This research investigates the effect of the addition of Thermally Expandable Particles (TEP) to a commercially available adhesive on the mechanical performance of bonded mixed material Single Lap Joints (SLJs) in lap shear tests. Investigated variables include additive concentration by weight (from 5 to 20%) and particulate size (ranging between 6 and 16 micrometers), for their effect on joint static and fatigue strength, as well as reversibility performance, as compared to those of SLJs bonded with the baseline adhesive with no additives. Each test joint is made by one Aluminum 6061 substrate that is adhesively- bonded to a composite substrate made of woven carbon fiber reinforced plastic 0/90/0 with epoxy matrix.