Study on Progressive Damage Assessment and Scarf Repair of Composite Honeycomb Structure

复合材料蜂窝结构渐进损伤评估及挖补修理研究

¹ School of Civil Aviation, Northwestern Polytechnical University, Xi'an 710072, China
² School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China
³ Damage Detection and Structural Maintenance Technology Lab, Aircraft Strength Research Institute of China, Xi'an 710065, China
⁴ Institute of Navigation Technology, Shanghai Engineering Center for Microsatellites, Shanghai 201203, China

Received: 20 January 2020

Abstract

As the widely application of composite honeycomb structure in aircraft Structural Significant Items(SSI) and other structures, the damage assessment and repair scheme because of the impact and other damages have become one of the most concerned issues in the civil aircraft composite structures. In view of the progressive damage assessment of composite honeycomb structure and it's adhesively scarf repair parameter influence, the finite element model based on honeycomb core equivalent model and 3D solid units C3D8 and zero thickness cohesive force unit COH3D8 is established. A special USDFLD program is developed with FORTRAN for ABAQUAS using 3D Hashin criterion Besant criterion and B-K criterion to realize the damage simulation of composite panels, honeycomb cores and adhesive. The relationships between the structural strength recovery rate and the repair parameters such as patch oblique angle, extra layers layup angle and extra layers thickness are studied for the perforation injured honeycomb structure. The results show that the decrease in the patch oblique angle leading to an increase in the internal shear stress of the adhesive, the increase in the angle between the extra layers of the patch and the external load, and the increase in the thickness of the extra layers causing stress concentration and premature instability at the lap edge, will significantly reduce the strength recovery rate of the repaired honeycomb structure. The perfect patch form with 1:10 cut oblique angle and only one extra layer of 0° layup angle is concluded, which achieves the optimal strength recovery effectiveness, reaching 95.72% of the non-damaged honeycomb structure.

摘要

复合材料蜂窝结构越来越广泛地应用于飞机承力结构件，其受冲击等损伤后的损伤评估与修理方案成为民机复材结构研究中最关切的问题之一。针对复合材料蜂窝结构渐进损伤评估及阶梯式胶接挖补修理问题，基于蜂窝芯子等效模型和C3D8R三维体单元及0厚度三维粘聚力单元COH3D8建立蜂窝结构渐进损伤分析和挖补修理参数研究的三维有限元模型；基于三维Hashin准则、Besant准则和B-K准则开发USDFLD程序实现复合材料层合板、蜂窝芯子和胶层的损伤模拟与失效；针对蜂窝结构穿孔损伤仿真研究补片挖补角度、额外层铺层角及厚度等参数对修理后结构强度恢复效果的影响规律。结果表明：补片挖补角度减小带来搭接处胶层内部剪应力升高，补片额外层铺层方向与外载荷夹角增大，以及额外层厚度增加导致搭接边缘出现应力集中而更易提前失稳，都会明显降低蜂窝结构挖补修理后的强度恢复效果。仿真分析结果表明挖补补片选取1层0°铺层的额外层和1:10的挖补斜率时，蜂窝结构穿孔损伤修理件的强度恢复效果最佳，达到无损件的95.72%。