Impact resistance of adhesive joints using laser-induced shock waves

The impact resistance of aluminum–aluminum joint bonded with FM-73 (American Cyanamid) structural adhesive was studied using laser-induced shock waves. The adhesive joint failed in a ductile mode, showing shock absorbtion ability through plastic deformation. All stages of the impact damage were identified from threshold damage through complete sample perforation. In the theoretical study, the damage induced in the target is obtained as follows. The shock wave is modeled by an expanding stress front, which creates a void population in the laser-impacted layer and extrudes a bulge at the far surface. The calculated extent of the bulge geometry compares well with that observed by us in the metal–adhesive–metal sandwiches. The voids coalesce into macro-damage or ductile failure fracture by a mechanism which is described by percolation theory.