a peculiar fibre packing arrangement. The research provides a unique database of data as well as automated statistically inferred tools that can provide a better insight into the fundamental mechanisms leading to tensile failure in longitudinally loaded composites, supporting the model development in two different phases: (a) at the initial stages, identifying phenomena and influences that should be included in accurate but parsimonious model formulation and (b) at a quantitative calibration/verication point, providing critical but previously unavailable numerical descriptions of micro-mechanical processes

MATLAB scripts for CT data assessment

This dataset supports the thesis entitled &#39;Understanding the damage accumulation and tensile strength in carbon fibre reinforced polymers using high resolution in situ computed tomography&#39; by Rosini.</span

A novel particle-filled Carbon-Fibre Reinforced Polymer model composite tailored for the application of Digital Volume Correlation and Computed Tomography

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