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.

High technology nanocomposite fibres: Development of melt spun semi-aromatic polyamide nanocomposite fibres

Novel polyamide nanocomposite fibres have been produced by compounding semi aromatic Poly (m-xylene adipamide) (MXD6) and organophilic Montmorillonite (MMT). Partially orientated fibres (POF) of MXD6 nanocomposite were obtained by melt spinning on a multifilament fibre extrusion system at three different speeds. The effect of the drawing velocity
on the mechanical properties of the filaments has been determined. Tensile measurements indicated that the introduction of the nanoparticies by melt intercalation improves the tenacity and toughness of the resulting polyamide fibres. The microstructure of the nanocomposites was examined by X-ray diffraction and Transmission Electron Microscope (TEM) and shown to
be an exfoliated disordered structure. The thermal stability of MXD6 nanocomposites was analysed by thermo gravimetric analysis (TGA) suggesting stabilisation of the clay and the polymer systems above 450°C.

Novel nanocomposite fibres for technical textile applications : synthesis and characterisation of poly(m-xylene adipamide) montmorillonite nanocomposites

Technical textiles, based on advanced polymeric materials, are an important segment of the synthetic textile market. This area has seen considerable growth in recent times, now accounting for almost 25% of all manufactured synthetic fibres, and has driven the recent development of a range of specialist high performance polymer fibres that are stronger, lighter or have improved heat and fire resistance. However, the increasing size of the market has highlighted the need for materials that have improved performance whilst maintaining low manufacturing costs. These factors have resulted in a change in how new specialty fibres are developed and the emphasis in this field is now on the upgrading or improving of the properties of commodity (conventional) fibres by modifying their properties to suit specific applications.

This paper will describe our work on preparing novel polymer nanocomposite fibres by the addition of clay nanoparticles during melt extrusion. The effect of the nanoparticles on the processing of the fibres and the result on the physical morphology and mechanical properties will be described.

Consistent model predictions for isothermal cure kinetics investigation of high performance epoxy prepregs

An accurate kinetics model is essential for understanding the curing mechanism and predicting the end properties of polymer materials. Graphite/epoxy AS4/ 8552 prepreg is a recent high-performance thermosetting composite modified with thermoplastic, which is being used in the manufacture of aircraft and military structures. The isothermal cures of this system along with another thermoplastic toughened high-performance prepreg, the T800H/3900-2 system, were investigated by real-time Fourier transform infrared (FTIR) spectroscopy. The cure rate was quantitatively analyzed based on the concentration profiles of both the epoxy and primary amine groups. Three autocatalytic models were used to determine kinetics parameters for both composite systems. The model which utilizes an empirical term, the final relative conversion (at different isothermal curing temperatures), describes the experimental data of both systems more satisfactorily than the model which applies a diffusion factor. The modeling results suggest that the curing of epoxy within both prepregs can be assumed to be a second order process.

固化条件对热塑增韧环氧树脂的固化动力学和相分离的影响

Thermoplastic toughened epoxy resins are widely used as matrices in modern prepreg systems.Different curing conditions play a great role in affecting the cure kinetics and phase behaviour of thermoplastic modified epoxies which further result in different mechanical properties of polymer matrix composites.Since the morphology of the cured thermoplastic/epoxy blends is directly related to the mechanical properties,it is essential to control processing conditions for obtaining desirable morphology.A polyethersulphone (PES) modified multifunctional epoxies,triglycidylaminophenol (TGAP) and tetraglycidyldiaminodiphenylmethane (TGDDM),was used for investigation.The cure kinetics and cured morphology of polymer blends heated at different heating rates and cured at different temperature were studied.It is shown that higher cure temperature and higher heating rate display similar effects in the epoxy conversion and the domain size of phase separated structure.

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Influence of helium atmospheric plasma treatment on surface and fracture-mechanical behaviour of quickstepTM cured bio-composites

This work investigated the potential of improving flexural properties of natural fiber (jute) reinforced biocomposites by atmospheric pressure helium plasma treatment. Composites were made by the use of combined hand lay-up and vacuum bagging technique followed by newly developed Australia patented Quickstep^TM curing. The physical properties of helium plasma modified fibers were investigated by means of wettability time, coefficient of friction (COF), atomic force microscopy (AFM) and chemical nature of the surface with ATR-FTIR and XPS. There was found a logical correlation between physical and chemical characteristics of the surface of fiber with the fracture mechanical behavior of their resulting biocomposites. In addition, the use of helium atmospheric plasma treatment prior to Quickstep^TM process has proved to be a potential way to positively alter the fracture-mechanical behavior of biocomposites. This study will lead to new commercial applications of natural fiber jute for the composite industry that go beyond wrapping and packaging.

Surface analysis of environmentally exposed painted composites manufactured from Quickstep and autoclave processes

The surface finishes of laminates produced by Quickstep™ and autoclave processes for use in automotive outer skin panels were compared. Automotive quality, painted carbon fibre samples, manufactured via both processes, were exposed to typical exposure environments including combinations of temperature (70, 120, 170°C), UV-B, humidity (95% RH) and immersion in water.

The microscopy and surface roughness results demonstrated that the surfaces produced by the Quickstep process were less susceptible to damage in the aging environments than the surfaces of the autoclaved samples. Quickstep samples displayed surface bubbling of only 5 μm, compared to the autoclaved surface bubbles which reached a diameter of 30 mm before bursting, with complete delamination occurring between the paint and the composite. The surface roughness measurements revealed the autoclave samples (Ra = 0.72 μm) were up to three times the roughness of the Quickstep samples (Ra = 0.23 μm).

Does baiting influence the relative composition of the diet of foxes?

The changes in the diet of foxes (Vulpes vulpes) in the Jervis Bay Region was assessed following a long-term baiting program by analysing the composition of fox faecal excreta (scats). In all, 470 fox scats were collected between April and August 2003 from two baited sites, Booderee National Park (BNP) and Beecroft Peninsula, and from two unbaited sites in the southern and northern parts of Jervis Bay National Park (SJBNP and NJBNP respectively). Diet was compared between these sites and mammalian diet was also compared from scats collected before baiting in 1996 and after baiting in 2000 at Beecroft Peninsula and in 2001 at Booderee National Park. In 2003, the most common species consumed by foxes was the common ringtail possum (Pseudocheirus peregrinus), except at unbaited NJBNP, where the swamp wallaby (Wallabia bicolor) was the most frequent dietary item. Significant dietary differences were found between unbaited and baited sites, with the long-nosed bandicoot (Perameles nasuta) and P. peregrinus featuring more in the diet of foxes from the baited sites. Marked increases in the frequency of occurrence of P. peregrinus and P. nasuta in fox scats occurred from before baiting through to after baiting. Relative fox abundance, as indexed by the number of scats collected per kilometre, was lowest in Booderee, followed by Beecroft, then SJBNP, with NJBNP having the highest relative abundance of foxes. We suggest that baiting did affect the diet of foxes on both peninsulas and that the dietary changes across baiting histories were intrinsically related to an increase in abundance in some taxa as a result of relaxed predator pressure following sustained fox control. However, the lack of unbaited control sites over the whole study precludes a definitive conclusion.

Entrepreneurship in Mexico : lessons for stakeholders in New Zealand

A “neighbour” separated by 6,000 km of Pacific, Mexico is by far New Zealand’s largest trading partner in Latin America and its 15th largest overall. With two-way trade worth NZ$584 million in 2002, many Mexicans grow up on New Zealand milk powder and baby formula. Not only is Mexico’s population of 100 million a huge potential economic partner in its own right, through its network of free trade agreements, Mexico has preferential access to 860 million consumers in 32 countries covering sixty percent of the world’s GDP.

Like New Zealand, Mexico is a “New World” country open to new ideas and innovation. Also like New Zealand, Mexico is known internationally for economic reforms that have created two outward-looking, world-trading, and competitive economies. During the last 50 years, the Mexican economy has shifted away from the once dominant sectors of agriculture and mining toward more industrial activities, especially in the major urban centres of Mexico City, Monterrey, Guadalajara, and other regional centres, where entrepreneurs are concentrated. With this shift, a new class of entrepreneurs arose with the support of the government.

One of those regional centres is the State of Sinaloa, with its capital city, Culiacán. Spearheaded by a visionary government and personified by the Secretary of Economic Development, Heriberto Felix Guerra. Secretary Felix is himself restaurant entrepreneur who owns a growing chain of “concept food” restaurants in the region.

It is no accident that when New Zealand Prime Minister Helen Clark visited Mexican President Vicente Fox Quesada on 15 November 2001, one of the topics of conversation was the fact that very day their two countries had been benchmarked as two of the world’s most entrepreneurial countries in the Global Entrepreneurship Monitor 2001 survey.

More germane, both countries have low-aspiration entrepreneurs who generate low levels of wealth and have low potential for growth. Both are dominated by micro-businesses that do not have high-value-added components and are not investment-ready and pre-qualified for risk capita.

This leads to the question, what can New Zealanders learn from the experience of Mexican entrepreneurship?

Assessing the strain experienced by managers and professional Australian footballers using an augmented job strain model

Generic models of job stress, such as the Job Strain Model (JSM), have recently been criticised for focusing on a small number of general work characteristics while ignoring those that are occupation-specific (Sparks & Cooper, 1999). However this criticism is based on limited research that has not examined the relative influence of all three dimensions of the JSM - job demand, job control and social support - and job-specific stressors. The JSM is the most commonly used model underpinning large-scale occupational stress research (Fox, Dwyer, & Ganster, 1993) and is regarded as the most influential model in the research on the psycho-social work environment, stress and disease in recent times (Kristensen, 1995). This thesis addresses the lack of information on the relative influence of the JSM and job-specific stressors by assessing the capacity of an augmented JSM to predict the strain experienced by managers and professional Australian footballers. The augmented JSM consisted of job-specific stressors in addition to the generic components of the model. Managers and professional Australian footballers represent two very different occupational groups. While the day-today roles of a manager include planning, organising, monitoring and controlling (Carroll & Gillen, 1987), the working life of a professional Australian footballer revolves around preparing for and playing football (Shanahan, 1998). It was expected that the large differences in the work undertaken by managers and professional Australian footballers would maximise the opportunities for identifying job-specific stressors and measuring the extent that these vary from one group to the next. The large disparity between managers and professional footballers was also used to assess the cross-occupational versatility of the JSM when it had been augmented by job-specific stressors. This thesis consisted of three major studies. Study One involved a survey of Australian managers, while studies Two and Three focused on professional Australian footballers. The latter group was under-represented in the literature, and as a result of the lack of information on the stressors commonly experienced by this group, an in-depth qualitative study was undertaken in Study Two. The results from Study Two then informed the survey of professional footballers that was conducted in Study Three. Contrary to previous research examining the relative influence of generic and job-specific stressors, the results only provided moderate support for augmenting the JSM with job-specific stressors. Instead of supporting the versatility of the augmented JSM, the overall findings reinforced the broad relevance of the original JSM. Of the four health outcomes measured in Studies One and Three, there was only one - the psychological health of professional Australian footballers - where the proportion of total variance explained by job-specific stressors exceeded 13%. Despite the generally strong performance of the JSM across the two occupational groups, the importance of demand, control and support diminished when examining the less conventional occupation of professional football. The generic model was too narrow to capture the highly specific work characteristics that are important for this occupational group and, as a result, the job-specific stressors explained significantly more of the strain over and above that already provided by the generic model. These findings indicate that when investigating the stressors experienced by conventional occupational groups such as managers, the large amount resources required to identify job-specific stressors are unlikely to be cost-effective. In contrast, the influence of the more situation specific stressors is significantly greater in unconventional occupations and thus the benefits of identifying these non-generic stressors are more likely to outweigh the costs. Studies One and Three identified strong connections between job-specific stressors and important characteristics of the occupation being studied. These connections were consistent with previous research and suggest that before attempting to identify job-specific stressors, researchers need to first become familiar with the nature and context of the occupation. The final issue addressed in this thesis was the role of work and non-work support. The findings indicate that the support provided by supervisors and colleagues was a significant predictor of wellbeing for both managers and professional footballers. In contrast, the level of explained strain accounted for by non-work support was not significant. These results indicate that when developing strategies to protect and enhance employee well-being, particular attention should be given to monitoring and, where necessary, boosting the effectiveness of work-based support. The findings from this thesis have been fed back to the management and sporting communities via conference presentations and peer-reviewed journals (refer pp 220-221). All three studies have been presented at national and international conferences and, overall, were well received by participants. Similarly, the methods, results and major findings arising from Studies One and Two have been critiqued by anonymous reviewers from two international journals. These papers have been accepted for publication in 2001 and 2002 and feedback from the reviewers indicates that the findings represent a significant and unique contribution to the literature. The results of Study Three are currently under review by a sports psychology journal.