Thin-ply laminated composites have recently gained increasing attention in the aerospace engineering field, due to enhanced design possibilities and positive size effects with regard to decreasing ply thickness. In this paper, the mechanical behavior of thin-ply laminate and TC21 titanium alloy hybrid joints with double-lap bolted structure under quasi-static loading was studied experimentally. X-ray computed tomography (CT) scanning and SEM microcosmic imaging at special stages of the whole loading process were used to clarify the progression of bearing damage and fastening hole deformation characteristics of laminates. A more gradual damage and failure in bearing was observed in all specimens from the stress-displacement curves. The final failure of hybrid joints is a combined mode of bolt tensile cracking and hole bearing deformation. More importantly, the common delamination of standard-ply composite laminated plates in the bearing failure plane and tensile failure plane was suppressed in thin-ply laminates, resulting in higher bearing failure strength and more damage accumulation. Therefore, the novelty of this work contributes to detailed experimental observations of the bearing failure mechanisms, which provide valuable information for developing accurate mechanism-based failure models to be used in simulations.

薄层层压复合材料最近在航空航天工程领域引起了越来越多的关注，这归因于增加的设计可能性和关于减小层厚度的正面尺寸效应。本文研究了薄叠层和双搭接螺栓结构的TC21钛合金混合接头在准静态载荷下的力学行为。在整个加载过程的特定阶段，使用X射线计算机断层扫描（CT）扫描和SEM微观成像来阐明层压板的轴承损坏和紧固孔变形特征。从应力-位移曲线可以看出，在所有试样中轴承的破坏和破坏程度都是逐渐的。混合接头的最终失效是螺栓拉伸裂纹和孔轴承变形的组合形式。更重要的是，在薄层板中，标准层复合层压板在轴承失效平面和拉伸失效平面中的常见分层得到抑制，从而导致更高的轴承失效强度和更多的损伤累积。因此，这项工作的新颖性有助于对轴承失效机理进行详细的实验观察，从而为开发用于仿真的基于机理的精确失效模型提供有价值的信息。