A device for manufacturing a composite product has a first folded layer with a first and second superposed portion extending from a respective first and second free end to a first bend connecting the first and second superposed portions, and a second folded layer with a third and fourth superposed portion extending from a respective third and fourth free end to a second bend connecting the third and fourth superposed portions, wherein the first and second folded layers are laid adjacent to each other in order that the second portion of the first folded layer is in contact with the third portion of the second folded layer, the first and second folded layers being oriented with respect to each other in order to extend from a first side including the first, second, third and fourth free ends to a second side including the first and second bend.