On the Potential Static Strength of Hybrid (Bolted/Bonded) Lap Joints with Functionally Graded Adhesives

In this paper, the potential static strength of hybrid (bolted/bonded)-termed HBB-joints with functionally graded adhesives (FGA) is theoretically investigated, in reference to the pure bolted joint, the pure bonded joint, and the HBB joint with homogeneous adhesive (HA). The investigation is performed on a particular in-plane tensile-loaded single-lap joint made of identical aluminum adherends with two lines of fasteners and three various adhesive symmetrical graduation laws. The stress analysis is performed using the macro-element technique within 1D-bar framework. Moreover, closed-form expressions for the bolt load transfer rates and maximal adhesive stresses of balanced single-lap HBB joint with two identical fasteners are derived. It is shown that the FGAs allow fort a better load sharing between the adhesive and the fasteners than the HA. Moreover, the use of FGAs instead of HA could lead to a potential static strength benefit for the adhesive layer part rather than for the fastening part.