Toughened adhesive and bonding method using the same

An adhesive film comprising a veil embedded in a curable matrix resin, wherein

• the curable matrix resin comprises one or more epoxy resins and at least one curing agent,
• the veil comprises randomly arranged polymeric veil fibers or glass veil fibers and a copolymer of polyamide 11 (“PA11”) and polyamide 12 (“PA12”) as a polymeric binder, which is in a solid phase at room temperature (20° C.-25° C.) and has a glass transition temperature of less than 350° F., as determined by Dynamic Mechanical Analysis;
• wherein the polymeric binder is distributed on the outer surfaces of the veil fibers and/or dispersed among the veil fibers throughout the veil.

A bonded structure comprising two substrates joined to each other and an adhesive film interposed between the substrates, wherein

• at least one of the substrates is a metallic substrate,
• the adhesive layer comprises a veil embedded in a curable matrix resin, which comprises one or more thermoset resins and at least one curing agent,
• the veil comprises intermingled, randomly arranged polymeric or glass veil fibers and a polymeric binder in an amount sufficient for holding the fibers together, wherein the polymeric binder is distributed on the outer surfaces of the veil fibers and/or dispersed among the veil fibers throughout the veil, is in a solid phase at room temperature (20° C.-25° C.) and has a glass transition temperature of less than 350° F. as determined by Dynamic Mechanical Analysis.