Textiles, Polymers and Composites for Buildings

G Pohl

• Publisher: Woodhead Publishing
• Year: 2010
• Print ISBN: 9781845693978
• eBook ISBN: 9781845699994
• Topic: Tecnología e ingeniería
• Subtopic: Métodos y materiales arquitectónicos

Textiles, polymers and composites are increasingly being utilised within the building industry. This pioneering text provides a concise and representative overview of the opportunities available for textile, polymer and composite fibres to be used in construction and architecture.The first set of chapters examine the main types and properties of textiles, polymers and composites used in buildings. Key topics include the types and production of textiles, the use of polymer foils and fibre reinforced polymer composites as well as textiles and coatings for tensioned membrane structures. The second part of the book presents a selection of applications within the building industry. Chapters range from the use of textiles in tensile structures, sustainable building concepts with textile materials, innovative composite-fibre applications for architecture, to smart textile and polymer fibres for structural health monitoring.With its distinguished editor and team of international contributors, Textiles, polymers and composites for buildings is an important reference for architects, fabric manufacturers, fibre-composite experts, civil engineers, building designers, academics and students. - Provides a concise and representative overview of the opportunities available for textile, polymer and composite fibres to be used in construction - Provides an insight into how high-tech textiles already influence our daily lives as well as potential applications in modern buildings - Features a thorough discussion of technical characteristics and requirements of textiles used for buildings and construction

1

Introduction

G. Pohl, Saarland University of Applied Sciences, Germany

At the 2008 Olympic Games in Beijing, a ‘Bird’s Nest’ of an arena served as the symbol and the expression of the entitlement to prestige which growing industrial nations are prone to displaying. This sports centre and the ‘bubbling’ Olympic swimming pools as neighbouring buildings remain fixed in the memory because of their chameleon-like vibrancy due to the light and transparent sheathing. In 2010, the Soccer City Stadium in Johannesburg, the Moses Mabhida Stadium in Durban and the Nelson Mandela Bay Stadium in Port Elisabeth became icons of the first football World Cup ever held on the African continent. Sheathing constructions, composed of light fabrics and polymer sheeting, have become a tool of modern architecture implemented not only as a multifaceted marketing instrument, but also as a kind of highly efficient large-scale protective suit for people. The utopia as envisioned by Richard Buckminster Fuller in the 1950s and Frei Otto in the 1960s and 1970s that called for the stretching of skins over cities like Manhattan or villages in the Antarctic, seem to have found themselves a reality when one looks at the projects mentioned above. Even though the specified covering distance of 2 miles has not (yet) been achieved, the materials for such projects are long since on the advance: in addition to steel, applications of textiles and polymers are playing a more and more important role for innovative projects.

Fritz Lang’s film ‘Metropolis’, which premiered in 1927 in Berlin and was thought lost until rediscovered in 1958 in Parisian archives, shows a utopian city with skyscrapers connected to each other via bridges, and aeroplanes that fly between the buildings through endless chasms seeming to be thousands of Grand Canyons. ‘Metropolis’ takes place in the year 2026 at a time when the population is split between workers who must live and die in the dark underground and the elite who enjoy a futuristic city of splendour. Had the film-maker been able to imagine the possibilities of textiles, fabrics, polymer sheeting, fibre composites or reinforced concrete for his constructions, then he would likely have presented a real utopian utopia. The upper world would have been completely distanced from stony high-rise buildings, resulting in lightweight climate-bubbles, transparent interiors and exteriors, traversable or simply visible public or private green spaces which would have resulted in a multi-layered cellular organism, which when covered by Buckminster Fuller’s dome, would be ready for self-sufficient space travel.

1.1 Tall – broad – climate efficient

From the idea of cellular climatic spaces in favour of a ‘futuristic city of splendour’, the possibility of implementation with present-day materials – which defines the constructive realisation – is not far off. Projects that eclipse even Fritz Lang’s ‘Metropolis’ constructions are springing up like mushrooms: at a height of 321.25 m, the luxury hotel in Dubai Burj al-Arab is much lower than the tallest building – Burj Khalifa at 828 m – but its 14,000 m² textile membrane serves to create climatised interior spaces. As a replacement for glass and instead of massive walls, here and in many other examples, such skins have become market-ready and available in a wide range of materials for various applications. The reason for the run on climate skins is a logical one: it is based upon the wish for the creation of an energy-efficient total concept that usually results in an onion-like sequence of multiple functional layers with a final outer shell that is able to acquire energy. City planning is also beginning to take on this tenor to the extent that textiles, polymers and lightweight constructive elements are finding broader application. An example of this is the planning undertaken by Norman Foster’s office for Masdar City in Abu Dhabi. The centre of this green city in the middle of the desert, Masdar Plaza, is covered by screens. These screens cast shadows on the ground during the daytime and become lit steles at night. During the day they convert sunlight into energy, in order to use the stored energy for lighting the evenings and turning the plaza into a luminous paradise. Furthermore, the screens enhance the cooling shadow effect because of their surface treatment with a reflective low-emissivity coating that reduces the long-wavelength radiation. Such surface treatments of textile materials have been successfully tested in projects such as the canopy above the boarding gates at the airport in Bangkok and are now in the phase of further technical and industrial development.

Screen constructions such as those in Masdar Plaza are definitely not an invention of contemporary times. Even before primeval times, humans were using screens to protect themselves from the sun or rain. Although the amphitheatres of the Roman Empire were created with broad lengths of fabric as flexible sunshades, it is only now that complex, sophisticated, mechanical constructions for lightweight superstructures and façades are possible. The seemingly floating structure built by Frei Otto in 1955 for the German National Garden Exhibition in Kassel as a temporary pillow-construction, and his delicate foldable screens for Pink Floyd concerts, are just a few examples in a series of countless developments of modern lightweight construction methods. As a result of the complexity that lies at the heart of this technology, not only structural engineers and architects concern themselves with these screens, but also physicists and other specialists in energy-efficient technologies. These industrially developed materials are being used in fully new ways: with the protection from sun and rain, it is important to unify the complexity of all necessary functions in one composite material. Furthermore, with façades, both low heat transfer and energy acquisition are usually required. The reduction of energy radiation exchange with the night sky should limit the ability of the building to cool off and similarly protect the building from overheating during the day – all of which can be achieved with fabrics.

Simple developments for the reflection of sunlight or the nightly back-reflection of interior warmth are things that have long been in use by greenhouses. For this application, lightweight fabrics are used, which are woven with the addition of aluminium strips. According to the density of the parallel-ordered aluminium threads, the permeability of the fabric for light and air can be varied – low emittance with low tech. The negative aspect of limited mechanical resilience and limited refractoriness is almost a non-issue with greenhouses, but buildings that are created to house larger numbers of people require more robust fabrics. Such fabrics are also available today: at the speed-skating rink for 2011 finalised by Behnisch architects and Pohl architects in Inzell, Germany, textile membranes with integrated fibres with low-emittance qualities are the constituent elements of an active-energy roof construction. The fabric functions as climatic shield, light reflector, sound insulation, fire protection, spatial closure and optical functionary.

Contemporary developments of construction technology have, with the help of textile elements, come to the point where massive construction methods succeed to a much lesser degree: in the assembly of materials with multiple characteristics and the formation of a new architectonic language of expression. The implementation of structural utopia in the age of generative design using scripting technologies is a great challenge for manufacturing, detailed construction and application of materials. The industry is not attuned to BLOB (Binary Large Objects) architecture. It is characterised by heavy materials, laying of stone upon stone, integration of normed steel profiles and manual assembly. The role of the tradesman in industrial society has been fundamentally oriented to the assembly of semi-finished components, which naturally leaves no space for individual material optimisations. This is quite different from the working method of the sail-maker, for example: semi-finished components are also used, namely fabrics and foils, but these are combined for an individual sail appropriate for the respective boat. This can also be found in the first tent-construction companies from Stromeyer and Bird, where buildings were crafted from individually cut and sewn or glued lengths of fabric. Today, the industry offers fabric composites that not only protect the bearing fibres but also have a layer to repel dirt and additional materials that have characteristics that we know from nature: bearing, covering, protecting, energy harvesting, attracting, transpiring, etc. For façade construction in the future, insulation and semi-permeability will be assigned the same high priorities as are offered by the breathable high-performance textiles in jackets and coats.

1.2 High-tech textiles already influence our daily lives

High-tech functional textiles for clothing have replaced cotton and leather. Most motorcyclists no longer wear leathers, which are heavy, too hot in summer and not efficiently waterproof, but rather have decided to wear much lighter protective clothing made from artificial materials, which in addition to a greater abrasion resistance are also well insulated against heat and cold, are waterproof and still have a good degree of permeability from within to outside. Protective clothing for the workplace is put under daily long-term strain. Special textiles prevent gases, poisons and chemicals from penetrating clothing. Gloves made from textiles with special fibres are soft inside and cut-resistant on the outside. This is not to imply that artificial fibres are better than natural fibres, for example high-performance polyethylene, also known by its market trade name Dyneema, is entwined with coconut thread: high-tech meets nature – the result is a hybrid composite thread that offers efficient protection from cuts and is used in safety gloves. The skin comes in contact with soft bamboo thread. Multiple-layered textiles in these gloves even keep out chlorine, ammonia and hydrocarbons.

Materials that can change their state are also being applied. Phase changing materials (PCMs) are applied in the construction industry with the help of encapsulated paraffin balls that are microscopically small – primarily in walls and ceiling elements. Some current building concepts with high interior climatic demands are also using PCMs. For textiles there are also developments where PCM components have been introduced into special mesh. The mesh creates a type of insulation, can absorb warmth and change its structure, and when it is cold it can release this warmth. This material has been developed as protective clothing for the workers on offshore drilling platforms; it keeps them cool during their transit by helicopter and can keep them warm for a long time should the craft be ditched. For buildings such applications remain to be applied.

Conductive fabrics are used not only in the textile industry but also as carbon fibre heating (CFP) moulds in the construction of fibre-reinforced polymers. In the textile industry, it is possible to include electrically conductive structures in the fabrics. They can be used to transmit energy or information, or even for the integration of electrical components. The advantage of the threads is that, as opposed to metallic filaments, they possess a degree of flexibility that does not negatively impact the conductivity of the threads. For the construction industry, ‘intelligent’ façades could be highly functional: façades that light up and also can absorb energy, photovoltaic façades, or façades that can deliver information or even function as medial façades. Complete circuits can be integrated, and heating façades can be created out of textiles. Light-emitting diodes (LEDs) can also be introduced into the textiles: surface mounted device (SMD)-LEDs are 1.6 mm long and can be used for advertising or lighting. Examples from the clothing industry and special materials show that innovative applications in architecture are at the nascent stages. With technical mass-production, such qualities as mentioned above can even be cost-efficiently produced and applied.

1.3 Features of the constructive formation of buildings with textiles, fabrics and sheeting

In most building applications, textile membranes are used in the form of laminated textiles. They are stabilised, in that they were mechanically or geometrically pre-stressed. Geometric pre-stressing can by synclastic (‘like a bowl’) or anticlastic (‘like a saddle’). Purely mechanical tensioning can take place in almost a flat plane, e.g. for advertising banners. Textile constructions require permanent tensioning, which is why such forms can be distinguished in that they create three-dimensional sweeps, have supporting elements (rods or bows), or utilise pneumatic pressure. The most common applications of fabric membranes use polyvinyl chloride (PVC)-coated polyester fabric and polytetrafluoroethylene (PTFE)-coated fibreglass fabric or fibreglass fabric with a silicon coating. The fabrics are usually made of warped or wefted threads in the long or cross directions and usually act anisotropically, which is to say that they display differing stiffnesses in respective directions. In coated fabrics, the durable fibres transfer the load, whereas the coating protects the fabric from environmental impacts, is responsible for the impermeability and dictates the level of transparency.

Sheeting is usually applied as ethylene tetrafluoroethylene (ETFE), which is a material that has no additional components. Meanwhile, sheeting is often combined with fibreglass belts or the sheeting is supported with steel cable. Sheeting is usually highly translucent and readily recyclable. The application usually dictates pneumatic constructions, which are composed of two, three or more layers of sheeting and use internal pressure to achieve the sheeting sweep and to provide stabilisation, assuming that the sheeting is stretched in a frame.

Roofs spanning great distances are often realised with textile membranes and sheeting in the most common lightweight-construction buildings. The primary load-bearing constructions are usually of steel or wood; however, in pneumatic structures this can be achieved with cell-like constructive elements or through the high interior air pressure of the well-known system of air-supported domes, although not with the same load-bearing capacity. Depending upon the type of fabric and coating, fabric membranes are appropriate for convertible constructions and can be used as façade materials or even for roofing. As a climate hull, fabric membranes are applied in multiple layers; pneumatic pillow-sheeting constructions can achieve insulation values with three layers that enable the creation of thermally unproblematic spaces. The inclusion of photovoltaic modules is still not sufficiently advanced, since the modules that are separate, flexible sheeting elements must be mounted onto the membranes and possess different distortion coefficients from the bearing membrane, and from a design perspective are still not found to be satisfactory. The production of fabrics with integrated photovoltaic threads is highly desirable, as is the crossover of qualities common to high-tech textiles from the clothing industry to that of the building industry.

1.4 Building with fibre-reinforced polymers

Building with fibres is a field that uses composite materials composed of fibres that are embedded in a polymer matrix. In aeronautics, in the aerospace industry and for high-performance yacht construction, application of fibre-reinforced polymers is no longer to be dismissed. Formula 1 racing cars are lighter and more physically stable due to the application of carbon fibre components. Developments in the USA at the end of the 1930s led to unsaturated polyester resin, composed of long-chain molecules that, due to their chemically unsaturated structure and their availability in dissolved form as a reactive fluid resin, were the first matrix used in the application of fibre-reinforced polymers. Quite early, the already known fibre glass was introduced to the polymer matrix, which resulted in a great improvement of the mechanical durability of the hardened product. Usually such fibre-composite constructions find their application in the form of constructive elements in a shell composed of multiple layers. Polymer shell elements made of fibre-reinforced polymers are usually constructed from an upper and a lower shell, with a three-dimensional core material inserted between, which are then glued together and create a closed and very stiff torsional box. This construction method with fibre-reinforced polymers allows for the arrangement of the fibres within the individual elements according to the main directions of load transfer, which in turn allows for the optimisation of the elements from a structural perspective towards effectiveness in material consumption and high load-bearing performance.

Through economical serial construction, thin-walled and lightweight elements are created. Lower weight not only saves expenditure in terms of the lower-dimensioned substructure necessary for bearing the load, but also helps to minimise usage of the expensive materials necessary for fibre-reinforced polymers. From a structural perspective, thin shells rapidly deform under small loads, which can be avoided through sweeps, folds or the application of sandwich construction techniques. Sandwich construction involves filling the inside of the shell with foam, paper or metal honeycomb or, in the construction of yachts, with balsa wood. Most shells are formed so that on the inside only membrane forces are acting and bending moments cannot occur. Shells and folded plates can effectively circumvent buckling. Advantages of this construction method are the reduction of the number of construction elements due to integral construction techniques, the high degree of reproducibility and form-exactness, great flexibility, surface durability and stability. In the ‘Tournesol’ swimming baths in France, the wall-element pan...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Textiles
• Chapter 1: Introduction
• Part I: Main types of textiles and polymers used in building and construction
• Part II: Applications of textiles and polymers in construction
• Index