A second focus of research at the GCC is the edge strength of glass. Why is this so relevant?
Matthias Seel: When a pane of glass is cut, lots of small cracks appear at the edges. Under unfavourable conditions – such as high levels of solar radiation – these can quickly enlarge and destroy the pane. Until now, this has been avoided by thermally tempering glass – an energy-intensive process. We are now researching methods to process the edges in such a way that thermal tempering can be dispensed with for such applications. The industry has a huge interest in this. The topic is also becoming increasingly relevant with regard to the thin and ultra-thin glass now coming onto the market. However, there are no patent remedies. So you can't say that grinding and polishing a glass edge makes it stronger per se. It always depends on what the processing looks like in detail and what the crack systems introduced in the process look like.
What practical benefits can such findings have?
Miriam Schuster: Our aim is to provide the industry and users with appropriate information sheets and to incorporate our research findings into standardisation.
We are also conducting research into replacing destructive tests with new, non-destructive ones. This applies, among other things, to the assessment of edge strength, nickel sulphide problems and glass strength. Ideally, glass manufacturers would even be able to test the strength of each individual pane inline, i.e. integrated into the production process.
Working with several partners, you are currently also researching frameless, self-supporting glass constructions. What is this about?
Miriam Schuster: Until now, glass shells have been constructed using a supporting structure – usually made of steel. We now want to replace this substructure with a fitting that is invisibly integrated into the insulating glass structure. The fitting is laminated into the edge of a laminated safety glass and the whole thing is then supplemented by another pane to form the insulating glass.
What are the main challenges here?
Miriam Schuster: The fittings must be able to transfer loads into the laminated safety glass. Of course, the glass must not break and adhesion between the fitting, film and glass must be guaranteed. This in turn presents challenges at various levels. For example, there is always a certain amount of ventilation when laminating safety glass. The metal fitting may hinder this process. In addition to conventional loads such as wind, it is also important to take temperature influences into account for the design and statics. On the one hand, the rigidity of the film changes, which influences the stresses in the glass. On the other hand, changes in air pressure or the ambient temperature create so-called climatic loads in the insulating glass. This causes them to bulge slightly.
At glasstec 2024, you will be exhibiting a staircase construction with steps made of bevelled glass. How does this design work?
Matthias Seel: When flat glass is bent or bevelled, it can withstand significantly higher loads. Working with a start-up from Freiburg, a process has been developed that makes such forming possible –- as unique pieces, without the moulds that were previously required for hot-bent glass. For the steps, we produce two glass elements that fit into each other, which are then laminated with a liquid resin. This results in a very transparent, slim and rigid construction. If you do it right, you can save around 80% on materials with this type of process – significant added value for architecture and sustainability.