基于高阶理论的加筋复合材料夹芯结构屈曲有限元模型

FINITE ELEMENT MODEL FOR BUCKLING OF STIFFENED COMPOSITE SANDWICH STRUCTURES BASED ON HIGHER-ORDER THEORY

加筋复合材料夹芯结构由于面板与夹芯层的力学性能差异较大,层间剪切变形明显,层间剪切应力对结构的屈曲特性影响非常明显.此外筋条与面板之间横向剪切变形也会显著地影响加筋夹芯结构的屈曲特性.因此,需要发展一种能准确计算面板与芯体之间、筋条与板之间横向剪切应力的模型来分析复合材料加筋夹芯结构的屈曲特性.文章推导了正弦型整体-局部高阶剪切变形理论,该理论满足面内位移、横向剪切应力连续条件和自由表面条件,并且未知量个数独立于加筋夹芯板的层数.基于此理论,结合离散的Kirchhoff三角形单元(DKT单元)构造了正弦型整体-局部高阶三角形板单元(SGLT),该单元满足面内位移在厚度方向的锯齿分布和横向剪切应力层间连续性条件,并通过两个数值算例验证了模型的准确性.随后评估了金属面板加筋夹芯板和复合材料面板格栅加筋夹芯板在各种几何、材料参数和边界条件下的屈曲特性.数值分析结果表明,建立的有限元模型能准确地预测加筋复合材料夹芯结构的屈曲行为.并且相较于三维有限元模型,建立的模型具有更高的计算效率.

Due to the large difference in mechanical properties between the faceplates and core,the interlaminar shear deformation of the stiffened composite sandwich structure is obvious,and the interlaminar shear stress has a significant impact on the buckling characteristics of the structure.In addition,the transverse shear deformation between stiffeners and plates will also significantly affect the buckling characteristics of the stiffened sandwich structure.Therefore,it is necessary to develop a mechanical model that can accurately calculate the transverse shear stresses between the faceplates and core and between stiffeners and faceplates to study the buckling characteristics of composite stiffened sandwich structures.Thus the sine type global-local higher-order shear deformation theory is derived.This theory meets the conditions of in-plane displacement,transverse shear stress continuity and free surface conditions,and the number of unknowns is independent of the number of layers of stiffened sandwich plates.Based on the theory,the discrete Kirchhoff triangular element(DKT element) is used to construct the sinusoidal global-local triangular plate element(SGLT),and the accuracy of the model is verified by two numerical examples.Then the buckling characteristics of metal stiffened sandwich plates and composite grid stiffened plates under various geometric,material parameters and boundary conditions are evaluated.The numerical examples show that the established finite element model can accurately predict the buckling behaviors of stiffened sandwich structures.And compared to the three-dimensional(3D) finite element model,the established model has high computational efficiency.