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

这个PFI: AIR技术翻译项目的重点是翻译一种使用形状记忆合金（SMA）和纤维增强聚合物（FRP）的新开发的复合修补技术。这些材料将作为易于安装和有效技术的一部分，用于修复钢结构的裂缝，特别是在交通基础设施中。采用这些SMA/FRP贴片是很重要的，因为在美国有近17万座钢桥在循环荷载条件下可能容易形成裂缝，比如由于交通。这些桥梁是在采用现行疲劳设计规定之前建造的。该项目将证明该技术对于修复钢桥中最棘手的裂缝类型是有效的，并将建立最合适的方法来准备钢结构的表面，以安装这些新的补丁。SMA/FRP贴片重量轻，无需重型设备即可轻松安装。它们不需要焊接、钻孔或其他不可逆的结构修改，而且它们可以被设计成完全阻止裂纹扩展。这些特点允许快速安装，更长的预计疲劳寿命，同时潜在地消除了重新修复相同裂缝的需要。对于目前最广泛使用的技术（如钻止裂孔），后续维修的需求被认为是主要问题之一。从研究发现到商业应用，该项目解决了以下技术差距：(i)目前安装复合材料贴片的最佳实践是对表面进行喷砂以去除污染物。老旧的钢结构通常含有含铅涂料，喷砂会带来环境风险，需要昂贵的保护措施。在本项目中，将确定不存在相同风险的表面制备技术，并量化表面制备对键行为的影响。（ii）初步试验表明，SMA/FRP贴片可有效修复一类裂缝，即应力引起的裂缝。这些补丁修复另一类裂缝的有效性，即变形引起的裂缝（基于不同的机制传播），将进行评估。（iii）将量化斑块在户外环境暴露条件下的长期耐久性。此外，参与该项目的博士后、博士生和本科生将通过工程和商业学生的联合活动获得技术转移经验，他们将共同确定市场潜力和最合适的技术进入市场的途径。

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.