▎ 摘　　要

There is an increasing demand for high-performance adhesive joints in the fields of aerospace, civil engineering and automobile engineering. However, stress concentrations at the edge of adhesive joints could result in prefailure and make the joints unreliable. In this work, functionally graded adhesives (FGA) are utilized to solve the above-mentioned issues. We incorporate graphene nanoplatelets (GNP) into the epoxy resin to produce composite adhesives with high modulus. These high-modulus adhesives, together with neat epoxy with mediummodulus, are placed in the center and edge of the bondline respectively, to create a modulus gradient. The asproduced FGA joints deliver superior mechanical performances over the mono adhesive joints, and highly tunable properties could be achieved by adjusting the relative sizes of the high-modulus and medium-modulus regions. For example, the FGA with the lateral size of high-modulus edge region: medium-modulus center region: high-modulus edge region of 1:3:1 exhibit significant 210.1%, 350%, and 1118.58% improvements in failure load, elongation at break and toughness, respectively. Such exceptional mechanical properties of FGA come from the rearranged stress distributions at the overlap. According to the numerical analysis, the gradient modulus in FGA can effectively decline the peel stress concentrations. In addition, based on the linear elastic material models for adhesive and adherends, it is found that the stress concentrations at the edge of the overlap could be suppressed by the medium-modulus region, while the GNP reinforced high-modulus region mainly provide load-bearing capacity of the joints, resulting in delayed adhesive joints failure.