Repair of a cracked steel member using CFRP strip

本课题是对碳纤维增强聚合物带(以下简称CFRP带)在疲劳裂纹修补中的应用进行的试验研究。2002-2003年进行了为期两年的疲劳试验。2002年，对一个裂纹试件进行了疲劳试验，该试件在裂纹尖端打止孔后修补了CFRP条带。试验结果表明，修复后试件的耐久极限随着碳纤维布宽度的增加而增大。即使CFRP条的宽度小于裂纹长度，在低应力区疲劳寿命也会迅速增加。因此，可以说，修复效果是显著的。2003年，对只修补了CFRP条的裂纹试件进行了疲劳试验。在这种情况下，并不是所有类型的试件都显示出耐久极限。然而，在提高疲劳寿命方面仍有足够的效果。并且，宽CFRP带的修复效果要好于窄CFRP带。此外，即使当CFRP条的宽度小于裂缝长度时，也可以判断该方法在实际应用中是足够的急救修复。上述研究表明，碳纤维加固带适用于有无止动孔的疲劳裂纹的修复。CFRP条带实际应用的可能性可以说很高。

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.