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SMA-Tufted CFRP Composites with Enhanced Interlaminar Toughness and Damage Detection Capabilities
No full textCarbon Fibre-reinforced polymer (CFRP) composites are widely used in high-performance structural applications due to their superior in-plane mechanical properties, lightweight design, and corrosion resistance. However, these laminated composites remain susceptible to delamination under out-of-plane or cyclic loading, which undermines their long-term damage tolerance. Delamination is also difficult to detect and may grow undetected under fatigue loading until it reaches a critical size, resulting in structural failure. Through-thickness reinforcement techniques, such as z-pinning, tufting, and hybridisation, have emerged as effective strategies to arrest delamination growth and improve interlaminar fracture toughness.This PhD research investigates the multifunctional properties of composite laminates reinforced orthogonally (through-thickness) using Shape Memory Alloy (SMA) wire tufts. The study explores the influence of tuft material, geometry, and distribution on interlaminar fracture toughness and fatigue behaviour under mode I and mode II loading. The multifunctional role of SMA tufts in delamination crack closure and damage detection is also investigated. Furthermore, a comparative study is performed to quantify the level of improvement in fracture and fatigue resistance achieved with SMA tufts compared to other conventional tufting materials.Composite laminates were fabricated using vacuum-assisted resin infusion, integrating carbon, copper, and shape memory alloy (SMA) tufts using a manual tufting process. Reinforcement parameters, including areal content, tuft density, angle, and filament morphology, were systematically varied. Standardised test procedures were followed to evaluate mode I and mode II fracture toughness, traction-separation property, and mode I fatigue crack growth resistance. Microstructural and fractographic analyses were conducted using optical microscopy, SEM, and X-ray computed tomography (CT) to identify the key toughening and strengthening mechanisms.The second technical chapter (CHAPTER 4) evaluated the effect of SMA tuft wire diameter, specifically thin (0.15 mm) and thick (0.25 mm) at 0.30% areal content, on the interlaminar fracture toughness of carbon fibre-reinforced polymer (CFRP) laminates. Mode I double cantilever beam (DCB) and mode II end-notched flexure (ENF) tests demonstrated that SMA tufts significantly improved delamination resistance in both modes, with mode I fracture toughness enhanced by approximately 14-fold. CT analysis revealed the formation of extensive crack-bridging zones as the dominant toughening mechanism.The third technical chapter (Chapter 5) presents a comparative assessment of CFRP composites tufted with carbon tow, copper, and SMA wires at a constant areal content of 0.3%. The results showed that both carbon and SMA tufts achieved similar improvements in mode I and mode II fracture toughness, exceeding nine-fold compared to untufted laminates. Chapter 6 extends this comparative analysis to mode I fatigue performance. SMA tufts provided comparable improvements to carbon tufts, while copper tufts offered the least enhancement due to lower strength and limited traction resistance. The performance differences were linked to the crack bridging efficiency of each material under cyclic loading.Chapter 7 focused on the multifunctional performance of SMA tufts in enabling delamination crack closure and in-situ damage detection. Thermal activation tests confirmed that thicker SMA tufts enabled higher levels of crack closure (35–50%) due to enhanced stiffness and buckling resistance. The crack closure function remained repeatable across four thermal cycles. When used for damage sensing, the SMA tufts enabled electrical resistance-based monitoring of delamination propagation under both mode I and mode II loading. Mode I sensing showed higher gauge factors (~14.6) compared to mode II (~0.5), with a measurable lag due to the development of bridging zones.The final chapter introduces a finite element modelling (FEM) framework to simulate mode I crack propagation in tufted composites. Developed in Abaqus/CAE, the model used a cohesive zone modelling combined with a traction-separation law for the tufts derived from the mode I bridging traction results for the tufts. The FEM results accurately predicted R-curve and steady-state toughness for carbon, copper, and SMA tufts at 0.30% areal content. The model was further used to predict performance at 0.15% and 0.45% areal content, revealing a nearly linear relationship between areal density and mode I fracture toughness.The findings from this thesis demonstrate that SMA tufts offer a viable solution for enhancing delamination resistance, delivering crack closure functionality, and enabling in-situ damage detection in composite structures. These contributions support the development of next-generation smart composites with integrated sensing and damage-tolerant capabilities.</p
Presence of Potentially Pathogenic Vibrio spp. in Seafood Available for Sale in Melbourne, Australia
No full textThe prevalence of seafood-associated human infections caused by Vibrio spp. is an ongoing concern globally, particularly in countries with high seafood consumption or rapidly warming coastal environments. In Australia, there have been increasing outbreaks related to Vibrio parahaemolyticus associated with consumption of raw oysters and significant knowledge gaps exist which inhibit risk management options for this pathogen. Little is known about the autochthonous Vibrio spp. strains that are present in Australian waterways or how they present in the seafood harvested in these waters. Compounding these unknowns is the lack of standardised methodology for analysing Vibrio spp. in seafood products.To address these knowledge gaps, this thesis presents an investigation into the presence, detection, and genetic diversity of V. parahaemolyticus in seafood available in Melbourne, Australia. Chapter 2 describes a retail market survey of raw and ready-to-eat seafood for Vibrio spp. using culture-based techniques. During this survey, 83 ready-to-eat seafood samples, comprised of 52 oyster samples and 29 prawn samples, were collected from seafood markets across Melbourne, Australia and analysed for the presence of potentially pathogenic Vibrio spp. Of the samples collected, 85% (n=45) of oyster samples and 17% (n=5) of cooked prawn samples contained one or more Vibrio spp. In total, 109 Vibrio isolates were collected during the survey, made up of 25 V. parahaemolyticus isolates, 4 V. cholerae isolates, 30 V. alginolyticus isolates and 50 V. diabolicus isolates. Of the V. parahaemolyticus strains isolated, MLSTs of clinical significance were isolated from Australian oyster samples, including ST50. Chapter 3 describes the development and utilisation of a real-time PCR-based detection workflow for V. parahaemolyticus and associated virulence genes (tdh and ureR as a surrogate for trh) in enrichment broths of market survey samples. This assay successfully amplified tdh and ureR reference strains however a significant finding of this study indicated that an important strain, ST50, does not possess the ureR gene despite containing the trh gene as determined by whole genome sequencing analysis (WGS) carried out in Chapter 4. Chapter 4 further investigated the genetic diversity, virulence potential, and phylogeny of the Vibrio spp. isolates obtained during the market survey through WGS analysis. This analysis revealed a large pangenome among the V. parahaemolyticus market survey isolates, highlighting the genetic diversity among the species. In addition, the virulomes and resistomes of all Vibrio spp. isolates were characterised, revealing the presence of Type III Secretion System 2 (T3SS2) components in three non-toxigenic V. parahaemolyticus strains. Analysis of resistomes revealed all strains carried intrinsic resistance genes, indicating no acquired antimicrobial resistance among the isolated strains. Together, these studies contribute to a better understanding of the prevalence and characteristics of potentially pathogenic Vibrio species in Australian seafood and inform future surveillance and detection strategies. This study represents the first market survey to date to assess the presence of Vibrio spp. in Australian seafood and also contributes to foundational genomic knowledge of Australian Vibrio spp. strains.</p
Dysregulation of cellular metabolism within the gut-brain axis is associated with behavioural changes in chronic intestinal inflammation
No full textBackgroundInflammatory bowel disease (IBD) is a chronic debilitating condition significantly affecting patient quality of life. Although the exact aetiology remains unknown, accumulating evidence has shown that disruption of the gut-brain axis may be related to the occurrence and development of chronic intestinal inflammation. Psychological disorders are highly prevalent in patients with IBD. However, an association between altered behaviour and dysregulated metabolic pathways within the gut-brain axis is yet to be explored.MethodsMetabolic multiplexed phenotyping system involving indirect calorimetry and flow-through respirometry monitors was used to assess energy metabolism in Winnie mice with spontaneous chronic colitis and C57BL/6 littermates. Depressive and anxiety-like behaviours were evaluated with light dark, open field, grooming, elevated plus maze, and forced swimming tests. To investigate underlying mechanisms of the metabolic changes in Winnie mice, glycolysis/gluconeogenesis, fatty acid ß-oxidation, tricarboxylic acid cycle and oxidative phosphorylation gene expressions were determined by transcriptome analysis using high-throughput sequencing of mRNA extracted from the distal colon and brain samples.ResultsOur findings showed that energy metabolism and spontaneous activity were reduced in Winnie mice corresponding to alterations in the expression of cellular metabolism-associated genes in the distal colon. Winnie mice displayed depressive and anxiety-like behaviours reflecting downregulation of glycolysis/gluconeogenesis, fatty acid ß-oxidation, tricarboxylic acid cycle and oxidative phosphorylation in the distal colon and brain. Subsequent analyses showed pro-inflammatory cytokine expression was upregulated in the Winnie mouse brain.ConclusionsThese data provide evidence that the dysregulation of cellular metabolism within the gut-brain axis underlies changes in behaviour and energy metabolism in chronic intestinal inflammation.</p
Enhancing structural integrity and crack resistance of rubberized concrete using aqua-thermally treated rubber aggregates and recycled tire steel fibers for structural applications
No full textIncorporating waste tire-derived rubber into concrete often results in significant strength reductions, primarily due to weak bonding at the rubber-cement interface. Despite various surface treatment methods for enhancing rubber adhesion, the mechanical performance of rubberized concrete remains inferior to conventional concrete. Reinforcing rubberized concrete with industrial steel fibers mitigates this limitation through the fiber-bridging mechanism. However, their high cost and environmental footprint restrict broader applicability. Although steel fiber recovered from waste tires offers a sustainable alternative, their incorporation remains challenging for fully restoring the mechanical performance of rubberized concrete. Employing rubber in its as-received condition intensifies this phenomenon, impairing the efficacy of fiber-bridging action. Consequently, this study assessed the synergistic effect of recycled tire steel fibers and rubber particles subjected to a novel aqua-thermal treatment. Both rheological and mechanical performances, including short-term and long-term strengths, were assessed across varying rubber and steel fiber contents. This combination restored compressive strength with rubber contents up to 12.5 %, surpassing previously reported performance levels. The flexural strength exceeded control values at rubber contents up to 15 %, further validating the efficacy of the proposed approach. Microstructural characterization techniques revealed enhanced synergy between aqua-thermally treated rubber and steel fibers within the concrete, explaining the underlying mechanism for observed performance gain. Additionally, the high-tensile strength of recycled tire steel fibers controlled both micro- and macro-crack propagation, enabling efficient stress transfer across the matrix. This mechanism transformed the brittle failure mode of concrete into a more ductile response, enhancing damage tolerance at failure. This dual-recycled material approach enables the production of high-performance rubberized concrete for structural applications, promoting sustainable construction well aligned with global low-carbon and waste reduction targets, while comprehensive durability testing continues.</p
Miyawaki forests-in-the-making: Enlivening values of human–nature care and gathering through the cultivation of Miyawaki forests
No full textIn recent years growing numbers of fast-growing ‘mini forests’ have been planted around the world using an approach for rapid urban greening known as the ‘Miyawaki method’. Originating in Japan, the Miyawaki method was first developed as a relatively novel ecological engineering approach to the afforestation of industrial and degraded landscapes. However, in recent years escalating climate impacts and loss of biodiversity has inspired a new generation of Miyawaki forest practitioners working globally in diverse ecological contexts. In this paper, we discuss the Miyawaki forest movement's evolution, and discuss its introduction into Australia through the lens of three Australian-based practitioners. Connecting Australian practitioners with the work of global practitioner networks, we explore the methods, practices and collaborations involved in the making of Miyawaki forests, before turning to how their value is being captured. We draw from a multi-species cities perspective to explore the multi-dimensional values and benefits of Miyawaki forests, which span both human and more-than-human ‘well-beings’ as sites of human–nature gathering, but also requiring collaboration across ecological, cultural and social spheres in order to be sustained over time.</p
A single nurse routing and scheduling problem for home-based chemotherapy and infusion services
No full textHome health care has expanded to include infusion treatments for chemotherapy and other diseases requiring periodic infusions. Scheduling these appointments is crucial and complex due to the urgency of treatment and their unique cyclic patterns over several months. This complexity arises because adding a new patient affects not only the immediate schedule but also has long-term implications. This paper presents a mathematical model for a single nurse routing and scheduling problem for home-based chemotherapy and infusion services. The aim is to maximise the number of priority-weighted new chemotherapy and infusion patients incorporated into the system by optimising the route and schedule for a single nurse, considering the cyclical nature of infusion treatments with an extended planning horizon. A novel matheuristic approach, the Temporal Decomposition and Filtering based Matheuristic (TDFM), is introduced to address this large-scale problem. Computational experiments on practical-sized problems demonstrate that the proposed solution approach, combined with commercially available solvers, is able to achieve high-quality solutions within a useful timeframe.</p
Effect of storage conditions on the physicochemical and Structural properties of spray dried milk-tea formula powders containing different lactose-to-maltodextrin and casein-whey ratios
No full textPowdered milk-tea offers a convenient and nutritious alternative to its liquid counterpart. While casein-to-whey protein (C:W) ratios are well-studied in milk-based formulas, their role in milk-tea powder stability remains underexplored. This study examined the effects of varying C:W ratios (80:20, 70:30) and lactose-to-maltodextrin (L:M) ratios (90:10, 80:20, 75:25) on the physicochemical and structural stability of spray-dried skim milk- tea (SM-T) and fat-filled milk-tea (FM-T) powders under storage at 11–65 % relative humidity (RH) and 25 °C or 40 °C for three months. Moisture sorption followed Type II isotherms, with SM-T showing greater uptake due to the hydrophilic nature of lactose and whey proteins, while FM-T retained less moisture due to fat's repellent properties. However, at RH >54 %, FM-T exhibited fat migration leading to interparticle adhesion and structural destabilization, whereas SM-T remained more stable due to plasticization-induced expansion without excessive coalescence. Browning increased with RH and temperature, with FM-T showing greater browning from lipid oxidation-driven Maillard reactions. Protein aggregation was influenced by formulation: FM-T showed disulfide-linked β-Lg aggregation under high RH and temperature, while SM-T formed non-covalent aggregates. SEM analysis revealed more collapse and agglomeration in FM-T at 40 °C, while SM-T particles remained intact. Overall, optimal storage stability occurred under RH </p
Mechanics by Design: Evolutionary Design Optimization of Multiscale Mechanical Metamaterials
No full textMechanical metamaterials represent a fundamental shift in materials science and engineering, enabling unprecedented mechanical properties through architected heterogeneity. While early studies predominantly focused on periodic architectures and single-phase materials, contemporary research has expanded to encompass non-periodic, heterogeneous, and hierarchical systems that offer enhanced and often unprecedented performance and novel functionalities, including mechanical computing. The present thesis explores such complex mechanical metamaterial systems and develops new methodologies to systematically classify, design, and optimize them.
A novel classification framework is introduced (Chapter 2) that abstracts periodic and non-periodic metamaterials as mechanisms that transform mechanical inputs into desired quasi-static or dynamic outputs. This transformation-based approach, inspired by modern computational architectures, enables a systematic perspective on inverse design, facilitating the identification of functional gaps and new design opportunities.
Next, the concept of conventional single-phase metamaterials is extended to composite metamaterials by incorporating material heterogeneity, thereby generating expanded effective property spaces (Chapter 3). To address the added design complexity, an automated evolutionary design framework is developed, capable of generating optimized 2D pentamode-like structures. These structures are shown to achieve extreme bulk-to-shear modulus ratios (B/G > 10,000), significantly surpassing conventional designs while mitigating stress concentration aspects inherent to classical pentamodes.
The hierarchical mechanical metamaterials are explored subsequently (Chapter 4). This study demonstrates that architectures incorporating multiple length scales can achieve enhanced mechanical performance. The proposed Hierarchical Metamaterial Automated Design (H-MAD) framework systematically optimizes both micro- and macro-scale features to produce structures with extreme mechanical moduli. The study shows that hierarchical pentamodes can attain B/G ratios of extremely high values (up to 15×10³), thus advancing the boundaries of mechanical property enhancement through hierarchical structuring.
The intersection of metamaterials and analog computing is investigated next, demonstrating how mechanical metamaterials can process information through elastic wave propagation (Chapter 5). By leveraging evolutionary optimization, the study maps metamaterial architectures to the equivalent of recurrent neural networks, enabling in situ mechanical signal classification. This work represents a step towards physically embedded computing within mechanical systems, offering an energy-efficient alternative to conventional electronic processors.
The major contributions of this thesis are presented, and the broader implications for metamaterial research and engineering applications are discussed (Chapter 6).
Collectively, these advancements—spanning classification, composite and hierarchical design, and wave-based computing—advance the boundaries of mechanical metamaterials, unlocking new possibilities for engineering applications through tailored, high-performance architectures.</p
Beyond Graphene: Unveiling the Structure-Property Relationship of Silicon Carbide (SiC) Through First Principles Calculations
No full textThe rising demand for smaller, more compact, and easily portable electronic devices has driven the shift from micro to nanoelectronics. For this progression, researchers need to incorporate low-dimensional nanomaterials, such as nanotubes, nanowires, and quantum dots, into nanoscale devices. These materials not only meet the requirements for device miniaturization but also facilitate the exploration of novel quantum phenomena not exhibited in bulk systems. This evaluation contributes to the fabrication of nanoscale devices, that offer high-performance, energy efficiency, and functional adaptability, which makes it foundational for advancing next-generation electronic devices.
A fundamental understanding of the physicochemical properties of low-dimensional materials is crucial for the design of compact, high-performance nanoelectronic devices. However, nanostructures of current benchmark materials such as carbon and silicon, reveals inherent limitations, such as chemical instability, limited bandgap tunability, and compatibility constraints. In this context, silicon carbide-based nanostructures offer a promising alternative due to their physicochemical, and tunable electronic properties. With this motivation, this doctoral thesis employs first principles density functional theory, to conduct a comprehensive investigation of the structural, physicochemical, and electronic properties, of both existing and theoretically proposed SiC based low-dimensional nanostructures. Additionally, the study explores various potential synthesis strategies. The computational findings assist in the possible experimental synthesis approaches for SiC nanostructures and emphasise their potential for various applications.
Atomically thin layered 2D SiC nanosheets are wide band gap semiconductors with excellent thermal stability, making them promising candidates for flexible nanoelectronic devices. However, due to the strong covalent bonding in bulk SiC, exfoliating monolayer 2D SiC remain experimentally challenging. In Chapter 3, we demonstrate that exfoliation of ultrathin SiC layers from bulk wurtzite SiC through a defect engineering approach may be feasible. Further, we explain the effect of defects on the structural and electronic properties of monolayer to tri-layer SiC nanosheets. Chapter 4 focuses on an approach to form single walled SiC nanotubes. While, experimental synthesis has commonly achieved the formation of multi-walled SiC nanotubes, the formation of single walled SiCNTs remains a significant challenge. In this chapter we used dangling edge bonds to control the technique as a novel alternative approach to the traditional method (i.e. cutting a 2D SiC nanosheet along its Bravais direction and rolling it into a single walled SiC nanotubes). Specifically, it is demonstrated that stacking of bilayer SiC nanoribbons can lead to the formation of single walled SiC nanotube via bond formation at the nanoribbon edges. Notably, this self-formation processes does not require any external energy. Further, the critical threshold diameter for successful tube formation was determined to be ~1.2 nm. Beyond that diameter, the nanotubes underwent radial deformation, limiting their structural stability. Chapter 5.1 addresses the radial deformation of larger diameter defective SiC nanotubes, utilizing a charge injection approach to mitigate this reconstruction. The injection of holes (electron) leads to an expansion (contraction) of the nanotube diameter. This results in an electromechanical strain that can reached up to 10.6%, which is significantly higher than conventional nanotubes such as CNTs or SiNTs. This strain response highlights the suitability of 1D SiC allotropes for applications in nanoelectromechanics. Chapter 5.2 demonstrates that defective SiC nanotubes are promising candidates for anode materials in alkali-metal ion batteries. The chapter provides detailed insights into their structural stability, bonding nature, and electrochemical behaviour. Furthermore, the anodic performance of defective SiCNTs is evaluated by analyzing their average intercalation voltage (AIV) profiles, confirming their suitability for energy storage applications. Finally, Chapter 6 investigates the influence of quantum confinement on the structural and electronic properties of SiC nanoflakes. A detailed analysis of edge geometry and flakes size reveals that physicochemical properties are highly sensitive to these factors. The tunability of these properties make potential for nanoelectronic applications.
Overall, the findings presented in this thesis range from the structural and physicochemical properties to novel synthesis strategies for SiC based nanostructures, all highlighting their potential in nanoelectronic and energy storage applications. We believe these insights will encourage further research in the field of nanoelectronics and support experimental efforts towards the synthesis of SiC based nanostructures.</p
A configurational approach to strategic change in family firms
No full textStrategic change is essential for an organization’s long-term performance and survival. Research has investigated how governance structures, organizational values, capabilities, and firm size, in isolation from one another, influence family firms’ strategic change, yet insights in family firm literature suggest the need to examine the fit among these dimensions. We employ a configurational approach and a framework built from models of fit in family firm literature to examine the interdependence among these dimensions. Using a primary dataset of 275 Belgian private family firms and fuzzy-set qualitative comparative analysis (fsQCA), we identify six configurations leading to high levels of strategic change and three configurations explaining low levels of strategic change. This study contributes to the literature by advancing our understanding of how multiple interdependent dimensions, namely, governance structures, organizational values, capabilities, and firm size, combine to better explain strategic change levels in family firms. The findings also provide concrete formulas for practitioners to create a fit among specific factors in these dimensions to promote strategic change.</p