INTEGRAL LAMINATED COMPOSITE STRUCTURE

1,248,548. Acoustical laminate. AMERICAN CYANAMID CO. 6 April, 1970 [19 May, 1969], No. 16145/70. Heading B5N. A laminate comprises a non-reticulated perforated outer metal or plastics layer having a thickness of from 1 to 250 mils. and a thicker, non-reticulated cavitated backing member which is either a sheet of metal or plastics having cavities at least 10% and not more than 90% through the cross-section thereof or a perforated metal or plastics layer having bonded thereto on the side opposite said outer layer a layer of metal or plastics, said backing member having a thickness of from 5 to 1000 mils. and at least, on the average three cavities per square inch of surface area, and the outer layer being bonded on the cavitated side of said backing member; the laminate having the following further characteristics: (i) the open area of said outer layer and said backing member ranges from 15% to 80%; (ii) the perforations in said outer layer and the cavities in said backing member are substantially devoid of adhesive or plastics material; (iii) the ratio of the shortest diameter (as defined) of a cavity or perforation to the distance between the centre of the cavity or perforation and the centres of adjacent cavities or perforations, respectively, is at least 0À5 but less than 1À0; (iv) at least nine, on the average, of the perforations of said outer layer are positioned over each cavity of said backing member; and (v) there are at least 50 acoustically active holes per square inch of laminate. Many adhesives and plastics and metal layers are specified, aluminium and steel being preferred. The laminates exhibit acoustical properties.