Experimental investigation of a new natural sandwich panel with oak cupules core under uniform out of plane compression

In this paper, natural sandwich panels containing two flat balsa woods as faces and some cup-like structures prepared from oak tree as the core are investigated, experimentally. The core is produced by routinely placing some cup-like structures called “cupule” in which the oak acorn is fixed. These structures are stuck to the faces by adhesive glue. Four groups of cupules with different heights and diameters are prepared and three different arrangements of cupules include four, nine and sixteen numbers of cupules are selected. The specimens are compressed quasi-statically in the out of plane direction. Specific absorbed energy of specimens are calculated and compared to find the best cupules geometry and arrangement and finally to choose an optimized natural energy absorber structures. Results show that the natural oak cupules can be used as sandwich core instead of other expensive and environmentally harmful cores such as foams, with a reasonable energy absorbing capacity.