Showing 4 results for Sandwich Structures
Rahmat Rahmani, Gholamhossein Rahimi,
Volume 14, Issue 5 (8-2014)
Abstract
In this paper the experimental and numerical study on flexural behavior of new type sandwich structures with glass-epoxy skins and a combinatorial core consist of foam and corrugated composite with trapezoidal geometry was investigated. After sample production by vacuum assisted resin transform molding technique; samples were tested according to standard and then the related load-deflection curves were obtained. Finite element analysis was applied for determining maximum deflection of samples by ABAQUS software. In experimental three series of samples with combinatorial core and three different pitch for trapezoidal corrugated composite in a foam core and one series of sample with simple foam core; have been product. In order to experimental accuracy of problem; three same samples have been product in each case and the average data have been used for results. It has been shown that the flexural stiffness was increased with decreasing in pitch; and the flexural stiffness to mass ratio was increased at first but then was decreased with decreasing in pitch. Finally the experimental and numerical results were compared and a reasonable agreement between them has been observed.
Nesa Pirmohammad, Gholam Hossein Liaghat, Mohammad Hossein Pol, Hadi Sabouri,
Volume 14, Issue 6 (9-2014)
Abstract
In this paper, ballistic impact on sandwich panel with composite face sheet made of Glass/Epoxy and aluminum honeycomb core has been studied. The solution is derived from a wave propagation model. At first both analytical and numerical solutions were clarified and their results were compared with experimental results. Some deformation patterns, failure modes and energy absorption mechanisms were identified by observation, such as: dynamic movement of the target, stretching, bending deformation, delamination, debonding, shear fracture honeycomb, tensile fracture of Glass/Epoxy and plug and petal formation in composite facings. The solution involves a four-stage and effective masses of the face sheets and core as the shock waves travel through sandwich panel are derived using Lagrangian mechanics. The resulting non-linear differential equation of motion was solved considering the local damage effects and corresponding energy absorptions. Also numerical model, analysis of the penetration process was performed by a nonlinear explicit finite element code, LSDYNA. The results of analytical solution and numerical simulation are compared with experimental tests. Ballistic impact tests is carried out on the samples by flat-ended projectile with 8/5 gr mass and 10 mm diameter in difference velocities.
Hossein Malekinejad Bahabadi, Gholam Hossein Rahimi, Amin Farrokhabadi,
Volume 16, Issue 6 (8-2016)
Abstract
Sandwich structures are consisted of two thin skins with high mechanical properties and a thick core with lower mechanical properties and weight. Due to high strength/ stiffness to weight ratio, these structures are used extensively in engineering structures such as aerospace structures, ship hulls, turbines blades, etc. Skin/core debonding is one of the major failure modes in these structures. In this paper, debonding resistance of sandwich panels with composite skins and a core consisted of PVC foam and a corrugated composite laminate is investigated both experimentally and numerically. Square geometry is considered for corrugated composite laminate and obtained results are compared with reference specimen with simple core made of PVC foam. The three point bend test with attached ENS fixture is used to perform the standard experimental test. The results have shown that in square specimen with 3 and 6 layer skin before the separation between skin/core, the specimens are failed from the middle of the upper skin, but for 8 layer skin, the skin/core debonding are accured before other modes of failure. The maximum skin/core debonding resistance for square specimen are increased 269.26 percent. Specimens are modeled in Abaqus and results show a reasonable agreement between experimental and numerical result.
M. Kazemi, A. Alavi Nia,
Volume 19, Issue 4 (4-2019)
Abstract
In this research, the ballistic strength of sandwich structures with aluminum face-sheet and polyurethane foam cores of various densities have been investigated. The effect of graded changes in the density of foam core and arrangement of foamed layers with different densities on the absorption of energy and the ballistic limit of sandwich structures at high velocity (160-300 m/s) under the impact of semi-spherical nosed cylindrical projectiles were investigated. Generally, five different types of panels were designed in dimensions of 100×100 mm2, 6 in each. In total, the prepared samples were 30. Numerical simulations were performed, using Ls-dyna software. The results of this study showed that, firstly, there is good agreement between the experimental and simulation results and, secondly, the experimental and simulation results showed that the ballistic limit and energy absorption of sandwich structures of the same mass with the graded foam core in the case a less density foam layer is on the side of the impact for the three-layer panels is, respectively, 5.5% and 11.5% higher than the panel with single-layer foam core and average density.
