The aim of this research is to analyse through practical and historical investigation the manner in which Doublecloth in the twentieth century has been transformed from a traditional woven technique to one of artistic innovation and challenge. The first series of woven samples and historic enquiry concerns the structure and pattern of doublecloth at a time when its industrial and craft-based use was for the production of decorative and utilitarian woven fabrics. The research focuses on the extent to which this technique was given aesthetic credibility by its altered profile at the Bauhaus and the subsequent influence of the writings and work of Anni Albers. While the philosophy and products of the Bauhaus and the role of Walter Gropius have been documented and widely debated the practice of textiles, and the influence on it of gender, class and the hierarchical practice of craft, has received little critical attention. The research seeks to redress this imbalance, evaluating why the output of the textile workshops was undervalued artistically and considered marginal to the products from other workshops. This leads to a consideration of the interface between the practice of Fine Art and the practice of Craft, between designing and making, between art and industry. The woven samples are a process of experimentation against which the historic stages can be tested and the technical constraints of contemporary practice can be explained. This primary material leads to a consideration of the new technology and the impact of Nuno doublecloth fabrics on the production of doublecloth for the mass market. The evidence suggests that while new fabric finishes and experimental pattern effects are desirable, the difficulties of hand production are so prohibitive, that it is only with computer aided technology that such ambitions can be met

Traditional weaving technologies have been utilised over the past twenty-to-thirty years in producing woven textile components that meet engineering requirements through the interlacement of high performance yarns such as carbon, glass and Kevlar. The end performance properties and lightweight characteristics of these fabrics have been adapted within the development of both flat multilevel and shaped configurations for the composites industry. The purpose of the present research required the employment of conventional weaving technologies with limited modifications for the production of 3D woven textile preforms in a variety of truss like configurations; therefore, generating a generic procedure for all yarn combinations and strut and node dimensions for production on dissimilar jacquard looms. The ultimate driving force behind the research was to produce a truss like configuration for the aerospace industry incorporating the design criterion of solid and hollow woven counterparts. This would enable the end truss configuration to have two functions; the first being a lightweight structure by the elimination of bonding applications, through the utilisation of a fully integrated fabrication process; secondly to incorporate hollow struts for a novel storage solution.

The objective of this project was to evaluate and model the effects of moisture, temperature, and combined hygrothermal aging on the durability of a graphite/epoxy woven composite material system. Imposed environmental and aging conditions were considered to be representative of service conditions for the engine of an advanced subsonic aircraft for which the composite system is a candidate material. The study was designed such that the results could be used in a residual strength based life prediction approach that accounted for both the mechanical fatigue and environmental conditions. Damage mechanisms and failure modes were determined through fatigue testing, residual strength testing, and nondestructive evaluation. The experimental data generally revealed little effect of environment on strength degradation during fatigue despite notable differences in damage accumulation processes. Modeling efforts were concentrated on initial stiffness, moisture uptake, and residual strength prediction, where the results from the first two efforts were intended to generate inputs for the life prediction. The Ishikawa and Chou fiber undulation and bridging model [22] was shown to provide an accurate stiffness prediction and was subsequently used in parametric studies to determine the effect of weave architecture and geometry. A moisture uptake model developed by Roy [16] for laminates containing single direction cracks was extended to predict moisture uptake in laminates containing cracks in directions parallel and transverse to the loading direction. The life prediction approach was based on ideas developed by Reifsnider and colleagues [36,37,43]. The intention in this case was to use the critical element paradigm to predict the combined effects of alternating environmental (temperature and moisture) conditions imposed during fatigue. Since experimental results indicated that temperature and moisture did not significantly affect the strength and life of the material, a successful life prediction analysis was performed as a function of only fatigue stress level and cycles. / Master of Science

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This PhD thesis presents an experimental investigation into the tensile properties, strengthening mechanics and failure mechanisms of three-dimensional (3D) woven composites with through-the-thickness (z-binder) reinforcement. 3D composites are being developed for the aerospace industry for structural applications in next-generation aircraft, such as wing panels, joints and stiffened components. The use of 3D woven composites in primary aircraft structures cannot occur until there has been a detailed assessment of their mechanical performance, including under tensile loading conditions. The aim of this PhD project is to provide new insights into the in-plane tensile properties, fatigue life, tensile delamination resistance and failure mechanisms of 3D woven composites with different amounts of z-binder reinforcement. Previous research has revealed that excessive amounts of z-binder reinforcement dramatically improves the tensile delamination toughness, but at the expense of the in-plane structural properties. For this reason, this PhD project aims to evaluate the tensile performance of 3D woven composites with relatively small z-binder contents (less than ~1%). The research aims to provide a better understanding of the manufacture, microstructure and tensile properties of 3D woven composites to assist the process of certification and application of these materials to aircraft structures as well as high performance marine and civil structures.

Woven (also known as textile) composites are one class of polymer matrix composites with increasing market share in aerospace, autmobile, civil infrastructure applications mostly due to their lightweight, their flexibility to form into desired shape, their mechanical properties and toughness. Due to the viscoelasticity of the polymer matrix, time-dependent degradation in modulus (creep) and strength (creep rupture) are two of the major mechanical properties required by engineers to design a structure reliably when using these materials. Unfortunately, creep and creep rupture of woven composites have received little attention by the research community and thus, there is a dire need to generate additional knowledge and prediction models, given the increasing market share of woven composites in load bearing structural applications. In this thesis, an analytical creep model, namely the Modified Equivalent Laminate Model (MELM), was developed to predict tensile creep of plain weave composites for any orientation of the load with respect to the orientation of the fill and warp fibers, using creep of unidirectional composites. The model was validated using an extensive experimental involving the tensile creep of plain weave composites under varying loading orientation and service conditions. Plain weave epoxy (F263)/ carbon fiber (T300) composite, currently used in aerospace applications, was procured as fabrics from Hexcel Corporation. Creep tests were conducted under two loading conditions: on-axis loading (00) and off-axis loading (450). Constant load creep, in the temperature range of 80–2400C and stress range of 1-70% UTS of the composites, was experimentally evaluated for time periods ranging from 1–120 hours under both loading conditions. The composite showed increase in creep with increase in temperature and stress. Creep of composite increased with increase in angle of loading, from 1% under on-axis loading to 31% under off-axis loading, within the tested time window. The experimental creep data for plain weave composites were superposed using TTSP (Time Temperature Superposition Principle) to obtain a master curve of experimental data extending to several years and was compared with model predictions to validate the model. The experimental and model results were found in good agreement within an error range of +1-3% under both loading conditions. A parametric study was also conducted to understand the effect of microstructure of plain weave composites on its on-axis and off-axis creep. Additionally, this thesis generated knowledge on time-dependent damage in woven composites and its effect on creep and tensile properties and their prediction.

Woven (also known as textile) composites are one class of polymer matrix composites with increasing market share in aerospace, autmobile, civil infrastructure applications mostly due to their lightweight, their flexibility to form into desired shape, their mechanical properties and toughness. Due to the viscoelasticity of the polymer matrix, time-dependent degradation in modulus (creep) and strength (creep rupture) are two of the major mechanical properties required by engineers to design a structure reliably when using these materials. Unfortunately, creep and creep rupture of woven composites have received little attention by the research community and thus, there is a dire need to generate additional knowledge and prediction models, given the increasing market share of woven composites in load bearing structural applications. In this thesis, an analytical creep model, namely the Modified Equivalent Laminate Model (MELM), was developed to predict tensile creep of plain weave composites for any orientation of the load with respect to the orientation of the fill and warp fibers, using creep of unidirectional composites. The model was validated using an extensive experimental involving the tensile creep of plain weave composites under varying loading orientation and service conditions. Plain weave epoxy (F263)/ carbon fiber (T300) composite, currently used in aerospace applications, was procured as fabrics from Hexcel Corporation. Creep tests were conducted under two loading conditions: on-axis loading (00) and off-axis loading (450). Constant load creep, in the temperature range of 80–2400C and stress range of 1-70% UTS of the composites, was experimentally evaluated for time periods ranging from 1–120 hours under both loading conditions. The composite showed increase in creep with increase in temperature and stress. Creep of composite increased with increase in angle of loading, from 1% under on-axis loading to 31% under off-axis loading, within the tested time window. The experimental creep data for plain weave composites were superposed using TTSP (Time Temperature Superposition Principle) to obtain a master curve of experimental data extending to several years and was compared with model predictions to validate the model. The experimental and model results were found in good agreement within an error range of +1-3% under both loading conditions. A parametric study was also conducted to understand the effect of microstructure of plain weave composites on its on-axis and off-axis creep. Additionally, this thesis generated knowledge on time-dependent damage in woven composites and its effect on creep and tensile properties and their prediction.

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No description available.