Adhesive Joints for Composite Sandwich Structures

A new approach is explored for joining of thick, woven E-glass/vinyl ester composite laminated plates to steel or composite plates, with applications in naval ship structures. Adhesive is applied along through-the-thickness contoured interfaces, employing tongue-and-groove geometry. Both experimental and finite element modeling results are presented. They show that adhesively bonded tongue-and-groove joints between steel and composite plates loaded in monotonically increasing longitudinal tension, are stronger than conventional strap joints even in relatively thin plates. In particular, a single 0.25 in. wide and 8 or 12 in. long steel tongue, bonded by the Dexter- Hysol 9339 adhesive to a groove in a 0.5 in. thick laminated plate, can support a 20,000 lbs tension force. This force is expected to increase in proportion to plate thickness. Simple design rules indicate that high joint efficiency can be achieved for any thickness of the joined plates.