Separation behaviour of sheet steel laminate during forming

The mechanism of separation during forming of steel/adhesive/steel laminated sheet used for acoustic damping depended on the ruling stresses and proximity of free edges. When bending occurred near a free edge, failure by shear at the interface was favoured. When bending, whether in deep drawing or by point loading, occurred remote from free ends and the resulting shear restraint in the adhesive was large, failure tended to occur by tensile separation occasioned by buckling of one sheet or by a combination of tension and shear. Tensile failure of the adhesive occurred by a void-growth mechanism reminiscent of that by which ductile failure occurs in metals. The stress required for delamination was decreased by prior plastic deformation of the adhesive in a manner which was virtually independent of strain history.