Feasibility of Hybrid Thermoplastic Composite-Concrete Load Bearing System

Thermoplastic composites have many advantages over thermoset composites such as being recyclable, rapidly manufacturable, and more impact resistant. The goal of this thesis is to assess the feasibility of using thermoplastic composites in structural applications through literature review, mechanical testing, design of a load-bearing hybrid composite-concrete structures, and the implementation of thermoplastic composites for tensile reinforcement of concrete. The study had four objectives covering the stated goal. Conduct a literature review to direct thermoplastic material selection Characterize thermoplastic material mechanical properties using standardized mechanical testing Design a hybrid composite-reinforced concrete beam, and Develop thermoplastic shear connectors to develop composite action between thermoplastic reinforcement and concrete Initially, thermoplastics that can be reinforced with E-glass fibers to be used as a structural part were investigated. Materials were selected for experimental characterization after extensive literature review based on performance, cost and manufacturing methods. Two industry accepted processes were selected for use in fabrication: vacuum infusion, a longstanding and highly accepted process traditionally used for the manufacturing of thermoset composites; and thermoforming, a fast production process that takes advantage of many properties of thermoplastic materials. Next, properties of these materials required for structural applications were quantified through mechanical testing. These properties include the modulus of elasticity, Poisson’s ratio and the ultimate strength in tension, compression and shear in principal material directions. Having a complete list of material properties is necessary in composite design. A design for a load-bearing composite-concrete beam was developed. In conventional construction, steel reinforcing bars are used to carry the tension in a concrete beam, but steel is susceptible to corrosion. These hybrid composite-concrete structures rely on the transfer of forces (composite action) between the thermoplastic composite, which acts as reinforcement, and the concrete section of the beam. The composite action is necessary for the composite reinforcement to develop tension through shear flow at the interface. The initial design to demonstrate the use of thermoplastic composites in this manner is the fabrication of a simple prismatic beam with the bottom-face reinforced with the composite. This provides a simple structure to demonstrate the feasibility of this technology for use in structural applications. Finally, the ability of the shear connectors developed to produce composite action in the proposed beam was experimentally assessed. Hybrid composite-concrete specimens were tested in compression to assess the feasibility of shear connectors (studs) to carry the shear flow at the interface between the thermoplastic reinforcement and concrete. Conclusions and recommendations are presented in Chapter 5. Recommendations for future work include the implementation of small-scale short-beam tests in four-point bending to further assess the degree of composite action being generated in the structure. Recommendations for future research on more effectively achieving composite action in hybrid thermoplastic composite-concrete members is also addressed

Feasibility of remotely manipulated welding in space. A step in the development of novel joining technologies

In order to establish permanent human presence in space technologies of constructing and repairing space stations and other space structures must be developed. Most construction jobs are performed on earth and the fabricated modules will then be delivered to space by the Space Shuttle. Only limited final assembly jobs, which are primarily mechanical fastening, will be performed on site in space. Such fabrication plans, however, limit the designs of these structures, because each module must fit inside the transport vehicle and must withstand launching stresses which are considerably high. Large-scale utilization of space necessitates more extensive construction work on site. Furthermore, continuous operations of space stations and other structures require maintenance and repairs of structural components as well as of tools and equipment on these space structures. Metal joining technologies, and especially high-quality welding, in space need developing

Two Clamped Pipe Support Connections for Oil and Gas Brownfield Projects

In the oil and gas industry, brownfield projects focus on the modification of or addition to an existing production facility that is fully operational and operating. Welding is typically avoided on these projects. The drilling of holes in existing primary structural elements is also prohibited. Clamped connections are often used when adding additional services in a brownfield project. There are different types of clamped connections utilized when a new structural support must be attached to an existing vertical structural pipe. The short bolt clamped connection is a well-established connection and typically used on offshore projects. The U-bolt clamped connection is an alternative connection, although its use in the offshore oil and gas industry is not as well documented. The main drawback to using the U-bolt clamp connection is the lack of a well researched and vetted design methodology. A preliminary analysis methodology is proposed in this thesis. The material, fabrication, installation, and maintenance of both the short bolt connection and U-bolt connection will also be discussed. The following thesis will end with recommendations for moving forward

Two Clamped Pipe Support Connections for Oil and Gas Brownfield Projects

In the oil and gas industry, brownfield projects focus on the modification of or addition to an existing production facility that is fully operational and operating. Welding is typically avoided on these projects. The drilling of holes in existing primary structural elements is also prohibited. Clamped connections are often used when adding additional services in a brownfield project. There are different types of clamped connections utilized when a new structural support must be attached to an existing vertical structural pipe. The short bolt clamped connection is a well-established connection and typically used on offshore projects. The U-bolt clamped connection is an alternative connection, although its use in the offshore oil and gas industry is not as well documented. The main drawback to using the U-bolt clamp connection is the lack of a well researched and vetted design methodology. A preliminary analysis methodology is proposed in this thesis. The material, fabrication, installation, and maintenance of both the short bolt connection and U-bolt connection will also be discussed. The following thesis will end with recommendations for moving forward

Friction hydro pillar riveting process of Ti-6AI-4V titanium sheet

Mechanical fasteners are used extensively in the joining of two or more metal plates or sheets. Riveted joints have been the joints of choice mainly for the Aerospace Industry. However for this research, Friction Hydro Pillar Processing has been used to develop and characterise a new riveting technique termed Friction Hydro Pillar Riveting (FHPR). Two overlapping 3.17 mm Ti-6Al-4V sheets were joined together using Ø6 mm rivet which was friction processed. This research has focussed on the initial development of Friction Hydro Pillar Riveting thereby establishing a basic understanding of the influences of main process parameters, rotational speed and axial force - and also joint configurations. The results showed that with a decrease in the bottom hole chamfer angle, there was resulting overall increase in the rivet joint pull off strength. From the best performing joint configuration in pull off tests, shear tests were conducted whilst a blind hole FHPR joint was also done and tested in pull off and shear strength. The shear test fracture surfaces exhibited ductile failure. The microstructure of the joints was thus evaluated. From parent material, heat affected zone and to weld zone there was a variation in the microstructure analysed. The hardness profiles showed increased hardness in the weld zone which partly explained the shear results. The hardness increase was mainly due to grain refinement in the weld zone by the Friction Hydro Pillar Riveting process

Welding Processes

Despite the wide availability of literature on welding processes, a need exists to regularly update the engineering community on advancements in joining techniques of similar and dissimilar materials, in their numerical modeling, as well as in their sensing and control. In response to InTech's request to provide undergraduate and graduate students, welding engineers, and researchers with updates on recent achievements in welding, a group of 34 authors and co-authors from 14 countries representing five continents have joined to co-author this book on welding processes, free of charge to the reader. This book is divided into four sections: Laser Welding; Numerical Modeling of Welding Processes; Sensing of Welding Processes; and General Topics in Welding

Friction hydro-pillar processing of carbon steels : a numerical investigation of joint structure, properties and material flow

A Soldagem por Fricção com Pino Consumível (Friction Hydro Pillar Processing - FHPP) é uma técnica inovadora de união em estado sólido utilizada para reparar componentes de parede espessa. Durante o processo, o pino é rotacionado contra uma cavidade usinada no local do defeito para induzir aquecimento por fricção e fluxo do material plastificado para preenchimento adequado. Este trabalho apresenta uma investigação abrangente do FHPP, com foco na relação das variáveis de processo com a microestrutura, propriedades da junta, e fluxo do material. Buscando uma compreensão mais profunda e otimização dessa técnica de soldagem, três estudos foram realizados em diferentes tipos de aço, com uma abordagem conjunta experimental e numérica. No primeiro estudo, foram examinados os efeitos das variáveis do processo na microestrutura e nas propriedades da junta resultante, ou seja, estudou-se como a força, a velocidade de rotação do pino e o tempo de processamento, influenciam na obtenção da junta soldada por FHPP no aço ASTM A36. Um modelo numérico foi desenvolvido para examinar a taxa de geração de calor, o campo de temperatura transiente e sua correlação com as variáveis de processamento. A partir da análise experimental e numérica foi possível desenvolver um método para estimar a distribuição de dureza das juntas. Baseando-se no estudo anterior, o segundo artigo de pesquisa foca no FHPP de aço AISI 4140. Os resultados enfatizam a importância da otimização da taxa de força do pino e do tempo de processamento para obter juntas livres de defeitos e preenchimento adequado de furos de trincas. O terceiro estudo aborda o fluxo de material durante o FHPP, um aspecto pouco relatado na literatura. Por meio de uma combinação de análise teórica e experimentos de tomografia computadorizada por raios-x tridimensionais (XCT), utilizou-se um inserto de liga de titânio para rastrear o fluxo de material durante o FHPP de um substrato AISI 4140. Um modelo numérico termomecânico axissimétrico foi desenvolvido para rastrear o fluxo do material. Os resultados mostraram que a porção central do pino se deforma em uma série de planos de cisalhamento em camadas, enquanto que o material plastificado mais externo radialmente flui pela folga entre o pino e a peça, com o excesso de volume sendo expulso como rebarba.Friction hydro-pillar processing (FHPP) is a solid-state joint technique employed for repairing thick-walled components using an external stud. During the process, the stud is rotated against a crack-hole to induce friction heating and flow of plasticized material for proper filling. This Ph.D. thesis presents a comprehensive investigation of FHPP, focusing on the determination of joint structure, material flow, and properties while considering the effects of processing variables. Contributing to a deeper understanding and optimization of the technique, three critical studies were carried out on different types of steel substrates with a joint experimental and numerical approach. The first study investigates the effect of processing conditions - such as stud force, rotational speed and processing time - on joint structure and properties in FHPP of ASTM A36 steel. A numerical model was developed. in which the rate of heat generation, transient temperature field, and their correlation with processing variables were examined. From experimental and numerical analyses results, a method to estimate the hardness distribution within the joints was presented. Building upon the previous study, the second research paper focuses on FHPP of AISI 4140 steel. The results emphasize the importance of optimizing stud force rate and processing time to achieve defect-free joints and proper filling of crack holes, offering valuable insights into the systematic and quantitative aspects of the technique. The third study addresses the material flow during FHPP, an aspect that is often underreported in the literature. Through a combination of theoretical analysis and three-dimensional X-ray computer tomography (XCT) experiments, a Ti-alloy tracer material was used to track material flow during FHPP of an AISI 4140 substrate. A thermo-mechanical axi-symmetric numerical model was developed to further investigate and track the material flow. The findings reveal stationary layer-wise shear planes in the central portion of the plug and flow of plasticized material from the tapered interface through the clearance between the plug and the substrate, with excess volume being extruded as flash

Development of a Hybrid Thermoplastic Composite and Concrete Deck System

Reinforced concrete is a widely used structural system in conventional construction. It is used to create beams, columns, slabs, walls, bridge decks, dams, and many other structures. Concrete is a relatively inexpensive material that is much stronger in compression than in tension. This leads to the need to combine concrete with other materials to make an efficient hybrid structure. In conventional construction, steel reinforcing bars (rebar) are often used to carry the tension in the structure, as they are widely available and their design is well understood. There are some situations where rebar is not effective such as highly corrosive environments. A continuous fiber-reinforced thermoplastic (CFRTP) panel could be used as non-corrosive tension reinforcement in concrete structures to replace steel rebar. In this research, three sets of composite CFRTP-concrete specimens were designed, manufactured, and tested to evaluate their use as a replacement for steel rebar in reinforced concrete construction. To function as the tension reinforcement for the structure, a shear connection mechanism was needed to create composite action between the CFRTP panel and the concrete. For this research, E-glass fiber-reinforced thermoplastic polyethylene terephthalate glycol (PETg) was selected for its good mechanical and hygro-thermal properties and relatively low cost compared to other thermoplastic composites. Each set of composite CFRTP-concrete beams was designed to meet the requirements for a bridge deck with stay-in-place formwork given in the AASHTO LRFD Bridge Design Specifications. The first set of specimens consisted of a flat CFRTP panel with friction welded thermoplastic shear studs as the shear transfer mechanism. When loaded in four-point bending, the specimens failed at the CFRTP-concrete interface at a load that corresponded to about 50% of the ultimate strength of the shear connection from stud testing. For the second and third iterations of testing, modifications were made to the CFRTP panels to increase their flexural stiffness, allowing them to function as stay-in-place formwork for the structure. This would reduce installation costs and times as formwork and shoring would not need to be erected or removed. The second set of specimens consisted of a corrugated CFRTP panel with steel dowels run through the webs as a shear transfer mechanism. The corrugations were created by stamp forming a flat panel in a mold. The corrugated hybrid beams were tested in four-point bending and reached 117% of the required design loading prior to failure. The final set of specimens consisted of a stiffened CFRTP panel where holes were cut into the stiffeners, allowing concrete to flow into the holes creating a concrete dowel that would bear directly onto the CFRTP to transfer shear. The stiffened panels were created by bonding angle- shaped CFRTP panels to a flat CFRTP panel. The stiffened hybrid beams were tested in four-point bending and reach around 128% of the required design loading prior to failure