American Society for Testing Materials‐National Meeting

Abstract

TWENTY years ago, there was no commercial production of metal‐to‐metal adhesive‐bonded structures, and much of the recent progress has resulted from a greater understanding of the molecular physics of the adhesive mechanism. Theoretical and experimental knowledge of the fundamentals of adhesion was reviewed as was experimental work in Germany on metal‐to‐metal adhesives. The European aircraft industry has put heat‐curing resins to general use. German research, however, has also covered room‐temperature‐curing adhesives which are specially valuable for repairs in the field. Since work in the United States has been confined largely to heat‐curing adhesives, the German work on room‐tempcrature‐curing adhesives was of considerable interest. Most of the metal‐to‐metal bonding adhesives used today are phenolic or epoxy‐modificd phenolic types. These, however, will withstand only short‐time exposure to temperatures above 500 to 1,000 deg. F. Prolonged high temperatures break down the polymer structure and drastically lower strength. Research was described in which an inorganic component (most satisfactory to date: arsenic pentoxide) was added to the organic adhesive to provide thermal resistance. Results definitely indicated that organic‐inorganic adhesive systems provide one solution to the thermal resistance problem. The high temperature resistance characteristics of five ceramic adhesives were presented. These inorganic adhesives were prepared as ceramic frits and applied to stainless steel, the material being considered for wings and control surfaces of missiles. Data from tests at 800 and 1,200 deg. F. showed great promise for this type of adhesive.