Date of Award

Summer 8-17-2018

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Department

Mechanical Engineering

Advisor

William Davids

Second Committee Member

Roberto Lopez-Anido

Third Committee Member

Senthil Vel

Abstract

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.

  1. Conduct a literature review to direct thermoplastic material selection
  2. Characterize thermoplastic material mechanical properties using standardized mechanical testing
  3. Design a hybrid composite-reinforced concrete beam, and
  4. 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.

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