Compression Panels Research Articles

Experimental Research Into the Effect Of External Actions and Polluting Environments on the Serviceablity of Fiber-Reinforced Polymer Composite Materials

The results of mechanical tests of fiberglass and CFRP specimens in transverse bending and interlaminar shear (the short-beam method) and of sandwich panels in tension and compression are presented. The effect of external polluting environments on the mechanical properties of fiber-reinforced polymer composite materials and structures is estimated. Stress–strain diagrams are constructed.

Overall buckling of lightweight stiffened panels using an adapted orthotropic plate method

The ultimate longitudinal bending strength of thin plated steel structures such as box girder bridges and ship hulls can be determined using an incremental–iterative procedure known as the Smith progressive collapse method. The Smith method first calculates the response of stiffened panel sub-structures in the girder and then integrates over the cross section of interest to calculate a moment–curvature response curve. A suitable technique to determine the strength behaviour of stiffened panels within the Smith method is therefore of critical importance. A fundamental assumption of the established progressive collapse method is that the buckling and collapse behaviour of the compressed panels within the girder occurs between adjacent transverse frames. However, interframe buckling may not always be the dominant collapse mode, especially for lightweight stiffened panels such as are found in naval ships and aluminium high speed craft. In these cases overall failure modes, where the buckling mode extends over several frame spaces, may dominate the buckling and collapse response. To account for this possibility, an adaptation to large deflection orthotropic plate theory is presented. The adapted orthotropic method is able to calculate panel stress–strain response curves accounting for both interframe and overall collapse. The method is validated with equivalent nonlinear finite element analyses for a range of regular stiffened panel geometries. It is shown how the adapted orthotropic method is implemented into an extended progressive collapse method, which enhances the capability for determining the ultimate strength of a lightweight stiffened box girder.

Evaluation on layering effects and adhesive rates of laminated compressed composite panels made from oil palm (Elaeis guineensis) fronds

The objective of this study was to evaluate layering effects and adhesive rates of laminated compressed panels manufactured from oil palm (Elaeis guineensis) fronds. Nine types of panels, namely 6-layer, 8-layer and 10-layer bonded with adhesive spread rates of 200 g/m 2 , 250 g/m 2 and 300 g/m 2 were manufactured. The results showed that both bending and internal bonding strength properties all types of panels increased with increasing number of layers and adhesive amount with an exception of 10-layer panels bonded with 300 g/m 2 . Mechanical properties of such samples were slightly reduced due to their possible brittleness as a result of effect of densification, high resin content and temperature. Thickness swelling and water absorption of the samples enhanced with increasing number of layer and adhesive content. 2014 Elsevier Ltd. All rights reserved.

Mechanical Properties and Behavior of Traditional Adobe Wall Panels of the Aveiro District

AbstractIn the Aveiro district, Portugal, adobe was a construction material extensively used until the middle of the twentieth century. Presently, many adobe constructions are still in use, presenting important cultural, social, and architectural value. Many of these constructions, however, are in a poor state of conservation, displaying severe structural anomalies. This negligence is in part due to a lack of knowledge concerning the mechanical behavior and properties of adobe masonry. The purpose of this paper is to contribute to this knowledge. Ten full-scale adobe wall panels were constructed in the laboratory with adobes collected from an existing construction and with mortar formulated with the composition traditionally used. Five wall panels were tested in simple compression and five wall panels in diagonal compression. From these tests it was possible to determine and evaluate the stress-strain relationships, strength, deformation, stiffness, and damage pattern of the adobe masonry walls. This know...

Dynamic anti-crushing behaviors of woven textile sandwich composites: Multilayer and gradient effects

Low-velocity dynamic compression tests were carried out to reveal the failure mechanism and the energy absorption capacity of multilayered woven lattice sandwich panels. Dynamic compression coupled with shear deformation results in typical softening deformation after the peak stress. The load–displacement curve is characterized by a long zigzag deformation. Multilayered woven lattice sandwich panels have deformation characteristics of type II structure. Compared with the quasi-static compressed panel, the impacted woven textile sandwich has similar failure mode but excellent energy absorption induced by greater dynamic strength. Strain rate effect of the structure was explained by dynamic buckling theory. Gradient structure, placing the hardest layer as the first impacted layer and the weakest as the last, has great benefits in terms of energy absorption efficiency and should be ideal to serve as an energy-absorbing structure.

Stiffness requirements for transverse stiffeners of rectangular CFT compression panels

This paper presents a more rational calculation of the minimum stiffness required for transverse stiffeners of stiffened concrete filled tube (CFT) compression panels. As longitudinal stiffeners are essentially compression members, transverse stiffeners are required to control the effective length. Both the longitudinal stiffener and transverse stiffener subdivide the compression panel in a grid pattern so the relatively thin plate can carry the induced compressive load in the most efficient manner. However, the provisions for the required rigidity of transverse stiffeners in the literature are inconsistent in general and in particular; do not exist in the case of the concrete filled compression panels. Here, the parameters that govern the behavior of the transverse stiffeners are identified theoretically using the column buckling approximation. In order to calibrate and quantify the analytical equations developed, incremental nonlinear analyses were performed on a large number of finite-element models. The numerically collected data were then used to validate the equations developed.

Design, Optimization, and Evaluation of Al–2139 Compression Panel with Integral T-Stiffeners

A T-stiffened panel was designed and optimized for minimum mass subjected to constraints on buckling load, yielding, and crippling or local stiffener failure using a new analysis and design tool named EBF3PanelOpt. The panel was designed for a compression loading configuration, a realistic load case for a typical aircraft skin-stiffened panel. The panel was integrally machined from a 2139 aluminum alloy plate and was tested in compression. The panel was loaded beyond buckling and strains, and out-of-plane displacements were extracted from 36 strain gages and one linear variable displacement transducer. A digital photogrammetric system was used to obtain full-field displacements and strains on the smooth (unstiffened) side of the panel. The experimental data were compared with the strains and out-of-plane deflections from a high-fidelity nonlinear finite element analysis. The test data indicated that the panel buckled at the linear elastic buckling eigenvalue predicted for the panel. The out-of-plane displacement measured by the digital photogrammetric system compared well both qualitatively and quantitatively with the nonlinear finite element solution in the postbuckling regime. Furthermore, the experimental strains compared well with both the linear and nonlinear finite element models before buckling. The weight of the optimized panel was 20% less than that of a T-stiffened panel optimized using conventional design techniques.

Compartment level progressive collapse analysis of lightweight ship structures

The continued development of large high speed ships, often constructed from aluminium alloy, has raised important issues regarding the response of lightweight hull girders under primary hull girder bending. In particular, the response of lightly framed panels in compression may be influenced by overall panel buckling over several frame spaces. Therefore, to provide improved ultimate strength prediction for lightweight vessels, an extended progressive collapse methodology is proposed. The method has capabilities to predict the strength of a lightweight aluminium midship section including compartment level buckling modes. Nonlinear finite element analysis is used to validate the extended progressive collapse methodology.

The effect of compressed infill panels on cyclic performance of exterior beam-column joints

The effect of compressed infill panels on cyclic performance of exterior beam-column joints

Non-linear idealisation error analysis of a metallic stiffened panel loaded in compression

The SAFESA procedure is an idealisation error control process developed for linear static finite element (FE) analysis. This paper investigates the application of this process to non-linear problems. The post-bucked collapse of a stiffened panel in compression is used as the case study. The main part of the paper presents the critical analysis of important modelling assumptions, including the material model, boundary conditions and geometrical imperfections. Several potential error sources are identified and then investigated using the non-linear FE code ABAQUS. The outcome of the analysis is an improved FE model and a quantification of the idealisation error.

Surface stress and strain fields on compressed panels of corrugated board boxes. An experimental analysis by using Digital Image Stereocorrelation

The complex behaviour of corrugated board packages under compression loading is investigated in this work. Original experimental data are obtained by using a Digital Image Stereocorrelation technique for measuring the displacement and strain fields of the panels’ outer liner of the tested boxes. The stress field is also estimated by accounting for the anisotropic mechanical behaviour of the outer liner, its residual stress state induced by the processing of the corrugated board and the effects of box manufacturing operations and compression. Results show that these fields are extremely heterogeneous on the panels’ surface. Most stressed areas are located along the panels’ edges. The elastic limit of the outer liner is reached quite soon during compression. Box geometry and panel flaps are of primary importance on the observed phenomena. This approach delivers useful information to improve kinematic and constitutive assumptions for buckling and post-buckling models of boxes or thin-walled sandwich structures.

VIRTUAL TESTING OF STIFFENED COMPOSITE PANELS AT AIRBUS

The steady increase of composite parts in civil aircraft over the last three decades has recently been followed by a radical increase of weight percentage composites in the structure. In the most recent long range aircraft under development by both Boeing and Airbus, most major structure components, not only of the wings but also of the fuselage, now consist of composites. This necessitates an increased use of efficient structural simulation capabilities. One important aspect of this is the virtual testing of shear compression panels at Airbus, which will be presented here. Having served well for Glare during the A380 development, it is currently undergoing considerable development to extend its capacity to composites. Summarized under the designation "Simulation of Panels in AirCraft", (SIMULPAC), this platform is here introduced and described in terms of functioning and methodology. It has played a major role in the initial A350 developments: in the first designs, during virtual testing of the configuration of new components and for predictions of the first real shear compression panels.

The development of a preliminary structural design optimization method of an aircraft wing-box skin-stringer panels

In the current paper a methodology for the design optimization of a skin-stringer panel of an aircraft wing-box is presented. The ability to resist the compressive load is assessed through a stability study to compute the critical buckling load of the stiffened panel while the ability to resist the tensile load is assessed through damage tolerance analysis of the lower wing panels. The design methodology of the compression panel included general and local failure modes as well as panel beam column analysis that are common in aerospace compression structures. Linear Elastic Fracture Mechanics theory is applied for the design of the tension panels where the Boundary Element Method is used to perform numerical crack growth analysis. Optimization routines have been developed and the design methodology is validated by comparison with several existing skin-stringer panels from four jet aircrafts and showed a good agreement. Finally, the developed design methodology has been used to design the skin-stringer panels of one complete bay in the wing-box of a DLR-F6 aircraft.

2D elastic analysis of the sandwich panel buckling problem: benchmark solutions and accurate finite element formulations

This paper is concerned with the elastic stability of a sandwich beam panel using classical elasticity. An exact solution for the buckling problem of a sandwich panel (wide beam) in uniaxial compression is presented. Various formulations that correspond to the use of different pairs of energetically conjugate stress and strain measures for the infinitesimal elastic stability of the sandwich panel are discussed. Results from the present two-dimensional analyses to predict the global and local buckling of a sandwich panel are compared with previous theoretical and experimental results. A new finite element formulation for the bifurcation buckling problem is also introduced. In this new formulation, terms that influence the buckling load, which have been omitted in popular commercial codes are pointed out and their significance in influencing the buckling load is identified. The formulation and results presented here can be used as a benchmark solution to establish the accuracy of numerical methods for computing the buckling behavior of thick, orthotropic solids.

Buckling and ultimate capability of plates and stiffened panels in axial compression

This paper presents extensive non-linear finite element (FE) analysis and formulation development work carried out on the ultimate compressive strength of plates and stiffened panels of ship structures. A review of contemporary designs for large ships was carried out. The existing formulae for plate ultimate compressive strength were reviewed and compared with non-linear FE analysis results. A semi-analytical formula for ultimate compressive strength assessments of stiffened panels was proposed and is described. The developed formula was verified against results using ABAQUS non-linear FE software for a series of 61 stiffened panels and a good agreement between the proposed formula and FE results were achieved. The method was verified against a large number of published FE results and was also compared with 58 experimental results. The developed method was also applied to the deck and bottom structures for a range of various sizes oil tankers and bulk carriers.

Mechanical behaviour and energy absorption of closed-cell aluminium foam panels in uniaxial compression

Thin and thick panels of two types of aluminium closed-cell foams of ∼0.20–0.31 g/cm 3 (ALPORAS) and ∼0.32–0.57 g/cm 3 (ALULIGHT) density were tested in uniaxial compression and the mechanical properties of the panels, plastic collapse strength, plateau stress and absorbed energy, were extracted. Their dependence on the foam density and specimen thickness was also ascertained. Micro-indentation tests were used to estimate the yield stresses of the parent materials. It was found that the higher density panels of ALULIGHT were also more anisotropic than the lower density panels of ALPORAS, and the collapse strength and the absorbed energy of both foams increased with density. More significant scatter the results was observed in the thin and higher density panels.

Maximization of Fundamental Frequencies of Axially Compressed Laminated Plates Against Fiber Orientation

Summary The applications of fiber-composite laminate materials to aerospace industrial such as spacecraft, high-speed aircraft, missile and satellite have increased rapidly in recent years. The most major components of the aerospace structures are frequently made of curved panels and subjected to various kinds of compressive forces. Therefore, knowledge of the dynamic characteristics of composite laminated curved panels in compression, such as their fundamental natural frequency, is essential. The fundamental natural frequency of composite laminated curved panels highly depends on the ply orientation, end conditions, geometries (i.e., aspect ratio and curvature) and compressive force. Therefore, proper selection of appropriate lamination to maximize the fundamental frequency of composite laminated curved panels in compression becomes a crucial problem. Research on the subject of structural optimization has been reported by many investigators and has been widely employed to study the dynamic behavior of composite structures. Among various optimization schemes, the golden section method is a simple technique and can be easily programmed for solution on the computer. In this investigation, maximization of the fundamental natural frequency of composite laminated curved panels in compression with respect to fiber orientations is performed by using the golden section method. The fundamental frequencies of the composite laminated curved panels are calculated by using the Abaqus finite element program. In the paper, the constitutive equations for fiber-composite lamina, vibration analysis and golden section method are briefly reviewed. The influence of the end conditions, the panel aspect ratio, the panel curvature and the compressive force on the maximum fundamental natural frequency, the associated optimal fiber orientations and the vibration mode of the laminated curved panels is presented and important conclusions obtained from the study are given.

Experimental study of inelastic buckling strength and stiffness requirements for longitudinally stiffened panels

An experimental study was conducted in order to verify a proposed equation for the minimum required stiffness for longitudinal stiffeners attached on compression plates. Nine test specimens of stiffened plates were fabricated and tested to their ultimate strengths. Test results are compared with the maximum strengths predicted for stiffened plates by finite element analysis and by the proposed SSRC type critical stress curve. Fairly good correlations were observed, thereby confirming experimentally the adequacy of the proposed equation for the minimum required stiffness of the longitudinal stiffener attached to the compression panel and a modified SSRC type critical stress curve encompassing both the buckling ranges of plastic yield and the transition zones. A set of conclusions is drawn from the experimental studies as to the buckling behaviors of stiffened plates.

Material characteristics of 3-D FRP sandwich panels

This paper presents an innovative 3-D fiber reinforced polymer (FRP), panels designed to overcome delamination problems typically encountered in traditional sandwich panels. The sandwich panels consist of GFRP laminates and foam core. The top and bottom consist of GFRP plates connected together with through-thickness fibers to achieve the composite action. The fundamental material characteristics of the panel in tension, compression, flexure and shear are critical for the use and structural design of these panels. This paper summarizes the findings of an extensive experimental program to determine the various parameters believed to affect the material characteristics of these sandwich panels. The influence of the panel thickness, through-thickness fiber configuration and density, and other parameters on the tension, compression, flexure and shear behavior of the panels are discussed.

Interior wall and partition construction

An improved interior wall construction that provides both sound attenuating and fire resistant properties. The improved wall construction eliminates the need for conventional vertical studs by including at least one rigid interior structural panel comprised of compressed straw. A compressed straw panel is situated in a substantially layered configuration with conventional non-woven insulation, at least one air space and a gypsum board sheet on each face. Connection between the compressed straw panel and at least one gypsum board sheet is comprised semi-flexible substantially Z-shaped resilient channel members. The Z-shaped channel members and compressed straw panel each being capable of partially attenuating sound energy passed therethrough.