• Structural Engineering and Mechanics
• /
• v.71 no.3
• /
• pp.283-290
• /
• 2019

In global competition manufacturing companies have to produce modern, new constructions from advanced materials in order to increase competitiveness. The aim of my research was to develop a new composite cellular plate structure, which can be primarily used for structural elements of road, rail, water and air transport vehicles (e.g. vehicle bodies, ship floors). The new structure is novel and innovative, because all materials of the components of the newly developed structure are composites (laminated Carbon Fiber Reinforced Plastic (CFRP) deck plates with pultruded Glass Fiber Reinforced Plastic (GFRP) stiffeners), furthermore combines the characteristics of sandwich and cellular plate structures. The material of the structure is much more advantageous than traditional steel materials, due mainly to its low density, resulting in weight savings, causing lower fuel consumption and less environmental damage. In the study the optimal construction of a given geometry of a structural element of a road truck trailer body was defined by single- and multi-objective optimization (minimal cost and weight). During the single-objective optimization the Flexible Tolerance Optimization method, while during the multi-objective optimization the Particle Swarm Optimization method were used. Seven design constraints were considered: maximum deflection of the structure, buckling of the composite plates, buckling of the stiffeners, stress in the composite plates, stress in the stiffeners, eigenfrequency of the structure, size constraint for design variables. It was confirmed that the developed structure can be used principally as structural elements of transport vehicles and unit load devices (containers) and can be applied also in building construction.

• Steel and Composite Structures
• /
• v.31 no.2
• /
• pp.133-148
• /
• 2019

This paper reports on the energy absorption characteristics of a lattice-web reinforced composite sandwich cylinder (LRCSC) which is composed of glass fiber reinforced polymer (GFRP) face sheets, GFRP lattice webs, polyurethane (PU) foam and ceramsite filler. Quasi-static compression experiments on the LRCSC manufactured by a vacuum assisted resin infusion process (VARIP) were performed to demonstrate the feasibility of the proposed cylinders. Compared with the cylinders without lattice webs, a maximum increase in the ultimate elastic load of the lattice-web reinforced cylinders of approximately 928% can be obtained. Moreover, due to the use of ceramsite filler, the energy absorption was increased by 662%. Several numerical simulations using ANSYS/LS-DYNA were conducted to parametrically investigate the effects of the number of longitudinal lattice webs, the number of transverse lattice webs, and the thickness of the transverse lattice web and GFRP face sheet. The effectiveness and feasibility of the numerical model were verified by a series of experimental results. The numerical results demonstrated that a larger number of thicker transverse lattice webs can significantly enhance the ultimate elastic load and initial stiffness. Moreover, the ultimate elastic load and initial stiffness were hardly affected by the number of longitudinal lattice webs.

• Computers and Concrete
• /
• v.27 no.2
• /
• pp.153-162
• /
• 2021

This paper aims to simulate the isotropic elastic damage theory of Liu Jun (2012) using the self-programmed UMAT subroutine in the interface of ABAQUS. Liu Jun (2012)'s method based on the mechanic theory can not be used interactively with the currently commonly used finite element software ABAQUS. The advantage of this method in the paper is that it can interact with ABAQUS and provide a constitutive program framework that can be modified according to user need. The model retains the two scalar damage variables and the corresponding two energy dissipation mechanisms and damage criteria for considering the tensile and compressive asymmetry of concrete. Taking C45 concrete as an example, the relevant damage evolution parameters of its tensile and compressive constitutive model are given. The study demonstrates that the uniaxial tensile stress calculated by the subroutine is almost the same as the Chinese Concrete Design Specification (GB50010) before the peak stress, but ends soon after the peak stress. The stress-strain curve of uniaxial compression calculated by the subroutine is in good agreement with the peak stress in Chinese Concrete Design Specification (GB50010), but there is a certain deviation in the descending stage. In addition, this paper uses the newly compiled subroutine to simulate the shear bearing capacity of the shear key in a new structural system, namely the open-web sandwich slab. The results show that the damage constitutive subroutine has certain reliability.

• Steel and Composite Structures
• /
• v.43 no.5
• /
• pp.565-579
• /
• 2022

This study investigated the yielding capacity and performance of seismic dampers constructed with steel ring plates using numerical and analytical approaches. This study aims to provide an analytical relationship for estimating the yielding capacity and initial stiffness of steel ring dampers. Using plastic analysis and considering the mechanism of plastic hinge formation, a relation has been obtained for estimating the yielding capacity of steel ring dampers. Extensive parametric studies have been carried out using a nonlinear finite element method to examine the accuracy of the obtained analytical relationships. The parametric studies include investigating the influence of the length, thickness, and diameter of the ring of steel ring dampers. To this end, comprehensive verification studies are performed by comparing the numerical predictions with several reported experimental results to demonstrate the numerical method's reliability and accuracy. Comparison is made between the hysteresis curves, and failure modes predicted numerically or obtained/observed experimentally. Good agreement is observed between the numerical simulations and the analytical predictions for the yielding force and initial stiffness. The difference between the numerical models' ultimate tensile and compressive capacities was observed that average of about 22%, which stems from the performance of the ring-dampers in the tensile and compression zones. The results show that the steel ring-dampers are exhibited high energy dissipation capacity and ductility. The ductility parameters for steel ring-damper between values were 7.5 to 4.1.

• Steel and Composite Structures
• /
• v.43 no.2
• /
• pp.229-240
• /
• 2022

The main objective of this work is presenting a mathematical model for the concrete slab with fiber reinforced polymer (FRP) layer under the impact load. Impacts are assumed to occur normally over the top slab and the interaction between the impactor and the structure is simulated using a new equivalent three-degree-of-freedom (TDOF) spring-mass-damper (SMD) model. The structure is assumed viscoelastic based on Kelvin-Voigt model. Based on the sinusoidal shear deformation theory (SSDT), energy method and Hamilton's principle, the motion equations are derived. Applying DQM, the dynamic deflection and contact force of the structure is calculated numerically so that the effects of mass, velocity and height of impactor, boundary conditions, FRP layer, structural damping and geometrical parameters of structure are shown on the dynamic deflection and contact force of system. Results show that considering structural damping leads to lower dynamic deflection and contact force. In addition, increasing the impact velocity of impactor yields to increases in the maximum contact force and deflection while the contact duration is decreased. The result shows that the contact force and the central deflection of the structure decreases and the contact time decreases with assuming FRP layer.

• Composites Research
• /
• v.22 no.3
• /
• pp.55-59
• /
• 2009

Microstrip antennas are low profile, are conformable to planar and nonplanar surfaces, are simple and inexpensive to manufacture, mechanically robust when mounted on rigid surfaces and are compatible with MMIC(Monolithic microwave integrated circuit) designs; they have been used in diverse communication systems. The rectangular microstrip patch antenna is designed for a central frequency of 12.5 GHz, and the final product is a $4{\times}1$ array antenna with curvature radius of 200 mm. The microstrip antenna is embedded in a sandwich structure which consists of skin and core material. After impact, the performance of damaged antenna is estimated by measuring the return loss and radiation pattern. The antenna performance was not affected by this impact damage.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.8
• /
• pp.2544-2548
• /
• 2011

Two pyridinecarboxamide cobalt dicyanide building blocks and Mn(III) compounds have been employed to assemble cyanide-bridged heterometallic complexes, resulting in three trinuclear cyanide-bridged $Co^{III}-Mn^{II}$ complexes: $\{[Mn(MeOH)_4][Co(bpb)(CN)_2]_2\}{\cdot}2MeOH{\cdot}2H_2O$ (1), $\{[Mn(MeOH)_4][Co(bpmb)(CN)_2]_2\}{\cdot}2MeOH{\cdot}2H_2O$ (2) and $\{[Mn(DMF)_2(en)_2][Co(bpb)(CN)_2]_2\}{\cdot}2DMF{\cdot}H_2O$ (3) ($bpb^{2-}$ = 1,2-bis(pyridine-2-carboxamido)benzenate, $bpmb^{2-}$ = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate, en = ethylenediamine). Single crystal X-ray diffraction analysis shows their similar sandwich-like structures, in which the two cyanide-containing building blocks act as monodentate ligands through one of their two cyanide groups to coordinate the Mn(II) center. For complex 3, it was further linked into one-dimensional structure by ethylenediamine acting as bridges. Investigation of the magnetic properties of complex 3 reveals weak antiferromagnetic coupling between the neighboring Mn(II) centers through the bridging ethylenediamine molecule. A best-fit to the magnetic susceptibilities of complex 3 gave the magnetic coupling constant J = -0.073(2) $cm^{-1}$.

• Composites Research
• /
• v.17 no.3
• /
• pp.15-22
• /
• 2004

Acoustic load generated by rocket propulsion system is one of major dynamic loads during lift-off phase so that it causes the structural failure and electronic malfunction of payloads. Acoustic loads can be greatly reduced by an appropriate acoustical design of nose faring structures. This paper deals with the acoustical design of the nose fairing structure for launch vehicle. It is well known that a honeycomb sandwich structure is a poor sound insulator because of its high specific stiffness. In this paper, the sound transmission characteristics of four kinds of honeycomb structures for noise fairing were investigated by means of numerical and experimental ways. In order to estimate transmission loss, infinite plate theory by Moore and Lyon and statistical energy analysis (SEA) method were used. The predicted results showed a good agreement with measured ones. These enabled us to determine a proper core material for nose fairing, which shows good sound insulation performance per weight.

• Journal of the Korea Convergence Society
• /
• v.10 no.4
• /
• pp.139-145
• /
• 2019

This paper investigated the strength and stiffness of composite truss unit structures. The model used is a core-filled model combining the Kagome model and the cube truss model. The material properties used for the analysis are 304 stainless steel with elastic modulus of 193 GPa and yield stress of 215 MPa. The theoretical equation is derived from the relative elasticity relation of Gibson - Ashby ratio, the analysis was performed using Deform 3D, a commercial tool. In conclusion, the relative elasticity for this unit model correlates with 1.25 times the relative density and constant coefficient, elasticity is inversely proportional to pore size. The relative compressive strength has a correlation with relative density of 1.25 times. Proof of this is a real experiment, the derived theoretical relationship should further consider mechanical behavior such as bending and buckling. In the future, it is hoped that the research on the elasticity and the stress according to the structure of the three-dimensional space will be continued.

• Composites Research
• /
• v.31 no.4
• /
• pp.122-127
• /
• 2018

Sandwich composites of carbon fiber reinforced plastic(CFRP) and polymer foam will be used to automobile and aerospace industry according to increasing importance of light weight. In this study, mechanical and heat resistance properties of sandwich composites were compared with type of polymer foam (polyethylene terephthalate(PET), polyvinylchloride(PVC), epoxy and polyurethane). All types of polymer foams were degraded to 30, 60, 120, 180 minutes in $180^{\circ}C$. After heat degradation, the polymer foams were observed using optical microscope and compressive test was performed using universal testing machine(UTM). Epoxy foam had the highest compressive property to 2.6 MPa and after thermal degradation, the mechanical property and structure of foam were less changed than others. Epoxy foam had better mechanical properties than other polymer foams under high temperature. Because the epoxy foam was post cured under high temperature. As the results, Epoxy foam was optimal materials to apply to structures that thermal energy was loaded constantly.