Thin layers of low modulus polymer sealants are frequently installed in riveted aircraft lap joints to prevent contact with moisture and retard corrosion. The mechanical effects of thin sealant and adhesive layers on riveted lap joints have resisted analysis and remain ill defined. In this research, thin sealant layers were tested to obtain their shear mechanical behaviors. Finite element analyses (FEA) and the TALA method were used to analyze lap joint behavior with variations in thickness and stiffness of sealant. FEA results are compared with experimental results to validate the computer models. Fatigue tests were performed to understand the effect of a thin sealant layer on the fatigue life of countersunk riveted lap joints. The analyses reveal that the sealant reduces the out-of-plane bending and the stress concentration factor (SCF). The parametric studies indicate that much larger reductions in SCF are possible with stiffer sealants and adhesives. The SCF values, deduced from the fatigue life measurements and S-N curves, correlate with the corresponding SCF values derived from the FEA/TALA analyses.
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