Browsing by Author "Tatar, Jovan"
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Item Bladder expandable robotic system and UV materials for rapid internal pipeline repair(SAMPE Conference Proceedings 2023, 2023-04-18) Tierney, John J.; Vanarelli, Alex; Fuessel, Lukas; Abu-Obaid, Ahmad; Sauerbrunn, Steve; Das, Shagata; Deitzel, Joseph; Tatar, Jovan; Heider, Dirk; Shenton, Harry W. III; Kloxin, Christopher J.; Sung, Dae Han; Thostenson, Erik; Gillespie, John W. Jr.This paper describes a novel composite placement process to fabricate stand-alone structural pipe within existing legacy pipelines—with no disruption in gas service. The process utilizes low-cost, UV-curable, glass fiber reinforced plastics (GFRP) for discrete preforms made from continuous fiber fabrics. These sections are designed to meet 50-year service life by addressing the unique loading conditions of the pipe repair allowing for the design customization of the preforms to accommodate the state of pipe corrosion, access points or other local features that may vary along the length of the pipe. The approach offers maximum design flexibility and customization while minimizing installation time and cost. The preforms are fabricated above ground using rapid automated manufacturing methods for quality control. The preforms are transported by a tethering system to the robot. The robot is comprised of a self-propelled dual inflation expandable bladder system that places, consolidates, and cures standard or custom composite sections along the entire pipe length in a continuous co-cure process. This system is designed to adapt to pipe features that include lateral tees, service connections, joints, gaps, and irregular cross sections. In addition, variable thickness composite sections can be placed along the pipe where exposed to high external loads under railroads, highways, airports or where soil erosion and movement occurs. This paper presents the robot design, assessment of UV curable resins, embedded sensing methods, and fabrication of pipe sections with this system.Item Core–Shell Rubber Nanoparticle-Modified CFRP/Steel Ambient-Cured Adhesive Joints: Curing Kinetics and Mechanical Behavior(Materials, 2024-02-04) Okeola, Abass Abayomi; Hernandez-Limon, Jorge E.; Tatar, JovanExternally bonded wet-layup carbon fiber-reinforced polymer (CFRP) strengthening systems are extensively used in concrete structures but have not found widespread use in deficient steel structures. To address the challenges of the adhesive bonding of wet-layup CFRP to steel substrates, this study investigated the effect of core–shell rubber (CSR) nanoparticles on the curing kinetics, glass transition temperature (𝑇𝑔) and mechanical properties of ambient-cured epoxy/CSR blends. The effects of silane coupling agent and CSR on the adhesive bond properties of CFRP/steel joints were also investigated. The results indicate that CSR nanoparticles have a mild catalytic effect on the curing kinetics of epoxy under ambient conditions. The effect of CSR on the 𝑇𝑔 of epoxy was negligible. Epoxy adhesives modified with 5 to 20%wt. of CSR nanoparticles were characterized with improved ductility over brittle neat epoxy; however, the addition of CSR nanoparticles reduced tensile strength and modulus of the adhesives. An up to 250% increase in the single-lap shear strength of CFRP/steel joints was accomplished in CSR-modified joints over neat epoxy adhesive joints.Item Development of a Recyclable Flax Fiber Reinforced Polymer Composite(Composites in Civil Engineering, 2023-06-28) Das, Shagata; Doshi, Sagar; Millan, Emmanuel; Mendez, Damaris; Luckenbill, Dan; Tatar, JovanThis study compared the mechanical properties of a recyclable flax fiber reinforced polymer composite (FFRP) with a covalent adaptable network (CAN) matrix to an FFRP composite with a conventional (unrecyclable) epoxy resin matrix. The results indicated that composites fabricated via vacuum-assisted resin transfer molding (VARTM) exhibited up to 19% higher tensile modulus and strength compared to those fabricated via hand layup, attributed to reduced air void content and more uniform fiber alignment. Microscopy evidence supported by mechanical property tests revealed superior adhesion of the CAN matrix to flax fibers compared to conventional epoxy resin. Additionally, a solvent-based method was demonstrated for separating fibers from the CAN matrix, facilitating reuse or upcycling.Item Diagnostic load testing and assessment of a corroded corrugated metal pipe culvert before rehabilitation(Structure and Infrastructure Engineering, 2023-11-15) Safari, Sajjad; DuBose, Tyler; Head, Monique H.; Shenton, Harry W. III; Tatar, Jovan; Chajes, Michael J.; Karam, Jonathan; Hastings, Jason N.Buried culverts are important structures within the civil infrastructure that convey water beneath roadways, bridges, and other systems while also being load bearing. However, many culverts are deteriorating and reaching the end of their design life span, where assessment methods to determine whether replacement or rehabilitation techniques such as spray applied pipe liners (SAPLs) are needed to extend their service life. In this study, mounted sensors and vision-based measurement techniques are used to assess the in situ conditions of a culvert consisting of corrugated metal pipes before being rehabilitated with geopolymer (cementitious-based) SAPLs. Results from diagnostic load tests (variating from static to dynamic) are presented to evaluate maximum deformations, verify the load-carrying effectiveness of the SAPLs, and compare results to design calculations due to the presence of a live load acting on the culvert.Item Mechanical behavior of UV-cured composite stepped lap adhesive joints(SAMPE Conference Proceedings 2023, 2023-04-18) Das, Shagata; Gillespie, John W. Jr.; Shenton, Harry W. III; Tatar, JovanJoints often control the design of composite structures because they represent locations of high stress concentrations. Adhesive joints offer several benefits over mechanically fastened connections such as reduced stress concentrations, and higher joint efficiency. This study evaluates the performance of stepped lap adhesive joints. The novelty lies in the implementation of UV-cured vinyl ester resin which allows integration of co-cured stepped lap joints in applications where fast curing at ambient temperatures is required. The experimental program consisted of a series of tensile tests on 20-ply 7781 E-glass laminates integrating UV-cured stepped lap joints, where the primary variables were stepped lap joint angle (ranging from 0.9° to 5.7°) and number of ply drops (ranging from 1 to 10). Physical properties of all the UV-cured joint panels, such as density, void content, fiber volume fraction, and hardness, were also evaluated and compared between the test groups. The preliminary findings indicate that reducing the scarf angle from 5.7° to 0.9° increased the joint strength by a maximum of 115%. The joint strength efficiency approached 100% of the laminate tensile strength for 19-step joints having a scarf angle of 0.9º.