Fatigue behaviors of steel honeycomb sandwich panels which were initially damaged by interface debond-ing were investigated through four-point bending tests. With a load ratio R =0.20 and load level r = 15% -90% , the effects of different debonding sizes were analyzed to obtain fatigue life S-N curves and fatigue limits. The critical defect size was determined by curve fitting and extrapolation techniques. It was 7.04mm when the fatigue threshold was set to 105. The failure mode results show that a transverse fracture near the debonding zone is prone to occur for the larger defect size of 30 ~40mm, while for a relatively small defect size of 15 ~20mm, the collapse and tear rupture of the honeycomb core wall at the debonding tip zone is the main fatigue failure.%借助四点弯曲装置,对含有初始芯面脱焊缺陷的钢质蜂窝夹芯板开展了室温疲劳行为研究.载荷比为0.20,载荷水平在15％ ～90％.通过考虑不同脱焊尺寸研究该类结构的失效,得到疲劳寿命S-N曲线和疲劳极限.利用曲线拟合和外推技术,得到疲劳阈值为105次不发生破坏的临界缺陷尺寸为7.04 mm.失效模式分析表明:当芯子和面层脱焊缺陷尺寸为30 ～40 mm时,较易发生脱焊区的整体横向断裂；缺陷尺寸为15 ～20 mm时,主要以脱焊尖端的蜂窝芯壁撕裂和坍塌为主.
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