Development steps towards innovative birch plywood sandwich panel production technology by integrating (heat insulation, vibration, damping, impact resistance) will be presented. It is proven than lightweight sandwich structures are mechanically the most efficient way of applying plywood for large span load-bearing applications. It allows to save significant amount of material and also to reduce weight of the structures. In addition, there is a possibility to integrate additional function in sandwich panel core by adhesive bounding with various foams or optimizing layout of stiffeners to increase performance in other fields of application. Accumulated knowledge starting from single coupon specimen tests up to various actual scale prototypes manufactured both in laboratory and manufacturing plant will be discussed.
In order to fully explore a multifunctional potential of plywood sandwich panels reliable and safe design methodology should be developed. For this reason reliable input data (mechanical and thermal properties) is necessary in order to acquire accurate numerical models. It has been found that there is great difference between birch specimens and properties of compressed birch veneer with adhesive. In addition series of bending tests (according to EN 789) have been performed for the sandwich panels with I-type stiffeners and corrugated core in order to validate accuracy of the numerical models. Some evaluation of multifunctional properties indicate that foam bounded sandwich panels have an advantage among others of vibration damping due to lower core stiffness. The results of low velocity impact tests shows that thin elastic middle layer improve penetration resistance of plywood board, although Impact resistance of large thickness panels is mainly dependant on resistance of outer surface layer. Results of mechanical and thermal performance optimisation of sandwich panels with natural foam core could be applied to pick the most efficient design between three response values or to design structures with lowest possible U-values.
Furthermore developed methodology of design of lightweight sandwich panels to match bending performance of conventional plywood boards developed within Latvia State research programme: Innovative and multifunctional composite materials for sustainable buildings (IMATEH) is approbated in scaffolding deck application.
Keywords: birch plywood, sandwich panel, innovative technology
Authors
Kalnins K.
Institute of Materials and Structures, Riga Technical University, Riga, Latvia
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