Rigid foam insulation boards and thin flexible fibrous sheets or strips are stacked in alternating layers with adhesive between the layers, and the stack is compressed while the adhesive cures to form a rectangular core panel or billet. In one embodiment, the parallel spaced sheets or strips extend diagonally...http://www.google.es/patents/US5462623?utm_source=gb-gplus-sharePatente US5462623 - Method of production of reinforced foam cores
