Abstract: A method and apparatus for reducing the fatigue crack growth rate of cracks in the aluminum alloy fuselage skin of aircraft structures. A fatigue crack is identified, the crack having a tip defining the direction of crack propagation. Temperature differentials are produced between a narrow strip of the skin and portions of the skin adjacent to this narrow strip. The narrow strip extends from the crack tip to a predetermined distance forward the crack tip. The temperature differentials produced between the narrow strip and adjacent unheated portions of the aircraft skin are sufficiently high so that the expansion due to heating causes plastic flow to occur in the heated strip. The plastic flow results in a residual tensile stress which acts in the direction of crack propagation when the system is returned to a normal service temperature. This residual tensile stress is of a sufficient magnitude to effectively retard the crack growth rate.

Abstract: Thin stable, substantially uniform, liquid crystal containing films are provided by coating a liquid crystal containing ink onto an inert substrate, which may be transparent, or opaque, optionally pigmented, particularly black pigment. The liquid crystal ink comprises an oil in water latex, where the latex contains a film forming polymer, a minor amount of an organic solvent for the liquid crystals, particularly a moderately water soluble organic solvent, which may be an individual solvent or a combination of solvents, the liquid crystals, and normally a thickening agent. The liquid crystal ink may be coated onto a wide variety of substrates and may then be coated with a protective coating or a dark backing. The laminated products can be used as ornamental articles of manufacture, for photographic reproduction, for temperature determination, and the like.