Thesis (Ph. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xxviii, 382 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains vi, 76 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 60-61).

Thesis (M.Sc.)--City University of Hong Kong, 2005. / At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.

Thesis (M.S.) in Civil Engineering--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaf 77).

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xvi, 204 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 155-158).

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains ix, 118 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 117-118).

Moisture ingress and thermal effects on carbon fibre reinforced plastic is a well understood phenomenon. For aircraft structures where safety is paramount this results in the use of worst case material properties, known as HOTAA/ET properties. In reality most structures are not fully saturated and are therefore penalised by using these worst case properties. This project attempts to fully understand the environmental effect on mechanical performance and accurately model a structures exposure to the environment, while still maintaining conservatism, to realise structural weight savings for aircraft. From the literature study it appears that this is the first attempt to link the mechanical property degradation brought about by environment, to classical laminate theory. By modelling individual ply property performance, based on each ply's level of saturation and linking it to a bespoke set of materials properties generated within the project, it is possible to accurately model the mechanical performance of a component. The model and modelling process derived within this project have been successfully validated by structural testing.

The mechanical properties of particulate filled polymers are influenced significantly by interfacial interactions. The adhesion between the polymer and the filler depends on the area of the interface and the strength of the interaction. The former is related to specific area of the filler while the strength of the interaction can be modified by surface treatment. This study is focused on comparing the reinforcing ability of muscovite and phlogopite with and without surface treatment. Muscovite and phlogopite are two common forms of mica. Mechanical properties such as Young's modulus, tensile strength, elongation and impact strength were used to compare the reinforcing ability of muscovite and phlogopite in EVA composites. The Young's modulus of the surface treated and non-surface treated composites increased with an increase in filler loading. Composites reinforced with muscovite had similar moduli compared to composites reinforced with phlogopite. The tensile strength of phlogopite reinforced composites increased with an increase in filler content while that of muscovite reinforced composites remained constant. Surface modification by both silane and stearic acid reduced the tensile strength of phlogopite reinforced composites. The tensile strength of stearic acid treated muscovite reinforced composites improved but not to the same extent as the silane treated composites. Both muscovite and phlogopite lead to a lowering of the impact strength at high filler loadings while the tensile impact strength of both muscovite and phlogopite reinforced composites improved when using silane and stearic acid. In non-surface treated systems, muscovite reinforced composites showed an initial increase in elongation while the elongation of phlogopite reinforced composites decreased with an increase in filler loading. Elongation at maximum load values, however, increased at low filler loadings, when using stearic acid. It can be concluded that stearic acid is not an effective coupling agent for mica/EVA composites and that the use of silane for phlogopite reinforced composites does not offer any improvement in mechanical properties. / Dissertation (MSc (Chemical Technology))--University of Pretoria, 2006. / Chemical Engineering / unrestricted

The degree of cure and temperature are consistent variables used in models to describe the state of material behaviour development for a thermoset during cure. Therefore, the validity of a cure kinetics model is an underlying concern when combining several material models to describe a part forming process, as is the case for process modeling. The goals of this work are to identify sources of uncertainty in the decision-making process from cure measurement by differential scanning calorimeter (DSC) to cure kinetics modeling, and to recommend practices for reducing uncertainty. Variability of cure kinetics model predictions based on DSC measurements are investigated in this work by a study on the carbon-fiber-reinforced-plastic (CFRP) T800H/3900-2, an interlaboratory Round Robin comparison of cure studies on T800H/3900-2, and a literature review of cure models for Hexcel 8552. It is shown that variability between model predictions can be as large as 50% for some process conditions when uncertainty goes unchecked for decisions of instrument quality, material consistency, measurement quality, data reduction and modeling practices. The variability decreases to 10% when all of the above decisions are identical except for the data reduction and modeling practices. In this work, recommendations are offered for the following practices: baseline selection, balancing heats of reaction, comparing data over an extensive temperature range (300 K), choosing appropriate models to describe a wide range of behaviour, testing model reliability, and visualization techniques for cure cycle selection. Specific insight is offered to the data reduction and analysis of thermoplastic-toughened systems which undergo phase separation during cure, as is the case for T800H/3900-2. The evidence of phase separation is a history-dependent Tg-α relationship. In the absence of a concise outline of best practices for cure measurement by DSC and modeling of complex materials, a list of guidelines based on the literature and the studies herein is proposed. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The use of natural fibers as reinforcement in thermoplastics presents an interesting alternative for the production of low cost and ecologically friendly composites. One of the advantages of using natural fibres is their low specific weight, resulting in higher specific strength and stiffness when compared to glass reinforced composites. Natural fibres also present safer handling and working conditions. They are non-abrasive to mixing and can contribute to significant cost reduction. This work is divided into two phases: Phase 1 deals with developing nonwoven mats composites from flax/polypropylene (PP) and evaluating their properties. Flax/polypropylene fibres (at different weight ratios) were processed by needle-punching technique in order to form nonwoven mats. The mats were compression-molded at a temperature of 180oC to form composite materials. The mechanical, thermal and viscoelastic properties of the composites were analyzed. Composites (untreated and silane-treated) were also subjected to varying conditions of temperature and humidity and the tensile properties of the conditioned and unconditioned composites were investigated. The mechanical properties (tensile, flexural and impact) of flax/PP composites were found to increase and reach maximum values at 30 per cent fibre loading and then decrease at higher fibre content. Thermal studies revealed that the composites were stable up to 320oC and samples containing 40 per cent flax fibres were found to exhibit greater thermal stability than neat PP. The dynamic mechanical analyses of the composites showed that the incorporation of flax in the composites resulted in an increase of the storage modulus with a maximum value exhibited by composite containing 40 per cent fibre loading. Composites containing chemically modified fibres exhibited low tensile modulus after conditioning. Phase 2 is based on the investigation of the effect of nano-calcium carbonate (CaCO3) on the properties of two types of polymer matrices: recycled PP and virgin PP. In this case, composites were prepared by melt-mixing and injection molding. The mechanical and thermal properties of the composites were characterized. The tensile modulus of the nano-CaCO3 filled PP (virgin and recycled) composites were found to increase and reach maximum at 30 per cent nano-CaCO3 loading, while the tensile strength decreased with increasing filler content. Thermal studies showed that the nano-CaCO3 filled PP samples exhibited a one-step degradation pattern and are thermally stable up to 450oC. The thermal stability of the samples was found to decrease following the addition of nano-CaCO3. SEM micrographs of the tensile fractured surfaces of composites of the nano-CaCO3 filled virgin and recycled PP revealed the presence of nano-CaCO3 agglomeration.