Investigation of a Relationship between Uniaxial and Biaxial Chemical Stress Crazing of Cast Acrylic
Interim rept. Jan-Dec 1990,
DAYTON UNIV OH RESEARCH INST
Pagination or Media Count:
Chemical crazing is directly responsible for many aircraft transparency removals. Laboratory chemical stress craze testing can be used to evaluate the effects of different chemical on aircraft transparencies. Most craze testing to date has been uniaxial, while the stress state in an installed aircraft transparency is biaxial. The uniaxial craze test is easier to conduct and requires less and more simple fixturing than the biaxial craze test. It is desirable to be able to use uniaxial data to predict the effects of a biaxial stress field on crazing. An experimental program was conducted to develop a relationship between uniaxial and biaxial chemical stress crazing of aircraft grade cast acrylic with isopropyl alcohol. ASTM Standard Test Methods F484 and F1164 were used as guidelines for the uniaxial craze testing and biaxial craze testing, respectively. Time to craze as a function of stress level was determined and used to develop relationships between uniaxial and biaxial crazing in the form of craze initiation criterion, utilizing theoretical and empirical equations.