温度—荷载耦合作用下泡沫复合材料夹层结构界面剥离机理研究

In recent years, sandwich structures with GFRP face sheets and a foam core have been widely used in structural engineering due to its advantages of low cost, high strength to weight ratios and convenient usage, but the coupling effects of temperature and loads could accelerate the propagation of interface delamination. Furthermore, most previous studies focused on influence of applied loads on interface delamination, and the temperature influence was ignored, which cannot correspond to the real engineering service environment. Hence, to address the mentioned issue, the research of the interface delamination of sandwich structures under the coupling effects of temperature and loads will be conducted in this project. The main research contents include three sections: （1）Based on the Reissner—Mindlin plate theory, the equilibrium equations of interface element will be derived. The analytical model of temperature stress distribution of interface will be obtained by determining the boundary conditions of interface element; （2）According to the elastic fracture theory, the expression of strain energy release rate considering the temperature stress distribution of interface will be derived. Meanwhile, the relationship between interface fracture toughness and mode mixity will be established;（3）On the basis of finite element method, the temperature-displacement increment approach will be proposed to study the propagation of delamination crack of under the coupling effects of temperature and loads. The above work can generate an theoretical framework to investigate the interface delamination of sandwich structures under coupling effects of temperature and loads, and aid engineers to design sandwich structures.

泡沫复合材料夹层结构由于自身的优异性在建筑工程领域得到广泛应用，然而在温度与荷载耦合作用下夹层结构界面剥离时有发生。现有研究侧重分析单一荷载因素下界面剥离机理，忽略了温度效应的影响，与工程实际服役环境不符。为了解决这一问题，本项目以温度—荷载耦合作用下泡沫复合材料夹层结构界面剥离机理为研究对象，拟开展以下研究内容：（1）基于Reissner—Mindlin板理论，运用界面微元法，建立平衡方程，通过对边界条件的确定得出界面温度应力分布模型；（2）以断裂理论为基础，引入界面温度应力分布模型，求解得到剥离尖端应变能释放率，建立断裂韧度与模式混合度之间函数关系，形成界面剥离的判定准则；（3）结合有限单元法，通过裂缝扩展增量迭代，建立温度位移增量法，分析夹层结构温度—荷载耦合作用下界面剥离裂缝扩展规律。最终可建立温度—荷载耦合作用下复合材料夹层结构界面剥离的理论分析框架，为夹层结构设计提供依据。

本项目以温度—荷载耦合作用下泡沫复合材料夹层结构界面剥离机理为研究对象，完成了以下研究内容：（1）试验研究了夹芯结构界面温度应力分布，同时基于Reissner—Mindlin板理论，运用界面微元法，建立几何方程和平衡方程，通过对边界条件的确定得出了界面温度应力分布模型，通过与试验结果相对比证明所得理论模型可以准确预测界面温度应力分布；（2）开展了高温作用下I型、II型、I-II混合型界面断裂试验，得到了荷载与裂缝长度及宽度的关系曲线，同时基于断裂理论，引入界面温度应力分布模型，求解得到了剥离尖端应变能释放率，建立了断裂韧度与模式混合度之间函数关系，形成了界面剥离的判定准则；（3）结合有限单元法，通过裂缝扩展增量迭代，建立了温度位移增量法，分析了夹层结构温度—荷载耦合作用下界面剥离裂缝扩展规律。 本项目的研究成果可用于夹层结构性能评估与设计，并已在南京玉竹楼夹芯楼板的设计中成功应用。