Development and test logics for structural silicone bonding design and sizing

Abstract

The application of structural silicone bonding requires dedicated design procedures due to technical challenges such as high degree of incompressibility of silicone, low Young’s modulus and non-linear material characteristics. Advanced bonding designs feature point-wise or line-type bonding geometries beyond the application range of ETAG 002 which is the European guideline for structural silicone glazing. No straight forward approach exists to extend the rules of ETAG 002 accordingly. In order to fill this gap, the following topics need to be addressed: (a) Silicone bonding material tests for the identification of elastic characteristics beyond ETAG 002, (b) Small sample tests for identification and quantification of failure mechanisms in addition to ETAG 002, (c) Structural mechanical analysis methods complementary to material and small sample tests, (d) Safety concept exploiting the above mentioned tests and analyses for ensuring adequate bonding performance. This paper outlines a comprehensive development approach answering this list in detail. Common material tests will be critically reviewed in view of fracture behaviour as small sample tests demonstrate a totally different failure mechanism compared to usually applied dog-bone or H-type sample tests. Complementary Finite Element Analyses based on material test characteristics allow correlating the test results with limit loading levels. These values serve for extrapolation from small sample test results to the envisaged full scale application. Within this extrapolation procedure, an adequate safety concept needs to be embedded accounting for temperature, humidity, aggressive environment etc. In this paper, a potential safety concept is presented for advanced line-type and point-wise bonding geometries.