Sandwich beam with a periodical and graded core manufactured using rapid prototyping

This article presents a technique for the production of graded sandwich cores, and a study of the effect of lengthwise grading of core properties for the facilitation of transverse loading. A significant failure mode of sandwich panels is caused by indentation of the foam core in regions at which local forces are introduced into the sandwich panel. The aim of this work is to synthesize a microstructure that can diminish this failure mode. By applying a rapid prototyping technique a periodic, open beam structure is synthesized. Additionally, the structure has been graded in the longitudinal direction by alternating over the beam diameter. The structure obtained is joined to aluminium face sheets to form a sandwich beam. The panel has been subjected to a three point bending test and the results have been compared to a finite element model, and further indentation tests show an increased transverse stiffness in the strengthened part of the beam.