Stiffened Composite Panel

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Numerical and Experimental Study on Stiffened Composite Panel Repaired by Bolted Joints under Compressive Load

Numerical and Experimental Study on Stiffened Composite Panel Repaired by Bolted Joints under Compressive Load

Numerical and experimental study was conducted to investigate the failure mode and strength performance of stiffened composite panel repaired by bolted joints under compressive load, and the results were then compared with those from virgin stiffened composite panel without any damage. A fi- nite element analysis model was established for repaired and virgin stiffened composite panels under compressive load, the 3D Hashin criteria was applied to identify the composite structure failure, and the secondary stress criteria was adopted to identify the adhesive failure between the base laminate and the stiffener. The failure modes of repaired stiffened composite panels were stiffened composite panels breaking off along the bolt joints. The experimen- tal results were consistent with the finite element analysis results, indicating the reliability of the finite element analysis model.
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Determination of the Fracture Parameters in a Stiffened Composite Panel

Determination of the Fracture Parameters in a Stiffened Composite Panel

A stiffened panel based on the dimensions of the plate mentioned in Section 5.1 has five stiffeners attached longitudinally on one side of the plate. This structure is designed by Boeing for the all-composite wing skin in a commercial aircraft [29]. A center crack of length 2a cuts through the central stiffener and the panel. Figure 5.7 shows the configuration of the panel as well as the detail dimensions of the stiffener. Due to the presence of stiffeners and geometry symmetry, one-fourth of the entire panel is modeled by finite elements, as shown in Figure 5.8. Both of the global and local Cartesian coordinate systems are defined in the same way they are defined in a plate. Hence the symmetric boundary conditions are imposed on the planes of X = 0 and Y = 0 ( a ≤ X ≤ w ). To prevent a free-body motion in Z-direction, a constraint in the Z- direction is also imposed on the node at (0, 0, –t), i.e. the point at the center of the panel's back side. Here t is defined as one half of the panel thickness that is not including the stiffener portion. A uniform displacement u ∞ equivalent to a strain value of 0.1% is prescribed on the far end at Y = l .
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Damage Assessment of an Integrally Stiffened Composite Panel through Dynamic Interrogation of Multiplexed Fiber Bragg Grating Sensors.

Damage Assessment of an Integrally Stiffened Composite Panel through Dynamic Interrogation of Multiplexed Fiber Bragg Grating Sensors.

excitation. Additionally, the surface mounted FBG sensors demonstrated an ability to sense minor changes in the transient response, and identified several trends that may be indicative of non-linear response in the specimen. Though these trends were not extremely strong, they do offer promising results for the potential use of FBG sensors as real-time structural health monitoring devices in aircraft. The limited sensitivity of the sensors to the changes in transient response may be a result of surface mounting the sensors. If the sensors were embedded within the carbon fiber panel, they would likely be much more sensitive to these changes and potentially offer more distinct indications of a transition to non-linear response in the panel. It should also be noted that while not the focus of this work, the dynamic response of multiple multiplexed FBG sensors were measured through high-speed, full- spectral interrogation for the first time.
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Finite Element Buckling Analysis Of Stiffened Plates

Finite Element Buckling Analysis Of Stiffened Plates

Instead of increasing the thickness of plates and there by increasing the cost of materials, stiffeners are provided. These stiffener elements presenting relatively small part of the weight of the structure substantially influence the strength of the structure under different loading conditions. It is assumed that stiffener will have the same displacement as that of plating. The stiffeners can be positioned any were within the plate element and need not necessarily be placed on nodal lines as the stiffness matrix of a stiffened plate element is comprised of the contributions of the plate element and that of the stiffener element. The stability of stiffened plate is determined from the arrangement and the loading conditions on the plates. There are three types of stiffening systems,
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On the flexural properties of multiscale nanosilica/E-glass/epoxy anisogrid-stiffened composite panels

On the flexural properties of multiscale nanosilica/E-glass/epoxy anisogrid-stiffened composite panels

In the present study, composite panels with an anisogrid lattice patterned reinforcements were fabricated. Silicone molds were used to fabricate the grid specimens. The main reasons of selecting silicone for making molds were its rubber state and bearing high elastic strains, which facilitate the removal of the specimen from the mold. The silicone compound used in this research consisted of RTV-3325 and 6H components which were mixed in 100:4 ratio by weight. The molds were obtained by pouring liquid silicone mixture over a pre-fabricated polyvinyl chloride (PVC) model (Fig. 2(a)) and then holding at room temperature for about 6 h to make it cure. The silicone mold is shown in Fig. 2(b).
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Experimental Test on Sandwich Panel Composite Material

Experimental Test on Sandwich Panel Composite Material

From tensile test and bending test of composite material, tensile strength and bending strength capacity of with hexagonal composite material is less compare to without hexagonal composite material, but it can be negligible. Hence sandwich panel composite material (with hexagonal structure) is acceptable in Automobile, Aerospace, and Marine engineering.

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A feasibility review of innovative prefabricated

A feasibility review of innovative prefabricated

used in practice for houses are: stiffened raft, footing slab, waffle pods, stiffened slab with deep edge 90.. beams and strip footings.[r]

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Innovative Cold Form Based Composite Section for Enhancing Sustainability in Built Environment

Innovative Cold Form Based Composite Section for Enhancing Sustainability in Built Environment

The pre-engineered steel buildings are widely used in the construction of industrial buildings. Very short erection time and higher strength to weight ratio are the major advantages of these systems. Some of the components like slabs and walls in PEB construction are still done on-site. This paper addresses this limitation through development of a composite panel using cold form steel section. The panel is experimentally analyzed for flexure and the results hence obtained are also simulated using finite element method.

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Online Full Text

Online Full Text

Recently, mesh reduction techniques (meshless or meshfree methods), which are independent of geometric elements, have emerged as effective numerical techniques for solving science and engineering problems. Over the past decade, there have appeared many kinds of meshless methods in the literatures [50-58], such as the element-free Galerkin (EFG) method, the reproducing kernal particle method (RKPM), hp-clouds, the partition of unity method (PUM), the meshless local Petrov-Galerkin (MLPG) method, the smoothed particle hydrodynamics (SPH), the corrected smoothed particle hydrodynamics (CSPH) and the modified smoothed particle hydrodynamics (MSPH). For the Hamilton canonical equation of composite laminates, Li [59-62] has established a class of meshless methods based on the modified Hellinger-Reissner variational principle and radial basis functions.
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An Experimental and Numerical Investigation of a Grid Composite Cylindrical Shell Subjected to Transverse Loading

An Experimental and Numerical Investigation of a Grid Composite Cylindrical Shell Subjected to Transverse Loading

Fig. 7 indicates 1700 N of load capacity for this structure under the mentioned boundary conditions. The behaviour of this structure changes linearly until approximately 1400 N. After a 7 mm deflection of the free end, the first reduction in the load variation is observed. This is the time that buckling or collapse takes place in the structure. In the failure analysis part of this paper, it will be illustrated that the collapse in the composite shell occurs in this point. Following this, the load increases again up to the maximum load capacity.

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Optimization Of Submarine Ring Stiffened Composite Pressure Hull Using Numerical Methods

Optimization Of Submarine Ring Stiffened Composite Pressure Hull Using Numerical Methods

In this paper, Tsai-Wu criteria is adopted to evaluate the failure of the composite material. The Tsai-Wu criterion predicts failure when the failure index in a laminate reaches one. The CFRP fiber shows better results as compared with the GFRP and BFRP fiber in case of failure index. In composites, the matrix is usually a polymer resin, such as epoxy, to bind the reinforcements together. The reinforcement will give the CFRP its strength and rigidity; measured by stress and elastic modulus respectively. Unlike isotropic materials like steel and aluminum, CFRP has directional strength properties. The properties of CFRP depend on the layouts of the carbon fiber and the proportion of the carbon fibers relative to the polymer. CFRP have higher tensile strength with lower density comparing with the others. It results a better performance regarding the failure index. The carbon fiber is selected as the material for the pressure hull model as per the comparison between BFRP and GFRP. The parameter set created with input and output variables. The input parameters include length, diameter, dimensions of stiffeners, thickness and pressure. Output parameters include body mass, deformation and stress. Response surfaces for different parameter sets are modeled. After creating response surface, three candidate points are obtained as optimization points. It shows minimum values for output parameters such as body mass, equivalent stress, and total deformation as the optimized values
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The state of the art in Dynamic Relaxation methods for structural mechanics Part 2: Applications

The state of the art in Dynamic Relaxation methods for structural mechanics Part 2: Applications

structures subjected to multiple load conditions by Topping [125]. Estefen and Harding also investigated the inter-ring buckling of cylindrical leg mem- bers by use of the DR scheme [35]. Analysis of a small-deflection beam was carried out with the aid of DR technique by Turvey and Der Avanessian [142]. In order to facilitate static analysis of non-linear problems, Rericha modified the DR method. He exploited continuous loading in time instead of the or- dinary step function of time. Inertia and damping forces arising during the loading process were kept at a minimum using an optimum load time his- tory [92]. In another study, Chou and Wu proposed a Dynamic Relaxation finite element method for metal forming processes [26]. Using a natural combination of Lyaponov’s dynamic criterion on stability and the modified adaptive DR method, Zhang et al. obtained an approach for predicting the bifurcation points of elastic-plastic buckling of plates and shells [169]. Qiang determined fictitious time and damping by Rayleigh’s principle [87]. In another investigation, Lewis used the DR process in the analysis of the non-linear static response of pre-tensioned cable net and pin-jointed frame structures [64]. The modified adaptive DR method (maDR method) was applied to study of the axisymmetric deformation mechanism of work-pieces in conical cup tests by Zhang et al. [170]. Chen et al. also developed a numerical method for modeling plane strain rolling based on DR technique [22]. Furthermore, Rao et al. investigated the use of the DR scheme in the problems with geometric and material non-linearities. It was found from numerical studies that in the case of geometric non-linearity, obtained steady- state solution compares well with the static solution. In this technique, the process of convergence to steady state can be accelerated by choosing higher mass densities and an appropriate mass proportional damping. On the other hand, when both non-linearities were existed, diverse steady-state solutions were obtained for different values of artificial damping [91]. The application of the DR method to study the post-buckling path of cylindrically curved panels of laminated composite materials during loading and unloading was also described by Wan-lin and Xiao-qing [160]. In another paper, Moncrieff and Topping introduced a new procedure for generating cutting patterns for membrane structures, by means of a two-dimensional Dynamic Relaxation analysis for each cloth [77].
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Analysis of damaging process and crack propagation

Analysis of damaging process and crack propagation

Abstract. Supervising and health monitoring of structures can assess the actual state of existing structures after initial loading or in the state of operation. Structural life management requires the integration of design and analysis, materials behavior and structural testing, as given for several examples. Procedure of survey of structural elements and criteria for their selection must be strongly defined as it is for the offshore gas platforms. Numerical analysis of dynamic loading is shown for the Aeolian vibrations of overhead transmission line conductors. Since the damper’s efficiency strongly depends on its position, the procedure of determining the optimum position of the damper is described. The optical method of caustics is established in isotropic materials for determination of the stress intensity factors (SIFs) of the cracks in deformed structures and is advantageously improved for the application to fiber- reinforced composites. A procedure for simulation of crack propagation for multiple cracks was introduced and SIFs have been calculated by using finite element method. Crack growth of a single crack or a periodical array of cracks initiated at the stiffeners in a stiffened panel has been investigated.
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Analysis of plates stiffened by mutually perpendicular ribs of variable depths by using the method of finite differences.

Analysis of plates stiffened by mutually perpendicular ribs of variable depths by using the method of finite differences.

So, it can be concluded that using only a few mesh points and applying the method of modified finite differences as ap­ plied in the case of a tapered beam, sufficiently precise solu­ tion of deflections of an orthogonally stiffened plate with ribs of variable rigidities may be obtained. Because such a plate is nothing but a generalized version of a one-dimensional problem

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Effect of Boundary Conditions on the Behavior of Stiffened and Un-Stiffened Cylindrical Shells

Effect of Boundary Conditions on the Behavior of Stiffened and Un-Stiffened Cylindrical Shells

The main purpose of this experimental investigation is to study the efficiency of boundary conditions, stiffeners and edge beams, on the cylindrical shells. To carry this inves- tigation, two experimental models are carried out. For the first one; two semi cylinder models with different boundary conditions are considered; pinned and fixed supports; and for the second one, two models; stiffened semi cylindri- cal shells with different boundary conditions, pinned and fixed are investigated. Figure 7 presents the UNIFLEX 300 machine and the shell model setup, and also presents the positioning of dial gauges. Figure 8a, b present the different boundary conditions used, and Fig. 9 shows the positioning of the stiffeners. Figure 10 presents the stiffened cylindrical shell reposed on rigid diaphragm and edge beams.
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Cylindrical shells made of corrugated sheets.

Cylindrical shells made of corrugated sheets.

unstiffened grain bins made of corrugated sheets are obtained. Curves are presented for the determination of the effective width of corrugated sheets (stiffened by vertical ribs) under frictional forces. These curves can be used in the design of stiffened grain bins. The shear slip at sheet-to-sheet and sheet-to-frame connections, p, has a pronounced effect on the magnitude of the effective width.

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Buckling Capacity Optimization of Stiffened Rectangular Plate under Uniform Normal Compression

Buckling Capacity Optimization of Stiffened Rectangular Plate under Uniform Normal Compression

Abstract—The stiffened rectangular plate was usually adopted in the blast airtight doors. In order to improve the buckling capacity of stiffened rectangular plate under uniform normal compression, the optimization model of stiffened rectangular plate was set up based on APDL and ANSYS commands, and the sequential linear programming method was executed to optimize the thickness of plate and the sizes of stiffeners. Moreover, we compared the mechanical property of the optimized stiffened rectangular plate with the theoretical value of no-stiffener plate with equal volume, and obtained the reasonable stiffener distribution based on the optimization results of five different longitudinal and transverse stiffener patterns. The results showed that the buckling capacity of stiffened rectangular plate under uniform normal compression could be improved by approximately 50% on the condition of reasonable stiffeners distribution.
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Buckling Analysis on Aircraft Fuselage Structure Skin

Buckling Analysis on Aircraft Fuselage Structure Skin

The main advantage of developing a closed form analytical solution like the one obtained using the smeared model is the ease with which parametric study can be performed. To demonstrate this advantage, the effect of modulus on the buckling load of an is grid stiffened composite cylinder was investigated using the smeared model developed. The analysis was performed for a wide range of skin thickness. It has been shown in Section 7.1 that buckling failure mode highly depends on the skin thickness. As a result the actual failure modes associated with some of the models analyzed might be different from global buckling failure mode. Hence this parametric analysis should only be used to appreciate the use of the smeared analytical model developed and to have a general idea of the effect of modulus on buckling load.The longitudinal modulus of the composite system was varied from 145Gpa to 192Gpa. The effect of modulus was studied on cylinders having shell thickness varying from 0.3 mm to 4 mm. Figure 15 below summarizes the results obtained.
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Numerical Investigations on Steel Plate Shear Walls – Stiffened and Un-stiffened

Numerical Investigations on Steel Plate Shear Walls – Stiffened and Un-stiffened

ABSTRACT: Steel plate shear walls have been one of the most prominently used lateral load resisting system. Research is done on the same for over a decade now. However, there has always been ambiguity in making a choice on kind of shear wall to be used. This work is a contribution to the above mentioned problem. In this work a comparative study has been done of two types of steel plate shear walls. i.e., stiffened and un-stiffened steel plate walls. This thesis consists of modeling of a 10 storey steel plate shear wall, both stiffened and un-stiffened using finite element software Ansys. Both stiffened and un-stiffened steel plate shear walls are subjected to lateral forces. These lateral forces are calculated by modeling a 10 story building with steel plate shear walls in Etabs and analyzing the same for combined effect of earthquake and wind. The most critical load combination is chosen and hence the storey drift and storey shear forces are noted from Etabs. Further these forces are applied in the finite element model of both stiffened and un-stiffened steel plate shear walls and non linear analysis is performed on these models. Three different plate thicknesses 8mm, 12mm and 16mm were used for un-stiffened spsw system and 3mm thick plate was used for comparison of un-stiffened, stiffened spsw with single strut and stiffened spsw with double strut.
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COLLISION ANALYSIS OF AN AUTOMOBILE BUMPER USING FEA

COLLISION ANALYSIS OF AN AUTOMOBILE BUMPER USING FEA

To reduce the impact, the body of the vehicle has to absorb most of the energy. Most vehicles use steel as the preferred material for bumpers. While this is efficient for impact resistance, it is heavy. In order to overcome this problem we propose to use steel with composites. Composites are one of the strongest as well as lightest structural materials available now. Composites can be used in conjunction with steel sheets to form very strong and light bumpers.In this thesis, we intend to come up with the optimum replacement of existing steel bumper with steel composite sandwich panels consisting of definite structure that will not only reduce the weight but also help reduce the impact in case of accidents.
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