The knowledge of the distribution of stresses produced in three-ply laminates when the temperature changes is very important in the design of airplane windshields. This paper gives the result of a photoelastic investigation on the thermal stresses produced in a three-ply laminate consisting of glass, polyvinyl butyral, glass, when the temperature drops slowly from 70 to −20 F. The maximum stress has been found to be about six and one-half times the average longitudinal stress at the mid-section of the glass. Failure characteristics of the laminates check well with these findings. No new methods have been developed in the paper; however, the presently available techniques had to be applied carefully to determine maximum tensile stresses of about 1300 psi on the interface, at a distance of about 0.007 in. from the edge, at low temperature.

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