Investigation of low‐velocity impact behavior of aluminum honeycomb composite sandwiches with GNPs doped BFR laminated face‐sheets and interfacial adhesive for aircraft structures

The low‐velocity impacts that represent the equipment drop during maintenance and production, crash and drops of luggage that may occur during transportation and bird strikes during takeoff may occur in aircraft parts where honeycomb composite structures are used. Therefore, the low‐velocity impact (LVI) resistance of aircraft components is crucial. In this study, the effect of graphene nano platelets (GNPs) on the LVI behaviors of the BFR (basalt fiber reinforcement) laminated face‐sheets and the interface adhesive between the face‐sheet and the aluminum honeycomb core for composite sandwich structures were investigated. LVI tests were applied to GNPs doped and un‐doped BFR/aluminum composite sandwich samples to determine the values of the impact forces, displacements, interaction times, and absorbed energy at two different energy levels of 10 J and 20 J. The surface damages in the impact zones of the GNPs doped and un‐doped BFR laminated top face‐sheets of the sandwich samples were investigated on a macro scale with liquid penetrant. The damage formation and development of GNPs were detected in the cross‐sectional micro‐images of the top face‐sheets. SEM analysis was accomplished to define the fracture mechanisms provided by GNPs. As a consequence of tests and damage analysis, it was reported that GNPs increase the impact resistance of BFR/aluminum honeycomb composite sandwiches and limit and reduce damage development. GNPs showed increases in force and rebound energies of approximately 16.1% and 21.1% for 10 J, and approximately 8.2% and 14.7% for 20 J, respectively. The main purpose is to define the effects of GNPs additives on the contact force, displacement, rebound energy and interfacial strength of face‐sheet and aluminum honeycomb core by performing to low‐velocity impact test (LVI) on BFR‐laminated aluminum honeycomb composite sandwich. In addition, it is aimed to examine the influences of GNPs on the formation, propagation of damage, and changes in damage types for the laminated face‐sheet and face/core interfaces and the damage at aluminum core walls under non‐penetrating damage conditions.