Achieving a Strong Friction-Lap Joint of Continuous Carbon-Fiber-Reinforced Plastic/Aluminum Alloy via a Surface Laser-Processing Pretreatment

It is difficult to achieve high-strength joints of metals to carbon-fiber-reinforced plastics (CFRPs) with high contents of continuous fibers with the poor fluidity. Herein, a special designed laser-processing pretreatment is conducted on the surface of 5052Al, and friction-lap joining (FLJ) is employed to join pretreated 5052Al to the CFRP with 50%-55% fiber content. The maximal tensile shear force and strength reach 4.06 kN and 18.04 MPa, respectively, with an increment of 72% compared to the untreated sample. It is the first time to achieve the high-strength joint of Al alloys to CFRPs with high contents of continuous fibers via FLJ. The joining area and adhesion work are quantified by theoretical calculations, and the residual stresses are visualized by finite-element analysis. The laser-processing pretreatment changes the plain Al alloy surface structure into the rough and porous structure, largely increasing the mechanical interlocking effect of the joint, and also changes the Al alloy surface wetting behavior and increases the adhesion work from 59.66 to 81.17 mN m(-1). That largely changes the chemical reaction feature between the CFRP and Al alloy, resulting in their tight bonding. In addition, the residual stresses weaken, which further improve the tight bonding effect.