Tensile Response of Adhesively Bonded Composite-to-composite Single-lap Joints in the Presence of Bond Deficiency

This paper studies the quasi-static tensile response of adhesively bonded composite-to-composite single-lap joints in the presence of weak and kissing bonds, as an attempt for characterisation of bond deficiencies likely to occur in polymer composite bonded repair. Cytec FM®94 adhesive film (0.25 mm nominal thickness) was used for all joints to bond two 2mm-thickness carbon fibre polymer composite laminates manufactured from unidirectional Hexcel M21/T800S pre-pregs. Peel-ply surface treatment was used for all joints. The bonds were deteriorated via five methods: pre-curing the centre of bond area prior to the cure of the bond edges, increasing the curing temperature rate, reducing the curing time, and embedding PTFE films over the centre of the bond. For the last method, the studies were carried out by embedding PTFE films on one and two sides of the adhesive film. The bond deterioration was followed by non-destructive inspections using ultrasound C-scanning. The ultimate failure load of the joints with defected bonds (i.e. weak and kissing bonds) was measured and compared to that of the joints with no defect (i.e. good bonds). It was found that rapid curing and short-time curing reduces more than 50% of the load carrying capacity of the single-lap joins in tension while the joints with weak bonds introduced by pre-curing of a large area of the bond (>60%) can take up more than 65% of the ultimate load of the joint with good bond. Also, optical microscopy of the bond surfaces after failure showed changes in failure type for the rapid and short-time cure, strongly correlated with their significant failure load reduction

Mechanical performance of composite bonded joints in the presence of localised process-induced zero-thickness defects

Processing parameters and environmental conditions can introduce variation into the performance of adhesively bonded joints. The effect of such variation on the mechanical performance of the joints is not well understood. Moreover, there is no validated nondestructive inspection (NDI) available to ensure bond integrity post-process and in-service so as to guarantee initial and continued airworthiness in aerospace sector. This research studies polymer bond defects produced in the laboratory scale single-lap composite-to-composite joints that may represent the process-induced defects occurring in actual processing scenarios such as composite joining and repair in composite aircrafts. The effect of such defects on the degradation of a joint's mechanical performance is then investigated via quasi-static testing in conjunction with NDI ultrasonic C-scanning and pulsed thermography. This research is divided into three main sections: 1- manufacturing carbon fibre-reinforced composite joints containing representative nearly zero-thickness bond defects, 2- mechanical testing of the composite joints, and 3- assessment of the NDI capability for detection of the bond defects in such joints

Implementing an inclusive social work curriculum

This paper discusses the implementation of an inclusive curriculum in social work education, in response to an Inclusive Curriculum project at the University of South Australia which aimed to develop principles and policies of inclusivity in curriculum within national priorities. The concept of \u27inclusivity\u27 is located within theories of identity, and international developments on inclusive education. We discuss the articulation of ideas on inclusivity in social work education through the \u27personal story\u27 of an individual social work educator\u27s practices within organizational policies and structures. We show how an educator\u27s \u27personal story\u27 is positioned within particular perspectives of knowledge and pedagogy, and influenced by other personal stories that produced a particular response to implementing an inclusive curriculum in social work.<br /

Growth of Carbon Nanotubes on HfO2 towards Highly Sensitive Nano-Sensors

Carbon nanotube (CNT) growth on HfO2 is reported for the first time. The process uses a combination of Ge and Fe nanoparticles and achieves an increase in CNT density from 0.15 to 6.2 mm length/mm2 compared with Fe nanoparticles alone. The synthesized CNTs are assessed by the fabrication of back-gate CNT field-effect transistors with Al source/drain contacts for nano-sensor applications. The devices exhibit excellent p-type behavior with an Ion=Ioff ratio of 105 and a steep sub-threshold slope of 130 mV/dec

Metal-catalyst-free growth of carbon nanotubes and their application in field-effect transistors

The metal-catalyst-free growth of carbon nanotubes (CNTs) using chemical vapor deposition and the application in field-effect transistors (FETs) is demonstrated. The CNT growth process used a 3-nm-thick Ge layer on SiO2 that was subsequently annealed to produce Ge nanoparticles. Raman measurements show the presence of radial breathing mode peaks and the absence of the disorder induced D-band, indicating single walled CNTs with a low defect density. The synthesized CNTs are used to fabricate CNTFETs and the best device has a state-of-the-art on/off current ratio of 3×108 and a steep sub-threshold slope of 110 mV/dec

A generalizable mechanism of CD24 signalling and its ability to specifically alter the biogenesis of B cell extracellular vesicles

CD24 is a variably glycosylated, glycophosphatidylinositol (GPI)-anchored cell surface protein. Its expression is dynamic during cellular differentiation and ligand interaction. While several decades of research have established that CD24 engages in many cell-type specific functions in many cases the ligands of CD24 are unknown, and researchers have relied on the use of antibodies to mimic ligand binding. Furthermore, as a GPI-anchored protein, CD24 must rely on in cis signalling partners, however little has been elucidated on the cell membrane-proximal signalling activities of CD24. Therefore, the work presented in this thesis presents a more comprehensive examination of CD24 expression, and function in multiple cell types, followed by an in-depth analysis in immature B lymphocytes. In B cells, CD24 is known to mediate the induction of apoptosis. To predict in cis and in trans partners of CD24, an analysis of CD24 mRNA expression, and its potential ligands was performed. In some tissues, such as B cells, an association was identified between CD24 and putative ligands, including Siglec-2. In other tissues, no significant associations were identified. Our previous investigation suggested that CD24 is involved in vesicle trafficking, Consistent with this, CD24 surface protein expression was shown to be dynamic within 1 h of Ab stimulation in WEHI-231 immature B cells and in ex vivo primary immature B cells. I found CD24 promotes the generation of plasma membrane-derived microvesicles (MVs). These MVs transported CD24 between cells. MVs also carried a variety of nucleic acid cargo, identified by RNA-Seq, and protein cargo as determined by mass spectrometry and flow cytometry. The incorporation of these cargos into MVs was variably influenced by CD24 stimulation. Overall, these data suggest that MVs generated in response to CD24 play a role in regulating mitochondria, and immune cell activation. Finally, a unifying hypothesis on the function of CD24 is presented herein, proposing its role as a moderating rheostat of cellular signalling rather than a de novo signalling receptor. Together, this work has significantly advanced our understanding of CD24 in B cells, and may provide insight for studies in other cell types or in diseases such as leukemia

A finite element study of fatigue crack propagation in single lap bonded joint with process-induced disbond

This paper presents a method for predicting fatigue crack propagation in adhesive bonded composite joints with an initial full-width disbond using finite element analysis and numerical integration of the material's fatigue crack growth rate law. Fatigue tests were conducted on single lap joints. Crack lengths were monitored from four runout corners. In-situ crack growth measurements were performed by ink injection to identify the crack front profile during fatigue loading. The crack growth was modelled using a fracture mechanics criterion considering two different crack propagation patterns. The material's fatigue crack growth rate law was determined experimentally using the standard double cantilever beam and end notch flexure specimens. Using the total strain energy release rate and the two crack scenarios, the numerical model predicted the lower and upper bounds of the measured fatigue crack growth rates of the lap joint