GERRARD'S CROSS, ENGLAND — Metal-faced sandwiches with polyurethane-based elastomer fillings are poised to replace the solid metal plates used in a range of civil and marine engineering structures. They even could be used to make complete ships, according to their developers.
The system is called SPS, for sandwich plate system, and involves injecting liquid PU between two steel plates, a process readily performed in a shipyard, according to the developers. Thanks to the inherent toughness of the PU elastomer after curing and its strong adhesion to the metal plates, the composite formed has all the strength of a conventional steel sheet — and more, with superior impact strength being one particular highlight.
The key benefit of SPS is that it greatly simplifies the fabrication process, cutting the time and materials used, which could result in major cost savings. Other benefits include reduced maintenance requirements, good thermal insulation, and superior vibration damping.
The SPS concept — originated by Stephen Kennedy, a Canadian structural engineer — has been the subject of a secretive, seven-year cooperative development program between Elastogran GmbH of Olching, Germany, and Ottawa, Ontario-based Intelligent Engineering Ltd. The work already has seen its practical — and highly successful — use in replacing part of the deck of a roll-on, roll-off ferry, the firms claim.
According to Kennedy's brother Michael, SPS now has approval from Lloyd's Register, one of the top three marine certification bodies, which leaves it poised for use across the shipbuilding sector, he said.
If that happens, it could create massive demand for the methylene diphenyl diisocyanate used to make the elastomers, according to Elastogran. An average ship could use 3.3 million pounds of PU elastomer, and about 2,000 new ships are made every year, said Reiner Hofmann, senior vice president-automotive and specialities at Elastogran's Olching site near Munich, Germany.
And, although he is not suggesting all ships immediately will use the new composites, shipping is just one possible application. Other uses include civil structures such as seating platforms in sports stadiums and bridge decks, he said in a recent interview at Intelligent Engineering's office in Gerrard's Cross.
More importantly, the system could revolutionize shipbuilding and the safety of ships, said Michael Kennedy, who has helped bring the concept to commercial fruition since his brother first conceived the idea about nine years ago.