Aluminum foam in shipbuilding
In shipbuilding, hatches, doors, frames and ship rudders can be made with aluminum foam. The foam absorbs hardly any water and can be made from seawater-resistant alloys. If the structure itself is built from metal foam sandwiches, the weight reduction means more can be carried for the same energy consumption and the draft can be reduced, with a weight saving of 20 to 30 %. Havel metal foam trialed this on the hull of an inland vessel in the funded ULIVES / MARTEC ERA-NET project.
Updated:
Why is aluminum foam worth using in shipbuilding?
In shipbuilding, aluminum foam brings a weight saving of 20 to 30 %. The effect is twofold: the draft falls, and more payload is possible for the same energy consumption. There is also vibration damping, for example in the gearbox structure, and lower manufacturing effort, because designs consist of fewer individual parts. The foam absorbs hardly any water and can be made from seawater-resistant alloys.
- Weight saving of 20 % to 30 %
- Lower draft
- Vibration damping (e.g. gearbox structure)
- Lower manufacturing effort (fewer individual parts)
- More payload possible
Which ship components are made from aluminum foam?
The areas of application range from structural elements of the hull through interior fit-out to foamed profiles: hatches, doors and frames as well as cabins, ceilings, exterior and interior walls, floor panels, funnels, stair elements and decorative elements. They also include foaming pipe profiles or segments, and structural components, for example for machinery and plant on board.
- Elements of the ship's hull
- Hatches, doors, frames
- Cabins, ceilings, exterior and interior walls
- Floor panels
- Funnels
- Foaming pipe profiles or segments
- Decorative elements
- Structural component (e.g. machinery and plant engineering)
- Stair elements
How does aluminum foam behave in seawater service?
The foam absorbs hardly any water and can be made from seawater-resistant alloys: two properties that make the material suitable for marine use. The ship's rudder is also among the components that can be made with aluminum foam. If the structure itself is built from metal foam sandwiches, the weight reduction lowers the draft for the same energy consumption; this was trialed on the hull of an inland vessel in the funded ULIVES / MARTEC ERA-NET project.
How are aluminum foam sandwiches joined to a steel ship?
Several joining techniques are documented for integration into steel shipbuilding: joining SAS (sandwich with steel cover layers) to steel by gas metal arc welding (MIG/MAG), joining aluminum to aluminum by gas metal arc welding, and joining aluminum to steel and AAS (sandwich with aluminum cover layers) to steel by explosion-clad transition profiles.
- SAS to steel
- Joined by MIG/MAG welding.
- Al to Al
- Joined by MIG/MAG welding.
- Al to steel / AAS to steel
- Joined by explosion-clad transition profiles.
Demonstrators
How much lighter is a ship's rudder made of metal foam?
Also asked: Has a rudder been built? · What does a rudder body in aluminum foam sandwich weigh?
A metal foam rudder body from Havel metal foam weighs 912 kg against 1,176 kg in conventional construction, that is 22 % less. It was built as a demonstrator at a scale of 1:1, measuring 2.6 × 1.4 × 0.5 m. Simpler manufacture is named as a second effect, because fewer individual parts have to be joined. The rudder is therefore the most thoroughly measured shipbuilding component made from the material: a real component at full size, not a calculation.
- Sources
- Brand content
Has a complete hull been investigated?
Also asked: What did the hull demonstrator show? · How much weight does a hull structure save?
Yes. Havel metal foam investigated the hull of an ice-going inland vessel on a demonstrator at a scale of 1:4, replacing longitudinal and transverse girders with SAS of 2 mm steel sheets and a 30 mm aluminum core, which allowed conventional stiffeners to be omitted; the total weight of the vessel fell by 25 % compared with the original design. Ice capability remains a matter for steel: up to 70 cm above the waterline, the hull is built conventionally in steel.
- Sources
- Brand content
How does a machinery foundation in sandwich construction perform?
Also asked: What did the drive foundation show? · Are there drawbacks in manufacture?
For a drive foundation, Havel metal foam achieves 20 % less weight compared with an original of 4.7 t. Of 125 m of seam, 40 m were laser welded, that is 32 %. There is one drawback: more preparation time is needed in the fastening area, because aluminum foam sits there. In a cost calculation this extra effort should be set against the weight saving, because it arises at the shipyard and not at the material supplier.
- Sources
- Brand content
Joining and corrosion
Can the composite be welded under shipyard conditions?
Also asked: Has laser welding been trialed? · How much seam was laser welded?
Yes, and it has been trialed under shipyard conditions. On the Havel metal foam demonstrators, 17 of 60 m of seam were laser welded on the rudder, that is 28 %, and 40 of 125 m on the drive foundation, that is 32 %. The proportions are the actual finding: laser welding works on this composite but is not the only type of seam in the component, and the shipyard plans for both. Trialed here means on a real component in a real manufacturing environment, not in the laboratory.
- Sources
- Brand content
What did the salt spray test show?
Also asked: How does the interface between foam and steel behave? · Does the sandwich rust in seawater?
In the salt spray test to DIN EN ISO 9227 NSS, Havel metal foam found corrosion on the steel sheet of the cover layer, but none at the interface between foam and steel. That is the more important part of the result, because the interface is the point at which a composite material usually fails in seawater. The test ran for 240 hours at Fraunhofer ICT, an accredited test laboratory; the test report documents the condition of the samples photographically, and the assessment of the finding is by Havel metal foam. The cover layer still needs corrosion protection, as a steel component does.
- Sources
- Brand content
- Independent test
How long and where was the salt spray test carried out?
Also asked: How many hours did the salt spray test run? · Which test laboratory carried out the corrosion test? · Which samples were tested in the salt spray?
Havel metal foam commissioned the test from Fraunhofer ICT in Pfinztal, a test laboratory accredited by DAkkS. The total test duration was 240 hours at 35 °C, with a sodium chloride solution of 50 g/l and a pH between 6.5 and 7.2; the samples were unprotected during the test, that is uncoated. Three build-ups were tested: plain aluminum foam without a cover sheet, a build-up with an aluminum cover layer and a build-up with a steel cover layer of DC01. The alloys of these samples do not match today's supplied variants AAS and SAS in every respect, which is why the test demonstrates the metallic composite and not a named product variant. For a specification, duration, temperature and concentration can therefore be documented.
- Sources
- Independent test
Has the composite also been tested in an industrial atmosphere?
Also asked: Are there other corrosion tests besides the salt spray test? · Was testing carried out to DIN EN ISO 6988?
Yes. Havel metal foam also had the composite tested in an alternating condensation climate with an atmosphere containing sulfur dioxide to DIN EN ISO 6988 or DIN 50018, at the same accredited test laboratory and on the same build-ups as in the salt spray test. One test cycle lasts 24 hours: 8 hours at 40 °C and 100 % humidity, during which condensation forms on the samples, followed by 16 hours of ventilation at 18 to 28 °C. This test reproduces an industrial atmosphere, which is the more relevant exposure for port and shipyard environments with exhaust pollution, and so complements the marine exposure of the salt spray test. Here too, the test report documents the condition of the samples photographically; the assessment is by Havel metal foam.
- Sources
- Independent test
Use and classification
How much weight does each application save?
Also asked: Where does SAS pay off, and where AAS? · Which saving is documented for each type of component?
Havel metal foam breaks the saving down by application. Sheets and especially ribs, replaced by SAS, give 20 to 25 %. Cabins, decks and upper and inner panels, replaced by AAS, give 25 to 30 %. Over-foaming steel tubes or segments comes to 15 to 20 %. The design therefore follows the task: steel cover layers where the structure carries load, aluminum cover layers where area and weight count.
- Sources
- Brand content
Is there a Module D certificate for shipbuilding?
Also asked: Is there an approval from a classification society? · What about Module D?
Not at present. The Module D certificate (DNV GL) needed for shipbuilding has expired and has not been renewed for now, as there is no current demand. It can be renewed at short notice if needed, and that is exactly the useful answer for a shipyard project. If you need the certificate for a project, raise it with Havel metal foam.
- Sources
- Brand content
Is there a delivered reference from passenger shipbuilding?
Also asked: Which shipyard has Havel metal foam already built for? · Which shipbuilding reference is there?
Yes. Havel metal foam's reference in shipbuilding is an upper deck for passenger ships. The reference stands for the type of component, not for an individual ship: Havel metal foam does not publish the year of build, the ship's name or the exact scope of supply. For a shipyard, the type of component is the usable information, because an upper deck is precisely the case in which weight sits far above the waterline and so affects stability and draft; the saving for decks in AAS is 25 to 30 %. The other evidence for the sector comes from the funded ULIVES project under MARTEC ERA-NET, in which Fraunhofer took part as a partner.
- Sources
- Brand content
Aluminum foam for your shipbuilding project
Straight to our specialist team, without going through sales.
- Prompt reply
- No account needed
- Your data stays confidential