title: Effect of accelerated weathering on physico-mechanical properties of polylactide bio-composites

authors: Sawpan, Moyeenuddin Ahmad

subjects: Science & Technology

abstract: In this work, injection moulded hemp fibre reinforced polylactide bio-composites of different fibre contents (0, 10, 20 and 30 wt%) were subjected to accelerated weathering of 12 h cyclic exposures of UV-light at 60 °C, water spray and condensation at 50 °C for 8, 16, 32, 48 and 64 cycles to study the changes in properties such as crystallinity, tensile, flexural, plane-strain fracture toughness (KIc) and strain energy release rate (GIc). The crystallinity of neat polylactide (PLA) was found to increase up to 50.6% after 64 cycles, whereas the crystallinity of composites of different fibre contents was found to increase in the range of 30.6 to 34.5% for 8 to 64 cycles. The overall mechanical properties (tensile, flexural, KIc and GIc) of the composites decreased as the number of cycles increased from 8 to 64. The crystallinity and the residual tensile strength, tensile modulus, tensile strain, KIc and GIc of the composites of 20 wt% fibres were found to be the highest after 64 cycles. In contrast, the residual flexural strength and flexural modulus of the composites of 30 wt% fibres were found to be the maximum after 64 cycles. Absorption of water, destruction of fibre integrity, degradation of PLA matrix, formation of cracks and pores were found to be the main causes of reduction in the mechanical properties of PLA bio-composites.

text: Effect of accelerated weathering on physico-mechanical properties of polylactide bio-composites In this work, injection moulded hemp fibre reinforced polylactide bio-composites of different fibre contents (0, 10, 20 and 30 wt%) were subjected to accelerated weathering of 12 h cyclic exposures of UV-light at 60 °C, water spray and condensation at 50 °C for 8, 16, 32, 48 and 64 cycles to study the changes in properties such as crystallinity, tensile, flexural, plane-strain fracture toughness (KIc) and strain energy release rate (GIc). The crystallinity of neat polylactide (PLA) was found to increase up to 50.6% after 64 cycles, whereas the crystallinity of composites of different fibre contents was found to increase in the range of 30.6 to 34.5% for 8 to 64 cycles. The overall mechanical properties (tensile, flexural, KIc and GIc) of the composites decreased as the number of cycles increased from 8 to 64. The crystallinity and the residual tensile strength, tensile modulus, tensile strain, KIc and GIc of the composites of 20 wt% fibres were found to be the highest after 64 cycles. In contrast, the residual flexural strength and flexural modulus of the composites of 30 wt% fibres were found to be the maximum after 64 cycles. Absorption of water, destruction of fibre integrity, degradation of PLA matrix, formation of cracks and pores were found to be the main causes of reduction in the mechanical properties of PLA bio-composites.

year: 2019

title: Constructive Analysis of Partial Differential Equations

authors: Wang, Michael Yuchuan

subjects: Partial Differential Equations

abstract: This thesis presents the results produced in the study of weak solutions of the Dirichlet Problem within Errett Bishop's constructive mathematics. It roughly falls into three major parts: a critical analysis of the classical approaches from a constructive point of view (Chapter 2); constructive results on the existence, stability, and maximality of weak solutions (Chapter 5); and related results on the domains discovered during the course of study on the Dirichlet Problem (Chapters 3 and 6). Chapter 1 introduces constructive mathematics, and Chapter 4 is an auxiliary one in which I give two different constructions of a cut-off function.

text: Constructive Analysis of Partial Differential Equations This thesis presents the results produced in the study of weak solutions of the Dirichlet Problem within Errett Bishop's constructive mathematics. It roughly falls into three major parts: a critical analysis of the classical approaches from a constructive point of view (Chapter 2); constructive results on the existence, stability, and maximality of weak solutions (Chapter 5); and related results on the domains discovered during the course of study on the Dirichlet Problem (Chapters 3 and 6). Chapter 1 introduces constructive mathematics, and Chapter 4 is an auxiliary one in which I give two different constructions of a cut-off function.

year: 1996

title: New observations on the stratigraphy and radiocarbon dates at the Cross Creek site, Opito, Coromandel Peninsula

authors: Furey, Louise

subjects: New Zealand

abstract: This paper re-examines stratigraphy and radiocarbon dates at Cross Creek in Sarah's Gully. Three new radiocarbon dates are presented for Layer 9, the earliest, and previously undated, occupation. This investigation is part of a programme of archaeological work being carried out on the Coromandel Peninsula. Although there are several individual research projects underway, they have a common theme related to the Polynesian settlement period on the Coromandel Peninsula. The two seasons of excavation at Tairua are being written up by Matthew Campbell of CFG Heritage on behalf of Roger Green. Louise Furey, also CFG Heritage, is researching a thematic study on early sites for the Department of Conservation, Archaeological research in the Opito area includes documenting a pollen sequence for Opito under a grant obtained from the Green Foundation for Polynesian Research: Pam Chester, Louise Furey and Brenda Sewell are participants. In addition, positively identifying the Kaharoa Ash in the Opito-Sarah's Gully area is a priority.

text: New observations on the stratigraphy and radiocarbon dates at the Cross Creek site, Opito, Coromandel Peninsula This paper re-examines stratigraphy and radiocarbon dates at Cross Creek in Sarah's Gully. Three new radiocarbon dates are presented for Layer 9, the earliest, and previously undated, occupation. This investigation is part of a programme of archaeological work being carried out on the Coromandel Peninsula. Although there are several individual research projects underway, they have a common theme related to the Polynesian settlement period on the Coromandel Peninsula. The two seasons of excavation at Tairua are being written up by Matthew Campbell of CFG Heritage on behalf of Roger Green. Louise Furey, also CFG Heritage, is researching a thematic study on early sites for the Department of Conservation, Archaeological research in the Opito area includes documenting a pollen sequence for Opito under a grant obtained from the Green Foundation for Polynesian Research: Pam Chester, Louise Furey and Brenda Sewell are participants. In addition, positively identifying the Kaharoa Ash in the Opito-Sarah's Gully area is a priority.

year: 2008