Metal-thermoplastic-metal laminates

Claim 1

A metal-thermoplastic-metal laminate comprising: (a) a thermoplastic core layer of thickness from about 0.01 inches to about 0.09 inches, said thermoplastic being selected from the group consisting of partly crystalline polyamides and polyesters having a crystalline melting point greater than about 130° C. and a tensile elongation greater than 15 percent; (b) a metal layer of thickness from about 0.002 inches to about 0.0085 inches laminated on each side of the thermoplastic core layer, said metal being an aluminum alloy selected from the group consisting of (i) aluminum alloys which have at least 90 weight percent aluminum, from about 0.4 to about 1.6 weight percent manganese and from 0 to about 1.3 weight percent magnesium, the weight percent of any other alloy metal being less than that of the manganese; (ii) aluminum alloys which have at least 90 weight percent aluminum and from from about 1.2 to about 5.3 weight percent magnesium, the weight percent of any other alloy metal being less than that of the magnesium; (iii) aluminum alloys which have at least 90 weight percent aluminum, from about 0.3 to about 1.3 weight percent magnesium and from about 0.2 to about 1.5 weight percent silicon, the weight percent of any other alloy metal being less than either that of the magnesium or that of the silicon, whichever is the greater; provided that, (A) the thermoplastic core layer thickness is less than (0.54-14t f )/d c inches and greater than the value for t m required in the relationship (t.sub.m +t.sub.f).sup.2 +[(E.sub.c ×10.sup.-7)-1]t.sub.m.sup.3 /(t.sub.m +t.sub.f)=25/(S-2000); (B) the tensile offset yield strength of said metal is greater than 15,000 lbs./in. 2 and at least ##EQU4## and (C) the tensile elongation of said metal is at least