Composite metal panels

A combination of predictable thermal and structural performance quickly led architects to see the benefits of using composite metal panels. Composite construction is the bonding together of layers of materials to form a rigid structure.The Mosquito bomber (Fig. 6.4) was an early example of composite construction in aircraft design. Composite construction is now extensively used in products as diverse as tennis rackets and jet aircraft.The principal form of composite construction is two thin sheets held apart by a lightweight core to which they are bonded. It is the spacing of the two sheets that is mainly responsible for the rigidity of the final composite: the wider the spacing, the greater the spanning capabilities of the finished product. Early developments of composite steel panels in the UK included the panels for the

Foamed Panel

Laminated Panel

Laminated Panel

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6.3 Types of metal cladding system.

Fabricated Panel

Fabricated Panel

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6.3 Types of metal cladding system.

6.4 Mosquito bomber

Bolt for tightening up gasket against the panel profile ^

Thermal insulation and plaster filler on expanded metal tray

Bolt for tightening up gasket against the panel profile ^

Composite Sandwich Plate

Steel plate dropped into slots at side of panel at intervals

Pressed steel panels with foamed insulation and slots in the side to receive fixing plates

Neoprene gasket supplied bonded to channel

Pressed steel panels with foamed insulation and slots in the side to receive fixing plates

Neoprene gasket supplied bonded to channel

Steel plate dropped into slots at side of panel at intervals

6.5 Oxford Regional Hospital Board joint (plan and section).

Oxford Regional Hospital Board System, I 963-73. A gasket joint designed by Jan Silva was based on a jointing principle developed by Jean Prouvé in which a neoprene gasket fixed to a steel channel is compressed against the panel profile by bolts at intervals up the height of the panel (Fig. 6.5).

Some difficulties were experienced in the foaming of the polyurethane insulation of these panels and in ensuring the integrity of the skins and the core material. The panel system was later abandoned in favour of a more conventional horizontal profiled high-tensile steel cladding with site-applied insulation.

The economics of using metal composite units depend upon standardization of unit sizes, and it is perhaps not surprising that their use tends to be associated with a system of coordinated dimensions. For example, during the 1970s, development in open system tendering by local authority consortia schools programmes, such as the South Eastern Architects Consortium (SEAC Mark 4), encouraged the

Panel Perfrisa Vertical

production of pressed metal panels mounted within a steel 'third member' subframe. Such panels were manufactured by Gordon Durham Aycliffe Ltd as Conatus panels, and by Brockhouse Lightform for SEAC Mark 4.These panels are no longer marketed, probably because they proved to be too expensive in comparison with other cladding materials when used for the variety of panel sizes required for school buildings.

The use of proprietary composite panels for industrial buildings has been more widespread, where standard-width panels are bolted back to a simple structural framework, and where the facade has no, or only a few, windows.Typically a facade unit of this type consists of a profiled sheet, thermal insulation and an internal lining, either produced as a composite unit in the factory or assembled separately on site (Fig. 6.6).

The Sainsbury Centre (Fig. 6.7) designed by Foster Associates in 1977 was one of the first uses of Superplastic aluminium for insulated composite panels and, more importantly, was one of the first non-commercial, non-industrial buildings to use an interchangeable panel system. Identical 1.8 m x 1.2 m panels were used for both walls and roof, with the weatherproofing joint detail dependent upon the neoprene gasket being mounted back against an aluminium carrier system.

The panels were manufactured by Superform Metals ITC Worcester using vacuum-forming techniques, from a special alloy patented by the British Aluminium Company.This'supral' alloy has the advantage over conventional aluminium alloy that it will flow or'run'atthe right temperature, and can be extended to ten times its original length. However; the process of manufacture is slow and costly, and some technical difficulties were experienced at first in forming the corners of the panels. Each outer tray was filled with 100 mm phenelux foam (curved decorative sections

Composite Sandwich JointsComposite Sandwich Plate

6.6 Early examples of proprietary box-type panel joints: (a) Briggs Amasco Perfrisa; (b) Booth-Murie Simplan 1200; (c) Hunter Douglas Luxalon.

Composite metal panels 119

Composite Metal Foam

being filled with polystyrene), and the inner skins were then pushed into the outer trays and pop-riveted together through a small section of phenolic foam core, which formed the thermal break at the edge of the panel. Thermal transmission of the panels was U=0.47 W/m2oC. For a detailed study of this construction see case study 22 in Brookes (1985).

The aim was to produce a U-shaped one-piece continuous ladder gasket, which fitted into an aluminium carrier system by Modern Art Glass, forming not only the main seal but also the guttering system (Fig. 6.8).These neoprene gaskets were manufactured by the Leyland and Birmingham Rubber Company as a lattice framework with two-way joints at mid-points of the overhang vulcanized on site using portable equipment (Fig. 6.9). In this way an interchangeable system of wall and roof panels was achieved. A similar

1800 x 1200 x75mm superplastic aluminium panels

Outside

1800 x 1200 x75mm superplastic aluminium panels

Outside

6.8 Detail of joint at Sainsbury Centre.

principle of continuous neoprene gaskets was later used at Gatwick Airport North Piers (Fig. 6.10).

The original panels on the Sainsbury Centre failed for a number of reasons and have been replaced by a flat composite panel by H. H. Robertson, which does not have the architectural effect of the original panels, nor is the replaced jointing gasket used in the same consistent way.

Composite panels were also used by Foster at the Renault Centre (Fig. 6.1 I), where 75 mm thick panels span 4 m between the vertical cladding support. The panel system, which was bolted to the vertical cantilevered columns by three fixings at each end of the panel, provided a very low-cost elevation. A large neoprene skirt takes up the deflection at the top of the assembly (Fig. 6.12). For further details of the construction see case study 21 in Brookes (I 985).

Porr Sta Slab Trak
6.9 Lattice gaskets used at Sainsbury Centre.

6.10 Assembly of panels at Gatwick Airport North Piers.

There are now essentially two types of composite panel.These are:

foamed polyurethane panels:

- continuous production;

- batch production;

laminated panels:

- continuous production;

- batch production.

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