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Highlights In this paper, the mechanical properties, damage modes, and bolt load distribution of the bonded‐bolted hybrid three‐bolt joint were investigated by a combination of experiments and numerical simulations. Acoustic emission (AE) was used to monitor the tensile process of the connection in real time, and the K‐means clustering algorithm was used to realize the cluster analysis of the damage modes. A numerical simulation model of the tensile process of the joint was established using ABAQUS simulation software. The progressive damage evolution of composite laminates, and adhesive layer was characterized by using the VUMAT subroutine, the B‐K failure criterion, and cohesive element with zero thickness, respectively. The results show that four main damage modes occur in composite laminates during tension: matrix cracking, delamination, fiber pull‐out, and fiber breakage, with corresponding peak frequency ranges of (0–80 kHz), (80–210 kHz), (210–330 kHz), and (330–375 kHz), respectively. The adhesive layer between the laminates mainly exhibits peeling failure because of the secondary bending effect. In the load‐bearing process, the adhesive layer was loaded first and failed, and the bolt loading was delayed. Meanwhile, the results of bolt load distribution showed that the bolts and the adhesive layer at both ends carried greater loads. Damage modes and damage evolution of the bonded‐bolted hybrid joint in tension were analyzed by combining acoustic emission technology and numerical simulation. The simulation of delamination damage in composite laminates was carried out by inserting zero‐thickness cohesive elements into the laminates, and the delamination damage between the carbon fiber layup and the adjacent glass fiber layup was analyzed. The effect of the inclusion of the adhesive layer on the mechanical properties of the joint and the distribution of the bolt load was analyzed. [ABSTRACT FROM AUTHOR]

Elium® Acrylic/Glass Fiber thermoplastic laminate composites are liable to develop irreversible local defects under quasi‐static loading. To reinforce the damaged material, repair is a cost‐effective mechanical alternative. The present study investigates the tensile behavior of an Elium® glass‐fiber‐based acrylic laminate composite panel, repaired by vacuum bonding with Elium® repair resin and double overlap of external patches (DP). The results obtained for all repaired laminate composites E190/GF_D(10, 20, 30)R with diameters 10, 20, and 30 mm showed an improvement in the mechanical properties of the repaired panels, compared with the drilled and pristine samples. Average load recovery rates were significant for E190/GF_D10R (7.9%, 3.55%, 13%) E190/GF_D20R (23%, 18%, 3.32%), E190/GF_D30R (7.2%, 9.36%, 32.37%) at strain rates of 0.001, 0.01, and 0.05 s−1 respectively. Finite element (FE) models for the virgin, drilled, and repaired composite, performed by coupling the Hashin criteria with the cohesive zone model (CZM), provided a relevant prediction of intra‐ and interlaminar failures of these woven laminated composites. Highlights: The effect of vacuum bonding repair with Elium E351 EOT resin was studied.Symmetrical repair of acrylic laminate drilled by fiberglass patches.Tensile strength of the repaired laminates was investigated.Intra‐ and interlaminar damage was predicted by finite elements modeling. [ABSTRACT FROM AUTHOR]

The present study investigates the flexural failure properties of a hybrid laminate beam subjected to three-point bending. A symmetrically laminated hybrid beam is constructed using high-strain and inexpensive glass fibre on the top layers and low-strain and expensive carbon fiber on the middle layers. Classical lamination plate theory is used to find the stress and strain distribution that occurs due to the bending moment on the compressive side. The theoretical failure limits of the laminated hybrid beam are analyzed considering the targeted span-to-depth ratios, volume fractions of the fibers and hybrid ratios using the Tsai-Wu failure criterion and Matlab codes. Using the graph of failure index versus hybrid ratios, the minimum thickness of carbon fiber needed for the delay of failure and cost efficiency of the laminated hybrid beam is identified by applying the linear interpolation method. The numerical results indicate that the failure index increases with the increasing loading span and decreases when the volume fraction of fiber increases. In particular, the placement of glass fiber on the top layer of the laminated hybrid beam might have contributed to obtaining higher strains and curvatures before the catastrophic failure properties of carbon fiber. The flexural stiffness of the laminates is found to increase when the hybrid ratio increases. Overall, it is noted that the theoretical analysis is one method that is less time-consuming and cost-effective than other alternative approaches, such as finite element methods and experimental tests to estimate the minimum thickness of high-stiffness and the expensive material needed to maintain the strength and stiffness of the hybrid composite structures over long periods. [ABSTRACT FROM AUTHOR]

In the present work, four layered Palmyra-Palm-Leaf-Stalk (PPLSF)/Glass hybrid composites laminates with six distinct stacking orders were made by following hand lay-up method. Different experiments were carried out to determine the tensile, flexural, impact and hardness of the laminates as per ASTM standard. The results reveal that the addition of glass fiber to PPLSF significantly enhanced the mechanical performance of the laminates. On successive replacement of PPLSF by glass fiber, an enhancement of properties such as 291.39% for tensile strength, 72.08% for flexural strength, 75.82% for impact strength, and 78.44% for micro-hardness was observed. Again, it is also noticed that the stacking order plays an important role in influencing the properties while comparing experimental finding of laminates with equal weight percentages PPLSF and glass fiber. Further to perform Finite Element Analysis (FEA), a 3D CAD model of tensile and flexural specimen was created in space-claim modeler of ANSYS R19.0 and subsequently imported to generate numerical predicted values. While comparing the numerical and experimental results, there was very good agreement among the results was found. Scanning Electron Microscope (SEM) was used for fractography analysis of the tested samples to examine the different mode of failures. [ABSTRACT FROM AUTHOR]

Orthotropic rectangular plates, featuring central cutouts and subjected to in-plane loading, are extensively employed across various engineering fields, including mechanical, automobile, aerospace, and marine. The introduction of a cutout inevitably leads to stress concentration within the plate. Incorporating carbon nanotubes (CNTs) into the polymer matrix composite has been noted to induce significant heterogeneity in stress fields. Functioning as bridges between the fibers and the matrix, CNTs can effectively mitigate stress concentration and enhance the damage tolerance of the composite. However, accurately determining stress concentration in CNT-based composites requires comprehensive understanding of the geometric discontinuity edge and well-defined evaluation techniques. Among these, the finite element method emerges as a straightforward yet precise approach for studying stress concentration around geometric discontinuities. The present work harnesses the finite element method to investigate stress concentration in CNT-based multiscale composite plates (Glass Fiber/CNT/Epoxy) with central cutouts under static in-plane loading. To validate the model, the derived results are compared with analytical data from conventional composite materials. Moreover, the impact of cutout size on stress concentration is examined for three distinct configurations: plates with a central circular cutout, plates with an elliptical central cutout (major axis in the longitudinal direction), and plates with an elliptical central cutout (major axis in the transverse direction). Preliminary findings suggest a correlation between increased cutout size and augmented percentage reduction in stress concentration. Notably, the maximum percentage reduction in stress concentration is observed in the case of plates hosting an elliptical cutout at the center with the major axis aligned in the transverse direction. [ABSTRACT FROM AUTHOR]

In this work, a fifth-order shear deformation theory is computed using the layer-wise model to determine non-dimensional fundamental frequencies. The theoretical, experimental, and finite element analysis (FEA) results are compared for a standard isotropic material. Hand layup technique is used to prepare glass fiber reinforced polymer composites (GFRPC) with selective layers filled with graphene and flyash. This technique helps to reduce the fabrication cost as the whole structure is not to be strengthened by the fillers. Six classes of the laminated-composite-plate (LCP) such as outer layer graphenated LCP (O-LCP), core layer graphenated LCP(C-LCP), functionally graded LCP (FG-LCP), LCPs only rich in graphene (G-LCP), LCPs only rich in flyash (F-LCP) along with a neat epoxy-glass LCP (N-LCP) are fabricated. A low-cost frequency measurement module is set-up to measure the fundamental frequency (FF) of the fabricated LCPs. FFs, amplitudes, non-dimensional stress parameters, and central deflection of the LCPs under harmonic load, the buckling strength, and displacements of the LCPs are calculated. It is found that harmonically excited C-LCP and O-LCP have better stability accompanied by lower deflections, followed by G-LCP as compared to other kinds of LCPs. Also, the addition of graphene increases the buckling strength of LCPs, which portrays that the local layer filling is a useful technique to enhance the strength of the LCPs. [ABSTRACT FROM AUTHOR]

Modeling and Methods: This work is devoted to the numerical dynamic bending characterization of delaminated multi-walled carbon nanotubes (MWCNTs) reinforced epoxy/glass fiber-based hybrid composite plate based on finite element method with displacement fields derived from classical laminated plate theory (CLPT). Verification: The accuracy and performance of the developed method were confirmed by a validation study with reference solutions available in the literature. Results: Various parametric studies were carried out to study the influence of MWCNTs content, delamination location, delamination interface, ply orientation, and end condition on the dynamic bending characteristics of the intact and delaminated hybrid laminated composite plate. Conclusion: The weight fraction of MWCNTs, delamination location, and clamping condition significantly influences the natural frequency. The natural frequencies also depended upon the ply configuration and delamination interface irrespective of the MWCNT loadings. However, anomalous trends were observed as far as the influence of end conditions is concerned. [ABSTRACT FROM AUTHOR]

Implementation of natural fibers like kenaf in composite laminates has been the focus of many researchers. The considerable price of Low-Velocity Impact (LVI) testing, as well as the time constraints imposed by the short duration of this experiment, and prior reports of the obedience of Quasi-Static Indentation (QSI) test findings to LVI test results, have encouraged researchers to employ QSI instead of LVI. This work compares the mechanical characteristics of composite laminates consisting of chopped glass and kenaf fibers as a core and investigates the effect of hybridizing the mentioned chopped fibers as the core of a laminate. Three types of laminates with different core materials were fabricated to do this research. The results showed that among the laminates with the same weight, kenaf core laminate has the highest resistance against indentation and has the best performance in terms of absorbed energy, peak load, and damaged region. Using chopped kenaf fiber instead of chopped glass fiber can increase the absorbed energy and the peak load by 36% and 17%, respectively. Also, hybridizing the mentioned chopped fibers has not fully maximized the properties of the composite laminate during the QSI test. Finally, finite element modelling of the laminates was performed, and the numerical and experimental results were pretty aligned. [ABSTRACT FROM AUTHOR]

In the present work, three different woven composite laminates were fabricated using the hand lay-up method. The woven reinforcement fibres were carbon fibres (CFRP), glass fibres (GFRP-W) and (GFRP-R) in combination with epoxy resin. Then, the central notch specimen tensile test (CNT) was used to measure the fracture toughness and the corresponding surface release energy ( G I C ). Then, the data were compared with the essential work of fracture (we) values based on the stored energy of the body to obtain a new standard fracture toughness test for composite laminates using relatively simple techniques. In addition to an extended finite element model, XFEM was implemented over a central notch specimen geometry to obtain a satisfactory validation of the essential work of fracture concepts. Therefore, the average values of ( G I C ) were measured with CNT specimens 25.15 kJ/m2, 32.5 kJ/m2 and 20.22 kJ/m2 for CFRP, GFRP-W and GFRP-R, respectively. The data are very close as the percentage error for the surface release energy measured by the two methods was 0.83, 4.6 and 5.16 for carbon, glass and random fibre composite laminates, respectively. The data for the fracture toughness of XFEM are also very close. The percentage error is 4.6, 5.25 and 2.95 for carbon, glass and random fibre composite laminates, respectively. Therefore, the fundamental work of the fracture concept is highly recommended as a fracture toughness test for composite laminates or quasi-brittle Material. [ABSTRACT FROM AUTHOR]

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The short beam shear performance of GLARE 3A-3/2 laminates with adhesive layers was investigated by combining the short beam test and the digital image correlation technique. The failure behavior was further analyzed based on finite element simulation and micro failure morphology. The results show an 8% and 58% difference in the short beam strength and bending displacement at failure of laminates along two orthogonal directions; The damage behavior of laminates is determined by the bottom unidirectional glass fiber reinforced plastic (GFRP) layers. The two typical failure modes are matrix and fiber fracture in the GFRP layer caused by local bending deformation, and interlaminar delamination between GFRP layers; The distribution of surface strain ε y indicates the damage initiation and evolution process. The simulation result of the finite element model established in ABAQUS/Explicit shows consistency with digital image correlation analysis, which provides an effective method to predict the damage behavior of specimens with different ply structures. [ABSTRACT FROM AUTHOR]

The failure of laminated composites under out-of-plane loadings is experimentally and numerically investigated. For flexure failure prediction, a modified failure criterion is proposed. A progressive failure algorithm is developed for numerical analyses. In experiments, quasi–isotropic and cross-ply laminated composites are fabricated by using unidirectional carbon fiber and glass fabric prepregs. Three-point bending test is performed and the accuracy of the failure algorithm is verified with experimental results. In addition, the flexure failure behaviors are compared with those of a commercial finite element analysis program using the other failure criteria such as maximum strain, maximum stress, and Tasi–Wu. [ABSTRACT FROM AUTHOR]

Through several decades of development, engineers have made the GLAss fiber REinforced aluminum material fit for aviation structures, e.g., the fuselage of Airbus A380. A request like 'GLARE + impact' in a web search engine gives hundreds if not thousands of scientific articles address the high impact resistance of GLAss fiber REinforced aluminum. GLAss fiber REinforced aluminum can be a suitable material for shielding systems to protect manned and unmanned spacecraft against micrometeoroids and orbital debris. However, it is hard to comprehend a rational reason why a thorough search in the relevant literatures yielded only a couple of articles focused on the ballistic impact response of GLAss fiber REinforced aluminum. Handful of studies have interrogated the damage of GLAss fiber REinforced aluminum using analytical, numerical and experimental methods. No physical model, yet has been proposed and validated to capture the damage of GLAss fiber REinforced aluminum upon collision with micrometeoroids. This study, therefore, introduced a new numerical model based on the smoothed particle hydrodynamics and the finite element method. The model was able to predict the exorbitant strain-rate of GLAss fiber REinforced aluminum. Besides, the model could approximate the cataclysmic amount of energy dissipated in the shockwave-induced collapse of GLAss fiber REinforced aluminum. The model assumed that the behavior of the S2-glass/FM94-epoxy composite material was orthotropic elastic prior to the onset of damage. After the damage initiation, the energy-based orthotropic softening governed the damage accumulation in the composite material. Looking at the outputs of the model, an impact of a 2 mm 2024-T3 aluminum sphere on a GLAss fiber REinforced aluminum 5–6/5–0.4 plate led to petals in the front aluminum layer, spallation of the rear aluminum layer and buckling of the inner aluminum layers. By contrast, the S2-glass/FM94-epoxy composite laminates conserved the imparted energy through membrane stretching before had been pierced. A test campaign, with the aid of a two-stage light-gas gun facility, was pursued to assess the model accuracy. It was found that the model predicted many of the experimental observations with a high degree of fidelity. • The response of GLAss fiber REinforced aluminum to hypervelocity impact was analyzed. • A shockwave of the high frequency band crushed the impact site. • The pressure of shockwave attenuated away from the impact site due to wave breaking at the GLARE interfaces. • GF/EP composite laminates stored substantial internal energy through elastic membrane deformation. • The impact at 9 km/s dislodged Al-spalls and GF/EP-splinters in the downrange debris cloud. [ABSTRACT FROM AUTHOR]

A Finite Element model of the thermoelastic effect in orthotropic composite laminates subject to cyclic loading is developed. A meso-scale approach is employed to model the thermoelastic effect at the lamina level and the through-thickness heat transfer. The model proved itself capable of modelling the dependency of the thermoelastic response on the loading frequency, presence of a superficial resin-rich layer, material system, and layup. Results show that a steady state response is reached almost immediately, after only a few loading cycles, and that in some cases, even for very high loading frequencies, adiabatic conditions are never fully onset. Numerical predictions also confirm that the presence of a superficial resin-rich layer strongly affects the through-the-thickness heat transfer and the measured thermoelastic signal. [Display omitted] [ABSTRACT FROM AUTHOR]

Ply wrinkles are commonly induced during thermal–mechanical manufacturing process of laminated composite structures or components. Fibre misalignment due to ply wrinkles compromises the structural integrity of a composite structure. The damage criticality can be assessed numerically based on non-destructive testing results. Geometric modelling is usually required and it is time-consuming if complex wrinkles have to be incorporated into the finite element model. This study presents an automated image-based three-dimensional geometric reconstruction method for thick laminates with complex ply wrinkles. The geometry of a thick laminate is reconstructed based on the limited inspection images from the sides of laminates. The two-dimensional geometric reconstruction of the detected wrinkled plies is done using a multiple Gaussian functions model or linear interpolation, while the intermediate plies are defined by distance-based interpolation. Based on the reconstructed two-dimensional geometries, the three-dimensional ply wrinkles are modelled via an inverse distance weighting interpolation method. To verify the proposed method, a thick glass fibre laminate with artificially induced wrinkles is manufactured and the cross-sectional geometries of the reconstructed model are compared well with and the realistic inspection data. Progressive failure analysis of a two-dimensional and a three-dimensional reconstructed model are compared in terms of damage progression and load versus nominal strain response to highlight the relevance of modelling three-dimensional wrinkles to obtain more accurate and efficient damage criticality assessments. • Automated geometric reconstruction and FE meshing of 3D ply wrinkles. • We simply use a cell phone to take pictures for the model reconstruction. • The reconstructed model showed agreement with the realistic wrinkle geometry. • Modelling realistic 3D wrinkles can be important. [Display omitted] [ABSTRACT FROM AUTHOR]

This study focuses on the effect of metal layer distribution in glass fibre reinforced aluminium laminates (GLARE) subjected to low velocity impact. Four GLARE variants specimens were considered in which the metal layers of different thicknesses were placed at various positions in the layup while keeping the same total metal layer thickness. Experiments and Finite element (FE) analysis were performed to understand the behaviour of the GLARE specimens. A user written material subroutine VUMAT which incorporates Hashin failure criteria along with Puck's action plane concept were used to predict the response of the composite layers. The damage was evolved for each failure mode using the exponential damage evolution law. Interface delamination between the layers was initiated by cohesive surface behaviour which includes the friction effect between the plies. It was found that placement of thinner metal layer on top of the laminate and its distribution inside the layup lowers the impact resistance of GLARE. Moreover, the patterns of delamination are also affected by the placement of metal layer within the laminates. It was further shown that the propagation direction of delamination is governed by the fibre direction of lower ply of the interface. [ABSTRACT FROM AUTHOR]

In this study, the formability of the FML (fiber metal laminate) sheets has been investigated by experimental and numerical methods. The sheets consist of an aluminum skin and a glass fiber reinforced core. Uniaxial tensile and stretch forming tests were performed to extract the forming limit diagram (FLD), experimentally. M-K (Marciniak-Kuczynski) method was implemented to extracting the FLD of the FMLs, numerically. The effect of skin and core thicknesses on formability was studied in variable and constant total thickness by numerical method. Finally, it has been cleared that the numerical model predicts the necking strains with less than 9% error. Also, it has been concluded that with doubling of core thickness in constant and variable total thickness, the average formability improves 15 and 23%, respectively, and with tripling core thickness, these values reach to 26 and 53%. In addition, with twofold increase of skin thickness in constant core thickness, the average formability enhances up to 76%. [ABSTRACT FROM AUTHOR]

This paper aims to study dynamic progressive failure properties of glass fiber composite/aluminium hybrid laminates under low-velocity impact. Intralaminar damage models using Puck failure criteria and strain-based damage evolution laws for composite layers are implemented by developing finite element codes using ABAQUS-VUMAT (user dynamic material subroutine), the interface delamination is simulated by bilinear cohesive model in ABAQUS and the mechanical properties of aluminium layers are described using the Johnson-Cook model. Effects of different layer thickness and impact energy on the impact force-time/displacement curves of glass fiber composite/aluminium laminates under low-velocity impact are discussed. Besides, damage evolution behaviors of matrix and delamination interface are explored. Finally, energy dissipation mechanisms due to intralaminar dynamic progressive failure, interlaminar delamination of composite layers and plastic deformation of aluminium layers are studied. Relatively good agreement is obtained between experimental and numerical results. [ABSTRACT FROM AUTHOR]

Glass fibre-reinforced plastic (GFRP) composite laminates are used in many industries due to their excellent mechanical and thermal properties. However, these materials are prone to the initiation and propagation of delamination crack growth between different plies forming the laminate. The crack propagation may ultimately result in the failure of GFRP laminates as structural parts. In this research, a comprehensive mathematical model is presented to study the delamination crack growth in GFRP composite laminates under fatigue loading. A classical static damage model proposed by Allix and Ladevèze is modified as a fatigue damage model. Subsequently, the model is implemented in commercial finite element software via UMAT subroutine. The results obtained by the finite element simulations verify the experimental findings of Kenane and Benzeggagh for the fatigue crack growth in GFRP composite laminates. [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]

The literature shows that variable amplitude loading can be much more severe than constant amplitude loading in a fatigue damage context. However, the underlying physical explanations for this are still unknown. Therefore, this paper investigates if the local energy release rate at each intralaminar crack tip in a tension/tension fatigue loaded multidirectional laminate can be used to determine the crack growth rate of these cracks subjected to variable amplitude loading. The local energy release rate is investigated through a developed finite element model in which any number of cracks can be included to account for their interaction. The position of the cracks is determined based on previous experimental work. The experimental results from the previous work are compared to the numerical results in this work. At similar crack density levels the energy release rates increase in the variable amplitude tests compared to constant amplitude tests, but not enough to significantly impact the crack growth rate. It is concluded that less than 5% of the increased crack density rate and crack growth rate caused by variable amplitude block loading is due to increases in local energy release rate. The primary reason is more likely found on a microstructural level. [ABSTRACT FROM AUTHOR]

• Puck's interactive failure criterion applied to non-hybrid laminates. • Finite element analysis originating from Representative Volume Element (RVE) stage. • Damage Initiation Criteria and Damage Evolution law integrated into the model. • Non-hybrid laminates comprising carbon fiber, aramid fiber, Ultra High Molecular Weight Polyethylene (UHMWPE) fabrics investigated. Material designers have extensively analyzed, utilizing failure theories, the dependability and service response of composite materials for their intended uses. To increase the precision and accuracy of performance prediction, failure theories have undergone numerous revisions. The current study uses the finite element method to predict the tensile response while also using Puck's failure criterion and the damage evolution law to composite laminates. Five non-hybrid sequences made of paperboard, ultra-high molecular weight polyethylene (UHMWPE), glass fibre, aramid fibre, and carbon fibre have been put through experimental investigation of tensile and three-point bending. The numerical analysis has been carried out using the Material Designer, ACP® and Structural Analysis modules of ANSYS® finite element software. The experimental results have been compared with the numerical results, to arrive at the set of empirical constants for the different materials. [ABSTRACT FROM AUTHOR]

• Underwater explosions can cause large deformations on naval composite structures. • Historically transient effects on fiberglass are predicted by quasi-static methods. • A dedicated shock test campaign is realized to characterize laminates dynamically. • A dynamic finite element model is validated to predict shock response in tests. • Experimental+numerical analyses validate modeling strategies for ships shock design. Non-contact underwater explosions (UNDEX) can cause extremely large deformations on naval composite structures related to heavily nonlinear phenomena. For this reason, for military purposes, used materials must have excellent shock resistance properties. Historically, the underwater shock transient effects on fiberglass laminates are predicted using quasi-static approaches. In this paper, the composite materials are characterized by experimental modal analysis as well as by a comprehensive series of shock tests, whose results are compared with numerical models. Namely, the MIL S 901 D Medium Weight Shock Machine (MWSM) was used to perform dedicated shock tests, in which composite specimens are supported on a special constraining structure designed to create large deflections and providing reproducible results. A dynamic implicit finite element model has been set, validated by modal analysis at first, and then applied to simulate the MWSM test behavior and to predict the structural response of different E-Glass polyester resin laminates. In the end, the complete comparison of numerical results and experimental data is reviewed to validate the modeling strategies for shock design of navy ships. [ABSTRACT FROM AUTHOR]

In this work, the natural frequencies and mode shapes of a number of cantilever glass fiber reinforced polymer composites (GFRPCs) and carbon fiber reinforced polymer composites (CFRPCs) are numerically obtained using the commercial finite element analysis software (ANSYS). The laminates under study include 8 ply cantilevered plates having a plate aspect ratio of 2 and fiber volume fractions of 0.3, 0.4, 0.5, and 0.6. The finite element analysis procedure is described. The natural frequencies and mode shapes calculated using ANSYS are first validated with the results obtained from previous literature. The agreement between the two results is found to be excellent. The effect of change in the matrix material, hybridization, and laminate stacking sequence on the natural frequencies and mode shapes are also investigated. It is found that hybridization and orientation of the outermost layer has more significant influence on the natural frequencies of the laminated composite plates compared to fiber volume fraction and change in the matrix material. [ABSTRACT FROM AUTHOR]

Influence of moisture absorption/desorption on the flexural properties of Glass-fibre-reinforced polymer (GFRP) laminates was experimentally investigated under hot/wet aging environments. To characterize mechanical degradation, three-point bending tests were performed following the ASTM test standard (ASTM D790-10A). The flexural properties of dry (0% Mt/M8), moisture unsaturated (30% Mt/M8 and 50% Mt/M8) and moisture saturated (100% Mt/M8) specimens at both 20 and 40 °C test temperatures were compared. One cycle of moisture absorption-desorption process was considered in this study to investigate the mechanical degradation scale and the permanent damage of GFRP laminates induced by moisture diffusion. Experimental results confirm that the combination of moisture and temperature effects sincerely deteriorates the flexural properties of GFRP laminates, on both strength and stiffness. Furthermore, the reducing percentage of flexural strength is found much larger than that of E-modulus. Unrecoverable losses of E-modulus (15.0%) and flexural strength (16.4%) for the GFRP laminates experiencing one cycle of moisture absorption/desorption process are evident at the test temperature of 40 °C, but not for the case of 20 °C test temperature. Moreover, a coupled hygro-mechanical Finite Element (FE) model was developed to characterize the mechanical behaviors of GFRP laminates at different moisture absorption/desorption stages, and the modeling method was subsequently validated with flexural test results. [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]

In this paper, vacuum assisted resin injection technique was employed to prepare the composite laminates with different plies ways. The macro-mechanical performances of the bolted joint of the composite laminates were investigated by experimental and finite element simulation. The influence mechanism of different parameters on the joint performance and failure models of the composite laminates were analyzed. A VUMAT subroutine was developed, according to the failure criteria and corresponding stiffness degradation criteria, to describe the progressive damage process of bolted joint composite laminates through finite element analysis method. The results indicated that the failure strength of composite laminates would be improved with the increasing of tightening torque, and the strength of three-ply-way hybrid composite laminates is higher than that of two-way hybrid laminates. The comparisons between numerical simulation results and experimental results showed that the developed subroutine can effectively predict the macroscopic response of bolted joint glass–fiber reinforced composite laminates. [ABSTRACT FROM AUTHOR]

• High-speed imaging and DIC are used to track damage progression during impact test • A proposed 3D FE model allows predicting the impact behavior of laminate composites • [0/90] 3s laminates failed due to fiber breakage at high compression impacted region • [±45] 3s laminates exhibited matrix cracking and delamination caused by high tension The aim of this paper is to describe the dynamic behavior of biaxial glass fiber reinforced laminate composites under low velocity impact test through finite element modelling. Experimental investigations by impact test performed using an instrumented drop weight testing machine were conducted on three-point bending composite samples in order to assess their impact damage resistance. Moreover, the experimental setup allowed the visualization of real-time damage progression of the impacted laminate composite via high-speed camera Phantom V2512 enabling to capture 83000 frames per second. Dynamic strain fields were extracted by Digital Image Correlation (DIC) method. Based on the experimental results, a numerical study of the impacted specimens was developed as a user subroutine VUMAT integrated to ABAQUS/Explicit in order to precisely capture the progressive dynamic failure of the laminate composite under impact test. In the proposed model, the damage and failure of each ply are accounted by a Hashin 3D damage-based behavior, and a cohesive zone model is employed to capture the onset and progression of inter-laminar delamination. A good experimental-numerical correlation was obtained for peak force and failure modes. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study about the bond behaviour between glass panes and glass fibre reinforced polymer (GFRP) laminates and the structural response of glass–GFRP beams. For this purpose, tests on glass–GFRP double-lap joints and tests on glass–GFRP hybrid beams were carried out. The finite element method was used and a discrete crack approach based on non-linear fracture mechanics was adopted. The bond between glass and GFRP is modelled by means of zero thickness interface elements. The material properties that characterize the interface, namely the shear stiffness, the cohesion and the mode-II fracture energy, are evaluated with the objective of simulating the experimental results obtained from double lap shear tests on glass–GFRP bonded joints. The obtained parameters, describing the bond-slip law between glass and GFRP, are then used to model the structural response of glass beams reinforced with GFRP. The numerical model is assessed by comparing the simulated structural responses and corresponding crack patterns with the experimental counterparts. This work contributes for a better understanding of the stress transfer mechanisms between glass and GFRP and the failure mechanisms found in the above-mentioned experimental tests, as well as to clarify the interpretation of the results obtained from those tests. [ABSTRACT FROM AUTHOR]

This paper investigates the through-thickness tensile behavior of woven glass fiber reinforced polymer (GFRP) composite laminates at cryogenic temperatures. Tensile tests were carried out with cross specimens at room temperature and liquid nitrogen temperature (77 K), and the through-thickness elastic and strength properties of the woven GFRP laminates were evaluated. The failure characteristics of the woven GFRP laminates were also studied by optical and laser scanning microscopy observations. A three-dimensional finite element analysis was performed to calculate the stress distributions in the cross specimens, and the failure conditions of the specimens were examined. It is found that the cross specimen is suitable for the cryogenic through-thickness tensile characterization of laminated composite materials. In addition, the through-thickness Young's modulus of the woven GFRP composite laminates is dominated by the properties of the matrix polymer in the given temperature, while the tensile strength is characterized by both, the fiber to matrix interface energy and the cohesion energy of the matrix polymer. [ABSTRACT FROM AUTHOR]

This article deals with the static response of thin circular simply supported GLAss REinforced fiber-metal laminates subjected to lateral indentation. The indentation response is initially predicted using ANSYS software and a three-dimensional (3D) nonlinear finite element analysis with geometric and material nonlinearities. From this analysis, the load-indentation and the strain energy-indentation curves are calculated. Regression of the obtained Finite Element Method (FEM) results, that takes into account a specific load-indentation relation, and comparison with previously published analytical formulas concerning the indentation of circular clamped GLAss REinforced plates, yields analytical formulas for the prediction of the GLAss REinforced plate indentation load and strain energy as a function of the central plate deflection. The derived analytical formulas are applied for GLAss REinforced 2-2/1-0.3, GLAss REinforced 3-3/2-0.4, and GLAss REinforced 3-3/2-0.3 circular plates with various diameters subjected to lateral indentation. The analytically predicted load-indentation and strain energy-indentation curves are compared with corresponding FEM results and a very good agreement is found. [ABSTRACT FROM AUTHOR]

Nominal strength reduction in cross ply laminates of [0/90]2s is observed in tensile tests of glass fiber composite laminates having central open hole of diameters varying from 2 to 10 mm. This is well known as the size effect. The extended finite element method (XFEM) is implemented to simulate the fracture process and size effect (scale effect) in the glass fiber reinforced polymer laminates weakened by holes or notches. The analysis shows that XFEM results are in good agreement with the experimental results specifying nominal strength and in good agreement with the analytical results based on the cohesive zone model specifying crack opening displacement and the fracture process zone length [ABSTRACT FROM AUTHOR]

Off-axis oriented tunnel cracking in a laminated structure is modeled using a special 2D off-axis finite element formulation, thus replacing full 3D finite element simulations with much less demanding 2D simulations. The 2D off-axis element is formulated as a user element in the commercial finite element code ABAQUS, and the user element code is made available for the reader. The finite element formulation is used to predict the steady-state energy release rate and the mode-mixity for either one isolated crack or multiple interacting tunnel cracks in the central ply of a [ 0 / θ / 0 / − θ ] s layup. The laminate is loaded uni-axially or bi-axially, and analyses are presented for glass and carbon fiber composites for arbitrary layup angles θ. The 2D finite element model is found to give precise predictions when comparing the detailed simulations made by a full 3D finite element model. It is demonstrated that despite being a 2D method, the model rigorously provides detailed solutions for the out-of-plane deflection and strain. With a speed-up of more than four orders of magnitudes, it is thus possible to perform new, detailed, and very accurate studies of the dependency of laminate thickness as well as neighboring cracks on off-axis tunnel cracking. • New 2D off-axis special finite element formulation. • Precise prediction of the energy release rate and mode mixity for tunnel cracking. • Four orders of magnitude speedup compared with a full 3D finite element model. • Made available as a user-subroutine for the finite element code Abaqus. [ABSTRACT FROM AUTHOR]

• Characterize experimentally the LVI behaviors of CFRPP and GFRPP respectively. • Develop a progressive failure model for both net and hybrid CFRPP/GFRPP laminates. • Explore the different factors on LVI responses of hybrid composite laminates. • Design the CFRPP/GFRPP hybrid composite laminates under multiple impacts. Low-velocity impact (LVI) on continuous fiber reinforced thermoplastics (CoFRTPs) has been extensively studied with a focus on single material. Impact characteristics and optimal design of hybrid CoFRTPs have not been well addressed even though they are of considerable advantages in balancing cost and performance. This study aims to develop design optimization of bio-inspired hybrid CoFRTPs to resist multiple impact loads. In this study, the LVI behaviors of carbon fiber reinforced polypropylene (CFRPP) and glass fiber reinforced polypropylene (GFRPP) composites were first characterized experimentally, respectively. Three typical failure modes were identified in both the CFRPP and GFRPP specimens, and GFRPP exhibited better impact toughness than CFRPP. Second, a progressive failure model (PFM) was developed for finite element analysis, and numerical results in LVI damage modes and force-displacement curves agreed quite well with the corresponding experimental data. Third, parametric studies indicated that peak energy absorptions of CFRPP and GFRPP specimens respectively decreased by 20.9% and 25.5% with impact angles varying from 0° to 30°, and design of helicoidal stacking configuration can effectively enhance the LVI resistances for both the CFRPP and GFRPP specimens. Hybridization of CFRPP and GFRPP enables to improve LVI resistances and reduce the material costs. Finally, a multiobjective optimization was performed to optimize material cost and LVI resistance of helicoidal CFRPP/GFRPP hybrid composites accounting for multiple impact loads, which increased the peak energy absorption by 31.0% and reduced material cost by 33.4% compared with the baseline design. This study is anticipated to introduce an optimum configuration of hybrid composites for bearing multiple low-velocity impact loads. [Display omitted] [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of seawater on the failure mode, first failure load and bearing strength behaviour of the pinned joint of fibreglass-reinforced woven epoxy composite prepregs. The specimens were kept in seawater for 3- and 6-month periods. After each period, their mechanical properties were examined. The edge distance-to-upper hole diameter (E/D), the two hole-tohole centre diameter (K/D), the distance from the upper or the lower edge of the specimen to the centre of the hole-to-hole diameter (M/D), and the width of the specimen-to-hole diameter (W/D) ratios were selected as parameters. Moreover, the finite element models of the specimens were developed using ANSYS software, and the Tsai-Wu criterion was used to obtain the first failure load. The numerical and experimental results were compared and were found to be in good agreement for the first failure load. [ABSTRACT FROM AUTHOR]

Abstract: In this contribution, the impact dynamic response and failure modes of fibre–metal laminated panels subjected to low velocity impact were investigated and presented. The fibre–metal laminate in this paper comprised of a layer of glass fibre-reinforced plastics sandwiched between two layers of aluminium alloy. Two different types of glass fibre-reinforced plastics were used for the fabrication: unidirectional and woven. A fairly extensive experimental investigation was conducted in conjunction with a detailed finite element analysis. The experiments were conducted using a standard drop-weight test machine and the finite element analysis was carried out using a commercially available finite element software. The results of maximum contact force, contact duration and corresponding failure modes are presented, compared and discussed in this technical paper. [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: The onset and evolution of the damage in three dimensions was studied by X-ray computed micro-tomography (XCT) in a notched glass fiber/epoxy cross-ply laminate subjected to three-point bending. It was found that damage began by formation of intraply cracks in the 90° plies followed by intraply cracking the 0° plies. Fiber fracture in front of the notch tip occurred at 65% of the maximum load and finally fiber kinking and interply delamination took place under the loading point. Finite element (FE) simulations were carried out to understand crack initiation and the redistribution of stresses upon crack propagation. The crack area corresponding to each damage mechanism was quantified from the XCT images, and this information was used to determine the effective fracture resistance curve of the cross-ply laminate. [Copyright &y& Elsevier]

In the present paper 3D rate sensitive constitutive model for modeling of laminate composites is presented. The model is formulated within the framework of continuum mechanics based on the principles of irreversible thermodynamics. The matrix (polyester resin) is modeled by employing a 3D rate sensitive microplane model. For modeling of fibers (glass) a uni-axial constitutive law is used. The fibers are assumed to be uniformly smeared-out over the matrix. The formulation is based on the assumption of strain compatibility between matrix and fibers. Total stress tensor is additively decomposed into the contribution of matrix and fibers, respectively. To model de-lamination of fibers, the matrix is represented by periodically distributed initial imperfection over the pre-defined bands, which are parallel to fibers. Physically, this assumption accounts for the matrix-fiber interface in a smeared way. The input parameters of the model are defined by the mechanical properties of matrix and fibers (elastic properties, strength and fracture energy), the volume fraction of fibers and by their spatial orientation. The model is implemented into a 3D finite element code. To assure mesh objective results crack band method is employed. The model is first calibrated using a few basic test results. Subsequently, the model is validated with several numerical examples for specimens loaded in uni-axial tension, uni-axial compression and shear. Comparison between numerical and test results shows that the proposed model is able to predict the resistance and failure mode of complex fiber-reinforced composite for different orientation of fibers and different loading conditions with sufficient accuracy. Finally, based on the qualitative type of the finite element analysis, it is demonstrated that the strain rate dependency becomes more important when the angle between the fiber and load direction increases. [ABSTRACT FROM AUTHOR]

Analytical and experimental methods are very demanding and sometimes even impossible to be applied for the analyis of complex structures. Numerical methods provide solutions about the integrity of the structure that is being examined with reasonable levels of confidence. GLARE (GLAss Reinforced) material is a fiber metal laminate, built up of laminates of thin layers of aluminum alloy and glass fiber/epoxy which are mechanically bonded together. Wing leading edge is technologically the most critical structural part and forms the front portion of the main wing of an aircraft The present work is an attempt to examine the structural integrity of the wing leading edge of a typical commercial aircraft using GLARE as a test material through numerical and Finite Element Analysis to establish its candidature in aerospace applications. The results are also experimentally validated. [ABSTRACT FROM AUTHOR]

In this article, an advanced laminated composite is developed, combining the high damping properties of shape memory alloy (SMA) with mechanical properties and light weight of a glass-fiber reinforced polymer. The composite is formed by stacking a glass-fiber reinforced epoxy core between two thin patterned strips of SMA alloy, and two further layers of fiber-glass reinforced epoxy. The bars of the laminated composite were assembled and cured in autoclave. The patterning was designed to enhance the interface adhesion between matrix and SMA inserts and optimally exploit the damping capacity of the SMA thin ribbons. The patterned ribbons of the SMA alloy were cut by means of a pulsed fiber laser source. Damping properties at different amplitudes on full scale samples were investigated at room temperature with a universal testing machine through dynamic tension tests, while temperature dependence was investigated by dynamic mechanical analyses (DMA) on smaller samples. Experimental results were used in conjunction with FEM analysis to optimize the geometry of the inserts. Experimental decay tests on the laminated composite have been carried out to identify the adimensional damping value related to their first flexural mode. [ABSTRACT FROM AUTHOR]

Abstract: Fatigue propagation of a through-the-thickness crack in thin woven glass laminates is difficult to model when using homogeneous material assumption. Crack growth depends on both the fatigue behaviour of the fibres and of the matrix, these two phenomena occurring at different time and space scales. The developed finite element model is based on the architecture of the fabric and on the fatigue behaviours of the matrix and the fibre, even if the pure resin and fibre behaviours are not used. That thus limits the physical meaning of this model. Basically, the objective of this simulation is to illustrate and to confirm proposed crack growth mechanism. The fatigue damage matrix is introduced with user spring elements that link the two fibre directions of the fabric. Fibre fatigue behaviour is based on the S–N curves. Numerical results are compared to experimental crack growth rates and observed damage in the crack tip. Relatively good agreement between predictions and experiments was found. [ABSTRACT FROM AUTHOR]

Abstract: Fiber metal laminates (FMLs) are layered materials based on stacked arrangements of aluminum alloy layers and fiber reinforced plastic (FRP) layers. FMLs have benefits over both aluminum and fiber reinforced composites. In this work, glass fibers and Kevlar fibers are used together and effect of fibers orientation on tensile behavior of this novel material is investigated. A modified classical laminate theory (CLT), which considers the elastic–plastic behavior of the aluminum sheets, and a numerical simulation method based on finite element modeling (FEM) are used to predict the stress–strain response of FMLs. Specimens were made and mechanical testing was performed to determine in-plane tensile properties of this type of FMLs. Good agreement is obtained between the models predictions and experimental results. Test results show that fiber sheets with zero orientation in laminate improve modulus of elasticity, yield stress and ultimate tensile stress considerably. Statistical analysis of data is done and an estimated response surface of ultimate tensile strength of the specimens as a function of fiber orientation in each layer is obtained. Also, the effect of the independent variables and interactions with their relative significance on the tensile behavior is specified. It is shown that Kevlar fiber orientation is the most important parameter between all variables and their interactions. [Copyright &y& Elsevier]

Abstract: Drilling induced damage in fiber reinforced plastic laminates results in high rate of parts rejection and also affects the in-service performance of the composite products with drilled holes. The tensile testing of composite laminates with drilled holes is necessary to render them satisfactory for application. The present research endeavor is an attempt to develop a generic finite element model in order to investigate to failure of uni-directional glass fiber reinforced plastics (UD-GFRP) composite laminates with drilled hole under uni-axial tensile testing. The results have been compared with the experimental work done earlier and are found to be in good agreement. [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: 3D multi-layer and multi-representative unit cell (RUC) models are presented in order to capture the failure mechanisms of Z-pinned laminated textile composites presented in part 1 [Huang H, Waas A. Compressive response of Z-pinned woven glass fiber textile composite laminates: experiments, this issue] of this two part sequel. Simulations of 1, 9, 16, and 25-RUC models are compared to establish cell number effects in representing the textile composites for strength predictions. Further, simulations using multi-layer representations of the textile laminate are conducted to account for unintended stacking effects that occur during the manufacturing cycle. From the results of these simulations, the 3-layer model that has 16-RUCs in each layer is found to be the most adequate representation of the 3D multi-layer and multi-RUC models. Simulations show that stacking effects (layers not compacting and consolidating exactly as intended, resulting in a phase shift) during the manufacturing of the laminates, influence the outcome of the predicted compression strength. [Copyright &y& Elsevier]

The embedment of micro-sensors and micro-devices into composite laminates for structural health monitoring systems leads to stress/strain concentrations due to geometrical and material discontinuities around such embedded inclusions, with high potential to initiate premature failures. This article presents the efforts to estimate the effects of these stress/strain concentrations induced by the integration of rectangular-shape sensors within unidirectional fiber-glass composites. The microcrack initiation sites and the failure load are predicted using finite-element simulations. Good agreement has been found between the numerical results and the experimental findings presented in an accompanying paper. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the cryogenic fatigue delamination behavior of glass fiber reinforced polymer woven laminates under Mode III loading. Fatigue delamination tests were conducted using split cantilever beam specimens at room temperature, liquid nitrogen temperature (77K) and liquid helium temperature (4K). A finite element analysis was also employed to calculate the energy release rate. The temperature dependence of the fatigue delamination growth rate vs. energy release rate range is discussed. Fracture surfaces were examined by scanning electron microscopy to identify the delamination mechanisms under fatigue loading. The important conclusion we reach is that the Mode III fatigue delamination growth rates of woven laminates at cryogenic temperatures are lower than that at room temperature. [Copyright &y& Elsevier]

Abstract: The present research examines experimentally and analytically the mixed-mode interlaminar fracture and damage behavior of glass fiber reinforced polymer (GFRP) woven laminates at cryogenic temperatures. The mixed-mode bending (MMB) tests were performed with the improved test apparatus, at room temperature, liquid nitrogen temperature (77K) and liquid helium temperature (4K). The energy release rates at the onset of delamination crack propagation were evaluated for the woven GFRP specimens using both beam theory and finite element analysis. The fracture surfaces were also examined to verify the fracture mechanisms. In addition, the initiation and growth of damage in the specimens were predicted by a damage analysis, and the damage effect on the mixed-mode interlaminar fracture properties at cryogenic temperatures was explored. [Copyright &y& Elsevier]