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

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.