Abstract: The critical stresses of stress\|solvent crazing,σ c,of a nonoriented aviation organic glass, YB-3(PMMA), were measured with various organic solvents and the craze morphology was observed. The effects of environmental factors such as water sorption, UV radiation, and their combination or cycling on σ c and the craze morphology were studied, and the influencing mechanisms were discussed.

Key words: aeronaut ical engineering, polymethyl methacrylate, environmentsult ravio, let radiation　effects