Semester

Summer

Date of Graduation

2026

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Hota GangaRao

Committee Co-Chair

Nithi Sivaneri

Committee Member

Victor Mucino

Committee Member

Eduardo Sosa

Committee Member

Chao Zhang

Committee Member

Levente Denes

Abstract

Railroad tank cars, being one of the most used means of transportation of hazardous material across the country, have not been structurally upgraded for a long time. Thus, the Pipeline and Hazardous Materials Safety Administration (PHMSA), a United States Department of Transportation (USDOT) agency, released a rule for safer transportation of highly hazardous and flammable liquids by railroad to enhance the design specifications of both the new and existing tank cars in May 2015. A multifunctional composite jacket is proposed as a new material to structurally enhance the railroad tank cars to withstand any accidents that could happen en route.

The method used to produce the composite jacket is the vacuum assisted resin transfer (VARTM). The composite is applied on the tank car before the infusion process. Once applied, the composite is then infused with resin and left to cure. The final product is made to meet the safety requirements of the DOT specifications. Composite materials offer high strength-to-weight ratios, corrosion resistance, durability, and superior impact and puncture resistance compared to conventional materials, making them well suited for railcar protection.

The VARTM process, governed by Darcy’s law, is driven mainly by pressure difference, and influenced by viscosity, permeability, temperature, and flowrate. These parameters directly affect infusion speed, void formation, and overall composite quality. This study experimentally and theoretically investigates the interaction of these variables with one another, with emphasis on temperature variation, to improve flow behavior, reduce manufacturing time and cost, and enhance structural performance of the final composite and meet safety standards on tank cars.

In this dissertation, different variables are systematically investigated to ensure a top-quality product. The experimental setup is adjusted and improved using various methods. Spiral tube spacing (inlet), resin bleeding time, fiber orientations are all different methods utilized during infusion and researched thoroughly to enhance the composite product. The combined effects of these parameters are experimentally evaluated and theoretically checked to maximize fiber volume fraction, flexural performance to improve mechanical performance, and produce high-quality composite jackets suitable for railcar applications.

This study investigates the impact of various factors on the performance of composite materials used in tank car applications, with a focus on energy absorption, flow dynamics, and structural durability. Through thickness stitching significantly improved the absorbed energy, increasing from 2908 J/kg to 5000 J/kg. Fiber orientation O3, characterized by ±45-degree angles, demonstrated enhanced bending performance and puncture resistance, shifting the failure mode from local shear to local compression. Wider spiral tube spacing led to slower resin flow and lower void content. A 12-minute resin bleeding time was found to improve fiber volume fraction (FVF). Darcy’s law, traditionally used to model the VARTM process, was empirically modified to account for temperature variations, reducing flowrate errors from 45% to 9%. Resin heating provided substantial structural benefits for the tank car application. Dynamic testing confirmed superior impact resistance with composites, manufactured using all the methods and control variables, sustaining 7312 Nm impact energy and a strain of -1702 µε compared to the conventional 11-gauge steel plate currently used by the DOT which can only withstand an impact energy of 4426 Nm. This confirms the material's suitability for high-impact resistance applications such as tank car jacket manufacturing.

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