Crack Formation in F-15 Aircraft Canopies
Interim rept. May-Sep 1992
DAYTON UNIV OH RESEARCH INST
Pagination or Media Count:
Cracks have been reported in F-15 transparencies. The cracks extend from the free edge of the transparency into the acrylic parallel to the transparency surface. Similar cracks were reported on F-4 transparencies in the early 1970s. Investigations at that time indicated that the crack growth had two phases crack initiation and crack growth. Crack initiation was attributed to absorption and desorption of moisture. Crack growth was caused by thermal stresses due to the difference in coefficients of thermal expansion between the stretched acrylic transparency and the fiberglass edge attachment. Tests have been performed on samples from F-15 canopies to validate the crack growth mechanism. Research on the F-4 cracks showed that crack growth does not occur if nylon-acrylic composite, which has a coefficient of thermal expansion similar to that of stretched acrylic, is used as an edge reinforcement material. F-15, Transparency, Acrylic, Crack growth, Absorption, Thermal expansion coefficient, Thermal stress, Nylon.