title: Using micro-mechanical modelling to predict short-fibre composite properties in computer-aided design of sporting equipment

authors: Ewart, Paul

subjects: flexural modulus

abstract: Computer-aided design (CAD) of sporting equipment requires knowledge of the mechanical properties of proposed materials. The mechanical properties of composite materials are often not as simple to obtain as those of conventional materials, in which case micro-mechanical modelling could be used in conjunction with CAD software. A micro-mechanical model was used to predict the flexural modulus of composite materials, based on the assumption of partial interfacial adhesion between composite components. It was found that the partial adhesion model was both practical and consistently accurate. The partial adhesion model accounted for adhesion between components by considering an ‘effective shear value’ at the interface. The model was compared to experimental data for glass, wood and carbon-fibre reinforced polyethylene. It was shown that the adhesion coefficient ranged between 0.1 for carbon fibre, 0.5 for glass fibre and 0.8 for the wood fibre composites. It was shown that using micro-mechanical modelling to predict composite mechanical properties, as opposed to simulating the comprehensive composites structure, computer processing time and file size can be reduced with little compromise in simulation accuracy.

text: Using micro-mechanical modelling to predict short-fibre composite properties in computer-aided design of sporting equipment Computer-aided design (CAD) of sporting equipment requires knowledge of the mechanical properties of proposed materials. The mechanical properties of composite materials are often not as simple to obtain as those of conventional materials, in which case micro-mechanical modelling could be used in conjunction with CAD software. A micro-mechanical model was used to predict the flexural modulus of composite materials, based on the assumption of partial interfacial adhesion between composite components. It was found that the partial adhesion model was both practical and consistently accurate. The partial adhesion model accounted for adhesion between components by considering an ‘effective shear value’ at the interface. The model was compared to experimental data for glass, wood and carbon-fibre reinforced polyethylene. It was shown that the adhesion coefficient ranged between 0.1 for carbon fibre, 0.5 for glass fibre and 0.8 for the wood fibre composites. It was shown that using micro-mechanical modelling to predict composite mechanical properties, as opposed to simulating the comprehensive composites structure, computer processing time and file size can be reduced with little compromise in simulation accuracy.

year: 2010

title: Reactive compatibilization of harakeke fiber-reinforced poly(lactic) acid/polybutylene succinate blend

authors: Akindoyo, John O.

abstract: Different blends of poly(lactic acid) (PLA) and polybutylene succinate (PBS), and their harakeke fiber-reinforced composites were studied. Scanning electron microscopy showed that the PLA and PBS are incompatible and poorly miscible. Tensile strength and tensile modulus of the blends were found to reduce as the amount of PBS increased. Reinforcement alone was not able to significantly improve the mechanical performance of the blend, which is lower than that of neat PLA. Therefore, simultaneous reinforcement and reactive compatibilization were performed using harakeke fiber, and dicumyl peroxide as reinforcement and compatibilizer, respectively. This produced about 201% increase in the crystallinity of PLA. Compared with the PLA/PBS blend, the dual effect approach increased the tensile strength and tensile modulus by 31% and 148%, respectively. Likewise, dynamic mechanical analysis showed that the thermomechanical properties of the composite greatly improved.

text: Reactive compatibilization of harakeke fiber-reinforced poly(lactic) acid/polybutylene succinate blend Different blends of poly(lactic acid) (PLA) and polybutylene succinate (PBS), and their harakeke fiber-reinforced composites were studied. Scanning electron microscopy showed that the PLA and PBS are incompatible and poorly miscible. Tensile strength and tensile modulus of the blends were found to reduce as the amount of PBS increased. Reinforcement alone was not able to significantly improve the mechanical performance of the blend, which is lower than that of neat PLA. Therefore, simultaneous reinforcement and reactive compatibilization were performed using harakeke fiber, and dicumyl peroxide as reinforcement and compatibilizer, respectively. This produced about 201% increase in the crystallinity of PLA. Compared with the PLA/PBS blend, the dual effect approach increased the tensile strength and tensile modulus by 31% and 148%, respectively. Likewise, dynamic mechanical analysis showed that the thermomechanical properties of the composite greatly improved.

year: 2024

title: Whānau aspirations, extracurricular activity  and positive youth development:  The leisure activity patterns and narratives of successful young Māori men and how they might inform  urban whānau raising tamatāne.

authors: Clarke, Gloria Hinemoa

subjects: Leisure

abstract: The purpose of this research is to offer parents and whānau (extended family groups) insight about the kinds of leisure activities that might make a positive contribution to their boys’ development. Focused on the positive developmental benefits of leisure participation in relation to Māori boys, and employing a kaupapa Māori framework and qualitative methods, this study represents a foray into new territory. 
	Conducted ‘by, with, and for’ Māori (the indigenous people of Aotearoa New Zealand), and guided by the question ‘How might the leisure activity patterns and narratives of successful young Māori men inform urban whānau raising tamatāne (Māori boys/sons)?’ the three-phase research design was strengths-based, collaborative, and both retrospective and prospective. In phase one, a group of 11 parents participated in focus group hui (gatherings) in which they established the criteria for ‘successful young Māori men’ (SYMM) based on their aspirations for their primary-school aged boys. In phase two, this whānau of interest then selected six SYMM from a pool of eight volunteers, who, along with one or both of their parents participated in one-off semi-structured interviews. In these interviews, we co-constructed life and leisure maps, and discussed how their childhood leisure activities and experiences contributed to their development and who they are today. In phase three, a selection of raw data from these interviews was prepared for a group analysis, during which the whānau of interest made three key observations: (1) As children and youth, these SYMM had participated in a number and range of organised and informal leisure activities including sport, kapa haka (Māori cultural performance), music, art, and for three of them, faith-based activities; (2) they were “connected” to their parent(s) and whānau; and (3) their leisure activities had brought them into contact with positive male role models. Consequently, the whānau of interest talked about increasing the number and variety of their boys’ leisure activities; how they could further support their boys’ leisure participation; and bringing more male role models into their boys’ lives. 
	The findings of this study support the current literature regarding extracurricular activity participation in relation to positive youth development, but also highlight some methodological issues and cultural and contextual nuances. The research supports international and local studies in which high-performing students participated in a number and combination of extracurricular activities. In contrast, however, the experiences and reflections of the SYMM in this study highlight the limitations of combining all sports and all arts into broad activity categories. The research participants’ leisure activities also point to the relevance and applicability of the Te Whare Tapa Whā model of health and wellbeing. Their involvement in kapa haka contrasts with the (North American) literature in which males are a minority in the performing arts, and while some studies indicate that participation in music making declines in high school, these young men began playing musical instruments in high school. Moreover, the salience and significance of the research participants’ casual leisure activities challenges the tendency to cast informal leisure as the antithesis of extracurricular activity participation. These findings raise questions about the applicability of using international activity categories in Aotearoa New Zealand research, and consequently the need to conduct our own leisure and positive youth development studies. 
Other topics raised in this thesis include rugby and masculinity, spirituality, and the tensions involved in building and honouring our children’s rangatiratanga (independence). The short answer to the research question is that a variety and balance of leisure activities has the potential to make positive contributions to boys’ lives. Implications, limitations, and recommendations for future research are also discussed.

text: Whānau aspirations, extracurricular activity  and positive youth development:  The leisure activity patterns and narratives of successful young Māori men and how they might inform  urban whānau raising tamatāne. The purpose of this research is to offer parents and whānau (extended family groups) insight about the kinds of leisure activities that might make a positive contribution to their boys’ development. Focused on the positive developmental benefits of leisure participation in relation to Māori boys, and employing a kaupapa Māori framework and qualitative methods, this study represents a foray into new territory. 
	Conducted ‘by, with, and for’ Māori (the indigenous people of Aotearoa New Zealand), and guided by the question ‘How might the leisure activity patterns and narratives of successful young Māori men inform urban whānau raising tamatāne (Māori boys/sons)?’ the three-phase research design was strengths-based, collaborative, and both retrospective and prospective. In phase one, a group of 11 parents participated in focus group hui (gatherings) in which they established the criteria for ‘successful young Māori men’ (SYMM) based on their aspirations for their primary-school aged boys. In phase two, this whānau of interest then selected six SYMM from a pool of eight volunteers, who, along with one or both of their parents participated in one-off semi-structured interviews. In these interviews, we co-constructed life and leisure maps, and discussed how their childhood leisure activities and experiences contributed to their development and who they are today. In phase three, a selection of raw data from these interviews was prepared for a group analysis, during which the whānau of interest made three key observations: (1) As children and youth, these SYMM had participated in a number and range of organised and informal leisure activities including sport, kapa haka (Māori cultural performance), music, art, and for three of them, faith-based activities; (2) they were “connected” to their parent(s) and whānau; and (3) their leisure activities had brought them into contact with positive male role models. Consequently, the whānau of interest talked about increasing the number and variety of their boys’ leisure activities; how they could further support their boys’ leisure participation; and bringing more male role models into their boys’ lives. 
	The findings of this study support the current literature regarding extracurricular activity participation in relation to positive youth development, but also highlight some methodological issues and cultural and contextual nuances. The research supports international and local studies in which high-performing students participated in a number and combination of extracurricular activities. In contrast, however, the experiences and reflections of the SYMM in this study highlight the limitations of combining all sports and all arts into broad activity categories. The research participants’ leisure activities also point to the relevance and applicability of the Te Whare Tapa Whā model of health and wellbeing. Their involvement in kapa haka contrasts with the (North American) literature in which males are a minority in the performing arts, and while some studies indicate that participation in music making declines in high school, these young men began playing musical instruments in high school. Moreover, the salience and significance of the research participants’ casual leisure activities challenges the tendency to cast informal leisure as the antithesis of extracurricular activity participation. These findings raise questions about the applicability of using international activity categories in Aotearoa New Zealand research, and consequently the need to conduct our own leisure and positive youth development studies. 
Other topics raised in this thesis include rugby and masculinity, spirituality, and the tensions involved in building and honouring our children’s rangatiratanga (independence). The short answer to the research question is that a variety and balance of leisure activities has the potential to make positive contributions to boys’ lives. Implications, limitations, and recommendations for future research are also discussed.

year: 2020