Laminated safety glass (LSG) consists of at least two glass panes bonded together by a polymer interlayer. In the event of fracture, this configuration has the advantage that glass fragments remain adhered to the interlayer and the laminate retains a certain residual load-bearing capacity. This characteristic post-fracture behaviour is influenced by numerous factors—most notably the geometry and arrangement of cracks, which play a decisive role in the post-breakage behaviour of laminated glass.

In particular, the delamination behaviour between the interlayer and the glass is a key factor governing the post-breakage response of laminated glass. The objective is to investigate how geometric parameters influence the delamination propagation in fractured laminates and how these parameters affect the post-breakage behaviour.

Possible focus areas of the thesis may include:

- Experimental tensile tests on controlled fractured laminated glass specimens and interpretation of the results.

- Numerical investigations of the residual load-bearing capacity of laminated glass considering delamination propagation.

- Development of analytical approaches to describe delamination and the resulting load transfer mechanisms.

The transformation towards a genuine circular economy in the construction industry requires that materials and products can be evaluated after use and, if necessary, reused in whole or in part. Laminated safety glass (LSG) consists of glass panes with plastic films in between and is used, among other things, for overhead glazing, balustrades and windshields.

Currently, laminated safety glass elements are usually crushed after their life. Direct reuse does not usually take place, as there are no criteria for deciding which laminated safety glass panes still have sufficient durability and composite effect.

The construction industry faces the challenge of massively reducing CO₂ emissions. Glass is energy-intensive to manufacture, but theoretically infinitely recyclable or – even better – directly reusable. The problem is that recycled glass can have lower surface strength than new glass due to surface defects, which means it has a reduced load-bearing capacity.

In order to be able to use glass safely in new windows and facades, both the limit state of load-bearing capacity (stress) and the limit state of serviceability (deformation/deflection) must be verified. In certain cases, the limit state of serviceability is decisive.

The strength of float glass depends largely on the duration of the load and the environmental conditions. This is due to subcritical crack growth: under tensile stress, water molecules from the air humidity react with the silicon-oxygen bonds at the crack tip. This causes existing microcracks to grow over time until they reach a critical length and the component fails.

The central hypothesis of this work is that laminating with a PVB film seals the glass surface so effectively that moisture is prevented from reaching the crack tip, or at least greatly delayed. As a result, the side facing the polymer could have a significantly higher effective strength than a free glass surface.

Laminated safety glass (LSG) consists of at least two glass panes that are bonded together by a polymer interlayer. In the event of fracture, this has the advantage that the glass fragments adhere to the interlayer, allowing the laminate to retain a residual load-bearing capacity. This characteristic post-fracture behavior is influenced by numerous factors – in particular, the geometry and arrangement of the cracks play a decisive role.

The aim of the study is to investigate how key parameters of the crack structure – such as the degree of fragmentation, geometry, orientation, and configuration of the cracks – affect the residual load-bearing capacity of laminated safety glass.

Context

A circular-economy approach seeks to extend the service life of resources and products by moving beyond traditional recycling towards reuse and remanufacturing. In architectural glass construction, this means dismantling glazing units, separating their components, cleaning them and upgrading them to new products. Recovered aged flat glass has already been used as a feedstock for laminated glass and insulating glazing units. However, the interaction of aged glass surfaces with new processing components — such as silicone sealants, polymer interlayers and metal coatings — has not been thoroughly investigated. Ageing phenomena such as changes in surface topography, chemical alterations, corrosion, surface damage and contamination occur due to exposure to weather cycles, UV radiation and mechanical loading throughout the glass’s service life. These changes may affect adhesion, durability and overall performance of new products manufactured from reclaimed glass. The aim of this thesis is to analyse these ageing mechanisms systematically and to assess their influence on the remanufacturing processes for aged float glass.

Possible topics for the thesis could include:

- Literature research on aging mechanisms of float glass

- Experiments on surface roughness

- Investigation of chemical changes on the glass surface

- Compatibility tests Evaluation of interactions between aged glass and finishing components

- Derivation of recommendations for action for the further processing of aged glazing and its integration into the circular economy

Languages: english or german

Context

Reusing flat glass requires reliable knowledge of its mechanical properties, particularly bending tensile strength, since glass fails at surface defects. The characteristic bending tensile strength of float glass is specified in DIN EN 572‑1 based on tests on new glass. Additional surface damage arising from manufacturing, processing, transport, installation, use (e.g., cleaning) and dismantling can significantly reduce the residual strength of aged glass. There is a lack of quantitative data on how ageing affects the strength distribution of reclaimed glazing. To make sound decisions on the structural reuse of aged glass, it is essential to determine its strength statistically and compare it with normative values. This thesis aims to contribute to the assessment of residual strength in aged glass panes, thereby providing a scientific basis for safe and economical reuse.

Possible topics for the thesis could include:

– Literature research on the characterization of the flexural strength of float glass,

- Literature research on studies to determine the strength of aged glazing and comparison with new glass,

- Experimental investigations: preparation of samples from dismantled insulating glazing from the 1990s and determination of the biaxial flexural strength of aged glass,

- Examination of the guideline for tested type statics of multi-pane insulating glass (IFT VE-15/1) and analysis of whether the determined strengths of aged glass allow reuse in accordance with the guideline.

Languages: english or german

Heat pumps have been identified as key technologies for decarbonizing the energy system. Heat pumps coupled to borehole heat exchangers are especially efficient.

In this thesis, a benchmark toolbox is developed to support the comparability of borehole heat exchanger models.

Laminated safety glass (VSG) consists of at least two layers of glass bonded together by a polymeric interlayer. This has the advantage that, in the event of a breakage, glass fragments adhere to the interlayer, and the laminate retains residual load-bearing capacity. To characterize the post-breakage behavior, tensile and bending tests can be performed on fractured VSG. For this purpose, VSG made of thermally tempered glass or annealed glass (float glass), which has been broken in either a defined or undefined manner, can be used.

Possible focus areas for a thesis could include:

- Development of a method for the reproducible production of VSG panes with varying degrees of fragmentation. The fragmentation levels should reflect those observed in head impact tests on windshields.

- Conducting tensile and bending tests on fragmented VSG panes and interpreting the results.

Vacuum insulating glasses (VIGs) are an innovative window technology with the potential to revolutionize energy-efficient buildings. Windows and transparent facade elements are the main sources of heat loss and CO2 emissions in buildings.VIGs consist of glass panes with a vacuum gap that minimizes thermal effects and improves the energy balance of building envelopes. Small spacers in the va- cuumed inter-pane space ensure stability over decades and significantly influence the behavior of VIGs. Investigation of this influence and the development of standards for the use of VIGs are crucial for the introduction of energy-optimized window and facade systems in Germany and Europe. VIGs could thus make a significant contribution to sustainability in construction.

Glass is a ubiquitous material in modern engineering applications, prized for its transparency, strength, and versatility. However, glass is inherently brittle, and its susceptibility to crack initiation and propagation poses significant challenges in structural and safety-critical contexts. Understanding how cracks propagate in indented glass specimens under subsequent loading is therefore critical for enhancing the safety and reliability of glass- based structures and products.

The outcomes of this thesis are expected to contribute to the knowledge base on glass fracture mechanics and safety assessment. Moreover, the findings may have practical implications for improving the design and perfor- mance of glass components in engineering applications, such as architectural glazing, automotive windshields, and electronic displays.

While the glass panes in conventional lattice shells are typically used only as infill elements, activating the full load-bearing potential of glass can contribute significantly to reducing the material and energy resources of substructures for glass facades.

A current research project is investigating the integration of local and linear connection structures in glass supporting structures, which should help to better exploit the structural potential of the glass panes used and thus reduce the steel consumption in substructures to a necessary minimum. This should ultimately enable the construction of transparent glass structures with a wide variety of shapes and applications.

Vacuum insulated glazing is a highly energy efficient glazing system. Yet, its setup (more precisely the array of support pillars necessary to withstand the high loads of atmospheric pressure (10 tonnes/m2)) evokes complex stress distributions and high stress gradients locally. This can result in the formation of so-called cone cracks which can develop into through-thickness cracks and can thus lead to catastrophic failure of these glazing units. In the design of VIGs it is typically assumed that the glass-pillar contact is not of concern if the separation of pillars is limited. Yet, investiga- tions of various VIGs show that cracks occur anyway and failure can originate at a pillar.

Vacuum insulating glasses (VIGs) are an innovative window technology with the potential to revolutionize energy-efficient buildings. Windows and transparent facade elements are the main sources of heat loss and CO2 emissions in buildings.VIGs consist of glass panes with a vacuum gap that minimizes thermal effects and improves the energy balance of building envelopes. Small spacers in the va- cuumed inter-pane space ensure stability over decades and significantly influence the behavior of VIGs. Investigation of this influence and the development of standards for the use of VIGs are crucial for the introduction of energy-optimized window and facade systems in Germany and Europe. VIGs could thus make a significant contribution to sustainability in construction.

In order to reduce the consumption of raw materials, the production of climate-damaging gases, and the generation of waste, the topic of the circular economy has been coming to the fore for some time. The circular economy is a holistic approach that aims to use raw materials and the resulting products efficiently and for as long as possible. It includes repairing, reusing and recycling.