Investigation of Composite Patch Performance Under Low-Velocity Impact Loading

Bonded fiber composite repair on damaged metal structures can be an effective method to restore load carrying capacity or increase damage resistance. Low velocity impacts can cause barely visible damage to the interior structure of laminated composites. Delamination between plies is of particular concern in these composites. Impacts may also create disbonds between the patch and metal substrate. A building-block approach was suggested to model impact damage to composite patches. Composite, adhesive, and metal substrate damage models were separately validated and then combined. Cohesive Zone theory modeled interlaminar composite damage and adhesive damage. Hashin failure criteria with energy dissipation based damage evolution modeled intralaminar damage to the composite. The Johnson-Cook plasticity model captured the metal substrate’s behavior. A full model of a hybrid composite-metal system was then assembled and validated. Finally, a sensitivity study was performed that found that increasing ply thickness and fiber content improved composite patch impact damage resistance.