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Abstract: Directed energy deposition (DED) additive manufacturing (AM) can fabricate, repair, and join near-net-shaped components for high-performance engineering applications, including biomedical, energy, and transport sectors. The broader adoption of DED remains constrained by the limited number of alloys available that can be reliably manufactured without imperfections, hence limiting mechanical properties. Here, we designed an Al-Ni-Ce-Mn-Fe AM alloy that can achieve an ultra-fine microstructure (<5 μm), uniform distribution of intermetallics, low residual stress (<32 MPa), and superior mechanical properties in as-built DED components. Compared to DED AlSi10Mg in the as-build state using the same conditions, the yield increased by 70%, and the ultimate tensile strength by 50%. DED-AM involves rapid cooling and complex thermal conditions, which largely influence the property of the final components. Post-characterization cannot capture the time resolved thermal behavior, hence offer limited mechanism-based guide for alloy design. In this study, we develop a novel multimodal characterization methodology for correlative in situ X-ray imaging, X-ray diffraction, and infrared imaging, enabling quantification of the in situ thermal-related behavior, including phase evolution, temperature distribution and stress accumulation during DED. We elucidated key mechanisms driving the structure refinement and stress development in this alloy. The insights gained into the interplay between alloy composition, thermal-related behavior, and performance under specific AM conditions informs next-generation material design tailored for AM technologies.

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Abstract: The collapse of the Apollo theatre ceiling, London, 2013, emphasised the importance of researching historic fibrous plaster ceilings. Ceilings are subject to dynamic forces, and this study identifies and quantifies dynamic loads in historic theatre ceilings by in-situ monitoring using accelerometers. Flexural, tensile and compressive tests were conducted on new and historic fibrous plaster to establish properties of ceiling panels and supporting fibrous plaster wads. Forces required to initiate microcracks and ultimate failure were compared with the magnitude of recorded accelerations. In-situ work made two important discoveries: technical activity in-between shows induces higher accelerations than performance sound pressure levels, and steel wire rope (supporting light/sound systems) making contact with ‘top hats’ (tubular channels in cylindrical drilled ceiling holes) is the primary dynamic loading in routine operation, with acceleration peaks typically ≈ 15 g (≈35 N force). Simulating accelerations in ceiling-panel laboratory tests resulted in displacements up to 0.1 mm and 200 microstrain. Results in new fibrous plaster established forces and displacements when initial microcracks occur in flexure (≈700 microstrain), tension (≈7000 microstrain) and compression (≈10000 microstrain). Results demonstrated that accelerations recorded in-situ would be insufficient to cause cracks in new, or well-maintained historic, theatre ceilings and wads. Ceilings in different buildings may vary in condition, therefore minimising steel wire rope-top hat contact would reduce the probability of ceilings sustaining damage. This study provides the first quantitative evidence of the dynamic behaviour and material performance of original wads and theatre ceilings, transforming understanding of their properties. Results will directly guide conservation policy and practice, enabling heritage engineers, conservation professionals, custodians and building owners, to make evidence-based decisions that enhance the long-term safety and preservation of historic interiors.

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Abstract: FeCo-2V soft magnetic alloys offer attractive properties for demanding electromagnetic applications. While their magnetic properties are well-characterised under static loading conditions, the evolution of these properties under cyclic mechanical loading, as seen in service, remains insufficiently explored. This study examines how fatigue deformation alters the magnetic behaviour of an FeCo-2V alloy. The investigation employed strain-controlled cyclic loading combined with Single Sheet Tester measurements across multiple frequencies. A modified Bertotti loss separation analysis quantified the contributions of hysteresis and eddy current losses to total core loss. Experimental results demonstrated an increase in coercivity, and significant core loss increase during early-stage fatigue, followed by more gradual changes at higher cycle counts. The abrupt initial property changes correlate with rapid dislocation accumulation, while subsequent stabilisation reflects saturated defect densities. Notably, hysteresis losses dominated the degradation, while eddy current losses remained stable throughout cycling. These findings establish clear relationships between cyclic loading and magnetic properties in FeCo-2V and may serve as the basis for non-destructive fatigue assessment through magnetic measurements.

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Abstract: This thesis develops and evaluates a fully automated deep learning workflow for segmenting voids and material phases in X-ray computed tomography of carbon fibre and flax fibre polymer composites. For the carbon fibre system, fibre, matrix, and void masks were generated through a reproducible Python-based pipeline combining slice-wise intensity normalisation, two-stage void detection, morphological refinement, and Otsu-based fibre–matrix separation, followed by targeted manual verification in Dragonfly. For the flax fibre system, segmentation masks were produced and refined manually and unified into a consistent three-phase labelling scheme (matrix, fibre, void). These reference datasets were then used to train five lightweight convolutional neural network architectures (UNet++, UNet3+, Attention UNet, DeepLabV3+ Transformer, and LR-ASPP Transformer) under identical conditions, using paired 256 × 256 patches, controlled label-safe augmentation, and a fixed slice-level train–validation split. A higher-load carbon fibre state (140 N) was withheld entirely from training and used exclusively to evaluate the models on previously unseen microstructural damage. The results demonstrate that compact encoder–decoder networks can accurately localise voids and robustly separate fibre and matrix phases across both composite systems, including under low contrast and evolving damage, while maintaining computational efficiency suitable for routine XCT workflows.

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Abstract: Understanding the degradation of large format lithium-ion pouch cells – critical for electric vehicle applications – is vital to extend their lifetime and allow potential second-life application. Here, the impact on capacity fade and material degradation in two end-of-life cells, which were additionally subjected to accelerated aging to mimic extended use in second-life applications, were examined using powder synchrotron X-ray diffraction, Raman spectroscopy and electrochemical impedance spectroscopy, complemented by detailed post mortem analyses. The dominant mechanism of capacity loss under these conditions was found to be lithium inventory depletion, driven by processes such as electrolyte decomposition, lithium plating and solid electrolyte interphase growth. Structural changes in the graphite anode, including amorphization and reduced active material, were more pronounced under severe overcharging conditions. The blended cathode showed lithium inventory loss in both phases, but 92–94% capacity recovery was observed on subsequent cycling in half cells vs Li, illustrating its robustness, with little structural degradation observed. The finding that electrolyte degradation/loss in these cells was a more critical contributor to cell degradation toward the knee-point than electrode active material degradation/loss indicates that increasing – or replenishing – the electrolyte content could be a strategy to extend the usable life of such cells.