جستجوی مقالات مرتبط با کلیدواژه « Repeated impact » در نشریات گروه « مکانیک »

GLARE is a kind of fiber-metal composites in which aluminum alloy sheets are used, along with composite laminates with glass reinforcements. In this paper, Glare FMLs were subjected to repeated low-velocity impact loading with an energy of 150 J. Repeated low-velocity impacts were applied using a drop-weight testing machine. To fabricate testing specimens, 2024-T3 aluminum alloy plates with a thickness of 1 mm as the face-sheets as well as the core made of the glass-epoxy composite were used. The epoxy glass laminate used also consisted of five layers of E-type single-sided glass fibers in the epoxy resin. Besides, 99.9% purity silica nanoparticles were added to the base material. To investigate the effect of adding nanoparticles on the behavior of FMLs under repeated low-velocity impacts, silica nanoparticles with a weight percentage of 0 to 4% were added to the matrix of the fabricated samples. The experimental results showed that the sample with 1% nanoparticles had better performance in terms of impact resistance so that after five loads, it was not seriously damaged; however, the perforation phenomenon occurred for samples with 3% and 4% nanoparticles in the second impact load.

In this study, an experimental investigation of repeated low velocity impact is performed on GLARE using drop weight testing machine. After the first impact on the plate, the second impact energy decreases and stays constant until the last impact. Damage due to repeated impact is investigated using visual inspection and C-scan. Three categories namely, no damage, small damage and serious damage are happened as a result of the first impact on the plate. The number of impacts required for the penetration is increased with decrease of the second impact energy. The threshold limit energy is defined as the maximum impact energy in repeated impact after the first impact which causes no damage on the specimen. For the successive impact energy larger than the threshold limit energy, the number of impacts becomes important, while for the successive impacts energies smaller than threshold limit energy, the number of impact has inconsiderable effect on damage occurrence.

In this study، repeated low velocity impacts on aluminum plate are investigated experimentally and numerically. In order to investigate the failure mechanism، Lemitre''s model of the continuum damage mechanics is used. Numerical simulation is carried out employing a Vumat subroutine in Abaqus FE package. Repeated impacts are performed on the plate with the same level of energy. Plastic deformation is observed on the plate in the first impact. During the subsequent impacts and prior to crack initiation، the effect of strain hardening on the aluminum plate is observed. After crack initiation، the stiffness of the structure decreases. As the impacts continue، stiffness further decreases and the damage area increases، finally perforation and penetration appear on the plate. Also، the present model is validated by the experimental results. Comparison of numerical with experimental results shows a good agreement for the force-time and force-displacement histories.