The dilational and compressive properties of a polymer sealant and analyses of the distortion and fatigue of sealed riveted lap joints

In aircraft structures, thin layers of sealants are frequently installed in riveted joints to restrict the entry of 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 tensile and compressive 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 are performed to understand the effect of a thin sealant layer on the fatigue life of non-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.