木材表面初始损伤对CFRP-木材界面粘结性能的影响

Effects of preexisting surface damage on bonding performance at CFRP-wood interfaces

  • 摘要: 为了研究木材表面初始损伤对碳纤维增强树脂复合材料(CFRP)-木材界面粘结性能的影响,以木材表面初始损伤率为变量,设计了4组(共12个)CFRP-木材双面剪切试件,分析了初始损伤对粘结界面破坏形态、荷载-应变曲线、应变分布曲线及界面承载力等力学性能的影响规律,探讨了木材初始损伤对界面力学性能的影响机制。试验结果表明:木材表面存在的初始损伤改变了CFRP-木材界面的破坏形态,随着损伤率的增加,剪切破坏面进入木材基体的深度逐渐变浅,界面的脆性破坏特征越显著;木材表面的初始损伤截断了木材纤维,破坏了木材表面的完整性,削弱了界面应力传递效率,增加了界面应力集中现象,使界面粘结承载力随着损伤率的增加而不断降低。本文通过对粘结界面微段的受力分析,推导了极限状态下界面应力分布计算表达式,建立了考虑木材表面初始损伤影响的CFRP-木材界面粘结承载力模型,界面粘结承载力预测模型的计算结果与试验结果的误差均小于6%,吻合较好。

     

    Abstract: Four groups of carbon fiber reinforced polymer (CFRP)-wood composite samples were prepared to study the effects of preexisting surface damage on the wood on the interfacial bonding in CFRP-wood composites. The effects of the extent of damage on the failure mode, load-strain, strain distribution and interfacial bearing capacity of the composites were analyzed. In addition, the influences of the damage on the mechanical properties of the interfaces were discussed. The experimental results show that the surface damage changes the failure mode of the CFRP-wood interfaces. As the extent of the damage increases, the shear failure surface is closer to the surface, and there are obvious characteristics of brittle failure at the interface. The preexisting surface damages cut the wood fibers, destroy the integrity of the surface fibers in the wood, weaken the interfacial stress transfer efficiency, concentrate the interfacial stress, and decrease the bearing capacity of the bonded interface. An expression for the interfacial stress distribution in the final composites was derived by analyzing the stress at bonded interface on the micron scale, and a model for the bearing capacity of the CFRP-wood interfaces that accounts for preexisting damage on the wood surface was established. The error between the calculation results of the interface bonding bearing capacity prediction model and the test results is less than 6%, which is in good agreement.

     

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