Experimental study on barely visible impact damage and visible impact damage for repair of small aircraft composite structure

This work is focusing on the low velocity impact damage evaluation and the external patch repair techniques of carbon/epoxy UD and fabric laminate adopted developing aircraft. The impact damages of composite laminates of the carbon/epoxy UD and fabric are simulated by the drop-weight type impact test equipment. The damaged specimens are repaired using the external patch repair method after removing the damaged area. The compressive strength test and analysis results of the repaired impact damaged specimens are compared with the compressive strength test and analysis results of the undamaged specimens and the impact damaged specimens. Finally, through investigation of compressive strengths of the damaged specimens at different environmental conditions, the damage criteria for repairable design of both the impact damaged UD and fabric laminate structure are suggested.