Bending strength of single-lap adhesive joints under hygrothermal aging combined with cyclic thermal shocks

Adhesive joints in the aeronautical sector are exposed to hostile environments, which may combine different temperatures and/or moisture conditions. Both subjects are conveniently reported in the open literature, but when they act together there is no consolidated knowledge about their effect on the mechanical strength of adhesive joints. Therefore, this work will study the effect of hygrothermal aging combined with cyclic thermal shocks on the flexural properties of single-lap adhesive joints. Adhesive joints involving ductile and brittle adhesives were exposed to different number of cycles, which combine two sequences of 12 hr with constant temperatures but different environments (water and air). It was possible to conclude, independently of the adhesive, that higher hygrothermal aging temperatures promote higher decreases of the failure load and maximum failure displacement, but they are only marginally affected by thermal shocks in air. Finally, a significant degradation of flexural properties occurs with the number of hygrothermal shocks, but the water/air environments reveals to be much more severe than water/water ones.