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Showing papers on "Composite laminates published in 2001"


Journal ArticleDOI
TL;DR: In this paper, the effect of voids on carbon/epoxy and carbon/bismaleimide fabric laminates is compared in terms of the corresponding fracture parameters and the shape and the location of the voids.

257 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented a method of extracting the damage size and position for highly orthotropic (unidirectional) carbon fiber-reinforced polymer (CFRP) composites.

251 citations


Journal ArticleDOI
TL;DR: In this article, the critical energy for delamination growth is separated in bending, shear and indentation contributions, and further growth depends on the number of delaminations developing, and is in thin laminates limited by the early occurrence of penetration.
Abstract: Analytical models are suggested for prediction of impact damage initiation and growth during quasi-static response caused by large mass impactors. Comparisons with experiments are presented for different layups, geometries and boundary conditions. The critical load for delamination growth is found almost insensitive to geometry and boundary conditions. The critical energy for delamination growth is separated in bending, shear and indentation contributions. Further growth depends on the number of delaminations developing, and is in thin laminates limited by the early occurrence of penetration. Observed delamination sizes are compared with a suggested upper bound and predictions based on the observed number of delaminations.

211 citations


Journal ArticleDOI
TL;DR: In this paper, various nonlinear interfacial constitutive laws describing the pre-and post-cracking behavior of FRP-concrete interface are introduced to solve the nonlinear inter-dimensional stress transfer problems.
Abstract: To effectively and efficiently utilize steel/FRP plates or sheets in strengthening civil infrastructures, a design strategy integrating the FRP properties and composite structural behavior needs to be adopted. The interfacial stress transfer behavior including debonding should be considered to be one of the most important effects on the composite structural behavior. In this paper, varieties of nonlinear interfacial constitutive laws, describing the pre- and post-cracking behaviour of FRP-concrete interface are introduced to solve the nonlinear interfacial stress transfer problems. Expressions for bonding capacity, interfacial shear stress distribution, initiation and propagation of interfacial crack are derived analytically.

201 citations


Journal ArticleDOI
TL;DR: In this article, various hygroscopic effects of such parameters as hygrothermal temperature, matrix volume ratio, void volume ratio (Vv), specimen thickness, lay-up sequence and internal stress were investigated for epoxy/carbon fiber composite laminates.
Abstract: In this study, various hygroscopic effects of such parameters as hygrothermal temperature, matrix volume ratio (Vm), void volume ratio (Vv), specimen thickness, lay-up sequence and internal stress were investigated for epoxy/carbon fiber composite laminates. The specimen thickness and lay-up sequence had little effect on the through-the-thickness water absorption behavior of composite laminates, but the other parameters affected the moisture absorption rate and equilibrium water uptake in different ways and intensities. The glass transition temperature of composite laminates was strongly affected and linearly decreased by the quantity of equilibrium water uptake. A characteristic length of moisture migration through the unidirectional laminates was proposed as a function of fiber angle to the exposed laminate surface. In this approach, the fibers imbedded in the matrix were assumed to act as a barrier to the penetrating water molecules, and the developed model was well compared with the experimental results.

177 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used GA for the optimal design of symmetric composite laminates subject to various loading and boundary conditions, and the results showed that GA can find the global optimal solution leading to a substantial decrease in the failure index.

159 citations



Journal ArticleDOI
Heung-Joon Park1
TL;DR: In this paper, the effects of stacking sequence and clamping force on delamination bearing strength and ultimate bearing strength of mechanically fastened joints (pinned and bolted) in carbon/epoxy composite laminates were examined using the acoustic emission (AE) technique.

143 citations


Journal ArticleDOI
TL;DR: In this article, a parametric analysis of the three-dimensional geometry was performed numerically using the finite element code ANSYS with special attention given to the detailed modelling of the area around the bolt in order to account for all damage modes.
Abstract: A three-dimensional progressive damage model was developed to simulate the damage accumulation and predict the residual strength and final failure mode of bolted composite joints under in-plane tensile loading. The parametric study included stress analysis, failure analysis and material property degradation. Stress analysis of the three-dimensional geometry was performed numerically using the finite element code ANSYS with special attention given to the detailed modelling of the area around the bolt in order to account for all damage modes. Failure analysis and degradation of material properties were implemented using a set of stress-based Hashin-type failure criteria and a set of appropriate degradation rules, respectively. In order to validate the finite element model, a comparison of stress distributions with results from analytical models found in the literature was carried out and good agreement was obtained. A parametric study was performed to examine the effect of bolt position and friction upon damage accumulation and residual strength.

142 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of temperature variations (low and high temperatures) was studied experimentally on impact damage to CFRP laminates, where a steel ball launched by the air gun was used to generate the CFRP laminate impact damage.
Abstract: In this paper, the effect of temperature variations (low and high temperatures) was studied experimentally on impact damage to CFRP laminates. The composite laminates used in this experiment were CF/EPOXY orthotropic laminated plates with lay-up [06/906]s and [04/904]s, and CF/PEEK orthotropic laminated plates with a lay-up of [06/906]s. A steel ball launched by the air gun was used to generate the CFRP laminate impact damage. For impact-damaged specimens, nondestructive evaluation (NDE), such as a scanning acoustic microscopy (SAM) was performed on the delamination-damaged samples to characterize damage growth at different temperatures. Therefore, this study was undertaken to experimentally determine the interrelations between impact energy and impact damage (i.e. the delamination area and matrix) of CFRP laminates (CF/EPOXY and CF/PEEK) subjected to foreign object damages (FOD) at low and high temperatures.

123 citations


Book
13 Nov 2001
TL;DR: In this article, the authors describe a technique for the Inverse Fourier Integration Response in Time Domain Poles and Complex Paths of a WAVs in the Wavenumber Domain.
Abstract: FUNDAMENTS OF WAVES IN ELASTIC SOLIDS Introduction Formulation of Longitudinal Wave in a Bar Free Wave Motion in Infinite Bars Free Wave Motion in a Finite Bar Forces Wave Motion in an Infinite Bar Forced Wave Motion in a Finite Bar Transient Waves in an Infinite Bar Remarks WAVES IN PLATES OF FUNCTIONALLY GRADED MATERIAL Introduction Element of Linear Property Variation Boundary and Continuity Conditions Transient Response Evaluation of Confluent Hypergeometric Function Examples Remarks FREE WAVE MOTION IN ANISOTROPIC LAMINATES Introduction Basic Equations Derivation of Dispersion Equation Strain Energy Distribution Examples Remarks FORCED WAVE MOTION IN COMPOSITE LAMINATES Introduction Basic Equations Boundary and Interface Conditions Displacement in the Wavenumber Domain A Technique for the Inverse Fourier Integration Response in Time Domain Poles and Complex Paths Examples Remarks CHARACTERISTICS OF WAVES IN COMPOSITE LAMINATES Introduction Dispersion Equation Group Velocities Phase Velocity Surface Phase Slowness Surface Phase Wave Surface Group Velocity Surface Group Slowness Surface Group Wave Surface Examples Remarks FREE WAVE MOTION IN ANISOTROPIC LAMINATED BARS: FINITE STRIP ELEMENT METHOD Introduction System Equation Examples Remarks FREE WAVE MOTION IN COMPOSITE LAMINATED BARS: SEMI-EXACT METHOD Introduction System Equation Examples of Harmonic Waves in Bars Edge Waves in Semi-Infinite Laminates Remarks TRANSIENT WAVES IN COMPOSITE LAMINATES Introduction HNM Formulation Equation in Wavenumber Domain Displacement in Wavenumber Domain Response in Space-Time Domain Response to Line Time-Step Load Response to Point Time-Step Load Techniques for Inverse Fourier Integral Response to Transient Load of Arbitrary Time Function Remarks WAVES IN FUNCTIONALLY GRADED PLATES Introduction Dynamic System Equation Dispersion Relation Group Velocity Response Analysis Two-Dimensional Problem Computational Procedure Dispersion Curves Transient Response to Line Time-Step Loads Remarks WAVES IN ANISOTROPIC FUNCTIONALLY GRADED PIEZOELECTRIC PLATES Introduction Basic Equations Approximated Governing Equations Equations in Transform Domain Characteristics of Waves in FBPM Plates Transient Response Analysis Interdigital Electrodes Excitation Displacement and Electrostatics Potential Response Computation Procedure Dispersion Curves Excitation of Time-Step Shear Force in y Direction Excitation of a Line Electrode Excitation of Interdigital Electrodes Remarks STRIP ELEMENT METHOD FOR STRESS WAVES IN ANISOTROPIC SOLIDS Introduction System Equation SEM for Static Problems (Flamant's Problem) SEM for Dynamic Problems Remarks WAVE SCATTERING BY CRACKS IN COMPOSITE LAMINATES Introduction Governing Differential Equations Particular Solution Application of the SEM to Cracked Laminates Solution in the Time Domain Examples of Scattered Wave Fields Characterization of Horizontal Cracks Characterization of Vertical Surface-Breaking Cracks Characterization of Middle Interior Vertical Cracks Characterization of Arbitrary Interior Vertical Cracks Remarks WAVES SCATTERING BY FLAWS IN COMPOSITE LAMINATES Introduction Applications of the SEM to Plates Containing Flaws Examples for Wave Scattering in Laminates SH Waves in Sandwich Plates Strip Element Equation for SH Waves Particular Solution Complementary Solution General Solution SH Waves Scattered by Flaws Remarks BENDING WAVES IN ANISOTROPIC LAMINATED PLATES Introduction Governing Equation Strip element Equation Assembly of Element Equations Static Problems for Orthotropic Laminated Plates Wave Motion in Anisotropic Laminated Plates CHARACTERISTICS OF WAVES IN COMPOSITE CYLINDERS Introduction Basic Equations Dispersion Relations Examples Remarks WAVE SCATTERING BY CRACKS IN COMPOSITE CYLINDERS Introduction Basic Equations Axisymmetric Strip Element Examples Remarks INVERSE IDENTIFICATION OF IMPACT LOADS USING ELASTIC WAVES Introduction Two-dimensional Line Load Two-dimensional Extended Load Three-dimensional Concentrated Load Examples Remarks INVERSE DETERMINATION OF MATERIAL CONSTANTS OF COMPOSITE LAMINATES Introduction Inverse Operation Uniform-Micro Genetic Algorithms Examples Remarks

Journal ArticleDOI
L-B Zhang1, L-J Wang1, X-Y Liu1
01 Feb 2001
TL;DR: In this paper, a general closed-form model for predicting the critical thrust force at which delamination is initiated at different ply locations is presented, and good correlation is observed between the model and the experimental results.
Abstract: Among the various forms of material damage, delamination due to drilling is one of the major concerns in machining a composite laminate. The thrust force has been cited as the primary cause of the delamination. The analysis for multidirectional composite laminates is based on linear elastic fracture mechanics (LEFM), classical bending plate theory and the mechanics of composites. This paper presents a general closed-form mechanical model for predicting the critical thrust force at which delamination is initiated at different ply locations. Good correlation is observed between the model and the experimental results.

Journal ArticleDOI
TL;DR: In this paper, the effect of delamination geometry on the compressive behaviour of laminated composite materials was investigated. But the results for any one geometry superimpose on those for all others, and the results of this study can be used to derive a graph of nondimensional failure load versus non-dimensional failure stress.

Journal ArticleDOI
TL;DR: In this paper, the buckling behavior of composite laminates with multiple delaminations under uniaxial compression was studied and the effects of different types of multiple delamination were examined.

Journal ArticleDOI
TL;DR: Sun et al. as mentioned in this paper adopted sublaminates governed by transverse shear deformable laminate theory to model such delamination, which converges as the sublaminate division is refined and the sizes of the delamination tip elements decrease.

Journal ArticleDOI
TL;DR: In this paper, the failure of transversely loaded unidirectional CFRP has been investigated by the use of mechanical and thermo-mechanical test methods and finite-element analysis.

Journal ArticleDOI
TL;DR: In this article, the compressive strength of composite laminates containing an open-hole can be predicted theoretically by using fracture mechanics based models such as the linear softening cohesive zone model.
Abstract: At present, the compressive strength of composite laminates containing an open-hole can be predicted theoretically by using fracture mechanics based models such as the linear softening cohesive zone model. In this approach, the inelastic deformation associated with fibre microbuckling that develops near the hole edge is replaced with an equivalent crack loaded on its faces by a bridging traction which is linearly reduced with the crack closing displacement. By making use of this model, and by establishing an equivalent hole diameter from X-radiographs and/or ultrasonic C-scan images, the residual compressive strength after impact can be predicted. This paper outlines how the ‘equivalent hole’ is determined and gives tabulated results of experimental and theoretical data. It is also shown that these data are in good agreement with each other for plain compression, open-hole compression and compression after impact strengths.

Journal ArticleDOI
TL;DR: In this paper, the authors used continuum damage mechanics (CDM) and fracture mechanics (FM) approaches to predict fatigue threshold in composite adhesively bonded joints using epoxy film adhesive.
Abstract: The prediction of fatigue threshold in composite adhesively bonded joints using continuum damage mechanics (CDM) and fracture mechanics (FM) approaches has been investigated. Two joint types were considered in this study: double lap (DL) and lap strap (LS) joints. The substrates, which were made of uni-directional (UD) or multi-directional (MD) composite laminates, were bonded together using an epoxy film adhesive. The joints were tested under fatigue loading with a load amplitude ratio of 0.1 at various test temperatures. Damage evolution laws were derived using thermodynamics principles. The number of cycles to failure was then expressed in terms of the stresses in the adhesive layer and material constants. The stresses were calculated from non-linear finite element analyses, considering both geometrical and material non-linearities. The damage laws generated for the UD/DL joint data were then used to predict the fatigue crack initiation thresholds for the MD/DL, UD/LS, and MD/LS joints. The FM approach...

Journal ArticleDOI
TL;DR: In this paper, the impact of matrix cracking-initiated damage on the response and the strength of composite laminates subjected to uniaxial tension was investigated, and the results of the experimental study are presented in this paper.
Abstract: An investigation was performed to study the impact of matrix cracking-initiated damage on the response and the strength of composite laminates subjected to uniaxial tension. Both experiments and analysis were conducted during the investigation. Extensive tests were performed on specimens with specially tailored ply orientations to characterize damage initiation and propagation induced by matrix cracks. The focus of the experiments was to characterize the matrix crack-induced damage progression and failure modes in composite laminates under uniaxial tension loads. Four basic damage modes were observed from the results of the study: matrix crack-induced microcracking, matrix crack-induced delamination, angle-ply-induced edge delamination, and Mode I edge delamination. The results of the experimental study are presented in this paper. Results from the analytical work will be presented in a subsequent paper.

Journal ArticleDOI
TL;DR: In this article, a Bragg sensor was used for bending tests on bare optical fibres and the results demonstrate the applicability of Bragg sensors for continuous monitoring of composite materials.
Abstract: Tests carried out on bare optical fibres with a Bragg sensor show the feasibility of using these sensors for strain sensing. They have been embedded into simple composite laminates and have been subjected to static loading in bending tests. The measured strain from the Bragg sensor is perfectly linear with the applied force. Optical fibres with a Bragg sensor have also been embedded into filament wound pressure vessels. Tests carried out on such a pressure vessel include both static and slowly varying load schemes. The Bragg signal is nearly perfectly linear with the applied pressure. The results demonstrate the applicability of Bragg sensors for continuous monitoring of composite materials.

Journal ArticleDOI
TL;DR: In this paper, both microwave curing and thermal curing of 24.5 mm (1 inch) glass/epoxy laminates were investigated through the development of a numerical process simulation and conducting experiments in processing in a conventional autoclave and a microwave furnace, and both numerical and experimental results show that volumetric heating due to microwaves promotes an inside-out cure and can dramatically reduce the overall processing time.
Abstract: In conventional processing, thermal gradients cause differential curing of thick laminates and undesirable outside-in solidification. To reduce thermal gradients, thick laminates are processed at lower cure temperatures and heated with slow heating rates, resulting in excessive cure times. Microwaves can transmit energy volumetrically and instantaneously through direct interaction of materials with applied electromagnetic fields, The more efficient energy transfer of microwaves can alleviate the problems associated with differential curing, and the preferred inside-out solidification can be obtained. In this work, both microwave curing and thermal curing of 24.5 mm (1 inch) thick-section glass/epoxy laminates are investigated through the development of a numerical process simulation and conducting experiments in processing thick laminates in a conventional autoclave and a microwave furnace. Outside-in curing of the autoclave-processed laminate resulted in visible matrix cracks, while cracks were not visible in the microwave-processed laminate. Both numerical and experimental results show that volumetric heating due to microwaves promotes an inside-out cure and can dramatically reduce the overall processing time.

Journal ArticleDOI
TL;DR: In this paper, a study using virtual crack closure technique is made for three-dimensional finite-element models of circular delaminations embedded in woven and non-woven composite laminates.

Journal ArticleDOI
Hyunjo Jeong1
TL;DR: In this article, a new approach for the analysis of transient waves propagating in anisotropic composite laminates is presented, where the wavelet transform (WT) using the Gabor wavelet is applied to the time-frequency analysis of dispersive flexural waves in these plates.
Abstract: A new approach is presented for the analysis of transient waves propagating in anisotropic composite laminates. The wavelet transform (WT) using the Gabor wavelet is applied to the time-frequency analysis of dispersive flexural waves in these plates. It can be shown that the peaks of the magnitude of WT in a time-frequency domain is related to the arrival times of the group velocity. Experiments were performed using a lead break as the simulated acoustic emission source on the surface of unidirectional and quasi-isotropic laminates. A method was developed to obtain the group velocity of the flexural mode as a function of frequency. Theoretical predictions were made using the Mindlin plate theory, which includes the effects of shear deformation and rotatory inertia. Our predictions on the dispersion of the flexural mode showed good agreement with the experimental results.

Journal ArticleDOI
TL;DR: In this article, the authors present two micromechanical models for the analysis of plain weave fabric composites, which utilize the representative volume cell approach to divide the representative unit volume of the woven lamina into subcells of homogeneous material.
Abstract: This paper presents two newly developed micromechanical models for the analysis of plain weave fabric composites. Both models utilize the representative volume cell approach. The representative unit volume of the woven lamina is divided into subcells of homogeneous material. Starting with the average strains in the representative volume cell and based on continuity requirements at the subcell interfaces, the strains and stresses in the composite fiber yarns and matrix are determined as well as the average stresses in the lamina. Equivalent homogenized material properties are also determined. In their formulation the developed micromechanical models take into consideration all components of the three-dimensional strain and stress tensors. The performance of both models is assessed through comparison with available results from other numerical, analytical, and experimental approaches for composite laminae homogenization. The very good accuracy together with the simplicity of formulation makes these models attractive for the finite element analysis of composite laminates.

Journal ArticleDOI
TL;DR: In this article, a shear-lag analysis associated with an energy release rate criterion is used to predict cracking development in each cross-ply laminate subjected to any fatigue loading.

Journal ArticleDOI
TL;DR: In this article, an accurate higher-order theory employing finite element procedure for the free vibration analysis of multi-layered thick composite plates is presented, which accounts for the realistic variation of in-plane and transverse displacements through the thickness.
Abstract: This paper deals with an accurate higher-order theory employing finite element procedure for the free vibration analysis of multi-layered thick composite plates. The theory accounts for the realistic variation of in-plane and transverse displacements through the thickness. The accuracy of the present model is verified by comparison with three-dimensional elasticity solutions for the vibration study of the composite laminates. The performance and the applicability of the proposed discrete model are also discussed among developed elements and alternate models, considering different parameters such as ply-angle, degree of orthotropicity, aspect ratio and boundary conditions.

Journal ArticleDOI
TL;DR: In this paper, a finite strip method for predicting buckling stresses of rectangular sandwich plates is described. But this method is based on a B-spline finite strip model and is not suitable for the case of composite laminates.

Journal ArticleDOI
TL;DR: In this paper, a comprehensive notch-edge damage analysis was performed by a combination of recording tests on video, plan-view photography and a de-ply technique, enabling a layer-by-layer analysis.

Journal ArticleDOI
TL;DR: In this article, it was shown that a block of negative stiffness material is unstable, but negative stiffness inclusions in a composite can be stabilized by the surrounding matrix and give rise to extreme viscoelastic effects in lumped and distributed composites.
Abstract: Particulate composites with negative stiffness inclusions in a viscoelastic matrix are shown to have higher thermal expansion than that of either constituent and exceeding conventional bounds. It is also shown theoretically that other extreme linear coupled field properties including piezoelectricity and pyroelectricity occur in layer- and fiber-type piezoelectric composites, due to negative inclusion stiffness effects. The causal mechanism is a greater deformation in and near the inclusions than the composite as a whole. A block of negative stiffness material is unstable, but negative stiffness inclusions in a composite can be stabilized by the surrounding matrix and can give rise to extreme viscoelastic effects in lumped and distributed composites. In contrast to prior proposed composites with unbounded thermal expansion, neither the assumptions of void spaces nor slip interfaces are required in the present analysis.

Journal ArticleDOI
TL;DR: In this paper, a set of fundamental dynamic equations of a two-dimensional higher-order theory for thick rectangular laminates subjected to in-plane stresses is derived through Hamilton's principle.