Ultrasonic Evaluation of Delimination Defects at FRP/Concrete Interface

Ehsani纤维增强复合材料（FRP）正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加强和修复现有的土木结构。大量的现场应用表明，与传统的修复技术相比，frp可以节省30%的成本。该技术的成功在很大程度上取决于施工质量，特别是环氧接缝，它必须将FRP板的应力传递到基材上。因此，非常需要开发无损评估（NDE）技术，以检测环氧胶合线上的任何缺陷或分层。这样的系统不仅可以用来确保建筑质量，还可以帮助检测结构在使用寿命期间可能形成的任何损坏，如紫外线、湿气渗透等环境影响。修复的质量将通过对内部缺陷、空隙和分层的超声检查进行无损监测，当试样不均匀时，例如要使用的复合材料层，评估两种不同材料或层之间的界面是一项更加困难的工作。如果两个界面是脱键或弱键，但彼此紧密接触，形成所谓的“接吻”或“滑动”键，则特别困难。因此，对于这种应用，兰姆波扫描技术似乎是优越的技术。＊＊＊

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. ***