13. Durability and Aging of Composite Aircraft Structures

The use of fiber-reinforced composites in aircraft structural components has significantly increased in the past few decades due to their improved specific strength and stiffness and superior resistance to both corrosion and fatigue with respect to their metal counterparts. Furthermore, current economic conditions require the use of most military and commercial aircraft beyond their original design service objectives; therefore, it is necessary to understand composite aging and in-service-induced damage to ensure the airworthiness and structural integrity of these airframes. Most aging aircraft studies conducted thus far have focused on metallic structures; however, as more composite components are being certified and used on aircraft structural components, it is necessary to address this aging concern for composite components as well. The primary objective of this chapter is to summarize the findings of the teardown conducted on a B-737 CFRP composite stabilizer after 18 years of service. The B-737-200 stabilizer was developed by Boeing as part of the NASA ACEE program initiated in July 1977. Five B-737 horizontal stabilizer shipsets were manufactured and certified in August 1982. As of March 2011, three shipsets have been retired from service, one has been sold to a foreign carrier, and one is owned by a commercial aircraft part supplier and has been reported for sale. This chapter provides highlights of the ACEE program, a summary of the B-737 horizontal stabilizer teardown activities, and results of the aging study. Results found indicate that the composite structure maintained its structural integrity over its service life and did not show significant degradation or detrimental signs of aging.