THE EFFECTS OF LASER-RADIATION AT 248 NM ON THE SURFACE CHARACTERISTICS AND JOINT PROPERTIES OF ALUMINUM ADHERENDS

Procedures presently used to prepare surfaces of aluminum adherends fo r bonding with structural adhesives entail the use of corrosive soluti ons that are environmentally hazardous. As an alternative, we investig ated whether eximer laser radiation can effectively be used to prepare the surfaces of aluminum adherends. The results indicate such a metho dology to be very promising. Using a KrF laser, at a radiant intensity of 1.67 x 10(13) W/m(2)/pulse, successive mm(2) regions of aluminum c oupons were irradiated for fixed numbers of pulses/region. This result ed in changes to the topographies and oxidation states of the surfaces . Symmetric lap shear joints from coupons so treated had considerably increased strains at fracture and 24% greater joint strengths as compa red with controls. The results further indicate that fracture toughnes s can be increased above that of presently used procedures. The topogr aphies of the treated and control surfaces were characterized using a new topographic characterizing system. An elastic model is presented t hat relates failure characteristics to experimentally-determined topog raphic parameters. The results suggest that different mechanisms for j oint enhancement are operative.