Parametric study of composite curved adhesive joints

Nowadays, the adhesive bonding method has a very strong presence in the most varied industries, especially in aeronautics, which strongly boosted the use of adhesively bonded joints. Curved bonded joints are commonly used in the aeronautical industry, where curved panels typically made of carbon fibre-reinforced polymer (CFRP) are joined to fabricate several fuselage parts. This work compares the performance of three adhesives (brittle, moderately ductile and ductile) in curved single-lap joints (SLJ) bonded with CFRP adherends, considering the modifications of the following geometric parameters: overlap length (L_O), adherend thickness (t_P) and adherends’ radius of curvature (R). For the analysis of these joints, the finite element method (FEM) was used with cohesive zone model (CZM), and the discussions of joint behaviour included the internal stresses of the adhesive, joint strength and energy dissipated at failure (U). Before the numerical analysis, validation with experiments was carried out considering flat SLJ, with positive results. The numerical study on the curved SLJ showed a significant maximum load (P_m) and U improvement by increasing L_O for the two ductile adhesives. For the same adhesives, bigger t_P reduced P_m. On the other hand, the brittle adhesive revealed to be only minor affected by these parameter variations. Thus, with this work, clear design guidelines are proposed for curved SLJ.