This paper presents the test results of temperature and load cycling of a thick polyimide quartz laminate. The specimens tested were all of the same geometry, a V-shaped coupon with an apex radius of 1.0 in. (2.54 cm), width of 1.0 in. (2.54 cm), and a thickness of 0.42 in. (1.07 cm). The load cycle is applied by creating a moment at the apex of the V of 52.5 in ∙ lb (5.95 Nm). For each load cycle, there are three thermal cycles, each consisting of a 10-min ramp up from room temperature to 550°F (288°C); a constant 20-min period at 550°F (288°C); and a 10-min ramp down from 550°F (288°C) to room temperature.
The V-shaped specimens were tested for ultimate bending strength at various times through the testing. Some specimens were tested before cycling began, and others were tested at convenient intervals during the cycling. Measurements were taken of the weight changes, thickness changes, and ultimate bending moment decreases. Plots of the relationships of physical properties to load/thermal cycling are presented as well as photomicrographs indicating effects of thermal cycling on the resin/fiber system.
From the test results, an empirical procedure for estimating the life of a thick laminate, subject to a similar environment, can be extrapolated.