title: Long/continuous bio-derived fibre reinforced PLA composites for FDM 3D printing

authors: Muthe, Lakshmi Priya

abstract: High mechanical performance applications often rely on fibre-reinforced composites using continuous synthetic fibres and petrochemical-based polymers. A shift towards bio-derived fibres and bio-derived polymers can reduce the reliance on non-sustainable materials. Long/continuous high-strength bio-derived fibres, such as flax and viscose, offer the potential to achieve mechanical properties similar to synthetic fibre composites. Polylactic acid (PLA), a sustainable bio-derived thermoplastic polymer known for its relatively high strength and stiffness compared to other polymers, is a promising alternative to petrochemical-derived counterparts. This study used long flax fibres and continuous viscose fibres in yarn form to reinforce PLA matrices, resulting in high-performance composite filaments. These filaments are designed for a recently developed and evolving manufacturing method, Fused Deposition Modelling (FDM) 3D printing, for which product performance has been limited by the commercially available filaments. Achieving high-performance FDM filaments requires addressing challenges related to fibre wetting and uniform fibre/polymer distribution, which this study addresses through impregnation and consolidation techniques. The research covers comprehensive experimental investigations into the physical, mechanical, and thermal properties of viscose, flax fibres, and PLA matrices. Successful outcomes include the development of long/continuous bio-derived fibre-reinforced composite filaments by employing two impregnation methods: solution and emulsion impregnation. Analysis covers the morphology, porosity, fibre weight fraction, and mechanical and thermal properties of the composite filaments and 3D printed composites.
Composite filaments were produced using three reinforcement yarns in their as-received form: viscose, two types of flax – standard flax and bleached flax. Viscose fibres were purchased in the form of fully continuous bio-derived fibres, while flax fibres were long and discontinuous, twisted into continuous yarns. Two PLA grades, PLA 2003D (in the form of granules) and PL 1005 (in the form of a PLA/water emulsion), were employed for solution and emulsion impregnation, respectively. Tensile testing of single fibres and matrices yielded results consistent with literature values. Bleached flax fibres exhibited the highest tensile strength (921.6 MPa), standard flax fibres displayed the highest Young’s modulus (31.8 GPa), and viscose fibres demonstrated the highest elongation at break (13.2%). PLA 2003D exhibited the highest tensile properties of the two PLA grades. Thermal stability, as assessed by TGA, demonstrated stability of both bio-derived reinforcements and matrices up to 250 oC. DSC analysis confirmed the semi-crystalline nature of PLA 2003D and the amorphous nature of PL 1005.
An impregnation and consolidation methodology was developed to produce composite filaments using both PLA solution and emulsion. Initially employing a single impregnation bath, it was later upgraded to dual baths in tandem for enhanced efficiency. A yarn spooler directed the fibre into the impregnation bath with squeezing rollers, followed by excess resin removal through a nozzle. The impregnated filament was collected on a winding mandrel and passed through a heated consolidation die. Various formulations with different impregnation cycles were tested for solution and emulsion impregnation methods. Polymer uptake depended on the affinity between the fibre and impregnating liquid, while yarn twist influenced polymer distribution. Emulsion impregnated composites exhibited higher polymer uptake due to better affinity between water and bio-derived fibres. However, solution impregnated composites showed better polymer distribution, particularly for twisted flax-reinforced filaments, relating to the efficient impregnation of PLA/DCM solution. For both impregnation methods, standard flax and bleached flax reinforced composites exhibited improved interfacial adhesion compared to viscose, attributed to mechanical interlocking between the rough surface of flax fibres and PLA in contrast to smooth viscose fibres. For PLA/viscose composites, emulsion impregnation resulted in higher tensile strength (254.7 MPa) and Young’s modulus (9.1 GPa), surpassing reported values in the literature. On the other hand, for PLA/standard flax and PLA/bleached flax, solution impregnation yielded superior tensile properties. Solution impregnated PLA/bleached flax, for the 7wt% x 3 formulation, had the highest tensile strength (356.1 MPa), while the 7wt% x2 tandem formulation showed the highest Young’s modulus (17.6 GPa) of all composites. The achieved tensile strength for PLA/bleached flax in this study also exceeded values reported in existing literature for PLA/flax composites.
The highest-performing formulations for each reinforcement, employing both solution and emulsion impregnation, were chosen to produce 3D printing filaments. A Makergear® FDM 3D printer, compatible with filament diameters of 1.4 to 2 mm, was utilized. Three filaments were pultruded together into one using a consolidation die to achieve the required filament diameter. PLA/viscose and PLA/bleached flax were selected for 3D printing in both solution and emulsion impregnation formulations, following an analysis of morphology, porosity, fibre weight fraction, and tensile properties of the multiple consolidated filaments. To further optimize diameter and enhance printability, the multiple consolidated filaments underwent melt-impregnation with additional polymer, resulting in 1.45±0.5 mm diameter filaments. Characterization of the 3D printing filaments revealed a reduction in tensile strength and Young's modulus due to increased polymer content.
Optical microscopy and porosity analysis of the 3D printed composites revealed increased porosity in the printed specimens compared to the filaments due to voids between the printed layers and pulling of the fibres onto the surface of the printed part because of the nozzle's drag force exerted during the printing process. Emulsion impregnated PLA/viscose exhibited lower porosity and printing defects compared to other composites relating to better affinity between PLA emulsion and viscose as mentioned earlier. Tensile strength and Young’s modulus values of the 3D printed composites decreased compared to the filaments due to printing induced defects mentioned previously. The highest tensile and flexural properties were obtained for emulsion impregnated PLA/viscose composites, demonstrating the significance of efficient impregnation. The 3D printed emulsion impregnated PLA/viscose composites displayed an impact strength greater than 127KJ/m2, which is higher than what has been reported in the literature for any PLA biocomposite.

text: Long/continuous bio-derived fibre reinforced PLA composites for FDM 3D printing High mechanical performance applications often rely on fibre-reinforced composites using continuous synthetic fibres and petrochemical-based polymers. A shift towards bio-derived fibres and bio-derived polymers can reduce the reliance on non-sustainable materials. Long/continuous high-strength bio-derived fibres, such as flax and viscose, offer the potential to achieve mechanical properties similar to synthetic fibre composites. Polylactic acid (PLA), a sustainable bio-derived thermoplastic polymer known for its relatively high strength and stiffness compared to other polymers, is a promising alternative to petrochemical-derived counterparts. This study used long flax fibres and continuous viscose fibres in yarn form to reinforce PLA matrices, resulting in high-performance composite filaments. These filaments are designed for a recently developed and evolving manufacturing method, Fused Deposition Modelling (FDM) 3D printing, for which product performance has been limited by the commercially available filaments. Achieving high-performance FDM filaments requires addressing challenges related to fibre wetting and uniform fibre/polymer distribution, which this study addresses through impregnation and consolidation techniques. The research covers comprehensive experimental investigations into the physical, mechanical, and thermal properties of viscose, flax fibres, and PLA matrices. Successful outcomes include the development of long/continuous bio-derived fibre-reinforced composite filaments by employing two impregnation methods: solution and emulsion impregnation. Analysis covers the morphology, porosity, fibre weight fraction, and mechanical and thermal properties of the composite filaments and 3D printed composites.
Composite filaments were produced using three reinforcement yarns in their as-received form: viscose, two types of flax – standard flax and bleached flax. Viscose fibres were purchased in the form of fully continuous bio-derived fibres, while flax fibres were long and discontinuous, twisted into continuous yarns. Two PLA grades, PLA 2003D (in the form of granules) and PL 1005 (in the form of a PLA/water emulsion), were employed for solution and emulsion impregnation, respectively. Tensile testing of single fibres and matrices yielded results consistent with literature values. Bleached flax fibres exhibited the highest tensile strength (921.6 MPa), standard flax fibres displayed the highest Young’s modulus (31.8 GPa), and viscose fibres demonstrated the highest elongation at break (13.2%). PLA 2003D exhibited the highest tensile properties of the two PLA grades. Thermal stability, as assessed by TGA, demonstrated stability of both bio-derived reinforcements and matrices up to 250 oC. DSC analysis confirmed the semi-crystalline nature of PLA 2003D and the amorphous nature of PL 1005.
An impregnation and consolidation methodology was developed to produce composite filaments using both PLA solution and emulsion. Initially employing a single impregnation bath, it was later upgraded to dual baths in tandem for enhanced efficiency. A yarn spooler directed the fibre into the impregnation bath with squeezing rollers, followed by excess resin removal through a nozzle. The impregnated filament was collected on a winding mandrel and passed through a heated consolidation die. Various formulations with different impregnation cycles were tested for solution and emulsion impregnation methods. Polymer uptake depended on the affinity between the fibre and impregnating liquid, while yarn twist influenced polymer distribution. Emulsion impregnated composites exhibited higher polymer uptake due to better affinity between water and bio-derived fibres. However, solution impregnated composites showed better polymer distribution, particularly for twisted flax-reinforced filaments, relating to the efficient impregnation of PLA/DCM solution. For both impregnation methods, standard flax and bleached flax reinforced composites exhibited improved interfacial adhesion compared to viscose, attributed to mechanical interlocking between the rough surface of flax fibres and PLA in contrast to smooth viscose fibres. For PLA/viscose composites, emulsion impregnation resulted in higher tensile strength (254.7 MPa) and Young’s modulus (9.1 GPa), surpassing reported values in the literature. On the other hand, for PLA/standard flax and PLA/bleached flax, solution impregnation yielded superior tensile properties. Solution impregnated PLA/bleached flax, for the 7wt% x 3 formulation, had the highest tensile strength (356.1 MPa), while the 7wt% x2 tandem formulation showed the highest Young’s modulus (17.6 GPa) of all composites. The achieved tensile strength for PLA/bleached flax in this study also exceeded values reported in existing literature for PLA/flax composites.
The highest-performing formulations for each reinforcement, employing both solution and emulsion impregnation, were chosen to produce 3D printing filaments. A Makergear® FDM 3D printer, compatible with filament diameters of 1.4 to 2 mm, was utilized. Three filaments were pultruded together into one using a consolidation die to achieve the required filament diameter. PLA/viscose and PLA/bleached flax were selected for 3D printing in both solution and emulsion impregnation formulations, following an analysis of morphology, porosity, fibre weight fraction, and tensile properties of the multiple consolidated filaments. To further optimize diameter and enhance printability, the multiple consolidated filaments underwent melt-impregnation with additional polymer, resulting in 1.45±0.5 mm diameter filaments. Characterization of the 3D printing filaments revealed a reduction in tensile strength and Young's modulus due to increased polymer content.
Optical microscopy and porosity analysis of the 3D printed composites revealed increased porosity in the printed specimens compared to the filaments due to voids between the printed layers and pulling of the fibres onto the surface of the printed part because of the nozzle's drag force exerted during the printing process. Emulsion impregnated PLA/viscose exhibited lower porosity and printing defects compared to other composites relating to better affinity between PLA emulsion and viscose as mentioned earlier. Tensile strength and Young’s modulus values of the 3D printed composites decreased compared to the filaments due to printing induced defects mentioned previously. The highest tensile and flexural properties were obtained for emulsion impregnated PLA/viscose composites, demonstrating the significance of efficient impregnation. The 3D printed emulsion impregnated PLA/viscose composites displayed an impact strength greater than 127KJ/m2, which is higher than what has been reported in the literature for any PLA biocomposite.

year: 2024-06-27

title: The nature of sustainability as viewed by European students

authors: Lockley, John

subjects: sustainability

abstract: Sustainability as a concept, though well understood in general terms, is often politically captured by interest groups and as such expressed through issues like concern for global climate change or the need to develop more efficient energy sources, to address regional, national or international priorities. Education for sustainability as a concept similarly is generally becoming well understood; however, it is expressed in different ways by different educational communities.
This research investigates a conceptual framework for the nature of sustainability to describe the way students and teachers from five European countries express their ideas of sustainability.
The results indicate that despite the diversity of education systems and the range of nationally important issues of sustainability identified by the participants from five significantly different European countries (from Eastern and Western, Northern, Central and Southern Europe), there exists a common understanding of the nature of sustainability that can be expressed through a conceptual framework. The framework, based on a matrix of sustainability aspects (ecological, social, cultural and economic) and concepts (equity, interdependence and personal responsibility for action), allowed dialogue to occur to such a large extent that the nearly 200 participants agreed to a common resolution for future action on living more sustainably, applicable across the five countries.

text: The nature of sustainability as viewed by European students Sustainability as a concept, though well understood in general terms, is often politically captured by interest groups and as such expressed through issues like concern for global climate change or the need to develop more efficient energy sources, to address regional, national or international priorities. Education for sustainability as a concept similarly is generally becoming well understood; however, it is expressed in different ways by different educational communities.
This research investigates a conceptual framework for the nature of sustainability to describe the way students and teachers from five European countries express their ideas of sustainability.
The results indicate that despite the diversity of education systems and the range of nationally important issues of sustainability identified by the participants from five significantly different European countries (from Eastern and Western, Northern, Central and Southern Europe), there exists a common understanding of the nature of sustainability that can be expressed through a conceptual framework. The framework, based on a matrix of sustainability aspects (ecological, social, cultural and economic) and concepts (equity, interdependence and personal responsibility for action), allowed dialogue to occur to such a large extent that the nearly 200 participants agreed to a common resolution for future action on living more sustainably, applicable across the five countries.

year: 2013-03

title: Kaupapa Māori Science

authors: Stewart, Georgina Marjorie

subjects: Kaupapa Maori

abstract: This thesis investigates how Māori knowledge and language articulate with current discourses of Pūtaiao education, and possible alternative articulations. A Kaupapa Māori version of critical discourse analysis methodology is developed and applied to discourses relevant to Pūtaiao, or Māori-medium science education. This topic represents an intersection between language, science, education, and culture - fields which are all highly politically charged. Therefore, it is essential that a politically robust Kaupapa Māori position be taken in relation to the research topic. Not only the issues being investigated but the underlying research paradigm must be interrogated using Kaupapa Māori theory at each stage of the project.

The goal is to study the range of possible meanings for the notions of 'Pūtaiao' and 'Māori science' by exploring the relevant dialectical issues, critiquing the assumptions and positions taken on language, knowledge, identity and ethos, in order to inform further Pūtaiao curriculum development. The research project is a narration of the larger story of Pūtaiao education: what is the current situation, how did it come about, what theoretical issues have been influential in this process, and what possibilities are there for further development of Pūtaiao curriculum and pedagogy? 

The thesis research consists of a series of discourse analyses of varying levels of focus and intersection with Pūtaiao:
Wāhanga 1: Translated NCEA L1 science and mathematics examinations, and a traditional Taitokerau oral text;
Wāhanga 2: Māori science curriculum policy;
Wāhanga 3: Multicultural science education research;
Wāhanga 4: Curriculum politics, preventive linguistics, language of science;
Wāhanga 5: Mātauranga, rationality, philosophy of science.

Each analysis takes the form of a narrative history, based on a selected corpus of previously published scholarship (in Wāhanga 1, including numerical data and oral tradition) on the issue under examination, from a Kaupapa Māori perspective. Mainly in the first two chapters, analysis at times also draws on 'personal narrative' accounts of previously unpublished details relating to Pūtaiao.
 
Additionally, an investigation of various qualified notions of 'science' is undertaken, beginning in Wāhanga 2, concluding in Wāhanga 5, in order to explore the nature and boundaries of science as a system of knowledge, and its relationship to other types or systems of knowledge. 

Synopses are included of the following concepts and theoretical issues impacting on the discourses under analysis: 
Wāhanga 1: Ethnicity, 'race', critical theory, Kaupapa Māori theory. 
Wāhanga 2: Science, scientism, science ideology and anti-science.
Wāhanga 4: Identity, linguistic purism, the Sapir-Whorf hypothesis.

Informed by this research, in Wāhanga 5 an original model for the relationship between mātauranga and science is proposed, and the notion of Kaupapa Māori science/epistemology is explored. An analogy between the Sapir-Whorf hypothesis and multicultural science is used to draw together the cultural debates in language and knowledge, which are surmised to intersect at the level of discourse. 

The final chapter presents a re-articulation of Pūtaiao as the notion of Kaupapa Māori science education, and some recommendations for language and content knowledge in further development of Pūtaiao curriculum policy.

text: Kaupapa Māori Science This thesis investigates how Māori knowledge and language articulate with current discourses of Pūtaiao education, and possible alternative articulations. A Kaupapa Māori version of critical discourse analysis methodology is developed and applied to discourses relevant to Pūtaiao, or Māori-medium science education. This topic represents an intersection between language, science, education, and culture - fields which are all highly politically charged. Therefore, it is essential that a politically robust Kaupapa Māori position be taken in relation to the research topic. Not only the issues being investigated but the underlying research paradigm must be interrogated using Kaupapa Māori theory at each stage of the project.

The goal is to study the range of possible meanings for the notions of 'Pūtaiao' and 'Māori science' by exploring the relevant dialectical issues, critiquing the assumptions and positions taken on language, knowledge, identity and ethos, in order to inform further Pūtaiao curriculum development. The research project is a narration of the larger story of Pūtaiao education: what is the current situation, how did it come about, what theoretical issues have been influential in this process, and what possibilities are there for further development of Pūtaiao curriculum and pedagogy? 

The thesis research consists of a series of discourse analyses of varying levels of focus and intersection with Pūtaiao:
Wāhanga 1: Translated NCEA L1 science and mathematics examinations, and a traditional Taitokerau oral text;
Wāhanga 2: Māori science curriculum policy;
Wāhanga 3: Multicultural science education research;
Wāhanga 4: Curriculum politics, preventive linguistics, language of science;
Wāhanga 5: Mātauranga, rationality, philosophy of science.

Each analysis takes the form of a narrative history, based on a selected corpus of previously published scholarship (in Wāhanga 1, including numerical data and oral tradition) on the issue under examination, from a Kaupapa Māori perspective. Mainly in the first two chapters, analysis at times also draws on 'personal narrative' accounts of previously unpublished details relating to Pūtaiao.
 
Additionally, an investigation of various qualified notions of 'science' is undertaken, beginning in Wāhanga 2, concluding in Wāhanga 5, in order to explore the nature and boundaries of science as a system of knowledge, and its relationship to other types or systems of knowledge. 

Synopses are included of the following concepts and theoretical issues impacting on the discourses under analysis: 
Wāhanga 1: Ethnicity, 'race', critical theory, Kaupapa Māori theory. 
Wāhanga 2: Science, scientism, science ideology and anti-science.
Wāhanga 4: Identity, linguistic purism, the Sapir-Whorf hypothesis.

Informed by this research, in Wāhanga 5 an original model for the relationship between mātauranga and science is proposed, and the notion of Kaupapa Māori science/epistemology is explored. An analogy between the Sapir-Whorf hypothesis and multicultural science is used to draw together the cultural debates in language and knowledge, which are surmised to intersect at the level of discourse. 

The final chapter presents a re-articulation of Pūtaiao as the notion of Kaupapa Māori science education, and some recommendations for language and content knowledge in further development of Pūtaiao curriculum policy.

year: 2007