Three-dimensional stress analyses of functionally graded adhesively bonded tee joint made of laminated Fiber Reinforced Polymeric (FRP) composite are carried out. The FE model of the tee joint is validated by comparing the stresses with the results available in literature. The tee joint is analyzed to determine 3-D stress components with flexible base boundary condition. The out-of-plane stresses (στ and τyz and τxz) components along the mid-surface of adhesive layer are determined for FRP composite right angled plates when it is subjected to pull-off loading. Further, an attempt has been made to improve the strength of recommended tee joint structure by reducing the stress concentration at the ends of overlap. This has been achieved by distributing stresses uniformly over the entire bond line by employing Functionally Graded Adhesive (FGA) material instead of using conventional single adhesive. Linear material gradation function profile has been used to grade the adhesive layer in the tee joint. Effect of the material gradation profile with different modulus ratios on out-of-plane stresses has been studied. Numerical simulation based on Finite Element Analysis indicates that out-of-plane stress levels reduce significantly.
Keywords: Functionally graded adhesive, Tee joint, Flexible base, Geometrical non-linearity.