碳纤维木材复合材结合层剪切蠕变性能研究

Shear creep properties for the bond layer at the wood-CFRP interface

为了研究碳纤维应用于建筑木构件及其节点加固工程中的长期承载性能,采用持续负载的剪切试验方法对碳纤维木材复合材结合层在高湿(温度60℃,相对湿度90%),低湿(温度24℃,相对湿度45%)环境条件下的蠕变性能进行了研究。结论表明:Burger模型可较精确地模拟复合材结合层的短期剪切性能(R2≥98%);高湿环境下结合层剪切蠕变量显著大于低湿环境,温度及相对湿度都是影响蠕变的重要因素;结合层厚度越大,剪切蠕变变形也越大,应力松弛较大,建议碳纤维与木材复合时施加一定的压力(0.05 MPa以上)以减少结合层厚度;高湿环境下高应力水平的蠕变速率最大,较短时间便出现结合层断裂,在碳纤维设计应用时,应确保结合层剪切应力水平在极限应力的50%以内。

To know more about the bond layer＇s long term properties between carbon fiber reinforced polymer（CFRP） sheets and the wood member as well as its connecting point,shear creep performance was studied using a consistent load with the Burger model.And samples were placed in dry conditions（temperature 60 ℃,relative humidity 90%） and wet conditions（temperature 24 ℃,relative humidity 45%）.Results showed that the Burger model precisely simulated the bond layer＇s short-term shear performance（correlative coefficient R2 ≥ 98%）.Compared to dry conditions,with wet conditions,the amount of creep was larger.Also,with an increase in thickness of the bond layer,creep deformation and stress relaxation increased.For high stress levels,a high creep rate,which could lead to a fracture of the bond layer,should be contained.Under the consideration of safety,a pressure（above 0.05 MPa） should be placed on the connection process between CFRP and wood to reduce the thickness of the bond layer.Also,in application,the shear stress level of the bond layer should be maintained within 50% of the maximum stress level.