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Combining advanced composites with complex 3D computer modelling offers architects the chance to move to more sculpted forms Moulding architecture

TECHNICAL; CI/SfB y

Some architects are moving away from the strict grids of the Modern toward more complex forms. For some, this enables the edict of 'form follows function' to be explored to its full potential. There may be a search for a more poetic or baroque approach to architectural design.

The palette of materials and technology and the means of modelling with computers make it easier to translate such ideas into built form. Increasingly architects are interested in metal-forming, casting and the new possibilities of fibre composites. Research is advancing in cadcam - the automated linking of design to manufacture.

In his classic article on technology transfer (ar, September 1987), Martin Pawley expressed surprise at the general non-acceptance of monocoque construction. He pointed to Future Systems' exoskeletal construction for its Grand Buildings competition entry which achieved a far higher net:gross ratio of serviced floorspace than any other competitor. Enric Miralles' Scottish parliament design and Gehry's Bilbao Guggenheim reflect a shift from straight-line grids to more monolithic or organic arrangements. The reluctance among designers to change partly reflects the available palette of materials, and perceptions of cost. But even when budgets and programme offer more opportunities, such as for the nasa space-capsule programme, designs remain curiously box-like (see illustration).

Surprisingly, it is now 30 years since Farrell and Grimshaw employed prefabricated structural plastics for bathroom pods at Sussex Gardens, Paddington (now demolished).These grp pods were based on ici prototype plastic bathrooms from five years earlier.

In 1983 Jan Kaplicky and David Nixon of Future Systems, reviewing monocoque construction, predicted the use of very strong fibres for advanced composite design in construction - for example, using carbon fibres on the extremities of grp sections where stresses are most intense. It is this combining of different materials within a matrix that continues to excite designers and is the key to economic use of advanced fibres. For instance, a Formula 1 racing-car chassis combines woven and unidirectional carbon fibre, kevlar fibre, very low-density core materials and machined parts.

Moulding the future

Research on cadcam for creating complex shapes is using knitting machines to create the non-uniform fabrics of pre-impregnated materials (fibre reinforcement with controlled amounts of resin) which are then laid up by hand and cured by heat and pressure.

In construction, research is under way to combine these advanced materials with metals and concrete. For example, James Broughton and others at Oxford Brookes University are researching the combination of carbon fibre, laminated timber and aluminium extrusions. Carbon fibre reinforced bridge cables (from Bridon Ropes) were used on the Blythe footbridge at Stoke on Trent, designed by Scott Wilson. However, such applications depend upon design data and prediction techniques available in few engineering practices. As International Composite News noted recently, 'many engineers regard composites as a technology still in its infancy'.

Current research by Brookes Stacey Randall, Taywood Construction and Advanced Composites Group aims to demonstrate the benefits of using high- strength lightweight composites for mouldable elements. Roof panels and cladding panels are obvious components for prototyping. Combinations of materials for secondary structural elements, such as Henket's glazing mullions at the Tyler Museum in Harlem, offer interesting possibilities. It is often development of component parts that has the greatest impact, as with the Catnic Lintel, first developed for the ibis housing system in 1981, or Pilkington's Planar fitting developed for Foster's Renault Centre in 1982. Small, complex mouldings offering strength, durability and adaptability may be the first to show the advantages of advanced composites over more traditional components.

Moulding techniques and vacuum forming need to match the requirements of the construction industry. Quality control standards may well be lower than for aerospace-sector clients, but requirements for large numbers of standard components may be greater. Advances in the formulation of low-temperature pre-impregnated materials can allow lay up and simple curing on site (aj 18.6.98).

There are none of the size limitations commonly associated with the dimensions of production lines and curing boxes. Systems of moulds joined together allow the manufacture of large sections which can be lifted into place without the use of particularly heavy plant.

Design modelling

These opportunities to create complex forms require developments in cad to predict form and performance. Current modelling software can be used for everyday surface modelling. Programs normally used in aerospace, such as Pro Engineer and Solid Works, are being adapted for use in building design. These should allow seamless transition from concept models through analysis to data generation for numerically controlled direct milling or making of patterns and moulds for casting, enabling rapid prototyping.

A current example of sculpted non-linear form is the concert hall and lyric theatre of Singapore Arts Centre (architect mwp/dpa). The complex shapes are formed from a space-frame grid with glazed infill and aluminium shading devices. The concept was developed by engineer Atelier One, modelling the surface geometry using Microstation, creating a mesh of equal-length elements to standardise their manufacture. The Bilbao Guggenheim too shows how 3D computer modelling and advances in metal forming can be used to great effect to enhance human experience.

Combining these modelling capabilities with the properties of advanced composites offers architecture the delights of form previously reserved for Mach2 aircraft.

Alan Brookes is a partner in Brookes Stacey Randall. Thanks to Adrian Potts of Advanced Composites and Martin Wilson of Taywood Engineering for their advice

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