CFRP板与钢梁粘结剥离破坏的试验研究

Experimental study on debonding failure of steel beams strengthened with a CFRP plate

粘结层是碳纤维增强复合材料(CFRP)板加固钢梁的最薄弱环节。通过对4根加固梁的静载试验及6根加固梁的疲劳试验研究了CFRP板加固钢梁的剥离破坏。在CFRP板底端部贴的应变片记录了试验过程中的应变变化,并结合理论分析,探讨了各项因素对板端应变的影响及CFRP板的剥离破坏过程。静载试验中记录的随外荷载变化的应变曲线以及疲劳试验中记录的随疲劳加载次数变化的应变曲线都能分为4个阶段。阶段Ⅰ为板端溢胶对板端作用的拉力的衰退阶段,板端溢胶逐渐失去作用;阶段Ⅱ为正应力衰退阶段,正应变开始减小,而剪应力继续增加,使得压应变的增加更快;阶段Ⅲ为剪应力衰退阶段,在达到压应变峰值后,剪应力和应变减小,直到应变为0;阶段Ⅳ为剥离破坏阶段。根据这一规律,利用板端的应变片可以很好地监控加固梁粘结层的性能变化及裂缝的萌生。

Adhesive bonding is the weakest link of steel beams strengthened with CFRP plates. This paper presents the results of an experimental study on debonding failure of steel beams reinforced with CFRP plates. Four specimens were tested under static loads and six specimens were tested under fatigue loads. Two strain gauges were mounted at the ends of the plate bottom. The strain recorded by the strain gauges was used to find the progress of the debonding in specimens. In accordance with the theoretical study and the test results, the curves of strain from both static tests and fatigue tests can be divided into four distinct phases. During phase Ⅰ, the spew fillet was losing its strength gradually. During phase Ⅱ, the spew fillet no longer affected the strain, and the peel stress at the plate end reduced gradually. Phase Ⅲ began when the strain reached the maximum compression and ended when the shear stress almost disap plate end. Debonding started in phase Ⅳ. Finally, it is suggested to use backface-strain technique to deterioration of the adhesive and crack initiation at the plate end.