BONDED REPAIR OF MINIMUM-GAUGE COMPOSITE SANDWICH STRUCTURES

The bonded repair of minimum-gage sandwich structures is investigated both experimentally and analytically. The experimental study focuses o n the amount of strength recovery and failure mode of repairs with var ious numbers of plies in the patch. A three-dimensional finite element model was developed to determine the stress and strain states in the patch, adhesive layer, and face sheets. The repair is modeled on a ply -by-ply basis and includes resin-rich areas between the patch plies, a nd adhesive pockets at the ply drop locations. The model is correlated with experimental data and a phenomenological failure model is develo ped that predicts the onset of damage and the failure mode.