Damage behavior and mechanical property investigation of CFRP/CFRP washer-bushing riveted joints

CFRP构件垫圈/衬套铆接损伤及拉剪性能试验研究

School of Aeronautics and Astronautics, Sichuan University, Chengdu 610092, China

Received: 20 January 2023

Abstract

Carbon fiber reinforced composites (CFRP) are prone to occur riveting damage. Therefore, the damage behaviors and mechanical properties of CFRP/CFRP washer-bushing riveted joints were investigated experimentally in this paper. Results showed that due to the uneven expansion of rivet shank and local pressure caused by upsetting head, CFRP/CFRP riveted joints occurred multiple damage modes by using net riveting method and bushing method. The damage was mainly located in the layer around the CFRP hole near the upsetting head. However, washer-bushing riveting method effectively limited the uneven expansion and the local pressure of upsetting head, and no obvious damage was observed. Load-displacement curves of direct riveted joints and washer-bushing riveted joints exhibited obvious linear stage, progressive damage stage and final failure stage in both tensile shear and pull-off tests. However, the bushing reduced the effective fastening area of upsetting head, and load-displacement curves of bushing riveted joints only included linear and failure stages. Besides, the tensile shear and pull-off peak load were also the lowest. Tensile failure modes of both net riveted joints and washer-bushing riveted joints were dominated by the coupling failure mode of shear failure and rivet pull-off. The CFRP connecting hole was observed with obvious shear damage and extrusion deformation area. Besides, pull-off failure modes were laminate fracture and ply delamination, and also accompanied by laminate bending deformation. In contrast, bushing riveted joints failed by rivet pull-off in both tensile shear and pull-off tests.

摘要

碳纤维增强复合材料(CFRP)易发生铆接损伤, 通过试验方法开展垫圈/衬套铆接损伤行为及其拉剪性能研究, 研究结果表明: 镦头不均匀膨胀及下压会导致净铆接和衬套铆接出现不同程度、多损伤模式铆接损伤, 而垫圈/衬套铆接后并未出现明显损伤。净铆接试件与垫圈/衬套铆接试件的拉剪力-位移响应呈现出明显的线性、渐进损伤和失效破坏的特征, 而衬套铆接由于减小了镦头与层板的有效紧固面积, 衬套铆接试件拉剪力-位移响应仅包含线性和失效破坏阶段, 其拉剪峰值载荷亦最低。净铆接试件和垫圈/衬套铆接试件的拉伸失效模式均为层板剪切与铆钉拉脱耦合失效, 拉脱失效模式为层板铺层断裂和分层, 且伴有层板弯曲变形; 衬套铆接试件拉剪过程中均发生铆钉直接拉脱破坏。