Optimization Design Of CCT Plate With One-side Bonded With Composite-material Patches Based On Remaining Fatigue Life

The structures of current aircrafts are mainly made of aluminum alloy. The aircrafts can often suffer some damage, most of which are fatigue crack and stress corrosion crack. .The damaged components must be replaced or repaired in order to prolong the service life of the damaged aircrafts and to ensure the flight safety. A new structural repair technology, i.e., the technology of repairing the damage structures of the aircrafts by composite patches, has been developed since the 1980s. Due to low weight, small stress concentration, low maintenance cost and much longer life of the adhesive bonded structures, the technology has been paid great attention and made rapid development in many countries with.The aluminum alloy structures, widely used in aircrafts, are investigated in this paper. Also, the problem of repairing the damaged metal plate with crack is studied by means of finite element method and experimental method. Firstly, the James-Anderson method,i.e., a new experimental method,is represented to determine the stress intensity factor(SIF)of the LF21 aluminum CCT(Center crack tension) plate repaired by composite patch. Secondly, the repaired LF21 aluminum plate with crack is numerical analyzed by finite element method and the modification factor of SIF is obtained. Then, the result of the modification factor is compared with the experiment one. Finally, the regularity of the residual fatigue life,for the aluminum alloy plate with central crack,affected by the length, width and thickness of the composite patches is studied according to the damage tolerance view. Meanwhile, the dimension of the composite patches is optimized and the critical size is obtained in order to get the best repair effect.