جستجوی مقالات مرتبط با کلیدواژه « Energy Absorption » در نشریات گروه « مکانیک »

In this article, the energy absorption in thin-walled corrugated pipes with and without lateral holes has been studied experimentally and numerically. In this study, these tubes have been used to absorb axial impact energy of a weight. These tubes absorb the force caused by the impact with asymmetric plastic buckling. If the force of the impacting body is greater than the minimum average buckling force, the tube will be dented and its length will decrease. The amount of pipe depression depends on the energy input to it, the geometric characteristics and the material of the pipe. In this article, it is shown that by piercing the thin-walled tube to absorb the same impact energy, the contraction length increases, and the longer the contraction length, the lower the initial force, and in other words, the possibility of control Power and damage are provided. There is a good agreement between experimental and simulation results.

The trapezoidal shape of composite corrugated cores has made it possible to increase their resistance against destruction. In this article, the effect of changing the geometric parameters of trapezoidal core edge angle and fiber angle in the porcelain layer of sandwich panels under quasi-static compressive loading has been studied. In the construction of composite panels used a combination of glass and metal fibers. The angle of the edges of the core is 46, 52, and 58 degrees, and the angle of the fibers in the porcelain layer is 30, 60, and 90 degrees are chosen. The absorbed energy and maximum force in the form of destruction samples were discussed after the quasi-static compression test. The results have shown that increasing the fiber angle from 30 to 90 degrees can increase the maximum force by 123% and energy absorption by 260%. The mechanism of plastic deformation of metal fibers and breakage of glass fibers in the area of plastic hinge formation at the edges of the core are the main mechanisms of destruction, and no delamination was seen in the plates. Also, the separation of the core from the top of the composite was not observed in the panel due to the high adhesion of the core and the tops of the plates, which indicates the high quality of these panels.

Sandwich panels are widely used in aircraft structures, such as the surfaces of the wing, radome and engine cowling, due to their optimal energy absorption compared to their low weight. Nowadays, hybrid sandwich panels are used in the aviation industry due to their different mechanical properties. The structure of sandwich panels consists of two thin layers and a core, the core prevents the effect of out-of-plane shear loads on the surface sheets and supports them against buckling. In this paper, the energy absorption and strength of sandwich panels with 2024-T3 aluminum plate as the shell and 5052 aluminum honeycomb as its core are investigated under quasi-static punch loading using two punchers with flat and spherical cross sections, experimentally and numerically. For numerical analysis, the explicit solution method is used in Abaqus finite element software. Failure modes in this test are classified as wrinkling of the panel, separation of the adhesive layer between the panel and the core, tearing of the panel, crushing of the core of the sandwich panel outside the plate, bending of the core of the sandwich panel inside the plate, and tearing of the core of the sandwich panel. The results of numerical analysis are in good agreement with the results of experimental samples. The minimum amount of energy absorption of sandwich panel experimental samples in the punch penetration test is 21.42 joules and the maximum is 25.13 joules.

Enhancing the failure behavior of laminated composite panels for various industrial, aeronautical and naval applications has been concerned by researchers and engineers. In the present paper, in order to create a fuselage time between the initial failure on the top composite panel and final failure due to failure of the bottom panel, an interlayer elastomeric foam was employed using epoxy adhesive and the failure pattern was compared between the single and sandwich composite panels for various layup methods of the laminates.  The examined layup methods are composed of a stronger direction, cross-ply and woven plies laminates, in which the enhancing influence of an elastomeric foam from PE-EVA blend (28% EVA) was observed in terms of maximum load carrying and energy absorption capacities. The objective for application of an elastomeric foam was omission of disadvantage by inflexible crushable foams. Although, the elastomeric foam supplied aa lower flexural modulus for the sandwich composite panels due to its lower shear rigidity, it could distribute stress concentration areas from the top to the bottom composite panels, to create a considerable fuselage to reach the ultimate strength via absorption of considerable energy. The results showed promising performance for failure response of elastomeric foam cored sandwich panels. Application of the interlayer elastomeric foam in the case of composite panels with lower stiffness showed larger enhancing effect.The objective for application of an elastomeric foam was omission of disadvantage by inflexible crushable foams. Although, the elastomeric foam supplied aa lower flexural modulus for the sandwich composite panels due to its lower shear rigidity, it could distribute stress concentration areas from the top to the bottom composite panels, to create a considerable fuselage to reach the ultimate strength via absorption of considerable energy. The results showed promising performance for failure response of elastomeric foam cored sandwich panels. Application of the interlayer elastomeric foam in the case of composite panels with lower stiffness showed larger enhancing effect.

Thin-walled tubes play a significant role in increasing the energy absorption in energy absorbing systems. Holed thin-walled tubes are a suitable option for use in these systems due to the ease of production and the lack of geometry complexity. In this paper, a new geometric pattern for holed thin-walled cylindrical tubes made of aluminum alloy 6061 is presented, to improve the energy absorption characteristics. To this aim, the Taguchi design of experiment method has been used to find the optimal levels of the geometrical parameters of the tube to achieve the maximum energy-to-weight ratio and the minimum effective equivalent strain. The number of rows of holes, the number of holes in each row, the diameter of the small hole and the diameter coefficient of the small hole were considered as the geometric (input) parameters of the tubes. The initial crushing force, the total absorbed energy, the ratio of energy to weight and the ratio of the maximum initial force to the average force were compared for the optimal layouts. Examining the results showed that the arrangement of the holes in the middle with 3 rows of holes, 8 holes in each row, diameter of the small hole of 5 mm and the diameter coefficient of 1.2 (the large diameter is 6 mm) will lead to the best energy absorption result.

In this research, energy absorption in sandwich panel structures with honeycomb core and skin made of glass-epoxy multi-layer composite, aluminum, and two-dimensional glass fabrics impregnated with shear-thickening fluid under low-velocity impact loading has been investigated. Polyethylene glycol 400 and hydrophilic fumed silica with nanometer dimensions were used to make the shear thickening fluid, and then a rheometer was used to verify the rheological properties of the fluid. The test was carried out at two heights of 100 and 500 mm with a drop weight device. The sandwich panel honeycomb core has been tested once filled with shear thickening fluid and again empty of shear thickening fluid. The results of the rheology test show that the viscosity value increases with the increase of the shear rate. The impact test results show an increase in energy absorption in the structure of sandwich panels filled with shear thickening fluid compared to empty sandwich panels. At the drop height of 500 mm, the absorption of specific energy in the sandwich panel structure with a skin made of two-dimensional glass fabrics impregnated with shear thickening fluid, the ratio of sandwich panel with a skin made of aluminum and composite increased by 27.93, and 9.47%, respectively, and energy absorption in The sandwich panel with composite skin has increased by 16.86% compared to the sandwich panel with aluminum skin.

Dragonfly wings are a fascinating composite microstructure and highly specialized flight organs well adapted for dragonfly flight behavior. This paper aims to investigate the effect of graphene nanoparticles on the strength of a sandwich structure inspired by the microstructure configuration of a dragonfly wing under quasi-static loading. Sandwich vein structures are made of glass/epoxy layers with different percentages of graphene nanoparticles. Polyurethane foam was used in the central core of the vein. After the quasi-static test, the crashworthiness characteristics of these structures were discussed. On the other hand, the effect of polyurethane foam on the amount of damage to the sandwich structure due to quasi-static force was investigated. Pictures of the damaged surface and the cut view of the damage were taken to check the damage in the manufactured samples, and the results were reported. Finally, Field Emission Scanning Electron Microscopes analysis was used to evaluate the distribution of graphene nanoparticles in the samples. The results showed that the presence of graphene nanoparticles in the resin of this type of sandwich structure with a foam core if it is less than one value, will not have much effect on the strength of the structure. On the other hand, if the graphene nanoparticles exceed a certain amount, it shows relatively good resistance.