泡沫夹芯面板非穿透损伤挖补维修有限元分析

Scarf-Patch Repair Analysis of Foam Core Sandwich Panel With Non-Penetrating Damage

建立了SR20飞机含非穿透损伤复合材料泡沫夹芯结构壁板挖补维修的三维有限元模型。分析了有限元模型的收敛性,给出了合理的网格划分密度。对单向拉伸和双拉伸载荷下含非穿透损伤泡沫夹芯结构进行了应力分析,给出了完好结构和维修后结构面板各材料主方向应力分布。基于最大应力准则给出了完好结构和维修后结构的单向拉伸强度和双向拉伸强度。分析结果表明,维修后的结构在单向拉伸状态下,初始损伤为面内剪切失效,应力极值点位于母板上临近维修铺层边界处与x方向结构对称轴约成30°的位置;双向拉伸状态下,初始损伤为纤维拉伸断裂,应力极值点位于母板上维修铺层边界处与x方向结构对称轴约成45°的位置。在理想修复状态下,单向拉伸时的强度恢复系数为85.8%,双向拉伸时强度恢复系数为96.7%。维修区域材料不连续,导致应力集中,使结构维修后强度下降。维修后强度随表面贴补铺层数增加而降低,原因为贴补铺层增大了局部刚度,使维修区域应力水平升高。

The three-dimensional finite element model of foam core sandwich panel with non-penetrating damage of SR20 airplane is established. The convergence of the model is analyzed and the effective mesh density is given. Stress analysis of the sandwich panel with non-penetrating damage under uniaxial and twin-axial tensile loading is car- ried out. The material principle direction stresses distribution of the sandwich panel with no defects and repaired panel are given. The uniaxial and twin-axial tensile strengths of the intact and repaired panel are calculated based on the strength criterion of maximum stress. It is shown that under uniaxial tensile loading, the initial damage mode of the re- paired panel is shear failure. The failure occurs on the motherboard which is beside the boundary of the repair area and about 30° to the x symmetry axis of the panel. Under twin-axial tensile loading, the initial damage mode of re- paired panel is the fracture of the reinforce fiber. The failure occurs on the motherboard which is near the boundary of the repair area and is about 45~ to the x symmetry axis of the panel. In the ideal repair status, the strength recovery coefficient of the repaired panel under uniaxial tensile loading is 85.8% , and 96.7% for the same repaired panel un- der twin-axial tensile loading. The strength of the repaired sandwich panel decreases due to the stress concentration caused by the material discontinuity of the repair area. The strength of the repaired sandwich panel decreases with the increase of the number of surface patches. This happens thanks to the increase of local stiffness caused by the addi-tional surface patches.