title: Evaluation of composite laminates interleaved with nanofibre and microfibre veils.

authors: Collins-Gargan, Rosalie

abstract: The research covered in this thesis aimed to investigate the use of nanofibre and microfibre veils in carbon fibre reinforced composites and assessed the potential of the veils to improve damage resistance during impact and fatigue loading. It was hypothesised that the interleavings would increase the amount of energy required for crack propagation because of toughening due to fibre reinforcement mechanisms such as crack deflection, fibre pull out and fibre breakage. The work was undertaken as a combined project between the University of Waikato (Hamilton, New Zealand) and Revolution Fibres Ltd (Auckland, New Zealand). 
During this investigation, six thermoplastic polymers were chosen (acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), polystyrene (PS), chlorinated polyvinyl chloride (CPVC), polymethyl methacrylate (PMMA) and polycarbonate (PC)) that could potentially be used for the electrospinning of polymer nanofibre veils. Nanofibre veils were successfully produced from PMMA, and a polymer blend of polyamide 6,6 (PA6,6) and PMMA, (referred to as 'nanoNyplex'). These veils, along with three other nanofibre veils (nanoPA6,6, poly vinyl butyral (nanoPVB), and poly ether sulfone (nanoPES)), three microfibre veils (polyphenylene sulfide (microPPS), polyetherimide (microPEI), and woven polyamide 6 (microtricot)) procured from other manufacturers, and three veils combining one of the nanofibre veils with each of the microfibre veils (microPPSnanoPA6,6, microPEInanoPA6,6, and microtricotnanoPA6,6) were then used as interleaves in the manufacture of carbon fibre reinforced epoxy composite panels. Interleaves were placed between every ply of prepreg. After curing the panels, test specimens were created to assess fatigue, vibration damping and compression after impact performance.
From the vibration damping study, it was found that the nanoNyplex interleaving improved damping the most. It was thought that energy dissipation was due friction brought about by the movement of the interleaving fibres in the matrix, resulting in friction due to weak adhesion between the nanoNyplex fibres and the epoxy matrix.
From the compression after impact (CAI) section of this study, it was found that specimens interleaved with nanoPA6,6, microPPS and microPPSnanoPA6,6 had the highest CAI strengths. From optical inspection, it appeared (in general) that as the CAI strength of the specimen increased, the length of the damage region also increased. However, those identified with the highest CAI strengths had shorter damage regions.
From the fatigue section of this study, it was found that the use of most interleavings, (apart from microtricot) increased the number of cycles to failure. Post fatigue test scanning electron microscopy confirmed that crack deflection was present for most interleaved specimens. Some evidence of pull out and breakage of the interleaving fibres was seen on the fracture surfaces of the nanoPA6,6, microPPS, microPEI, microPEInanoPA6,6 and microPPSnanoPA6,6 interleaved specimens.
For both CAI and fatigue, it was found that improvement was generally greater with veils that had a large number of fibres per unit area and high adhesion strength with the matrix. However, for CAI it seems that high fracture toughness was also desirable.

text: Evaluation of composite laminates interleaved with nanofibre and microfibre veils. The research covered in this thesis aimed to investigate the use of nanofibre and microfibre veils in carbon fibre reinforced composites and assessed the potential of the veils to improve damage resistance during impact and fatigue loading. It was hypothesised that the interleavings would increase the amount of energy required for crack propagation because of toughening due to fibre reinforcement mechanisms such as crack deflection, fibre pull out and fibre breakage. The work was undertaken as a combined project between the University of Waikato (Hamilton, New Zealand) and Revolution Fibres Ltd (Auckland, New Zealand). 
During this investigation, six thermoplastic polymers were chosen (acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), polystyrene (PS), chlorinated polyvinyl chloride (CPVC), polymethyl methacrylate (PMMA) and polycarbonate (PC)) that could potentially be used for the electrospinning of polymer nanofibre veils. Nanofibre veils were successfully produced from PMMA, and a polymer blend of polyamide 6,6 (PA6,6) and PMMA, (referred to as 'nanoNyplex'). These veils, along with three other nanofibre veils (nanoPA6,6, poly vinyl butyral (nanoPVB), and poly ether sulfone (nanoPES)), three microfibre veils (polyphenylene sulfide (microPPS), polyetherimide (microPEI), and woven polyamide 6 (microtricot)) procured from other manufacturers, and three veils combining one of the nanofibre veils with each of the microfibre veils (microPPSnanoPA6,6, microPEInanoPA6,6, and microtricotnanoPA6,6) were then used as interleaves in the manufacture of carbon fibre reinforced epoxy composite panels. Interleaves were placed between every ply of prepreg. After curing the panels, test specimens were created to assess fatigue, vibration damping and compression after impact performance.
From the vibration damping study, it was found that the nanoNyplex interleaving improved damping the most. It was thought that energy dissipation was due friction brought about by the movement of the interleaving fibres in the matrix, resulting in friction due to weak adhesion between the nanoNyplex fibres and the epoxy matrix.
From the compression after impact (CAI) section of this study, it was found that specimens interleaved with nanoPA6,6, microPPS and microPPSnanoPA6,6 had the highest CAI strengths. From optical inspection, it appeared (in general) that as the CAI strength of the specimen increased, the length of the damage region also increased. However, those identified with the highest CAI strengths had shorter damage regions.
From the fatigue section of this study, it was found that the use of most interleavings, (apart from microtricot) increased the number of cycles to failure. Post fatigue test scanning electron microscopy confirmed that crack deflection was present for most interleaved specimens. Some evidence of pull out and breakage of the interleaving fibres was seen on the fracture surfaces of the nanoPA6,6, microPPS, microPEI, microPEInanoPA6,6 and microPPSnanoPA6,6 interleaved specimens.
For both CAI and fatigue, it was found that improvement was generally greater with veils that had a large number of fibres per unit area and high adhesion strength with the matrix. However, for CAI it seems that high fracture toughness was also desirable.

year: 2015

title: From pillow to podium: a review on understanding sleep for elite athletes

authors: O'Donnell, Shannon Lea

subjects: exercise

abstract: Sleep is considered vital to human health and well-being, and is critical to physiological and cognitive functioning. Elite athletes experience high training and competition demands, and are often exposed to various factors, situations, and environments that can cause sleep impairments. Previous research has shown that athletes commonly experience sleep loss in the lead up to and following competition, which could have significant impacts on their preparation, performance, and recovery. In particular, the results from previous research show significant reductions in total sleep time (~1:40 h:min) and significant increases in sleep latency (~45 minutes) following evening competition. Napping is common in both the training and competition setting in athletes; however, research on the effect of napping on physiology and performance is limited. In contrast, research on strategies and interventions to improve sleep are increasing in the athletic population, with sleep hygiene research resulting in significant improvements in key sleep indices. This review investigates the physiological importance of sleep in athletes, current tools to monitor athletes’ sleep, the role of sleep for cognitive functioning and athletic performance, the prevalence of sleep disturbances and the potential mechanisms causing sleep disturbances, the role of napping, and different intervention strategies to improve sleep.

text: From pillow to podium: a review on understanding sleep for elite athletes Sleep is considered vital to human health and well-being, and is critical to physiological and cognitive functioning. Elite athletes experience high training and competition demands, and are often exposed to various factors, situations, and environments that can cause sleep impairments. Previous research has shown that athletes commonly experience sleep loss in the lead up to and following competition, which could have significant impacts on their preparation, performance, and recovery. In particular, the results from previous research show significant reductions in total sleep time (~1:40 h:min) and significant increases in sleep latency (~45 minutes) following evening competition. Napping is common in both the training and competition setting in athletes; however, research on the effect of napping on physiology and performance is limited. In contrast, research on strategies and interventions to improve sleep are increasing in the athletic population, with sleep hygiene research resulting in significant improvements in key sleep indices. This review investigates the physiological importance of sleep in athletes, current tools to monitor athletes’ sleep, the role of sleep for cognitive functioning and athletic performance, the prevalence of sleep disturbances and the potential mechanisms causing sleep disturbances, the role of napping, and different intervention strategies to improve sleep.

year: 2018

title: Kia matatau ki te reo: Factors influencing the development of proficiency in te reo Māori with adult learners

authors: Rātima, Matiu Tai

subjects: te reo Māori

abstract: This thesis sought to answer the question: what factors help or hinder adult Māori second language learners to become proficient speakers of te reo Māori? I ask this question at a moment in history when te reo, like other indigenous languages, sits on the edge of a precipice in terms of its survival as a living language. Ambivalence and inaction will almost certainly constitute a push towards oblivion. Nothing less than concerted effort can pull te reo back from the brink. But what kind of concerted effort is needed and how can individual learners optimise their efforts to learn te reo?
Te reo must survive because, as Sir James Henare put it, ‘ko te reo te hā o te Māoritanga’, meaning ‘the language is the essence of Māori culture.’ Without te reo the very survival of Māori people as Māori is in doubt. My questions and the thesis occupy a multidisciplinary space, drawing on research from adult second language acquisition, teaching pedagogy and language revitalisation. The thesis makes an original contribution to all three bodies of literature by examining data from a previously untapped source; successful adult Māori language learners. 
I interviewed 17 participants. All highly proficient second language speakers of te reo. All learned te reo as adults.  Adult second language learning of endangered languages is broadly acknowledged in Second Language Acquisition (SLA) as essential to re-establishing Intergenerational Transmission of Language (ITL) in the home to ensure an endangered language is passed on to future generations.
The interview questionnaire was based loosely on 10 help/hinder factors I identified through a review of the literature from the three research fields (adult second language acquisition, teaching pedagogy and language revitalisation). The ten factors identified in the review were; language aptitude, age, learner attitudes and motivation, learning strategies, instruction, agency and anxiety, wairua (the spiritual dimension), demography, language status, and language planning.

text: Kia matatau ki te reo: Factors influencing the development of proficiency in te reo Māori with adult learners This thesis sought to answer the question: what factors help or hinder adult Māori second language learners to become proficient speakers of te reo Māori? I ask this question at a moment in history when te reo, like other indigenous languages, sits on the edge of a precipice in terms of its survival as a living language. Ambivalence and inaction will almost certainly constitute a push towards oblivion. Nothing less than concerted effort can pull te reo back from the brink. But what kind of concerted effort is needed and how can individual learners optimise their efforts to learn te reo?
Te reo must survive because, as Sir James Henare put it, ‘ko te reo te hā o te Māoritanga’, meaning ‘the language is the essence of Māori culture.’ Without te reo the very survival of Māori people as Māori is in doubt. My questions and the thesis occupy a multidisciplinary space, drawing on research from adult second language acquisition, teaching pedagogy and language revitalisation. The thesis makes an original contribution to all three bodies of literature by examining data from a previously untapped source; successful adult Māori language learners. 
I interviewed 17 participants. All highly proficient second language speakers of te reo. All learned te reo as adults.  Adult second language learning of endangered languages is broadly acknowledged in Second Language Acquisition (SLA) as essential to re-establishing Intergenerational Transmission of Language (ITL) in the home to ensure an endangered language is passed on to future generations.
The interview questionnaire was based loosely on 10 help/hinder factors I identified through a review of the literature from the three research fields (adult second language acquisition, teaching pedagogy and language revitalisation). The ten factors identified in the review were; language aptitude, age, learner attitudes and motivation, learning strategies, instruction, agency and anxiety, wairua (the spiritual dimension), demography, language status, and language planning.

year: 2013