PFI:AIR-TT: Shape Memory Alloy (SMA) Fiber Reinforced Polymer (FRP) Patch for Repair of Cracked Metallic Structures

点击翻译按钮获取中文摘要

This PFI: AIR Technology Translation project focuses on translating a newly developed composite patching technology using shape memory alloys (SMA) and fiber reinforced polymers (FRP). These materials will be used as part of easy-to-install and effective techniques to repair cracks in steel structures, specifically in transportation infrastructure.   The adoption of these SMA/FRP patches is important because there are nearly 170,000 steel bridges in the United States that may be susceptible to the formation of cracks under cyclic loading conditions such as due to traffic.  These bridges were constructed prior to the adoption of current fatigue design provisions. The project will result in a proof-of-concept that the technology is effective for repairing the most troublesome types of cracks that form in steel bridges and will establish the most appropriate methods to prepare the surfaces of steel structures to install these new patches. The SMA/FRP patches are lightweight and can be easily installed without heavy equipment. They do not require welding, drilling or other irreversible modification of the structure, and they can potentially be designed to completely halt crack propagation.  These features allow for rapid installation, and longer projected fatigue lives while potentially eliminating the need to re-repair the same cracks. The need for subsequent repairs has been cited as one of the primary concerns with the currently most widely used techniques such as drilling crack-stop holes. This project addresses the following technology gap(s) as it translates from research discovery toward commercial application: (i) The current best practicing for installing composite patches is to grit-blast the surface to remove contaminants. Older steel structures typically contain lead paint and grit blasting poses an environmental risk that requires expensive protective measures. In this project, surface preparation techniques will be identified that do not present the same risks and the influence of surface preparation on bond behavior will be quantified. (ii) Preliminary testing has demonstrated that the SMA/FRP patches are effective at repairing one class of cracks, namely stress-induced cracks. The effectiveness of these patches to repair another class of cracks, namely distortion-induced cracks (which propagate based on a different mechanism), will be evaluated. (iii) The long-term durability of the patches under out-door environmental exposure conditions will be quantified. In addition, personnel involved in this project, post-doc, Ph.D. students, and undergraduate students, will receive technology transfer experiences through joint activities between engineering and business students who will, together, identify the market potential and most suitable path to market for the technology.