螺栓预紧力对复合材料单搭沉头螺栓接头静载性能影响

Effect of bolt preload on bearing response of single-lap,countersunk composite bolted joints

根据ASTM 5961试验标准设计了复合材料单搭沉头螺栓接头试件,通过试验和仿真分析了螺栓预紧力水平对其静拉伸性能影响规律。试件为准各向同性铺层的碳纤维环氧树脂层合板,试验过程中利用非接触全场应变测量系统2D数字图像相关技术(DIC)对沉头板表面应变场数据进行了采集。基于ABAQUS/Standard隐式分析模块建立了复合材料单搭沉头螺栓接头的静拉伸三维有限元模型,分析了螺栓预紧力和摩擦系数对沉头孔周挤压应力的影响规律。结果表明:当接头承受拉伸载荷时,沉头孔周区域受螺栓挤压损伤最为严重;增加螺栓预紧力可提高螺栓孔2%变形的承载强度,但对接头极限承载强度的提升效果较小。有限元应力分析表明,增加螺栓预紧力或增大层合板之间的摩擦系数均有利于减轻孔周应力集中程度,提高复合材料单搭沉头螺栓接头的承载性能。

Experimental and numerical studies on the bearing response of single-lap,countersunk composite joints which were designed according to ASTM 5961 under various bolt preload were presented.The specimens were manufactured from carbon fiber/epoxy unitapes with quasi-isotropic lay-ups.To obtain a more accurate hole strain,2D digital image correlation(DIC)measurement technique was used.Three-dimensional finite element model was constructed using ABAQUS/standard and validated by comparing to the experiment.The validated model was used to provide a detailed stress analysis around the hole boundary considering various bolt preload and friction conditions.The results show that countersunk hole is the region where the severest damage occurs,and bolt preload could significantly improve the 2%hole deformation bearing strength but only slightly increase the ultimate bearing strength.Through stress analysis,increasing either bolt preload or friction between laminates are found to have an active effect on relieving stress concentration,and will make a better bearing performance of single-lap,single-bolt,countersunk composite joints.