T800碳纤维增强复合材料双剪单钉连接的拉伸试验及强度估算

为系统地研究T800碳纤维增强复合材料螺栓连接的力学性能，首先，对T800碳纤维增强复合材料双剪单钉连接进行了面内准静态拉伸试验，探讨了铺层比例、铺层顺序、螺栓直径以及固化工艺对复合材料螺栓连接刚度和2%偏移挤压强度的影响；然后，根据试验结果得到了T800碳纤维增强复合材料螺栓连接的应力集中减缓因子；最后，结合相应铺层比例的无缺口层合板的应力集中减缓因子和拉伸强度，建立了复合材料连接最终挤压强度的工程算法。结果表明:当螺栓断裂时，连接的最终挤压强度由螺栓剪切强度和螺栓直径/板厚比决定；连接存在挤压和剪切2种失效形式，与±45°铺层比例有关；工程算法的计算结果与试验结果吻合良好。所得试验结果和工程算法可为T800碳纤维增强复合材料螺栓连接的初步设计提供理论依据和技术支持。 

Tensile tests and strength estimation for double-lap single-bolt j oints in T800 carbon fiber reinforced composites

In order to investigate the mechanical properties of bolted joints in T800 carbon fiber reinforced compos-ites systematically,in-plane quasi-static tensile tests were carried out on double-lap single-bolt joints in T800 carbon fiber reinforced composites firstly,and the effects of ply ratio,ply sequence,bolt diameter and curing method on stiffness and 2% offset bearing strength of composite bolted joints were discussed.Then,based on test results, stress concentration relief factors for bolted joints in T800 carbon fiber reinforced composites were obtained.Final-ly,combining the stress concentration relief factor and tensile strength of un-notched laminates with the correspond-ing plies,an engineering approach for the ultimate bearing strength of composite bolted joints was established.The results show that when bolt fractures,the ultimate bearing strength of joints is decided by the shear strength of bolt and the bolt diameter/laminate thickness ratio.Joints have two collapse modes concluding bearing and shear,and they are related with the ±45°ply ratio.The calculated results of engineering approach agree well with the test re-sults.The test results and engineering approach obtained can provide theoretical proofs and technological supports for the preliminary design of T800 carbon fiber reinforced composite bolted joints.