This paper attempts to develop a viscoelastic model for studying the viscoelastic behavior of a bi-adhesive joint and investigate the effect of the bi-adhesive order on distributions of the adhesive time-dependent shear stress. Stiff adhesive was located in the middle and the flexible adhesive was located at the ends of the overlap. If these two adhesives are used together, it is planned to investigate how this combination will be reflected in the time-dependent variation of the shear strain and shear stress of the bi-adhesive joint. A concept of the bond-length ratio was defined that describes the quantity of these adhesives in terms of adhesive length in the overlap, and then four different bond-length ratios were selected. Expressions describing the variation of shear stresses with respect to time for each of the three regions were obtained analytically. The shear moduli of the viscoelastic adhesives were defined using the Maxwell-Wiechert model with three units. Numerical analyses were also performed using ABAQUS finite element (FE) code. Finally, the results obtained from both FE analyses and analytical solutions were compared. It was observed that the viscoelastic effect range in the bi-adhesive joint was mainly related to the material properties of the flexible adhesive used at the ends of the overlap. However, it was seen that the presence of a limited amount of stiff adhesive in the midportion of the bi-adhesive overlap significantly limits the viscoelastic effect.
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