Study of the creep behaviour of stitched woven composites

An experimental and theoretical study of the tensile creep behaviour of woven fibre composites stitched with cotton, and carbon threads, along or perpendicular to the loading direction with different densities is presented. The results of creep tests, conducted at ambient temperature and various elevated temperatures with low to high stress levels are reported.

A social ecological model of ICT cooption : surveillance creep in the information age

A model for ICT cooption is introduced using the example of ’surveillance creep’ which is the phenomenon of increasing dataveillance as the result of the introduction of seemingly benign, useful and convenient technological artefacts. The model identifies and discusses five main components of ICT artefact development and deployment: design, properties, affordances, appropriation and agent interests and locates them in a complex interrelated social ecology. The model provides a way to empirically examine how and why technology favours particular social or organisational outcomes.

Characterization and analysis of delamination fracture and nanocreep properties in carbon epoxy composites manufactured by different processes

Delamination resistance and nanocreep properties of 2/2 twill weave carbon epoxy composites manufactured by hot press, autoclave, and Quickstep^TM process are characterized and analyzed. Quickstep is a fluid filled, balanced pressure heated floating mold technology, which is recently developed in Perth, Western Australia for the manufacture of advanced composite components. Mode I and Mode II interlaminar fracture toughness tests, and nanoindentation creep tests on matrix materials show that the fast ramp rate of the Quickstep process provides mechanical properties comparable to that of autoclave at a lower cost for composite manufacturing. Low viscosity during ramping process and good fiber wetting are believed to be the reasons that this process produces composites with high delamination and creep-resistant properties. Nanocreep properties are analyzed using a Kelvin–Voigt model.

Challenging librarians : the relevance of the doctorate in professional practice

We, as librarians, are adept at challenging academics, students and administrators about the crucial role of information literacy in higher education and lifelong learning. Consequently, the push for strategic partnerships with academics is frequently in the foreground of our thinking. Concomitantly, the push for academic status for librarians is raised occasionally, particularly as a pay and equity issue. Yet, our purposes may appear somewhat misguided or rhetorical when contrasted to the nominal prerequisites required for professional practice, especially when compared with those of academics. The issues of information literacy and knowledge production within a knowledge economy compound such debate. This paper argues that ‘credential creep’ is catching up with librarians in the university sector. In order to be regarded as integral to academic endeavour, those of us who ‘teach’ information literacy may need to match the qualifications normally required by academics. Consonant with this proposal is the Australian and New Zealand Information Literacy Framework: Principles, Standards and Practice (Bundy, 2004) of the Australian and New Zealand Institute for Information Literacy (ANZIIL) and the Council of Australian University Librarians (CAUL). The Framework mirrors many of the desired outcomes of a doctoral degree, a degree possessed by approximately one per cent of Australian librarians but, in comparison, by more than fi fty-four per cent of Australian academics. This paper challenges—not academics—but librarians, to embrace the notion of undertaking doctoral study to enhance our professional (or amateur) practice and our information literacy. The recommendation is derived in essence from my study on doctoral research and information literacy (Macauley, 2001). It also incorporates the current discourse on these issues and uses personal narrative to articulate the findings. It seeks also to explore those tensions and contradictions commensurate with practising what we preach.

Manufacturing process effects on the mode I interlaminar fracture toughness and nanocreep properties of CFRP

Quickstep ™ is a fluid filled floating mould technology which was recently developed by an Australian company of the same name. The Quickstep and conventional autoclave manufacture of composites were compared by investigating the mode I interlaminar fracture toughness and nanocreep propeties of HexPly914 carbon epoxy composites. It was found that composites cured using the Quickstep technology had significantly higher fracture toughness (1.8 times) than the composites cured via autoclave for this system. DMTA (dynamic mechanical thermal analysis) results showed a higher Tg (glass transition temperature) for the material manufactured by the Quickstep than that cured by the autoclave. FTIR (Fourier transform infrared spectroscopy) spectra did not indicate any difference in cure chemistry between the two processes. Nanocreep experiments were performed to explore the viscoelastic properties of the epoxy matrix of composites. The KelvinVoigt three-element model was applied to analyse the indentation creep behaviour of both composites.

Birds, buffers and bicycles : a review and case study of wetland buffers

Wetland buffers separate wetlands from surrounding land uses that are incompatible with wetland values. Buffers are established to fulfil a variety of needs. However, not all functions which are attributed to buffers are mutually compatible. In particular, their use as major recreational zones is not necessarily compatible with reducing disturbance to wetland wildlife, such as birds. This paper examines the buffer around an urban wetland at Altona, Victoria, which is extensively used by recreationists. The presence of a bicycle trail within the buffer might effectively reduce its size and effectiveness, and cause ‘buffer creep’ whereby the effective separation distance between people and birds is reduced. It might also unintentionally facilitate unauthorised access into an otherwise ‘off-limits’ wetland. While social support is critical for wetland conservation, the existence of recreation in buffers does not automatically confer high awareness of local wetlands. The success of buffers as a conservation tool will depend upon setting a clear objective for buffers, careful design and management, and evaluation of effectiveness to optimise the potential benefits for wetlands and their fauna.

Mechanical properties of aged Mg-4Y-3RE alloy

This paper describes tensile properties of a peak-aged Mg-4Y·3RE alloy at room temperature to 823 K with 10^-5 - 10^-1 s^-1. The Mg alloy exhibited high strength (> 250 MPa) at room temperature to 473 K. However. the strength rapidly decreased at 573 K. It is suggested that a large decrease in strength at 573 K is attributed to grain boundary sliding. Also, elongation increased rapidly at 723 - 823 K. This is likely to arise from the relatively high strain rate sensitivity of about 0.3 due to the glide-controlled dislocation creep.

Defect assessment procedures for high temperature applications : final report TW5-TTMS-005, D5

The objective of this task is to develop the high temperature part of a design code for fusion reactor components build from EUROFER. This development includes fracture mechanical rules for the assessment of detected defects under creep and creep–fatigue conditions. The assessment procedures R5, R6, JNC, A16, Partial Safety Factors were investigated and tested. As the most suitable procedure is chosen R5 and it is further verified by comparison with finite element simulations using the EUROFER material data. These simulations consist of evaluation of C(t) parameter for several geometries (CT specimen,cylinder with fully circumferential crack subjected to the internal pressure, cylinder with semi–elliptical circumferential crack subjected to the internal pressure and Mock-Up test blanket module (TBM) geometry). The R5 procedure provides very good accordance with FE simulations and it is suitable for lifetime assessment. Therefore the guide for R5 application is implemented in the report.

Artificial Muscles Based on Polypyrrole/Carbon Nanotube Laminates

A novel method for the periodical assembly of laminates of forest-drawn carbon nanotube (CNT) sheets and polypyrrole (PPy) is described. The method produces composite films in which the volume fraction and orientation of CNTs can be controlled. Actuator stroke and strength is increased and work capacity per cycle doubled when nanotube orientation is perpendicular to the actuation direction. Most importantly, these PPy/CNT laminates have dramatically decreased creep during actuation, which has been a major barrier for the application of PPy actuators.

Biomechanics of the sclera in myopia: Extracellular and cellular factors

Excessive axial elongation of the eye is the principal structural cause of myopia. The increase in eye size results from active remodelling of the sclera, producing a weakened scleral matrix. The present study will detail the biomechanics of the sclera and highlight the matrix and cellular factors important in the control of eye size. Scleral elasticity (load vs. tissue extension) and creep rate (tissue extension vs. time) have been measured postmortem in human eyes. Animal models of myopia have allowed the direct relevance of scleral biomechanics to be investigated during myopia development. Recently, data on tissue matrices incorporating scleral fibroblasts have highlighted the role of cellular contraction in scleral biomechanics. Scleral elasticity is increased in eyes developing myopia, with a reduction in the failure load of the tissue. Scleral creep rate is increased in the sclera from eyes developing myopia, and reduced in eyes recovering from myopia. These changes in biomechanical properties of the sclera occur early in the development of myopia (within 24 h). Alterations in scleral biomechanics during myopia development have been attributed to changes in matrix constituents, principally reduced collagen content. Although the biochemical structure of the sclera plays a critical role in defining the mechanical properties, recent studies investigating the cellular mechanics of the sclera, implicate myofibroblasts in scleral biomechanics. Scleral myofibroblasts have the capacity to contract the matrix and are regulated by tissue stress and growth factors such as transforming growth factor-ß. Changes in these regulatory factors have been observed during myopia development, implicating cellular factors in the resultant weakened sclera. Changes in the biomechanical properties of the sclera are important in facilitating the increase in axial length that results in myopia. Understanding the matrix and cellular factors contributing to the weakened sclera may aid in the development of a clinically appropriate treatment for myopia.

Properties of bio-based polymer nylon 11 reinforced with short carbon fiber composites

In this work, micro-composite materials were produced by incorporating 3-mm long reclaimed short carbon fibers into bio-based nylon 11 via melt compounding. A systematic fiber length distribution analysis was performed after the masterbatching, compounding and an injection moulding processes using optical microscopy images. It was found that the large majority of the fibers were within the 200-300 μm in length range after the injection moulding process. The mechanical (flexural and tensile), thermo-mechanical, and creep properties of the injection moulded materials are reported. We found that an enhancement in flexural and Young's modulus of 25% and 14%, respectively, could be attained with 2 wt% carbon fiber loading whilst no significant drawback on the ductility and toughness of the matrix was observed. The creep resistance and recovery of the nylon 11, tested using dynamic mechanical thermal analysis at room temperature and 65°C, was significantly improved by up to 30% and 14%, respectively, after loading with carbon fiber. This work provides an insight into the property improvement of the bio-based polymer nylon 11 using a small amount of a reclaimed engineered material. © 2014 Society of Plastics Engineers.

Experience and the artist's body : resisting the Uber-artist construct in socially engaged performance

Looking back over the past 20 years of my practice, the vista is littered with ambiguities of process and form within socially engaged performance. Sifting through the debris, one question arises: what have I been doing?; another might be: what have I been making? What feels relevant to me is the aggregate of my experiences; the who I am. With the current sector creep towards instrumentalising arts for social agendas, the value and relevance of experience ebbs. Demands on artists extend well beyond aesthetic skill, process facilitation and project management. In this essay, I critique the risk within socially engaged practice of art becoming subservient to social agendas and consider how the shift towards an uber-artist construct renders the sector unsustainable.

Investigation on the effect of cutting fluid pressure on surface quality measurement in high speed thread milling of brass alloy (C3600) and aluminium alloy (5083)

The quality of a machined finish plays a major role in the performance of milling operations, good surface quality can significantly improve fatigue strength, corrosion resistance, or creep behaviour as well as surface friction. In this study, the effect of cutting parameters and cutting fluid pressure on the quality measurement of the surface of the crest for threads milled during high speed milling operations has been scrutinised. Cutting fluid pressure, feed rate and spindle speed were the input parameters whilst minimising surface roughness on the crest of the thread was the target. The experimental study was designed using the Taguchi L32 array. Analysing and modelling the effective parameters were carried out using both a multi-layer perceptron (MLP) and radial basis function (RBF) artificial neural networks (ANNs). These were shown to be highly adept for such tasks. In this paper, the analysis of surface roughness at the crest of the thread in high speed thread milling using a high accuracy optical profile-meter is an original contribution to the literature. The experimental results demonstrated that the surface quality in the crest of the thread was improved by increasing cutting speed, feed rate ranging 0.41-0.45 m/min and cutting fluid pressure ranging 2-3.5 bars. These outcomes characterised the ANN as a promising application for surface profile modelling in precision machining.