Abstract: In order to research the evolves regularities and mechanism of bending properties of composite repaired structures for civil aircraft structures when dealing with environmental changes, the bending behavior and failure mechanism of benzoxazine composite laminates under dry/hygroscopic conditions are systematically researched by means of electronic universal material testing machine, scanning electron microscope and laser confocal microscope. Results show that the bending strength of the bulk material/autoclave, bulk material/thermal compensation instrument, non-bulk material/autoclave,non-bulk material/thermal compensation instrument repair test plate can be restored to 99%,95%,97%,87% of the intact sample at room temperature. After heatmoisture treatment,the flexural properties restoration ratesare respectively reduced to 65%, 56%, 60%, 34%.
Bending fracture analysis shows that the failure mode of the intact specimen is tensile fracture of the fiber,and the failure mode of the repaired specimen is tensile fracture and debonding pull-out of the fiber. In summary,the fiber/resin interface bonding of the repaired specimen has the best performance by usingthe bulk repair material/ hot-pressing pot curing method.

Key words: benzoxazine carbon fiber resin matrix composites, scarf patch repaired, hygrothermal aging, bending test, fracture analysis