title: Fibrillation - Improving the fibre/matrix adhesion of lyocell fibres for use in short fibre-reinforced and 3D printed composites

authors: Graupner, Nina

subjects: additive manufacturing

abstract: This study investigates the influence of fibrillation of lyocell fibres on the mechanical properties of
compression moulded polylactide (PLA), polypropylene (PP) composites, and 3D printed PLA
composites. Fibrillation was shown to reduce the strength and elongation at break of the fibres without
affecting the Young's modulus compared to untreated fibres. Nevertheless, fibrillation in composites
resulted in a 1.15 higher strength for PP composites and 1.62 for PLA composites. Young’s modulus
and impact strength were increased by factors of 1.41 and 1.38 for PP composites and 1.2 and 1.23 for
PLA composites. Applying the fibrillated fibres in 3D printed PLA shows a significant increase in the
mechanical properties. For example, with a fibre mass fraction of 30%, the tensile strength of the
composites with fibrillated fibres was increased by a factor of 1.18 compared to composites with
untreated fibres. The use of maleic anhydride in the PLA matrix in combination with composite heat
treatment further increased the strength by a factor of 1.46. With a strength of 85 MPa, a Young's
modulus of 7.2 GPa and an elongation at break of 3.2%, these are some of the highest values reported
for this kind of 3D printed materials.

text: Fibrillation - Improving the fibre/matrix adhesion of lyocell fibres for use in short fibre-reinforced and 3D printed composites This study investigates the influence of fibrillation of lyocell fibres on the mechanical properties of
compression moulded polylactide (PLA), polypropylene (PP) composites, and 3D printed PLA
composites. Fibrillation was shown to reduce the strength and elongation at break of the fibres without
affecting the Young's modulus compared to untreated fibres. Nevertheless, fibrillation in composites
resulted in a 1.15 higher strength for PP composites and 1.62 for PLA composites. Young’s modulus
and impact strength were increased by factors of 1.41 and 1.38 for PP composites and 1.2 and 1.23 for
PLA composites. Applying the fibrillated fibres in 3D printed PLA shows a significant increase in the
mechanical properties. For example, with a fibre mass fraction of 30%, the tensile strength of the
composites with fibrillated fibres was increased by a factor of 1.18 compared to composites with
untreated fibres. The use of maleic anhydride in the PLA matrix in combination with composite heat
treatment further increased the strength by a factor of 1.46. With a strength of 85 MPa, a Young's
modulus of 7.2 GPa and an elongation at break of 3.2%, these are some of the highest values reported
for this kind of 3D printed materials.

year: 2024

title: Sink or swim? Sleep in highly trained adolescent swimmers during the in-season phase of training

authors: Ashby, Claudia Renee Georgia

abstract: Sleep is vital to the physiological and cognitive functioning in humans, however, disruption to sleep is a growing issue. Requirements of training in high performing adolescent athletes is increasing but it is largely unknown what effect this has upon their sleep. Extra-curricular activities such as sport, music, and part-time work are all contributing factors to the sleep disturbances adolescents’ experience. Until now, limited research has been available on high performing adolescent athletes sleep as most research has focused on sleep in elite adult athletes. Research to date has illustrated that elite adult athletes experience disruptions to their sleep due to training and competitions which subsequently impacts their recovery, performance and fatigue. The few studies to investigate adolescent athletes have found that sleep has significant effects on injury occurrence, academic performance, mental health, and obesity, as discussed in the literature review in the first chapter of this thesis. Furthermore, through the limited previous research, it has been found that adolescent athletes sleep is disrupted on nights preceding early morning training sessions. The second chapter of this thesis includes an original study investigating the sleep of highly trained adolescent swimmers. Fifteen adolescent swimmers volunteered to participate in this study, where their sleep was measured via subjective and objective measures over a two-week ‘normal’ in-season training phase. Participants subjectively recorded their total sleep time (TST), sleep latency (SL), and wake episodes (WE) through a daily sleep diary. In conjunction, objective sleep indices (TST, SL, WE, total time in bed (TTB), wake after sleep onset (WASO), sleep efficiency (SE), sleep onset time (SOT), and wake time (WT) were measured through a wrist actigraph device. Analysis revealed that participants significantly overestimated their sleep duration by approximately one hour per night compared to their objective TST. Furthermore, on evenings preceding early morning training (EARLY), participants TST and TTB was significantly less compared to nights preceding day trainings (DAY) and rest days (REST). Finally, the third chapter of this thesis summarises the overall findings of the thesis, as well as highlighting practical applications, and potential future research directions.

text: Sink or swim? Sleep in highly trained adolescent swimmers during the in-season phase of training Sleep is vital to the physiological and cognitive functioning in humans, however, disruption to sleep is a growing issue. Requirements of training in high performing adolescent athletes is increasing but it is largely unknown what effect this has upon their sleep. Extra-curricular activities such as sport, music, and part-time work are all contributing factors to the sleep disturbances adolescents’ experience. Until now, limited research has been available on high performing adolescent athletes sleep as most research has focused on sleep in elite adult athletes. Research to date has illustrated that elite adult athletes experience disruptions to their sleep due to training and competitions which subsequently impacts their recovery, performance and fatigue. The few studies to investigate adolescent athletes have found that sleep has significant effects on injury occurrence, academic performance, mental health, and obesity, as discussed in the literature review in the first chapter of this thesis. Furthermore, through the limited previous research, it has been found that adolescent athletes sleep is disrupted on nights preceding early morning training sessions. The second chapter of this thesis includes an original study investigating the sleep of highly trained adolescent swimmers. Fifteen adolescent swimmers volunteered to participate in this study, where their sleep was measured via subjective and objective measures over a two-week ‘normal’ in-season training phase. Participants subjectively recorded their total sleep time (TST), sleep latency (SL), and wake episodes (WE) through a daily sleep diary. In conjunction, objective sleep indices (TST, SL, WE, total time in bed (TTB), wake after sleep onset (WASO), sleep efficiency (SE), sleep onset time (SOT), and wake time (WT) were measured through a wrist actigraph device. Analysis revealed that participants significantly overestimated their sleep duration by approximately one hour per night compared to their objective TST. Furthermore, on evenings preceding early morning training (EARLY), participants TST and TTB was significantly less compared to nights preceding day trainings (DAY) and rest days (REST). Finally, the third chapter of this thesis summarises the overall findings of the thesis, as well as highlighting practical applications, and potential future research directions.

year: 2021

title: 'Entitled to a History': The World of Alice Tawhai's Short Stories and the Maori Literary Tradition

authors: Modlik, Kimberley

subjects: Alice Tawhai

abstract: New Zealand short story writer Alice Tawhai is one of the latest additions to the Maori literary tradition. Her three collections of short stories, Festival of Miracles, Luminous and Dark Jelly, deal with issues not entirely unique to New Zealand – from gang life, to domestic violence, to drug and alcohol abuse – and take as their primary subject an alienated, marginalized and disenfranchised underclass. This means she is likely to be read as speaking solely for the Maori experience.  This thesis will revise this misconception, which in effect ghettoizes or marginalizes Tawhai’s work.

Influential women writers of the Maori literary tradition, such as J. C. Sturm, Patricia Grace and Keri Hulme, have taken a particular interest in the long legacy of colonialism in New Zealand, especially of the impact of that legacy on Maori women. This thesis demonstrates that while Tawhai’s work engages with these familiar notions, her gaze is not limited to these issues. This thesis therefore places Tawhai’s work within that tradition and matrilineal genealogy before going on to show how she moves the paradigm beyond the usual grievances of biculturalism and colonialism, orienting her work instead around the increasingly multicultural experience of contemporary life in New Zealand.

The first section of this thesis will establish a platform for reading Tawhai in regards to her literary legacy and in the context of contemporary thinking, drawing on cultural theorist Stuart Hall and his theory on identity formation and identity politics as well as indigenous writings experts Patrick Evans and Chadwick Allen. This thesis will then move into its second section, which is an analysis of some of the overarching themes that can be found in the short stories of Tawhai’s literary foremothers, Sturm, Grace and Hulme. These include, for example, racism and discrimination, loss of ancestral lands, problems to do with urbanization and family violence.

The third and final section of this thesis will then consider Tawhai’s representation of contemporary experience, taking a particular interest in her portrayals of contemporary multicultural ethnic identities as well as the flexible and provisional nature of gendered and sexual identities today. The final subsection will then analyze her representations of the new family and social structures that may have replaced the traditional family model.

Through a close reading of her short stories and an appreciation of the legacy that she bears, this thesis will show how Tawhai’s work is a larger lens of contemporary New Zealand society as well as a significant addition to the Maori literary tradition.

text: 'Entitled to a History': The World of Alice Tawhai's Short Stories and the Maori Literary Tradition New Zealand short story writer Alice Tawhai is one of the latest additions to the Maori literary tradition. Her three collections of short stories, Festival of Miracles, Luminous and Dark Jelly, deal with issues not entirely unique to New Zealand – from gang life, to domestic violence, to drug and alcohol abuse – and take as their primary subject an alienated, marginalized and disenfranchised underclass. This means she is likely to be read as speaking solely for the Maori experience.  This thesis will revise this misconception, which in effect ghettoizes or marginalizes Tawhai’s work.

Influential women writers of the Maori literary tradition, such as J. C. Sturm, Patricia Grace and Keri Hulme, have taken a particular interest in the long legacy of colonialism in New Zealand, especially of the impact of that legacy on Maori women. This thesis demonstrates that while Tawhai’s work engages with these familiar notions, her gaze is not limited to these issues. This thesis therefore places Tawhai’s work within that tradition and matrilineal genealogy before going on to show how she moves the paradigm beyond the usual grievances of biculturalism and colonialism, orienting her work instead around the increasingly multicultural experience of contemporary life in New Zealand.

The first section of this thesis will establish a platform for reading Tawhai in regards to her literary legacy and in the context of contemporary thinking, drawing on cultural theorist Stuart Hall and his theory on identity formation and identity politics as well as indigenous writings experts Patrick Evans and Chadwick Allen. This thesis will then move into its second section, which is an analysis of some of the overarching themes that can be found in the short stories of Tawhai’s literary foremothers, Sturm, Grace and Hulme. These include, for example, racism and discrimination, loss of ancestral lands, problems to do with urbanization and family violence.

The third and final section of this thesis will then consider Tawhai’s representation of contemporary experience, taking a particular interest in her portrayals of contemporary multicultural ethnic identities as well as the flexible and provisional nature of gendered and sexual identities today. The final subsection will then analyze her representations of the new family and social structures that may have replaced the traditional family model.

Through a close reading of her short stories and an appreciation of the legacy that she bears, this thesis will show how Tawhai’s work is a larger lens of contemporary New Zealand society as well as a significant addition to the Maori literary tradition.

year: 2014