| With the rapid development of automobile lightweight technology,the lightweight materials of modern automobile body are developing towards the trend of mixed use of various materials.The lightweight material connection technology of car body is widely used,and the connection performance between different lightweight materials has attracted much attention.Especially in the new lightweight material carbon fiber reinforced composite(CFRP)and traditional lightweight material aluminum alloy,the mechanism of the connection has been widely studied by scholars.At present,many scholars have carried out many experimental studies on the mechanical properties of single-lap joints with single connection mode and hybrid connection mode.However,the connection mechanism and basic mechanical characteristics of the dissimilar material single lap joint between different connection technologies have not been clearly explained.And different connection technologies have their own advantages,in different body parts have not exactly the same connection application.Especially in the body of some special structures,such as the connection between the B-pillar and the threshold,the connection of the engine hood plate and so on.Therefore,for automotive lightweight connection technology,the evaluation of quasi-static mechanical properties of different joint connection modes has a high value of guiding design.In order to further explore the quasi-static mechanical properties of single-lap joint of dissimilar materials,lots of innovative studies have been carried out.The main contents are as follows:(1)The quasi-static mechanical properties of the single-lap bonded joint of dissimilar materials were studied experimentally.Several experimental variables were designed: three kinds of adhesives(DP840,Araldite2015,DP8010)and whether the pre-hole is filled with adhesives.The peak load,failure displacement and initial stiffness were compared and analyzed intuitively through the force-displacement curve.The digital image correlation(DIC)technique was used to monitor the strain of the joint,and the fracture process,strain distribution and evolution of the bonded joint were recorded accurately.In addition,the section failure modes of the specimen were analyzed statistically,and the area ratio of different failure modes was calculated.Scanning electron microscope(SEM)was used to observe the fracture morphology and reveal the micro-failure behavior among different failure modes.The results show that the open hole filling adhesive can effectively reduce the strain concentration around the pre-hole of the substrate and uniformly distribute the load to decrease the stress concentration;there are differences in the properties of different adhesive joints,which are mainly caused by the different curing methods of adhesives and the different adhesion forces of adhesive macromolecules to the surface of the substrate.(2)The quasi-static mechanical properties of the single-lap riveted joint of dissimilar materials were studied experimentally.Several experimental variables were designed: four kinds of rivet materials(aluminum alloy 1A97,aluminum alloy 2A10,aluminum alloy 6061,and steel 304)and two riveted directions(the rivets are inserted from the side of the aluminum alloy substrate,and the rivets are inserted from the side of the carbon fiber composite substrate).The results show that the failure modes of dissimilar materials in single lap riveting joints are not exactly the same,such as shear failure of rivets and damage of CFRP substrates;the rivet material should be matched with the substrate material,too strong rivet is not conducive to the optimization of rivet connection effect;the rivet inserted from the CFRP substrate had more excellent mechanical properties,which has certain reference value for the actual riveting application.(3)The quasi-static mechanical properties of the single-lap hybrid joint of dissimilar materials were studied experimentally.Several experimental variables were designed: four hybrid connections(DP840 adhesive + 6061 aluminum alloy rivets,DP840 adhesive + 1A97 aluminum alloy rivets,Araldite2015 adhesive + 6061 aluminum alloy rivets,Araldite2015 adhesive + 1A97 aluminum alloy rivets)and two riveting directions the same as before.The results show that the hybrid joint has a positive interaction effect compared with two single joints;the failure modes and failure process were different in four hybrid connections,and it mainly depends on the performance effect between two single connection;the effect of different rivet insertion directions on the hybrid joint was similar to the riveted joint,and the hybrid joint inserted from the side of CFRP substrate shows better mechanical properties... |
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