Abstract: A sandwich construction element (100) is disclosed. The sandwich construction element comprises a first element (101) with a face, extending in a longitudinal direction with a thickness and a height being smaller than the longitudinal length, and a second element (102) with a face, extending in the same longitudinal direction as the first element with a thickness and a height being smaller than the longitudinal length, wherein the second element is facing the flat face of the first element (101). The sandwich construction element further comprises an open core structure (103) arranged between, and operatively connected to the first element (101) and the second element (102), wherein the open core structure comprises a plurality of close packed tetraeder structures (201).