Repair of a cracked steel member using CFRP strip

本项目是应用碳纤维增强聚合物条（以下简称CFRP条）修复疲劳裂纹的实验研究。这项研究在2002年到2003年进行了两年。2002年，对裂纹进行了疲劳试验，在裂纹尖端钻孔后修补CFRP条进行了修复。试验结果表明，随着CFRP条宽度的增加，修复试件的耐久极限增大。在低应力范围内，即使CFRP条的宽度小于裂纹长度，其疲劳寿命也能迅速提高。因此，可以说修复效果明显。2003年，使用仅通过修补CFRP条来修复裂纹的试件进行了疲劳试验。在这种情况下，并没有在所有类型的标本中显示持久极限。然而，在提高疲劳寿命方面有足够的效果。宽的玻璃钢条比窄的玻璃钢条修复效果好。此外，即使在CFRP条宽度小于裂缝长度的情况下，该方法也足以作为一种实用的急救修复方法。在高应力范围内，修复效果较好。从上述研究可以看出，CFRP条适用于带或不带止孔的疲劳裂纹修复。CFRP带材实用化的可能性可以说是很高的。

This project is an experimental study on an application of Carbon Fiber Reinforced Polymer strip, hereinafter called CFRP strip, to repair of a fatigue crack. The study was done for two years in 2002 to 2003.In 2002, fatigue tests were performed using a specimen with the crack which was repaired by patching the CFRP strip after drilling stop holes at the crack tips. It was known from the results of the tests that an endurance limit of the repaired specimen was increased according to increase of width of the CFRP strip. Even if width of the CFRP strip was shorter than the crack length, fatigue life was increased rapidly in the region of the low stress range. Therefore, it was able to be said that the repair effect had shown up notably.In 2003, fatigue tests were performed using a specimen with the crack which was repaired by only patching the CFRP strip. In this case, an endurance limit was not shown in all types of specimen. However, therewassufficient effect in an improvement of fatigue life. And, the wide CFRP strip showed higher repair effect than narrow CFRP strip. In addition, even when width of the CFRP strip was shorter than the crack length, it was judged that this method was enough practically as a first-aid repair. Moreover, the higher repair effect was shown in the region of the high stress range.From the above-mentioned studies, it was clear that the CFRP strip was applicable to repair of a fatigue crack with or without a stop hole. Possibility of practical use of the CFRP strip can be said to be high.