Fiber-reinforced Plastic Beams Research Articles

Computer Simulation of Composite Beams Dynamic Behavior

The paper is devoted to the computer simulation of polymer composite beams dynamic behavior. The use opportunity of one-dimensional beam models for the design of composite elements instead of three-dimensional ones is discussed. The tree-dimensional modeling is implemented using the finite-element software SIMULIA Abaqus considering the orthotropic properties of the composite material. For the one-dimensional modeling two hypothesis of the internal friction – local and nonlocal – are applied and compared. The Kelvin-Voigt hypothesis is used as a local damping model. The nonlocal model is based on the nonlocal mechanics principals and obtained using the Galerkin method. The example glass fiber reinforced plastic beam with the fixed ends is considered under an instantly applied load. The parameters of the nonlocal damping model are defined using the least squares method. The flexibility of the nonlocal damping model is shown and the use opportunity of one-dimensional beam models for the design of composite elements is justified.

Calibration of nonlocal damping model based on numerical simulation results

The paper is devoted to polymer composite beams dynamic behavior simulation. The nonlocal damping model is used as a model of the internal friction. The vibration process is considered in this paper using the beam with fixed ends as an example. Equation of beam motion considering nonlocal damping is solved by Galerkin method to develop the model. The required number of eigenmodes is obtained for the beam under an instantly applied distributed load. The influence of nonlocal damping model parameters variation on the beam vibration process simulation results is considered under a periodic deterministic distributed load. The calibration of nonlocal damping model consists of defining its parameter known as influence distance which characterize the level of the nonlocal properties in material. Calibration is carried out with the least squares method using the numerical simulation data. For this purpose the results of 3D finite element modeling of thermoset vinyl ester fiber reinforced plastic beam vibrations under the instantly applied load were used. The 3D finite element model of the beam was created in SIMULIA Abaqus taking into account the orthotropic properties of the material. The calibrated model was justified for the beams with changed geometry. The results presented in this paper were obtained during the research for the PhD thesis.

Bracing FRP I-section beams to avoid lateral-torsional buckling

This article explains as to how lateral-torsional buckling can be avoided in fiber-reinforced plastic (FRP) beams having an I-shaped cross section and subjected to major-axis bending. To enable a FRP beam to be able to develop its maximum bending moment capacity corresponding to material cracking of the extreme fibers, a number of lateral braces need to be provided. Herein, a procedure is outlined for determining the required number of lateral braces for a FRP I-section beam. It is shown that a FRP beam loaded about its major cross-sectional axis can experience a drastic reduction in its bending moment capacity if such lateral bracing is not provided, whereas it can develop its maximum load-carrying capacity up to the cracking of the extreme fibers if a sufficient number of lateral braces are provided.

Local Web Buckling of Composite (FRP) Beams

Local buckling analysis of thin-walled open or closed section fiber-reinforced plastic beams is presented. In the analysis, the web is modeled as a long orthotropic plate with rotationally restrained edges. Explicit expressions were developed for the buckling analyses of rectangular (long) plates in a companion paper. These results are applied to develop explicit expressions for the calculation of the web buckling of beams with thin-walled cross sections. At last, the applicability of the method is demonstrated by numerical examples and the results are verified by finite element calculations.

Stability of FRP Beams under Three-point Loading and LRFD Approach

This article presents the results of an experimental and theoretical study of I-section fiber-reinforced plastic (FRP) beams subjected to a gradually increasing midspan load. The load is applied about the beam major axis from the compression flange side through a point below the shear center. The boundary conditions are flexurally and torsionally pinned. A 4 2 1/4 in. 3 pultruded I-section is adopted for the study and beam span lengths of 108, 96, 84, and 72 in. are used. The flexural-torsional response of the FRP beams is studied experimentally up to the maximum loadcarrying capacity. The experimental peak loads are compared with those arrived at theoretically using an equilibrium approach and are found to be in good agreement. To obtain a design expression for estimating the beam buckling load, an elastic buckling moment expression from the load and resistance factor design (LRFD) specification of the American Institute of Steel Construction is first modified. Next, a LRFD approach for the beam is outlined and its use demonstrated through analysis and design examples.

Delamination detection in smart composite beams using Lamb waves

This paper presents a feasibility study on using Lamb waves to detect and locatethrough-width delamination in fiber-reinforced plastic beams. An active diagnostic systemis proposed for clamped-free specimens. It consists of a piezoelectric patch and anaccelerometer both mounted near the support. Such a system can locate damage in anabsolute sense, that is, a priori knowledge on the response from pristine specimens is notrequired. The fundamental anti-symmetric Lamb wave mode is chosen as the diagnosticwave. It is generated by applying a voltage in the form of sinusoidal bursts to thepiezoelectric patch. The proposed system was applied to locate delaminations in somefabricated Kevlar/epoxy beam specimens. With an appropriate actuating frequency,distortions of waveforms due to boundary reflections can be reduced. Based on their arrivaltimes and the known propagating speed of Lamb waves, the delaminations can be located.The errors associated with the predicted damage positions range from 4.5% to 8.5%.

Dynamic pulsebuckling and postbuckling of composite laminated beam using higher order shear deformation theory

Abstract The dynamic pulsebuckling and postbuckling response of fiber-reinforced plastic (FRP) laminated beams, having initial geometric imperfections, subjected to an axial impact was simulated by the finite difference method. The Timoshenko beam theory was used to construct the analytical model in which all inertia components of the beam that affect the dynamic response were considered. The von-Karman non-linear strain–displacement relationship was used to describe the beam's response and the higher order shear deformation theory was used to model the displacement field of the beam. The influence of boundary conditions and amplitude of imperfection on the pulsebuckling and postbuckling response of FRP beams was investigated. The results obtained from the proposed formulation agree well with those of the 3D-finite element analysis. The numerical results show that the rotary restraints do not significantly affect the critical pulsebuckling momentum.

OS09W0037 Delamination detection of composite beams using Lamb waves

This paper presents a feasibility study on locating through-width delaminations in fiber-reinforced plastic beams using Lamb waves. An active diagnostic system, consisting of a surface-mounted piezoelectric patch and a vibration sensor, is proposed. The fundamental anti-symmetric Lamb wave mode is chosen as the diagnostic wave. It is generated by applying to the patch an excitation voltage in the form of sinusoidal bursts. Experiments are performed to reveal the wave propagation in clampedfree Kevlar/epoxy beams. The results are used to verify the accuracy of a finite element (FE) model. The FE model is then applied to locate delaminations in some artificial beams. By performing Wavelet Transform (WT) on the predicted acceleration traces, the propagating Lamb waves can be extracted. Based on the arrival times of the extracted waves, delaminations are located with satisfaction. Improve-ment on the damage localization process is possible by eliminating the boundary reflections as well as a priori knowledge on both the size and depth of the delamination.

350 繊維強化複合材料の減衰特性評価における支持条件の影響について

This paper studies the experimental damping evaluation of Fiber Reinforced Plastic (FRP) materials. For this purpose, FRP laminated composite plates are made of unidirectional FRP pre-preg sheets, and FRP beam test pieces are cut out from it. Free vibration experiments are carried out by the cantilevered beams. There is a discussion about the effects of the compression torques of squall vices when making FRP plates and the support torques at fixed edge of the test beams on the evaluation for natural frequencies and damping ratios (logarithmic decrements) obtained from the experimental data.

Peeling failure of reinforced concrete beams with fibre-reinforced plastic or steel plates glued to their soffits

In recent publications by the first author and his associates, a theoretical model (backed by extensive test data by others) for premature plate peeling failures of reinforced concrete beams strengthened in flexure by gluing steel plates to their tension sides was reported. The primary purpose of the present paper is to extend this theoretical model to cases where fibre-reinforced plastic (FRP) (as opposed to steel) plates are used for upgrading reinforced concrete beams in flexure. As in the case of steel, due to large variations in the spacings of stabilized cracks within the concrete cover zone (by a factor of, say, 2) a unique solution for the FRP plate peeling load does not exist, and one needs to resort to theoretical upper/lower bounds, with the lower bound being the appropriate one for design purposes. For steel plates, a simple preliminary design approach is to keep the plate width to thickness ratio above 60. However, no such simple value for the plate width/thickness ratio has been found for externally bonded FRP plates (which, unlike steel plates, are available with a wide range of ultimate strengths and Young's moduli); hence the pressing need for a reliable theoretical model. Finally, with the theoretical predictions for FRP and steel-plated beams backed by nearly 170 (mainly large-scale) test results from a number of independent sources, covering a wide range of beam design parameters, the proposed model is thought to be reliable and generally applicable.

A computational approach for analysis and optimal design of FRP beams

Fiber-reinforced plastic (FRP) beams are thin-walled or moderately thick-walled open or closed sections consisting of assemblies of flat panels. We present a computational approach with the computer program FRPBEAM (1994) for the response evaluation of pultruded FRP beams in bending. This program combines micro/macro-mechanics analyses with the Mechanics of Laminated composite Beams (MLB) model and an explicit stability solution to analyze, design, and optimize FRP shapes. In FRPBEAM, the ply stiffnesses are predicted by micromechanics formulas, based on the fiber volume fraction of each lamina, and the panel laminate properties are computed from the ply stiffnesses and macromechanics. The MLB model is used to analyze the overall response of FRP beams in bending, and the Tsai–Hill failure criterion is adopted to predict first-ply-failure loads. An example of a laminated box beam is used to demonstrate the accuracy of the computer program for predicting beam displacements and ply stresses in relation to finite element analyses. A stability Rayleigh–Ritz method is included in the program and used to evaluate the critical buckling loads for pultruded I-beams. Through parametric studies with FRPBEAM and a multiobjective optimization scheme, the fiber architecture of an existing I-beam is optimized, and based on a recommended practical design, the I-beam section is produced by pultrusion and subsequently tested in bending. The predicted response with FRPBEAM correlates well with the experimental results. As illustrated by design analysis and optimization examples presented in this study, the experimentally and numerically verified computer program can be used to analyze existing FRP shapes and develop new optimized shapes for the civil structural market.

Vibroacoustic properties of a composite harp soundboard

The concert harp has survived through the years much as it was in the 18th century; the construction is still labor intensive, the performance variable, and the durability questionable. These problems can be attributed to the most important part of the harp, the soundboard. Harp soundboards are constructed of spruce wood, which is adversely affected by time, temperature, humidity, and handling. An investigation is underway to replace this fragile sitka spruce soundboard with a more durable material while maintaining acceptable sound quality. The soundboard, a sitka spruce laminate, is already anisotropic; thus, it lends itself to replacement by a carbon fiber reinforced plastic (FRP) laminate. Experimental modal analysis was used to determine vibratory properties of two harp soundboards and uniform spruce beams. Finite element models (FEMs) of the spruce soundboard and beams were developed. The beam FEM aided in the application of laminate theory to determine the lamina stacking sequence to construct a similar composite beam. After experimental verification of the FRP beam, this understanding was applied to construct a FEM of the fiber soundboard. Techniques used to develop and analyze the FRP harp soundboard will be presented.

Analysis and design of fiber reinforced plastic composite deck-and-stringer bridges

A comprehensive study on analysis and design of fiber reinforced plastic (FRP) composite deck-and-stringer bridges is presented. The FRP decks considered consist of contiguous thin-walled box sections and are fabricated by bonding side-by-side pultruded thin-walled box beams, which are placed transversely over FRP composite stringers. In this study, we review the modeling and experimental verification of FRP structural beams, including micro/macro-mechanics predictions of ply and laminate properties, beam bending response, shear-lag effect, and local and global buckling behaviors. A simplified design analysis procedure for cellular FRP bridge decks is developed based on a first-order shear deformation macro-flexibility (SDMF) orthotropic plate solution. The present approach can allow the designers to analyze, design and optimize material architectures and shapes of FRP beams, as well as various bridge deck configurations, before their implementation in the field. Experimental studies of cellular FRP bridge decks are conducted to obtain stiffness coefficients, and an example of a cellular FRP deck on optimized winged-box FRP stringers under actual track-loading is presented to illustrate the analytical method. The experimental-analytical approach presented in this study is used to propose simplified engineering design equations for new and replacement highway FRP deck-and-stringer bridges.

Local Buckling of FRP Beams and Columns

Fiber‐reinforced plastic (FRP) structural members with open or closed thin‐walled sections are being used as beams and columns for structural applications where buckling is the main consideration in the design. Analytical models for several local buckling modes under axial and shear loading, taking the flange‐web interaction into account, are developed. Experimental data correlating predicted and observed behavior are presented for some commercially available structural shapes. Failure envelopes are developed for box‐ and I‐shape FRP columns and beams. The analytical models presented can be used to predict the behavior of any new pultruted material. The Rayleigh‐Ritz method is used in this work to analyze anisotropic flanges of box and I‐beams. The anisotropy of the material is introduced by ±45° angle‐ply layers introduced recently by pultruted manufacturers to improve the buckling strength of columns as suggested by this investigation.