Geometry effect on the static strength of curved composite bonded joints

Abstract

In this work, the behavior of composite curved adhesive joints under pressure (p) is analyzed; such joint configuration has applications in aircraft fuselages. The chosen substrates were Carbon-Fiber Reinforced Polymer (CFRP) and three substrate thicknesses (tP) were studied. In addition, three different curvature radii (R), and eight overlap lengths (LO) were evaluated, while only one adhesive type was used. An internal pressure of 1 MPa was considered in all cases. The analyses were performed using the finite element method (FEM) and cohesive zone modelling (CZM). The increase in LO causes a linear increase in the peak peel stresses (σyy), affecting the thinner joints more; these peak stresses were located in the joint's knee region. Pmax was also found influenced by tP and LO, being again the effect more noticeable on the thinnest substrate; however, for LO≥40 mm the effect was negligible. As tP increased, Pmax had no significant improvement for LO≥20 mm. Although increasing R causes a slight reduction in the peak stresses, the stresses along the bond line were more uniform. Although R had no significant effect on Pmax, it increases joint compliance. In conclusion, the chosen adhesive allowed to successfully explore the different geometric parameters where the thinner joints with the largest R showed the best performance.