The 16 November 2006
The new panel of possibilities offers by glass induces a need of information emanating from architects, engineers and designers. In order to provide answer to these questions, the first part of the colloquium presents the new trends in creation and construction given by glass, properties and mechanical behaviour under different loading conditions.
Expert: Pr. Pluvinage Mechanical laboratory of Reliability, Université Paul Verlaine - Metz
Trends in civil engineering
Glass as a transparent material allows light to pass through when protect against rain. Glass with few emissive layer offer a large panel of performances for environmental needs, solar control and thermal comfort. The concept of auto cleaning glass remains from a long time as a dream. However, after a long research and development program, this hope has been concretised by a double action process, which acts on natural elements for a clean window without organic waste.
New fire protect glass are offered for different windows in steel, wood or aluminium. These windows as response to the market needs offer a large transparency ally with technical performance of solar control, low emissivity and security. Now glass resisting to a large panel of attacks and keeping transparency to natural light are present
Trends in car manufacturing
During the last forty years ; the surface occupied by windows in cars has been multiplied by two. In the same time techniques and windows shapes become more complex. This trends to an increasing of the window surface is following with an increase need of intimacy, thermal comfort and openings.
More comfort (visual, thermal, acoustic…), more safety (reduction of ejection and introduction risks), more audacious car design are asking. In addition, to these needs, constrains connected with environment respect have to be taken into account ( weight reduction, less utilisation of temperature control, recycling possibilities). Car windows are an important component in modern car not only for a sophisticated design but also by offering a large panel of technical applications such as solar glass, rain sensors, antenna with integrated circuits.)
Glass and Innovation
The use in construction of glass beam is possible by using the good compression resistance of glass an avoid its use in tension. In this case, metallic reinforcements are gluing over the tensile part of the beam and allow a redistribution of efforts. This technique offers new perspectives for construction using glass beams. Introduction of residual stresses on glass surface is often use to increase fracture resistance and reliability of brittle materials.
A new reinforcement technique has been developed for different glass composition of calcium sodium silicate. The new process uses a two step ionic exchange. During the second step, some ions present during the first step are taken off. This relaxes partially the external load and produce compressive load under surface. Only for higher load, a crack initiates and propagates in glass. This technique is named ESP.
Nanoglasses
Improvement of wear and scratching resistance needs a nano structure on surface. When applying a nano film, during polymerisation it growths in direction to surface. Microscopic indentationare filled and a covalent link is established with glass. The fist step of treatment consists with vaporisation on glass surface of a silicone nano film with chloral atoms. These chloride atoms reacts with water vapour and produces hydroxyls (OH) of molecular chains with free ends. A second layer is vaporized after.
During this step, the molecules of this layer are stick on molecular chains of the first film. This last step increases considerably hydrophobicity and durability of the surface without any contact point for humidity and pollutants. This nano film fills microscopic scratch of upper glass surface increasing scratching resistance .This process generates a permanent chemical link which reduce considerably cleaning of glass surface . Recently, a brittle to nano ductile transition in glass has been pointed out nano-ductile fracture under stress corrosion which explains an increasing of fracture resistance .
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