Investigating impact behavior of polymeric composite laminate bolted joints: A numerical and experimental approach

In this study, the effect of preload on bolted joints in composite plate connections under impact loading is investigated. Delamination, a common failure mode in composite structures, occurs around joints due to stress concentration. To prevent delamination, preload is applied to the bolted area. Experimental samples of composite plates connected by bolts were manufactured using the Vacuum Infusion method. These specimens were subjected to low velocity impacts with energies of 26 J and 35 J. The conducted experiment was then simulated using ABAQUS software. Due to material limitations, degradation behavior was programmed using VUMAT subroutine in Fortran software. The simulation results were compared with the experimental data, showing good agreement. The simulation revealed the delamination area around the hole in the composite plate. By applying different preload forces (1 MPa, 10 MPa, and 105 MPa) to the areas around the bolt, a significant reduction (46%) in the delamination area was observed. This highlights the effectiveness of applying preload force and clamping in improving joint strength and reducing delamination.