Ultrasonic Evaluation of Delimination Defects at FRP/Concrete Interface

9800345 Ehsani纤维增强复合材料（FRP）正在迅速成为一种可行的新型建筑材料。 也许这些材料最适合的应用领域是现有土木结构的加固和修复。 许多现场应用表明，与传统的修复技术相比，FRP可以节省约30%的成本。 该技术的成功在很大程度上取决于施工质量，特别是环氧树脂接头，它必须将应力从FRP板转移到基底。 因此，有一个非破坏性评估（NDE）技术的发展，可以检测任何缺陷或分层环氧树脂粘接线的巨大需求。 这样的系统不仅可以用来确保建筑质量，而且还可以帮助检测在结构寿命期间可能由环境影响（例如紫外线、湿气渗透等）形成的任何损坏。 修复的质量将通过对内部缺陷、空隙和分层的超声波检查进行非破坏性监测，当试样不均匀时，例如要使用的复合层，两种不同材料或层之间的界面评估是一项非常困难的工作。 如果两个界面是脱粘的或弱结合的，但彼此紧密接触，形成所谓的“吻接”或“滑动”结合，则这是特别困难的。 因此，对于这种应用，兰姆波扫描技术似乎是上级技术。 ***

9800345 Ehsani Fiber Reinforced Composites (FRP) are fast becoming a viable new construction material. Perhaps the most suitable area of application for these materials is in the field of strengthening and rehabilitation of existing civil structures. Numerous field applications have demonstrated that FRPs can result in some 30% cost savings compared to conventional rehabilitation techniques. The success of the technique depends to great extend on the quality of the construction, and in particular, the epoxy joint which had to transfer the stresses from the FRP plate to the substrate. Consequently, there is a great need for development of Non-Destructive Evaluation (NDE) techniques which could detect any flaws or delaminations in the epoxy bond line. Such a system could not only be used to ensure quality of construction, but could also help with detection of any damage that may form during the life of the structure by environmental effects such as ultraviolet rays, moisture penetration, etc. The quality of rehabilitation will be monitored nondestructively by ultrasonic inspection of internal defects, voids and delaminations, when the specimen is not homogeneous, such as a composite layer that is to be used, evaluation of interfaces between two different materials or layers is a much harder job. It is specially difficult if the two interfaces are debonded or weakly bonded but are in close contact with each other forming what is called "kissing" or "slip" bonds. Hence for this applicaiton the Lamb wave scanning technique appears to be the superior technique. ***