Panel flutter analysis of perforated plate repaired by VSCL bonded patch using the multi-patch IGA approach

The crashed structure fixing procedures using the bonded repair patches seems highly frequent in the aeronautical vehicle's maintenance. The resulting composite repaired perforated thin-walled plate is generally a complex geometry with a relatively high computational cost. The present study focuses on the linear panel flutter analysis of the perforated flat panels repaired on one side by an external bonded tow-steered variable stiffness composite patch. A variable stiffness laminate repair design can increase the composite structural performance. It also provides high flexibility toward tailoring the structure's mechanical properties. The potent multi-patch NURBS-based isogeometric analysis formulation is implemented based on the first-order shear deformation theory of plates. In the context of the multi-patch geometry modeling approach, the repaired perforated panel is divided into several separate but connected adjacent geometries. Assuming sufficiently thin repair laminates, an aerodynamic loading according to the first-order piston theory is applied. Consequently, the performance and accuracy of the implemented formulation are approved. The panel flutter behavior of various repaired perforated plates is inspected through some parametric studies on geometry, layup, boundary conditions, and flow direction. It is found that the critical flutter pressure parameter is decreased for wider cutouts with the changes dependent on the hole layout. It is found that the optimal position of the VSCL repair and cutout zone depends strongly on the type of base plate boundary conditions.