Novel liquid composite connections for glass structures

The combination of transparency, high quality finish, durability and relatively low cost make glass a unique material in buildings. While glass itself is an ancient material, its properties are still comparatively unknown. It is only due to its recent popularity that research on developing its structural performance has increased. One of the current most critical issues in the structural use of glass is how is the best way to connect this material to the substructure as well as to adjacent panels/other glass pieces.
Until recently the only option for connections in high stress applications was the use of bolted assemblies in fully toughened glass. Therefore, this project endeavors to identify the potential mechanical suitability for the use of glass in its alternative conditions (i.e. annealed and toughened) as these are already widely used in the construction industry. However, the use of bolted connections for joining brittle materials is highly inefficient due to large tensile stress concentrations in the parent material. Consequently, focus will be given on developing novel and simultaneously viable alternative bonding solutions for structural glass applications. One obvious solution is adhesive bonding as this evenly distributes the load, reduces stress concentrations and requires very little surface preparation. The main drawback of adhesives is that their long-term performance (i.e. under long-term loading as well as environmental ageing) is not easily quantified and the effect of differential thermal expansion on adhesive joints remains unresolved. These uncertainties lead to prohibitively large safety factors limiting their use dramatically.
Generally, the use of adhesives and structural interlayers as alternatives to bolted connections has been investigated. This project seeks to address the uncertainties associated with their durability and stability by investigating their structural behavior over load time and temperature. In more detail, cyclic long term actions (such as self-weight, temperature cycles, freeze-thaw cycles, solar radiation and fluctuating wind pressures) and accelerated ageing tests can be carried out to validate the performance of the adhesives regarding fatigue, creep and embrittlement. However, due to substantial improvements in adhesive technology, recent experimental research has shown that glass failure might eventually be the limiting factor in design of connections. Hence, this project aims to illustrate the failure mechanisms of the proposed innovative joints and especially the shear failure in the glass phase of the joint (i.e. glass plucking).
Additionally, attempts will be made to establish the potential suitability of extending the research to include other materials that can replace the conventional used in bolted/adhesive connections, chosen from the properties listed on manufacturers' datasheets and consultation with industrial experts. To this purpose, the project focuses on the examination of these materials to establish a substantiated material law for their mechanical and thermal behavior. Apart from this, another potential route is to examine the possibility of incorporating processes (e.g. diffusion bonding) used to bond other structural materials (e.g. engineered ceramics) and the potential applicability of these techniques in glass connections.