Abstract
The aim of this research is to establish a testing scenario, allowing an evaluation of the durability for sandwich panels. In the context of this research, sandwich panels are thin, metal-faced, three-layer panels with rigid core materials. A literature review has been carried out, highlighting the fact that, up to now, only limited research in the area of sandwich durability has been conducted. The research carried out up to date tried to distinguish between suitable and unsuitable materials for sandwich applications. This report tries to take a more accurate, quantity-driven approach, which includes the consequences of material property deterioration on design procedures. In a first introduction, the principle mechanical behaviour of sandwich structures together with the specific failure modes is presented. Different typical components and their basic properties are described. An introduction to the current state of the art with reference to the actual standards and regulations is given. Different aspects of durability impacts are shown. The shortcomings of durability evaluation in the current state of the art are presented and a plan of action to overcome the shortcomings is given. This includes the development of a mathematical model, connecting tensile strength perpendicular to the faces with wrinkling strength. For polyurethane core panels, chemical reactions based on auto-oxidation under the presence of oxygen and diffusion models for oxygen into polymer matrixes are presented. An artificial ageing scenario is derived. Measurements from internal climates in mineral wool panels are combined with an existing ageing model. On the base of the obtained results, the ageing models presented in prEN 14509, the European standard for sandwich panels, are discussed. Finally, a complete testing and evaluation scenario, accessing sandwich durability, is proposed.