Repair of a cracked steel member using CFRP strip

该项目是应用碳纤维增强聚合物带（以下简称CFRP带）修复疲劳裂纹的实验研究。该研究从2002年到2003年进行了两年。2002年，使用在裂纹尖端钻止孔后修补CFRP条修复的裂纹试件进行了疲劳试验。从测试结果可知，修复后的样本的耐久性极限随着CFRP条宽度的增加而增加。即使CFRP带的宽度比裂纹长度短，疲劳寿命在低应力范围内也能迅速增加。因此，可以说修复效果显着。2003年，用仅修补CFRP条修复的裂纹试件进行了疲劳试验。在这种情况下，所有类型的样本都没有显示出耐久性极限。然而，对于疲劳寿命的提高具有足够的效果。并且，宽CFRP条比窄CFRP条表现出更高的修复效果。另外，即使当CFRP条的宽度比裂纹长度短时，也判断该方法作为急救修复实际上是足够的。而且，在高应力范围区域显示出较高的修复效果。从上述研究可以清楚地看出，CFRP条适用于修复有或没有止动孔的疲劳裂纹。 CFRP条的实用化可能性可以说很高。

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.