Search

Bending-active elastica beam is a structural configuration that is based on the elastic deformation of an initially straight beam. This deformation occurs when horizontal displacements are applied to a sliding support, causing the beam to bend into an arched shape. Previous research has focused on the stability of small-scale bending-active structures, thus not considering material strength, which is crucial in real-scale applications and structural design. This paper investigates the short-term structural behavior of bending-active elastica beams using pultruded glass fiber-polymer composite profiles, as used in real-scale structures. A series of short-term bending and service load application experiments were performed considering different bending degrees and loading scenarios. These results were used to validate finite element modeling. They demonstrated that steeper bent beams experience material failure, while shallower ones exhibit snap-through buckling. Material failure initiates on the tensile side of the beams, with cracks initiating at locations of maximum curvature. Higher bending degrees and symmetric loading result in higher maximum loads than lower bending degrees and asymmetric loading. A strain-based failure criterion, which can serve for structural design, is derived. [ABSTRACT FROM AUTHOR]

• Mode I fracture process is characterized for GFRP-steel bi-material interface. • Double-cantilever beam experiments supplemented by detailed DIC measurement. • Accurate modeling of crack initiation, fiber bridging and propagation by new CZM. • Four-linear traction-separation law derived from DIC measurements and iterative FEA. Debonding is characterized as the governing failure mode in the innovative wrapped composite joints made with glass fiber composite material wrapped around steel hollow sections without welding. The prerequisite for predicting debonding failure of wrapped composite joints is to obtain fracture behavior of the composite-steel bonded interface. The mode I fracture behavior of the bonded interface was experimentally investigated using glass fiber composite-steel double cantilever beam (DCB) specimens. The crack length a and the crack tip opening displacement (CTOD) during the test were accurately measured by analyzing the digital image correlation (DIC) data while the strain energy release rate (SERR) was calculated through the extended global method (EGM). The cohesive zone modeling (CZM) was utilized in the finite element model with the proposal of a four-linear traction-separation law to simulate the mode I fracture process. An approach is introduced to determine the critical stages of the proposed four-linear cohesive law by combining accurate measurements of crack length a and CTOD, along with SERR values. The validity of the four-linear cohesive law and the introduced approach to determine the critical stages were confirmed by good agreement in both global and local behavior between the testing and the FEA results. [ABSTRACT FROM AUTHOR]

Compared with other green natural fibers, ramie has higher mechanical properties and lower cost. In this study, ramie and glass fiber are made into composite circular tubes by two-dimensional braiding, and their torsional mechanical properties and damage mechanisms are investigated. The results show that under the unit wall thickness, compared with the pure glass fiber circular tube, the maximum torsion angle of the hybrid circular tube with ramie and glass fiber spindle ratio of 1:3 increases by 78%, the weight is reduced by 22%, the cost is reduced by 14%, the maximum torque is increased by 10% and the torsional stiffness is reduced by 18.75%. When the loading direction is the same as the implantation direction with more glass fiber content, the failure is caused by buckling. When the loading direction is the same as the implantation direction with more ramie content, the failure is caused by matrix fracture or fiber fracture. The numerical simulation results of the damage model are consistent with the experimental data and the damage morphology, which verifies the effectiveness of the finite element model. These conclusions provide a reference for the engineering application of composite circular tubes with environmental protection, lightweight and anti-torsion failure ability. [ABSTRACT FROM AUTHOR]

Abstract In this paper, compaction behaviors of glass fiber non-crimp fabrics (NCFs) were investigated via finite element analysis (FEM). Firstly, the compaction mechanism of NCFs was analyzed, it suggested the compaction process is mainly characterized by the decrease of macro pores and micro pores, a novel and reasonable constitutive model (porous elastic) was proposed. Then, the feasibility of modeling the compaction process for NCFs with the porous elastic material via FEM was explored. A macroscale model of NCF was established firstly, the simulation complies well to the experimental results. Then, the mesoscale models were attempted, and the effect of model parameters on simulation results were investigated, including the model size, platen location, warp cross-sectional shape. Results show that the size of mesoscale model and compaction platen position have little effect on the compaction behavior, while the cross-sectional shape of the warp yarn has a slight influence on the simulation results. Finally, compared the warp yarn cross-section changes of simulation with experimental data, it was revealed that variations in yarn cross sections in the model have a good agreement with experimental results, except that the macro-porosity differs slightly. [ABSTRACT FROM AUTHOR]

Abstract The precast concrete sandwich panel (PCSP) is a popular structural type used for prefabricated construction. In this study, three kinds of glass fiber reinforced polymer (GFRP) connector, including a flat plate, a corrugated plate, and a hexagonal tube connector, were investigated for potential use in PCSPs. In-plane direct shear tests were conducted to evaluate the performance of the connectors based on a typical push-out configuration (i.e., three concrete wythes linked with connectors and two rigid foam layers in between). Twenty-five specimens were tested, and the parameters investigated consisted of GFRP laminate thickness, projected length, and shear force direction. The shear force vs. relative slip relationships and failure modes of all types of connector were compared and are discussed in detail in this paper. Meanwhile, finite element (FE) analysis was conducted to reproduce the test results. All three types of GFRP connector exhibited a progressive failure manner in spite of the linear brittle nature of the FRP materials; the corrugated plate connector achieved higher deformability than the flat plate connector, particularly when the GFRP laminate thickness was small; and the hexagonal tube connector exhibited similar behavior along two orthogonal directions, making them well suited for use as two-way connectors. The developed FE model was able to well predict the peak shear load and stiffness of all types of connector based on comparisons with the test results. [ABSTRACT FROM AUTHOR]

Abstract This paper studies the feasibility of improving structural performance of composites in the presence of stress concentrators. Matrix grading through local deposition of additive-enhanced matrices and fibre steering by varying fibrous architecture are examined independently and in combination on a glass-fibre triaxial braided composite subjected to open hole tensile test. Stiffened and toughened matrices were incorporated through precise point-wise injections of liquid reactive resin into dry preforms (Liquid Resin Printing). Fibre steering was implemented by varying the braiding angle along the length of the braided sleeve. It has been shown that these novel forms of architecture modification enable a significant improvement in composite strength through a variety of deformation mechanisms. This includes local stiffening of composite in the direct vicinity of the stress concentrator and damage accumulation away from the stress concentrators. The experimental observations are explained by using simple finite-element models. [ABSTRACT FROM AUTHOR]

Abstract The compressive kinking behavior of non-slender unidirectional glass fiber-reinforced polymer (GFRP) specimens has been analyzed by finite element (FE) models. The experimentally observed imperfections, including the initial fiber waviness throughout the entire specimen volume and the scattered resin/interface defects, were taken into account in the FE models. The birth-and-death method was employed to simulate the progressive damage to the material. The consideration of the coexistence of initial fiber waviness and initial resin/interface defects was found to be essential for accurate modeling of the kinking failure process. Kinking was initiated due to the disproportional increase of the fiber microbuckling at the locations of initial defects. The numerically obtained peak load, fiber microbuckling amplitudes, kink band angle and width, and compressive strain concentrations at the kink band edges were well predicted compared to the experimental results. The number of defects was less significant than the fact that defects existed that served as initiation points of the kink band formation. [ABSTRACT FROM AUTHOR]

Using a FEA homogenization technique, this study presents the influence of interphase region on composites. Numerical models using Abaqus ™ are developed in order to predict the mechanical behavior of a unidirectional composite (E-glass fibers/epoxy) under monotonic transverse traction. A Representative Volume Element description with a random distribution of the fibers is used. Linear elastic constitutive materials and Kinematic Uniform Boundary Conditions are considered. A numerical/experimental comparison is made in order to validate the model. The thickness and the modulus of the interphase have been determined by experimental measurements based on Atomic Force Microscopy and introduced in the numerical simulation, the effect of these properties as well as the effect of the interphase Poisson’s ratio, on the effective elastic properties of the composite is discussed. The obtained results are in good agreement with the experimental values previously measured by tensile test on macroscopic samples. The fact of considering the interphase improves the accuracy of the prediction of the composite's mechanical elastic behavior. [ABSTRACT FROM AUTHOR]

Synergistic effects on shear resistance of ultra-high-performance hybrid-fiber-reinforced concrete (UHP-HFRCs) at high strain rates was investigated using a new shear test setup. Two UHP-HFRCs: L05S10 (containing 0.5 vol-% long and 1.0 vol-% short fiber) or L10S05; and, two ultra-high-performance mono-fiber-reinforced concretes (UHP-MFRCs): L15S00 (containing 1.5 vol-% long fiber) or L00S15, were tested. The L05S10 generated high synergy in shear resistance whereas the L10S05 did little. Synergies were significant for shear strength, shear peak toughness, but not for shear strain capacity. Moreover, the L00S15 produced the highest rate-sensitivity although the shear response of both UHP-MFRCs and UHP-HFRCs was generally sensitive to the applied strain rates. The experimental shear strengths were well-matched with the theoretical calculations. [ABSTRACT FROM AUTHOR]

This paper aims to present a methodology to predict the anisotropic and non-linear behaviour of glass fibre reinforced plastics using finite element methods. A material model is implemented in order to remedy the need of multiple material definitions, and to control the local plastic behaviour as a function of the fibre orientation. Injection moulding simulations traditionally provide second order orientation tensors, which are considered together with a homogenization scheme to compute local material properties. However, in the present study, fourth order tensors are used in combination with traditional methods to provide more accurate material properties. The elastic and plastic response of the material model is optimized to fit experimental test data, until simulations and experiments overlap. The proposed material model can support design engineers in making more informed decisions, allowing them to create smarter products without the need of excessive safety factors, leading to reduced component weight and environmental impact. [ABSTRACT FROM AUTHOR]

Composite pipes have become a viable alternative to metallic pipes in several applications. Flow-accelerated erosion and internal surface attack often result in thickness thinning that may compromise the structural integrity of the pipe and lead to its failure. In this paper, we investigate how the internal surface damage is reflected on the vibration behavior of a composite pipe conveying fluid. The defected pipe-fluid system is modeled using the extended Hamilton’s approach and discretized using the wavelet-based finite element method. The modal characteristics of the pipe vibrations have been obtained by solving the generalized eigenvalue problem. The developed model was validated and some benchmark solutions are presented to highlight the effects of the internal wall-thinning on the vibrational behavior of composite pipes conveying fluid. The obtained results facilitate the future research by revealing the potential of using the vibration signature as a basis for detection of erosion-induced internal defects in pipelines. [ABSTRACT FROM AUTHOR]

The elastic orthotropic behavior of thin woven composites is studied combining a numerical and experimental strategy. For thin materials, in-plane properties are measured by classical tensile tests and digital image correlation. The out-of-plane properties are derived performing finite element simulations at the level of the internal structure of the laminate. Indeed, the glass fiber arrangement in the yarn and the weaving pattern are defined based on microtomography and SEM observations. So a representative unit cell is found. A statistical approach is further proposed to derive the behavior of the warp and fill yarns, since the fiber position may fluctuate between yarns. For the considered laminate, the matrix (resin and ceramic inclusion) behavior is unknown and difficult to measure. Therefore an inverse method is proposed. By comparing with measured in-plane elastic moduli, behaviors of the matrix, of yarns and of the laminate are defined. The present homogenization strategy is exemplified by laminates used in printed circuit boards for high frequency applications. This approach has also been applied to investigate the evolution of the elastic moduli of the laminate with temperature. Those information, usually not available in the literature, are important when dealing with reliability of printed circuit boards during thermal cycles. [ABSTRACT FROM AUTHOR]

This paper studies failure behaviors of glass fiber/PC resin thermoplastic composites under transverse tension and shear loads using explicit finite element method. Microscopic long fiber/matrix composite representative volume elements with randomly distributed fibers and periodic boundary conditions are established by ABAQUS-PYTHON script language. The finite-deformation viscoplastic Gurson model is used for predicting the plastic deformation and void growth of thermoplastic glassy polymer matrix, which is implemented using ABAQUS-VUMAT explicit subroutine. The bilinear cohesive model with finite-thickness interface element is used to simulate the fiber/matrix debonding. Three important issues are explored: first, effects of the cohesive interface strength on the plastic deformation and void growth of composites are studied using three mesh models and three fiber distributions. Second, failure surface under different tensile and shear displacement ratios is obtained, compared with the predictions using the Hashin and Puck failure criteria developed mainly for thermoset composites. Finally, the influence of the plastic softening effect of matrix on the strain concentration or localization behaviors is discussed. Results show the tension/shear load ratio and the cohesive interface strength produce large effects on the void growth and failure surface of composites, but fiber distribution shows a small effect on transverse load-bearing ability of composites. [ABSTRACT FROM AUTHOR]

The study concerns glass-polyester laminates, i.e. polyester resin reinforced with E-glass balanced plain weave fabric and/or E-glass mat. Experimental 3-point bend tests were carried out on homogeneous laminate beams reinforced with glass fabric or glass mat and on mixed laminate beams and plates reinforced with a glass fabric/glass mat ply sequence. In order to select the adequate failure criteria, bend tests on homogeneous laminate beams were modelled numerically and simulated using MSC.Marc finite element code. In relation to laminae reinforced with glass fabric the Hashin Fabric failure criterion was selected, and in reference to laminae reinforced each with glass mat the Max Strain failure criterion was selected. The adequacy of the selected failure criteria was validated experimentally by bend tests on mixed laminate beams and plates. Good qualitative and quantitative agreement of the simulated pressure force vs. deflection charts with those of the experimental tests was obtained. [ABSTRACT FROM AUTHOR]

In order to extend the use of pultruded glass fiber reinforced polymer (GFRP) composite materials in civil engineering, a systematic study on pultruded GFRP laminate is important and realistic for the design and construction of GFRP structures in bridge engineering. A practical method to evaluate the fiber volume fractions and the equivalent thickness of each lamina is proposed considering that a typical pultruded FRP profile is not truly laminated structure in rigorous sense. The elastic modulus and ultimate strength of each lamina were predicted based on micromechanics. In terms of the facts that lack of knowledge of the majority of bridge engineers on the behavior of composites, an innovative carpet plots with different fiber volume fraction are adopted to finish the laminate design procedure without much complicated calculation. In addition, a continuum damage model considering lamina shear nonlinearity, lamina damage along thickness direction, innovative damage evaluation methods, loading/unloading strategy and viscous methods to alleviate the convergence difficulties is proposed and implemented via user material subroutine. Three different types of pultruded GFRP laminate were fabricated, and material properties have been tested to validate the numerical and theoretical models. The Finite element simulation results agreed well with tests and could provide reference for the design and construction of GFRP structures. [ABSTRACT FROM AUTHOR]

An unstructured mesh Galerkin finite element method is used to obtain estimates of the viscoelastic moduli of short glass fiber reinforced polymer composites. Periodic Monte Carlo models with 125 identical inclusions are studied. Both spheroidal and spherocylindrical inclusions are considered. The estimates are compared against predictions of the dilute approximation, Mori-Tanaka (MT) and self-consistent (SC) models. It is shown that at small fiber fractions, the dilute approximation (Eshelby) model is exact. However, for the axial stiffness the dilute regime is limited to fiber volume loadings of a few tens of a percent while typical short glass fiber polymer composites have fiber loadings from 10 to 20 percent. It is found that in this concentrated regime, both MT and SC models give excellent predictions for all but the axial stiffness modulus. To assess the feasibility of reliable stiffness and vibration damping design of composite structures from short fiber reinforced polymers, Monte Carlo models with various fiber orientation distribution (FOD) states are studied. It is shown that the quick Voigt (constant strain) orientation averaging procedure gives excellent viscoelastic stiffness predictions provided that the finite element estimates are used for the required moduli of the basis FOD state with fully aligned fibers. [ABSTRACT FROM AUTHOR]

In this study, a low-velocity impact test of glass fiber-reinforced polypropylene (GFPP) composites was simulated considering interlaminar fracture toughness. In the simulation, intralaminar and interlaminar damage were modeled using the continuum damage mechanics (CDM) and cohesive zone method (CZM) models, respectively. The B-K criterion was used for the interlaminar damage model along with experimental results, which were obtained from fracture toughness tests of modes I and II and the mixed mode. Low-velocity impact tests were performed to verify the developed damage model, and various characteristics such as delamination and the force–displacement were evaluated. Finally, it was found that the developed damage model with interlaminar fracture toughness can be used to accurately predict the impact behavior of GF/PP composites, including interlaminar delamination. [ABSTRACT FROM AUTHOR]

This attempt proposes a Finite Element Approach (FEA) to investigate the tribological behavior of glass fiber reinforced polyester composite. The 3D finite element model was developed upon ABAQUS/Explicit. The Johnson-Cook criteria were considered for describing the material behavior and damage of both fiber and matrix phases. The fiber/matrix interface behavior was, however, modeled using a thin cohesive zone (CZ). A mixed-mode loading concept was specially adopted to predict delamination propagation within the interface. The prevailing wear mechanisms owing to Multi-Scratch Test (MST) were inspected at variable load and attack angle, using scanning electron microscope (SEM). Wear maps were built to highlight the correlation between friction coefficient and wear mechanisms. Predictions of both elementary and interacting mechanisms showed excellent correlation with observations. It was revealed that material removal process varies sensitively with the dominating failure mode. The proposed approach exhibits good ability not only in predicting active mechanisms but also in detecting damage sequences governing the surface integrity during scratching. [ABSTRACT FROM AUTHOR]

In this paper, a multiscale approach is presented for strength and tensile modulus prediction of carbon nanotube (CNT) reinforced glass–epoxy composite. At the micro-scale, the three-dimensional representative volume element is obtained by randomly orienting the carbon nanotube in the resin according to the weight percentage. The interphase of the nanotube and resin is modeled using a cohesive element method. The behavior of the resin is accounted with a quasi-brittle non-local damage model. At the Mesoscale, the representative volume element is estimated by using the weight percentage of glass fiber and resin generalized with nanotubes. Finite element analyses were conducted to estimate the effective mechanical properties through numerical homogenization. The effect of different percentages of carbon nanotubes on tensile behavior was investigated experimentally and numerically. The results show that adding carbon nanotubes improves the tensile modulus by about 25% and the tensile strength by about 53%. In the numerical study, the strength of the composite is predicted with good accuracy by modeling the damage of resin, glass fibers, and fracture toughness mechanisms of carbon nanotubes such as bridging and pull-out of carbon nanotubes. A good agreement was observed between the simulation results and the experimental results at different percentages of carbon nanotubes. [ABSTRACT FROM AUTHOR]

Based on a Finite Elements Analysis homogenization technique which uses a Representative Volume Element with a random distribution of the fibers, this article presents the adequate characteristics to obtain a mesoscopic model which predicts the mechanical behavior of a unidirectional glass fiber-reinforced polymer composite under monotonic transverse traction. A parametric study is made and finally an appropriate model was chosen to present the comparison between experimental and numerical results. The mesh and the RVE size/fibers size ratio are the most sensitives attributes. Considering the numerical model is in the framework of elasticity and elasto-plasticity, it is in good agreement with the macroscopic response. To improve the accuracy of the model, a further study accounting the interface and damage phenomenons as matrix cracking and fiber/matrix debonding is suggested. [ABSTRACT FROM AUTHOR]

This paper details a study on the application of Thermoelastic Stress Analysis (TSA) for the investigation of delamination damage propagation in glass fibre reinforced composite materials. A woven Glass (0/90)/Epoxy composite sample containing a purposely created delamination was subjected to a step-cyclic loading (varying mean level) whilst monitoring the thermoelastic response of the sample with an infrared camera. A finite element analysis (FEA) was performed using cohesive elements to simulate the propagation of the delamination under a monotonically increasing axial load. It is shown that the delamination crack length inferred from the TSA results is consistent with microscopic analysis of the sample, and that the measured crack growth rate is in reasonable agreement with simulation results. [ABSTRACT FROM AUTHOR]

In this paper, results of flexure tests aimed at improving the structural behavior of softwood beams reinforced with unglued composite plates and at developing an effective alternative to the use of organic resins are presented. The addition of modest ratios of GFRP ( Glass Fiber Reinforced Polymer ) composite strengthening can prevent tension failure in timber beams. However the application of organic matrices presents problems of reversibility, compatibility and durability with timber and poor performance at high temperatures. The increment in capacity and stiffness and the analysis of the failure modes is the central focus of this paper. The experimental campaign is dealing with a significant number of un-reinforced and reinforced beams strengthened with unbonded GFRP plates. A 3-dimensional finite element model is also presented for simulating the non-linear behavior of GFRP-reinforced softwood beams. The ability of the numerical model to reproduce experimental results for the load–deflection curves is validated. [ABSTRACT FROM AUTHOR]

This study proposes a mixed-mode fracture criterion for glass fiber reinforced composite laminates based on numerical and experimental biaxial loading. An optimal cruciform geometry is introduced first based on finite element (FE) simulation. Characterization testing is performed successively on uniaxial and cruciform specimens to determine equivalent loaded area, notch sensitivity behavior and critical fracture toughness properties of cross-ply GFRP laminates. In experimental biaxial testing, two types of crack orientations (0°, 45°) are studied with varying crack lengths. The experimental failure points show that cross-ply GFRP laminates attain higher load bearing capability under biaxial tensile–tensile loading compared to uniaxial testing. Appropriate non-dimensional geometry factor relevant to cruciform shape is determined based on experimental data points and FE simulation. Eventually, a mixed-mode fracture criterion is proposed for cross-ply composite laminate based on the findings from biaxial experimental loading. [ABSTRACT FROM AUTHOR]

We report a new approach to measure orthotropic properties of short glass fibre reinforced thermoplastics at the macroscopic scale taking into account all microstructural details. 3D imaging technique based on X-ray micro-tomography is used to assess fibrous architecture of an injected part at different positions characterised by different fibre flow histories. Finite element computation is used as a multiscale process, firstly by computing orthotropic parameters at a micro-scale for hundreds of bi-phasic 3D domains composing the macrostructure of the composite at all studied positions. Results are implemented in a second finite element computation as a collection of orthotropic material models composing the heterogeneous structure of the composite. [ABSTRACT FROM AUTHOR]

Presented research aims to prove the appearance of lateral-distortional buckling mode by observing the beams' deflection characteristics. Eight-layer channel and lip-channel cross-section glass fibre reinforced polymer (GFRP) beams subjected to pure bending in the web plane were discussed. The Finite Element Method and the Semi-Analytical Method were used to perform all calculations. Deflection angles at the beams' ends show that the lateral deflection sharply increases from load close to critical one and in the post-buckling range. It was observed that for simply supported beams subjected to bending, the lateral-distortional global buckling mode is accompanied by rotation at support in the flange plane. In the FEM approach, the lowest buckling mode is usually considered in beams subjected to bending, and the angle of rotation in the load plane corresponding to the critical bending moment is only analysed. However, in the interactive buckling analysis, the horizontal rotation at the supports is accompanied by the global mode, and its impact is often neglected due to its high bifurcation value compared to the lowest mode. Moreover, in the paper, the influence of this mode on the equilibrium paths, the critical buckling load, the load-carrying capacity, distributions of internal membrane forces, and vertical and horizontal angle of rotation was investigated. [ABSTRACT FROM AUTHOR]

A large debate animates the community about the mechanical performance of complex parts obtained by injection moulding (IM) of short glass fibre reinforced polymer (SGFRP) composites. Difficulties to measure exact fibre length and orientation distributions in complex geometries are limiting in terms of basic understanding of damage mechanisms in industrial parts and fatigue design improvement. In this work, we are interested to shed more light on the mechanical performance of short glass fibre reinforced polyamide composites in correlation to local microstructural heterogeneities which are caused by inserts used during IM. For such purpose, we combine X-ray microtomography (μ-CT) and finite element computation to determine the elastic modulus in various positions in an open hole plate configuration with a dissymmetric fibre distribution. Our predictions show that effective properties do not vary significantly around the hole in all space directions. However, stress profiles (through the thickness) far enough from the hole reveal a five-layer quasi symmetric structure evolving to three-layer near the cylindrical insert. We believe that such alteration is responsible for the observed failure of the composite at precisely the positions of highly affected fibre distribution. [ABSTRACT FROM AUTHOR]

This study is focused on the finite element analysis of the hygro-elastic stresses experienced by unidirectional composite structures instrumented by Fiber Bragg Grating (FBG) sensors. One of the significant advantages of this method is that by taking into account the complex geometry of elaborated specimen and their different constituents with heterogeneous hygroscopic and mechanical properties. In the first time, the obtained results were compared with the results obtained owing to an analytical solution deduced from the simplified concentric cylinders approach. This comparison allows us to evaluate the reliability of the concentric cylinders approach which cannot account for every aspects of the actual geometry of the studied samples. Besides the numerical results were compared to the experimental characterization of the mechanical states deduced from the Fiber Bragg Grating measurements. [ABSTRACT FROM AUTHOR]

Abstract: This study conducted a finite element analysis of the piezoelectric damage monitoring of unidirectional glass fiber epoxy composites to estimate the electric charge signals from the composite materials against the external load or the internal crack length. To verify the results of the finite element analysis, the calculated electric charges were compared with the results of a previous research. In addition, the crack length during Mode I fatigue tests of the DCB specimen was estimated and compared with the measured data. The estimated electric charge signals from the finite element analyses showed tendency similar to that of the measured ones, and could predict the crack propagation. [Copyright &y& Elsevier]

Abstract: Composite sandwich structures are widely used in the high-performance applications where weight reduction is one of the most attractive design parameters. However, structural sandwich components have low resistance to out-of-plane impact due to the thin outer composite skins and the highly deformable cores. The present paper deals with a finite element study on the impact response of sandwich panels, obtained combining phenolic resin-based glass fiber reinforced plastics as skins and phenolic resin-impregnated aramid paper honeycomb structure (Nomex) as core. The numerical analysis has been performed using the LSDYNA software enabling to account for the main sandwich failure modes occurring during impact. The honeycomb core structure and composite skins have been modeled by means of solid and shell elements respectively. The properties of the finite element model have been calibrated on a series of experimental outcomes in order to achieve numerical parameters for both composite facesheet and orthotropic honeycomb material models. The major concerns are related to damage mechanisms, influence of strain-rate effects and energy absorbing capability. The model is validated using the results from experimental impact tests performed on different initial impact conditions. Good agreement was obtained between numerical and experimental results in terms of impact damage and force–displacement trend. [Copyright &y& Elsevier]

Prognostics and health management (PHM) algorithms to predict the electromechanical behavior of double cantilever beam (DCB) composites were proposed using the particle filter method, which is a physics-based prognostics tool. The composites consisted of carbon fibers and carbon-glass hybrid fibers, whose warp and weft were carbon and glass fibers, respectively. The electrical resistance was changed by mechanical deformation as the cracks propagated. Finite element analysis (FEA) supported the empirical data in that mechanical stress along the through-thickness direction of each section and a detour of the electrical path via the crack tip caused resistance changes. Previous prognostics research which used data-driven or physics-based prediction were limited to predict future material behavior in real time due to long calculating time or high dimensional physical model. To develop the real time prognostic tool, the particle filter required sectioning and guiding, even though it only analyzed numerical values with a given physical equation. The sectioning and guiding processes were based on the empirical analysis and the FEA results. The handling was optimized by controlling the number of sections and coefficients of the physical equation. Therefore, this study successfully extracted the remaining useful lifetimes of composites within 4.54% and 5.71% of prediction error for carbon fiber and carbon-glass hybrid fiber based DCB composites, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The design of concrete structures reinforced with glass fibre reinforced polymer (GFRP) bars is influenced by their reduced stiffness and brittleness. In hyperstatic structures, the methodology used in force analysis depends on the ductility of the structural systems, which in this case, being essentially provided by the concrete, can be potentially increased by confining concrete in critical zones. This paper presents experimental and numerical investigations about the flexural behaviour of continuous beams reinforced with GFRP bars, namely of their service and failure responses, and the effect of increasing concrete confinement in critical cross-sections. A calculation procedure to quantify the confinement effect in beams due to the reduction of the spacing between shear stirrups is first presented. The experimental investigations comprised a comparative study in which two-span concrete beams reinforced with either GFRP or steel bars were tested in bending. In the former, the effect of reducing the shear stirrups spacing was analyzed together with the under- and over-reinforcement at the central support and midspan cross-sections, respectively. The development of a crack hinge in the continuity support zone highlighted the better performance of beams under-reinforced on the top layer with GFRP bars compared to “equivalent” beams reinforced with steel, namely at the resistance level. In addition, the confinement at critical zones increased significantly the strength and ductility. The numerical investigations included the development of non-linear finite element models for all beams tested – numerical results are in good agreement with test data and seem to confirm the confinement effect observed in the experiments. [Copyright &y& Elsevier]

Abstract: This paper presents three dimensional (3D) finite element (FE) models of the low-impulse localised blast loading response of fibre-metal laminates (FMLs) based on an 2024-O aluminium alloy and a woven glass-fibre/polypropylene composite (GFPP). A vectorized user material subroutine (VUMAT) is developed to define the mechanical constitutive behaviour and Hashin’s 3D failure criteria incorporating strain-rate effects in the GFPP. In order to apply localised blast loading, a user subroutine VDLOAD is used to model the pressure distribution over the exposed area of the plate. These subroutines are implemented into the commercial finite element code ABAQUS/Explicit to model the deformation and failure mechanisms in FMLs. The FE models consider FMLs based on various stacking configurations. Both the transient and permanent displacements of the laminates are investigated. Good correlation is obtained between the measured experimental and numerical displacements, the panel deformations and failure modes. By using the validated models, parametric studies can be carried out to optimise the blast resistance of FMLs based on a range of stacking sequences and layer thicknesses. [Copyright &y& Elsevier]

Abstract: This paper studies the high-velocity impact response of sandwich plates, with E-glass fibre/polyester face-sheets and foam core, using finite-element models developed in ABAQUS/explicit code. The failure of the face-sheets was predicted by implementing Hou failure criteria and a procedure to degrade material properties in a user subroutine (VUMAT). The foam core was modelled as a crushable foam material. The numerical models were validated with experimental data obtained from scientific literature. The contribution of the foam core on the impact behaviour was evaluated by the analysis of the residual velocity, ballistic limit, and damaged area. [Copyright &y& Elsevier]

Abstract: The present work aims to obtain failure modes and failure loads for multi-pin joints in uni-directional glass fibre/epoxy composite laminates by finite element analysis and validating the results with the experimental work. In multi-pin joints, the effect of variation in pitch-to-diameter ratio (P/D) is also important, in addition to side width-to-diameter (S/D) and edge-to-diameter (E/D) ratios. A two-dimensional finite element model is developed using ANSYS software. Tsai–Wu failure criteria associated with material property degradation is used in the analysis to predict failure load and to differentiate failure modes. The results from experimental and finite element analysis showed that it is very important to consider the affect of E/D, S/D and P/D ratios in designing multi-pin joints. [Copyright &y& Elsevier]

Abstract: This paper presents the design, analysis, and fabrication of a reusable pultruded GFRP (glass fiber-reinforced-polymer) deck panel that can be used to furnish the roadway surface of temporary structures. A five-cell GFRP deck panel is proposed here to overcome the steel corrosion and fatigue problems of conventional steel deck panels. A finite element analysis was carried out to design the cross-section and to evaluate the structural performance of the proposed GFRP deck panel within the design limits. The GFRP deck panels were successfully fabricated in accordance with the proposed cross-sectional profile and GFRP stacking patterns and have been installed in a construction site. The findings and recommendations for future study are also summarised. [Copyright &y& Elsevier]

Abstract: This paper presents results of the feasibility of carbon/epoxy composites (CFRP) as a future helicopter flexbeam material. Torsional behaviors of unidirectional CFRP and glass/epoxy composites (GFRP) with the same resin matrix were investigated. The initial torsional rigidity of CFRP was almost identical to that of GFRP. The torsional rigidities calculated using finite element analyses (FEA) agreed with the experimental results: the torsional rigidities are governed mainly by the material’s shear stiffness. Torsion fatigue tests were also conducted by controlling the angle of twist of the sinusoidal wave under a constant tensile axial load. No catastrophic failure occurred with either GFRP or CFRP, although decreased amplitudes of torque and torsional rigidities were observed according to the number of cycles. Results of X-ray CT inspections and numerical calculation by FEA revealed that degradation of a torsional rigidity is caused mainly by splitting crack propagation along the fiber direction. The torsion fatigue life of CFRP was superior to that of GFRP. Consequently, results confirmed that CFRP exhibits excellent properties as a torsional element of a helicopter flexbeam in terms of torsional rigidity and tension–torsion fatigue behaviors. [Copyright &y& Elsevier]

Abstract: There are various ways to connect a GFRP deck and girder which have been adopted as systems worldwide such as connection systems that use shear connectors and mechanical connection systems that use bolts or clamps, and recently there has been a study on a system to connect GFRP deck and steel girder using a bonding agent. In this study, an attempt was made to review and analyze the composite level of GFRP decking and a girder bolt connection system using the already proposed GFRP deck shape. In addition, an attempt was made to estimate the decreased rate of the composite level at various bolt connection intervals using the calculated strain and deflection, and also the analytical values of the composite level were compared with prior test results. [Copyright &y& Elsevier]

Glass fiber-reinforced composites have been used as a secondary barrier structure in LNG cargo containment systems (CCS) for their excellent strength and corrosion resistance. However, during LNG transport, the tanks experience periodic thermal and bending stress because of the cryogenic environment. These conditions degrade the mechanical properties of the composites in the CCS. In this study, finite element analysis was conducted using the mechanical properties of each composite. A quasi-static tensile test was carried out, and the coefficients of thermal expansion were used to obtain the mechanical properties. To verify the reliability of the numerical analysis, modeled structural unit specimens were manufactured, and 3-axis strain gauges were attached to measure thermal strain under cryogenic conditions. Validation of the strain between experiments and computation was performed, and the finite element analysis was conducted based on the observed mechanical properties and their reliability. [ABSTRACT FROM AUTHOR]

The fiber-reinforced composite (FRP) shaft need to consider vibration performance of the transmission system to improve work efficiency, comfort, service life and safety. The fiber materials and tubes containing metal connectors are important parts of the FRP shaft so that the study on the vibration performance of these two key components is of great significance for an in-depth understanding of the vibration performance of shafts. The finite element analysis (FEA), pulse vibration excitation technique (PVET) and formula computing were used to study the effect of the vibration characteristics of shafts. This study revealed that increasing the modulus of the fiber is one of the effective methods to increase the natural frequency of the FRP tube and the damping ratio of the carbon FRP tubes were slightly smaller compared with basalt and glass fiber. The FEA of FRP tube results were not distinct from the measured and calculated results so that these FEA results were relatively reliable. The damping of the tube with metal flanges at both ends were weaken compared the FRP tube. This work will be of great significance to the optimization design of the vibration performance of FRP shafts. [ABSTRACT FROM AUTHOR]

Pultruded Fiber-Reinforced Polymers (FRP) are innovative structural elements that are experiencing a steady increase in use for different structural applications. Due to their appealing properties that set them apart from traditional construction materials, such as magnetic transparency and excellent strength-to-weight ratio, numerous experimental and numerical studies have been performed in the last decades to assess their performance as structural components. The description of the micro- and macro-scale mechanical features of FRP elements requires multiple levels of information to be accurately characterized to predict their strength, and as a result, researchers have developed computational models with varying levels of complexity to parametrize their response and investigate design parameters through numerical simulations. This paper presents a critical review of the current state-of-the-art in numerical modeling of structural fiber-reinforced polymeric elements for the prediction of their mechanical behavior under serviceability and failure limit state conditions, with particular attention devoted to pultruded Glass Fiber Reinforced Polymers (GFRP), and their use as load-bearing structural elements. The most commonly adopted numerical methods for the solution of this set of problems range from classical Finite Element Method (FEM) approaches to eXtended Finite Element Method (XFEM), Virtual Crack Closure Technique (VCCT), Cohesive Zone Modeling (CZM), Multiscale Reduced Order Modeling (ROM), as well as Random Lattice Modeling (RLM) techniques recently developed by the co-authors. Each one of these methods has its own distinctive features and brings specific challenges and capabilities that will be presented and discussed in detail in the manuscript. This paper, therefore, aims at illustrating the reliability of existing numerical models for the simulation of FRP structural elements and draw conclusions and recommendations for future research, discussing 160 references from the available literature. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the structural response of hybrid composite/metal bolted joints using an experimental investigation and finite element analysis. The primary motivation for this work is to provide alternatives to conventional hull construction techniques using modular hybrid construction methods. The main objective is to implement a watertight hybrid connection concept that provides access using removable panels on a ship hull. The hybrid joint developed is used to connect fiberglass reinforced composite panels to a metal sub-structure. An experimental study was conducted to quantify the performance of various hybrid joints with various geometries, loaded in flexure. The test results show that, for resisting bending loads, joints with metal cap plates can be made stronger and rotationally stiffer than standard bolted joints, while also mitigating opening of the joint, thereby improving the ability to seal the connection for watertight integrity. Local shell and detailed solid finite element analyses of the connections are presented. Simplified shell finite element models were developed for implementation into global models of the structure and good correlation with the test results was observed with respect to connection stiffness. Nonlinear response of the connection was predicted using detailed plane strain contact models to capture the three-dimensional effects. The results of this study were used to select a connection geometry, which was subsequently incorporated into the hydrostatic testing of a full-scale four-panel assembly. [Copyright &y& Elsevier]

Abstract: A composite bridge deck system assembled from a modular profile with double-rectangular cells has been developed for light-weight vehicles. This paper presents the experimental characterization of the flexural performance of pultruded GFRP decks under static loading. Several tests were carried on single module and adhesively bonded modules. The specimen details such as dimensions, material properties and fiber architecture are given. Numerical verification is performed by using the general purpose finite element package ABAQUS. Experimental set-up, instrumentation, testing procedure, failure modes and the results of these experiments have been discussed in detail. [Copyright &y& Elsevier]

Abstract: The influence of cylindrical defects on the tensile strength of glass fiber/vinyl-ester composite pipes was evaluated. The properties were determined using the ring test. The radius and depth of the defects were varied, and the significance of their effect on the results obtained was verified using the analysis of variance between groups (ANOVA). The analysis showed that the depth of the defects has a stronger influence than the radius, and that the interaction of these parameters is not relevant. The fractographic analysis showed delamination and clusters of pulled-out fibers as the main fracture characteristics, and that the fracture initiates at the internal surface of the rings. The distribution of the circumferential stress, calculated through finite element analysis, validates the fractographic analysis. The finite element analysis showed a significant stress and strain increase at the internal surface of the rings, close to the edge of the internal steel disks of the grips of the fixture equipment. The variation of both stress and strain is due to the presence of bending at this position. [Copyright &y& Elsevier]

Abstract: This paper presents the design evolution process of a composite leaf spring for freight rail applications. Three designs of eye-end attachment for composite leaf springs are described. The material used is glass fibre reinforced polyester. Static testing and finite element analysis have been carried out to obtain the characteristics of the spring. Load–deflection curves and strain measurement as a function of load for the three designs tested have been plotted for comparison with FEA predicted values. The main concern associated with the first design is the delamination failure at the interface of the fibres that have passed around the eye and the spring body, even though the design can withstand 150kN static proof load and one million cycles fatigue load. FEA results confirmed that there is a high interlaminar shear stress concentration in that region. The second design feature is an additional transverse bandage around the region prone to delamination. Delamination was contained but not completely prevented. The third design overcomes the problem by ending the fibres at the end of the eye section. [Copyright &y& Elsevier]

Abstract: This work presents a three-dimensional flow visualization of the injection process for a glass fiber reinforced plastic (GFRP) beam-column connection also known as a GFRP cuff. Previous work on flow visualization is extended by highlighting the stage-wise process of the injection and the dependence on three-dimensional qualities. The work also provides finite element model adaptations suggested by three physical flow experiments performed in a GFRP cuff mold. The first experiment revealed the nature of the injection in the actual GFRP cuff mold; the second explored the effects of varying the size of void spaces and cutting channels in the fibers; the last experiment shows that small deflections of the mold allow the resin to flow freely to channels which distribute resin into the fibers. The final section of this paper provides the results of a finite element model of the injection process. The results reveal that including the adaptations suggested by the experiments greatly increases the accuracy of the numerical simulation. [Copyright &y& Elsevier]

Abstract: This paper outlines a study on the fracture behaviour of a glass fibre reinforced polymer T-joint commonly used in composite marine vessels. Finite element analysis was conducted using the virtual crack closure technique (VCCT) to investigate the fracture behaviour of the structure. The structure analysed contained initial disbond in various locations with various sizes under a straight pull-off load. The strain energy release rate (SERR) at the disbond tips were used to predict the failure loads and crack growth mechanism of the structure. The experimental results validated the VCCT as a tool for assessing the fracture behaviour and damage criticality of such structures. It was also discovered that skewed loading affected the SERR at the crack tips which altered the fracture behaviour of such structures, therefore sensitivity analysis is recommended to enhance the prediction accuracy. [Copyright &y& Elsevier]

Abstract: This paper presents the finite element analysis (FEA) and simple methods of analysis of an innovative hybrid FRP-concrete bridge superstructure system. The hybrid superstructure was designed, and its one-fifth scale model was tested under quasi-static loading. Three trapezoidal glass fiber reinforced polymer (GFRP) box sections were bonded together to make up a one-lane superstructure, and a layer of concrete was placed in the compression zone of those sections. This new design was proposed in order to make the best of each constituent material, and to increase stiffness of GFRP composite structures. A detailed finite element model was created to predict the static flexural behavior of the bridge superstructure under live loads. Results from the FEA have shown that a linear FEA can accurately predict the static behavior of this new bridge superstructure under design live loads. Moreover, nonlinear constitutive models of concrete and GFRP were incorporated in the FEA code to examine the bridge behavior beyond its elastic range. And, simple analytical methods including the beam analysis and the orthotropic plate analysis were also presented in this paper, and their accuracy was validated. [Copyright &y& Elsevier]

Stitching advanced graphite/epoxy composites in the through-thickness direction improves the interlaminar fracture toughness. The Mode I energy release rate of a graphite/epoxy composite, with and without stitching fibers, was experimentally determined using double cantilever beam specimens. The fibers employed in this research are not densely stitched. Three different fibers, namely Para-Aramid fiber, Glass fiber, and PAN-based carbon tow fiber, were used to study the effect of fiber stiffness on the strain energy release rate. The 3-D finite element model combined with the crack closure integral method is employed to obtain the GI and GIC values. Experimental results were compared with finite element analytical calculations and good agreement was found. The first mode of strain energy release rate of stitched specimens is about three to six times that of unstitched specimens depending on the stiffness of the stitched fibers. [Copyright &y& Elsevier]

The present work studies the mechanical behaviour of single-lap joints of PP reinforced with glass fibres. Failure loads were obtained experimentally for different superposition lengths (15, 30, 45 and 60 mm). A 2D numerical analysis was developed using the finite element method, and assuming a plane strain state, an orthotropic behaviour for the laminates and an elastic–plastic behaviour for the adhesive. It was found that the positions where σyy and τxy stresses have their maximum values, which are near the extremities of the joint and close to the interface adhesive/adherends, move inside the joint with load increasing. An equivalent stress was defined from σyy and τxy and was obtained for the failure loads obtained experimentally. This quantity varies 9.7% with superposition length, which can be considered reasonable therefore can be used as a damage criterion for single-lap joints. [Copyright &y& Elsevier]

Depending on fiber size and volume fraction, polymer matrix type, processing temperature, injection speed, etc., short fiber reinforced composites produced by injection molding may exhibit complex fiber concentration, orientation and length distributions at different locations, causing large variations in their mechanical properties. In this work, a representative volume element (RVE) scheme is developed to describe the elastic properties of short glass fiber reinforced PA6,6 composites produced by injection molding. In the RVE formulation, fiber length is assumed to follow a two-parameter Weibull distribution, and a new concept, namely preferential angle, is introduced to account for the preferential alignment of fibers at different locations of injection molded composites. A random sequential insertion algorithm is developed to implement the fiber length distribution and fiber preferential alignment, and finite element method (FEM) is employed to analyze the relations of the elastic properties of RVE with three parameters, that is, the mean length, volume fraction and preferential angle of the fibers. Based on the FEM results, quantitative formulas for these relations are obtained. It is found that the variations in the mean length, volume fraction, and preferential angle of the fibers can cause large variations in elastic moduli and elastic anisotropy of the RVE. [ABSTRACT FROM AUTHOR]