冻融/干湿环境影响下CFRP板-钢界面黏结性能试验

Experimental Study on the Interface Bond Properties of CFRP-Plate-Steel-Plate Joints in Freeze-Thaw/Dry-Wet Environments

恶劣环境影响下纤维增强复合材料(CFRP)板加固钢结构的黏结界面是薄弱环节。为掌握恶劣环境对加固界面黏结性能的影响程度,制作了干湿、冻融和冻融/干湿交互环境作用的CFRP板-钢双搭接试件,开展了试件的拉伸试验,分析了试件破坏模式、极限承载力、界面剪应力及分布、黏结-滑移关系和界面刚度变化等。结果表明:多数试件发生CFRP板表面纤维剥离破坏模式和CFRP板表面纤维剥离与黏结剂间剥离的混合破坏模式,界面峰值剪应力出现在靠近试件钢板接缝处两侧黏结界面,初始剥离始于该区域,远离该区域的界面剪应力迅速降低,超过CFRP板有效黏结长度后不再变化。干湿环境作用对试件破坏时的极限承载力、界面峰值应力、界面刚度、断裂能有一定影响,但不明显;冻融环境试件破坏时的极限承载力、界面峰值应力、界面刚度、断裂能比其他2种环境相对大,而冻融/干湿环境试件在3种环境中最小,表明冻融/干湿循环交互作用加剧了试件界面黏结性能的降解程度。同时,多数环境组试件黏结-滑移曲线仅存在上升段,少数环境组试件黏结-滑移曲线存在下降段,但从峰值应力到最终完全破坏历经时间较短,其延性不明显。冻融、冻融/干湿环境作用对加固界面黏结性能有较大的影响,干湿环境作用影响较小,在加固设计中应重点考虑冻融、冻融/干湿环境作用的影响。

The bond interface of steel structures strengthened with carbon-fiber-reinforced polymer(CFRP) plates is a weak link under the influence of harsh environments. To understand the influence of a harsh environment on the bonding performance of the bond interface, CFRP-plate-steel double lap joint specimens were made from dry-wet, freeze-thaw, and freeze-thaw/dry-wet interaction environment actions, and tensile tests of the specimens were performed. The failure modes, ultimate bearing capacity, interfacial shear stress distribution, bond-slip relationship, and interfacial stiffness changes of the specimens were analyzed. The results show that the surface fiber peeling failure mode of the CFRP plate and the mixed failure mode between the surface fiber peeling of the CFRP plate and lnterface peeling between the surface of the CFRP plate and the adhesive occurred in most specimens. The peak interfacial shear stress appears at the bonding interface on both sides near the steel plate joint of the specimens, where the interfacial initial peeling begins, and the interfacial shear stress far from this area decreases rapidly, which does not change after exceeding the effective bonding length of the CFRP plate. The influence of the dry-wet environment on the ultimate bearing capacity, interface peak stress, interface stiffness, and fracture energy is not apparent, and the ultimate bearing capacity, interface peak stress, interface stiffness, and fracture energy of the specimens of the freeze-thaw environment are larger than those of the other two environments. Conversely, the specimens of the freeze-thaw/dry-wet environment are the smallest in the three environments. This indicates that the degradation of the bonding properties of the specimens is exacerbated by the freeze-thaw/dry-wet cycles alternating action. Moreover, there is only an increasing stage in the bond slip curve of most environmental groups and a descent stage in the bond-slip curve of a few environmental groups. However, the time from the peak stress to the final complete failure is short, and its ductility is not evident. The research shows that freeze-thaw and freeze-thaw/dry-wet environments have a significant impact on the bonding performance of the reinforced interface, and the effects of a dry-wet environment have less impact. The effects of freeze-thaw and freeze-thaw/dry-wet environments should be considered in reinforcement design.