Glass Fiber Reinforced Aluminum Laminates Research Articles

Identifying the contributions of constituents to the fracture performance and failure mechanism of fiber metal laminate

AbstractFiber metal laminate (FML) is a damage‐tolerant material that has gained special attention in the aircraft industry. To clarify the confusing contributions of constituents to the quasi‐static fracture performance and failure mechanism, six kinds of glass fiber reinforced aluminum laminates (Glare) were designed. Quasi‐static fracture tests were carried out to examine their crack resistance, stable crack extension, and residual strength. Moreover, postmortem characterizations were performed to reveal the macro and micro failure morphologies. It was found that the glass fiber reinforced polymer (GFRP) layers can positively contribute to Glare's quasi‐static fracture performance due to its in‐situ quasi‐brittle but not completely brittle fracture characteristics, which was shown by the special plateau formed on P–Δa curve of Glare, and by the improved crack resistance, longer critical crack length, and higher residual strength in Glare with higher content of GFRP. However, the enhancement achieved by increasing the volume fraction of GFRP was not as effective as by increasing the aluminum thickness, since thickening aluminum in a limited range could increase the fracture toughness and promote the delamination and fiber pull‐outs in Glare. To further identify the effect of the properties of the metal layer, a titanium‐reinforced Glare was designed and tested. It was found to transform the fracture process to be titanium dominant, which delayed the fracture of GFRP and meandered the fracture path, then resulted in superior quasi‐static fracture performance than the basic Glare.

A simulative study on the effect of friction coefficient and angle on failure behaviors of GLARE subjected to low-velocity impact

Abstract The aim of this paper is to study the effect of friction coefficient and impact angle on the failure behaviors of glass fiber reinforced aluminum laminates (GLARE) under the low-velocity impact (LVI) loading. A methodology is developed in commercial software ABAQUS/Explicit, and its accuracy is verified based on the results of comparison between simulation and experiment. In the simulation, Johnson–Cook flow stress model and surface-based cohesive behavior are carried out to simulate the damage evolution of aluminum alloy layers and delamination at the interface. Further, both the dynamic response history and damage mechanism characterization of these hybrid laminates are presented and compared carefully. Additionally, due to the advantage of simulation, it is accurate and easy to discuss on the evolution of the damage contour consisting of the damage degree of composite and metal layers as well as the interface between them. Finally, the influence rules of friction coefficient and angle on the failure behaviors of GLARE under LVI are drawn clearly.

Quasi‐static fracture characterization of fiber metal laminate with crack resistance curve based on δ5

AbstractFiber metal laminate (FML) is a hybrid composite typical in aircraft industry. It is necessary to effectively characterize the quasi‐static fracture performance of FML, considering the importance of damage tolerance design of aircraft structures and the complicated fracture mechanism of FML. In present investigation, glass fiber reinforced aluminum laminates (Glare) with middle cracks were tested under quasi‐static tensile load. The experimental crack resistance curve (R curve) based on the special crack opening displacement at original crack tip (δ5) was used for revealing the superior crack resistance of Glare laminate to aluminum sheet, which expressed in crack extension aspect was the extended critical crack length. This was thought to be benefit from the contributions of glass fiber layers and fiber/metal delamination, by performing the progressive damage analysis. Since δ5 can embody the elastic–plastic response of the crack but without need to interactively correct for crack tip plasticity. The δ5‐R curve‐based macro and meso fracture models were proposed to accurately predict the residual strength and stable crack extension of Glare laminate, which gave further evidence for the effectiveness of δ5‐R curve in characterizing the quasi‐static fracture performance of FML.

Effects of Thermal Residual Stresses on Tensile and Interlaminar Shear Behaviors of GLARE Laminates

The residual stresses caused by curing, forming and machining process significantly affect the mechanical behaviors of composite materials, especially for super hybrid structure like GLARE (glass fiber reinforced aluminum laminates). In this work, the curing thermal residual stresses characteristics of GLARE and corresponding effects on tensile and interlaminar shear behaviors were investigated. Firstly, the characteristics of residual stresses were described by a finite element (FE) model and verified by layer removal method. Then, thermal residual stresses were incorporated into FE mechanical behavior prediction models in the form of predefined field to analyze the effects on tensile and interlaminar shear behaviors. The corresponding simulation conclusions were consistent with the experimental observations. The results indicated that there were about 40 MPa tensile residual stress in aluminum layers and 70 MPa compressive residual stress in GFRP (glass fiber reinforced polymer) layers of GLARE. Residual stresses had obvious reduction effect on the yield strength of GLARE, and the prediction accuracy was hence improved by 9%. Moreover, the failure mode of tensile tests was hardly affected by the residual stresses, but the tensile strength and the initial damage loads were reduced slightly. In interlaminar shear tests, the peak load and initial damage load were reduced by the residual stresses in the adhesive layers of GLARE, and the interlaminar shear strength was slightly influenced. An edge failure mode caused by edge effect was observed during the propagation of the delamination cracks, which was verified by interlaminar shear finite element models and SEM (scanning electron microscope) images.

POSTFATIGUE LIFE PREDICTION OF GLARE SUBJECTED TO LOW-VELOCITY IMPACT

In this study, at first, the dynamic progressive failure of Glass-Fiber-Reinforced aluminum laminates (GLARE) under low-energy impact with intra laminar damage models implementing strain-based damage evolution laws, Puck failure criteria using ABAQUS-VUMAT,were modeled. For interface delamination, bilinear cohesive model; and for aluminum layers the Johnson-Cook model was implemented;and the fatigue life of the fiber metal laminates of GLARE subjected to impact was obtained; and the numerical and experimental results of the model were compared with each other. With regard to the very good match betweenthe numerical and experimental results, the results of the finite element model were generalized and expanded, and with the use of the multilayer neural network, the numerical model was extracted and then, by applying the meta-innovative algorithm, the maximum fatigue life of GLARE was determined atthe highest level with very low-velocity impact,and the best configuration of three-layer GLARE was selected.The findings indicated that the best configuration of hybrid composite GLARE based on conventional commercial laminates that can tolerate low-velocity impacts with 18J impact energy and a 349MPa fatigue load with a frequency of 10Hz was [Al/0-90-90-0/Al/0-90-0/Al/0-90-90-0/Al] with 13016 cycle lifetime.

Lightweight scheme selection for automotive safety structures using a quantifiable multi-objective approach

Abstract The main objective of this paper is to propose a quantifiable multi-objective evaluation approach method to rationalize the subjective evaluation in the selection of lightweight scheme for automotive safety components, which can be applied in the selection of materials and structures in lightweight design of automobiles and other products. The proposed method combines intuitionistic fuzzy number theory, entropy method and Technique for Order Preference by Similarity to Ideal Solutions (TOPSIS) to deal with uncertainty in the decision-making process. Intuitionistic fuzzy number theory was used to quantifies the subjective evaluation of decision makers. Entropy method and fuzzy logic theory were utilized to objectively weight the criteria and decision makers, and The TOPSIS method is used to assess the pros and cons of alternatives. To assess and validate the effectiveness of the proposed method, three automotive bumper systems using different materials and structures, namely, high strength steel (HSS), polymer composite-metal hybrid (PMH), and glass fiber-reinforced aluminum laminates (GLARE) were taken as example, some qualitative criteria including recyclability and easy manufacturability as well as several quantitative criteria such as the weight, cost, crash safety (energy absorption, peak impact force and maximum deflection), were considered and balanced. According to the findings, the evaluation results of the proposed method are consistent with the evaluation results of the existing VIKOR method and TOPSIS method, which verifies the correctness of the proposed method. In addition, from the perspective of sensitivity analysis results and method principles, it is proved that the proposed method is superior to the other two methods in robustness and efficiency.

Spring-back and failure characteristics of roll bending of GLARE laminates

Roll bending is a cost-effective and efficient sheet forming process. In this paper, spring-back of glass fiber reinforced aluminum laminates (GLARE) in roll bending process was investigated by numerical and experimental methods to explore the formability characteristics of the laminates. Failure modes of GLARE with diverse curvatures were revealed using scanning electron microscope (SEM). Moreover, the curvature radii of the laminates after roll bending were measured with an arc height gauge. The results definitely corroborated that distinct differences existed among three GLARE variants in spring-back and damage modes. GLARE 2A (which fibers direction are parallel and same with roll direction) exhibited larger spring-back than the other two laminates. Meanwhile, greater top roller displacement led to smaller spring-back. Tensile fracture appeared in the 0° fiber/epoxy layers, while matrix cracking occurred in the 90° fiber/epoxy layers along with the growth of curvature. However, no obvious delamination was observed at different layers. Besides, the critical curvature radius of GLARE 2A, GLARE 2B (which fibers direction are parallel and perpendicular to roll direction) and GLARE 3 (which fibers direction are perpendicular to each other)was located in 100 mm ∼ 114 mm, 67 mm ∼ 100 mm and 118 mm ∼ 131 mm, respectively, which proved roll bending feasible for manufacturing GLARE with small curvature. In order to facilitate further research in the future, the finite element model of roll bending was established, and the accuracy of the model was verified by experiments.

Influence of metal layer distribution on the projectiles impact response of glass fiber reinforced aluminum laminates

The effect of the distribution of aluminum layer through the thickness of fiber metal laminates (FMLs) on their projectiles impact response is studied using high speed 3D digital image correlation technique (DIC). The FMLs consisting of aluminum alloy 2024-T3 sheets of thicknesses 0.3 mm, 0.4 mm, and 0.6 mm and glass fiber reinforced epoxy layers (two layers with each of 0° and 90°) were prepared by the hand layup process followed by vacuum bagging. The metallic layers are placed at different locations through the thickness of four different layups while keeping the total metal layer thickness constant. The hemispherical and conical nose projectiles of the same mass are impacted normal to the FMLs plate using nitrogen gas gun. The performance of the FMLs is evaluated using different parameters such as the deformation history, residual deformation and also the surface and internal damages. FML 4/3–0.3 in which the two adjacent composite layers with different fiber orientations separating by an aluminum layer exhibited the highest deformation with hemispherical projectile impact for the same impact energy level. The deformation was found to be lower and nearly same for the other three FMLs. This observation is also noticed in the case of drop weight impact (low velocity impact). The FML 2/1–0.6 in which the composite layers were stacked together exhibited a comparatively higher lateral spread of delamination and interlayer opening with hemispherical projectile impact when compared to FML 4/3–0.3, indicating that the lateral spread of damage within the FML can be decreased by distributing the aluminum layers in the FML. This is also observed in the case of drop weight impact.

Effect of metal layer placement on the damage and energy absorption mechanisms in aluminium/glass fibre laminates

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.

Mechanical Characterization and Finite Element Investigation on Properties of PLA-Jute Composite

materials are on high demand in recent days amongst high performance products that need to be strong enough in severe loading conditions. It can be developed with a suitable combination of matrix and reinforcement materials to meet the requirement of specific applications. The present work attempts to form composite plates using a combination of natural polymers and fibers to improve certain properties. The focus is to develop a biodegradable composite of comparable properties with those available commercially. The formed plates are tested to determine different mechanical properties such as tensile strength, impact resistance, hardness etc. The thermal parameters are also determined by DSC (Differential scanning calorimetry) test. A finite element analysis is conducted and the results have been compared with Graphite epoxy composite for checking the effective use of this material. responses along with vibration behavior of laminated composite plates have been extensively investigated. Pandya and Kant (6) has proposed a C0 continuous displacement finite element formulation of laminated composite plates under transverse loading using Higher order Shear Deformation theory. The static behavior of laminated composite and sandwich plates is studied analytically using Navier's technique based on higher order refined theory by Kant and Swaminathan (7). Soltani et al. (8) has analyzed nonlinear tensile behavior of glass fibre reinforced aluminium laminates using finite element modeling. Attallah et al. (9) presented 3- D solutions of laminated composite plates by using a combined finite strip and state space approach. Bharet al. (10) analyzed the significance of the HSDT over the FSDT for laminated composite stiffened plates by using FEM. Grover et al. (11) investigated the static and buckling analysis of laminated composite and sandwich plates in the framework of a new inverse hyperbolic shear deformation theory and this theory is based on shear strain shape function. Kumar et al. (12) studied static analysis of thick skew laminated composite plate with elliptical cutout based on 3-D elasticity theories. Riyah and Ahmed (13 investigated stresses of composite plates with different types of cutouts. Rezaeepazhand and Jafari (14) analytically analyzed the stresses of composite plates with a quasi-square cutout subjected to uniaxial tension based on Lekhnitskii's theory. Static analysis of isotropic rectangular plate with various support conditions and loads are studied by Vanamet al. (15) using finite element analysis (FEA). A recent study detailed the effect of cutout orientation on SCF (16).

Low-velocity impact damage on glass fibre reinforced aluminium laminates: experiments and finite element analysis

In order to investigate the failure mechanism of glass-fiber reinforced aluminum( GLARE) laminates under impact loading,the anti-low speed impact performance by a dropweight test on GLARE was presented,and the damage response of GLARE laminates in the test was given. The study first analyses the curves of time-contact force,time-deflection,time-absorbed energy,deflection-contact force,and the damage to two aluminum layers of the test specimen. Next,a numerical methodology in ABAQUS is employed to simulate the response in low-velocity impact of GLARE laminates and establish the finite element model. After comparing the time-contact force,timedeflection,time-absorbed energy,and the damage to aluminum layers under different circumstances of impact energy between experimental and simulation results,the reliability of the finite element model method was validated. After comparing the damages to composites and aluminum under different impact energy,no big difference in the damage to the composite layer was found. However,more damage in the aluminum layer when the impact energy is higher was found,proving that the aluminum layers play an important role in the entire anti-impact performance of materials.

A manufacturability improvement of glass-fiber reinforced aluminum laminate by forming an effective crystallographic texture in V95 alloy sheets

Theoretical notions and formation modes of the crystallographic texture of sheets made of the V95pch aluminum alloy, which intensifies the formation of parts made of glass-fiber reinforced aluminum laminates by stretch forming, are presented. The deformation texture (orientations S and Bs) is formed during hot rolling; it becomes stronger during further cold rolling. The recrystallization texture is formed during annealing (orientations [011]〈100〉, [023]〈100〉). An increase in the limiting stretch-forming coefficient after cold rolling is provided by two-stage annealing, which includes rapid heating at the continuous heat treatment line and subsequent complete annealing in an in-and-out furnace with slow cooling.

Investigation on the Tensile Strength of GLARE Laminate with a Hole

As for the case of tensile plastic deformation of glass fiber reinforced aluminum laminates (GLARE), the finite element analysis model of the tensile strength of GLARE laminates with a hole is established by means of ABAQUS software under tensile load. The modeling is found to be in good agreement between the simulation results and the experiment data in the failure strength. On the basis of the finite element model, the tensile strength of GLARE laminates containing a hole in other ply modes is simulated, and the influences of the hole size and ply angle on the tensile strength are given in this paper.

Studying the Tensile Behaviour of GLARE Laminates: A Finite Element Modelling Approach

Numerical simulations based on finite element modelling are increasingly being developed to accurately evaluate the tensile properties of GLARE (GLAss fibre REinforced aluminium laminates). In this study, nonlinear tensile behaviour of GLARE Fibre Metal Laminates (FML) under in-plane loading conditions has been investigated. An appropriate finite element modelling approach has been developed to predict the stress–strain response and deformation behaviour of GLARE laminates using the ANSYS finite element package. The finite element model supports orthotropic material properties for glass/epoxy layer(s) and isotropic properties with the elastic–plastic behaviour for the aluminium layers. The adhesion between adjacent layers has been also properly simulated using cohesive zone modelling. An acceptable agreement was observed between the model predictions and experimental results available in the literature. The proposed model can be used to analyse GLARE laminates in structural applications such as mechanically fastened joints under different mechanical loading conditions.

The impact properties and damage tolerance and of bi-directionally reinforced fiber metal laminates

Fiber metal laminates are an advanced hybrid materials system being evaluated as a damage tolerance and light weight solution for future aircraft primary structures. This paper investigates the impact properties and damage tolerance of glass fiber reinforced aluminum laminates with cross-ply glass prepreg layers. A systematic low velocity impact testing program based on instrumented drop weight was conducted, and the characteristic impact energies, the damage area, and the permanent deflection of laminates are used to evaluate the impact performance and damage resistance. The post-impact residual tensile strength under various damage states ranging from the plastic dent, barely visible impact damage (BVID), clearly visible impact damage (CVID) up to the complete perforation was also measured and compared. Additionally, the post-impact fatigue behavior with different damage states was also explored. The results showed that both GLARE 4 and GLARE 5 laminates have better impact properties than those of 2024-T3 monolithic aluminum alloy. GLARE laminates had a longer service life than aluminum under fatigue loading after impact, and they did not show a sudden and catastrophic failure after the fatigue crack was initiated. The damage initiation, damage progression and failure modes under impact and fatigue loading were characterized and identified with microscopy, X-ray radiography, and by deply technique.

Tensile Behavior and Fracture Toughness of Glass Fiber Reinforced Aluminum Laminates According to Fiber Layer Orientation

The objective of this study is to investigate the tensile behavior and fracture toughness of glass fiber reinforced aluminum hybrid laminates (GFAL) in association with the fracture process using plain coupon and single-edge-notched specimens. The tensile properties of GFAL, such as elastic modulus and ultimate tensile strength, were clearly dependent on the fiber orientations. In particular, the superiority of GFAL0 in KIC and GIC was much more pronounced than that of monolithic Al 1050. However, a transverse crack parallel to the fiber orientation reduced the toughness of GFAL considerably. Microscopic observations of the fracture zone in the vicinity of the crack tip exhibited various modes of micro-fracture in the respective layers as well as fiber fractures and interface delamination between fiber composite and Al layers. Such a damage evolution in GFAL depending on the fiber layer orientation had strongly influence upon the tensile behavior and the toughness of GFAL.

Fatigue behaviour and life prediction of fibre reinforced metal laminates under constant and variable amplitude loading

Fatigue crack growth of fibre reinforced metal laminates (FRMLs) under constant and variable amplitude loading was studied through analysis and experiments. The distribution of the bridging stress along the crackline in centre-cracked tension (CCT) specimen of FRMLs was modelled numerically, and the main factors affecting the bridging stress were identified. A test method for determining the delamination growth rates in a modified double cracked lap shear (DCLS) specimen was presented. Two models, one being fatigue-mechanism-based and the other phenomenological, were developed for predicting the fatigue life under constant amplitude loading. The fatigue behaviour, including crack growth and delamination growth, of glass fibre reinforced aluminium laminates (GLARE) under constant amplitude loading following a single overload was investigated experimentally, and the mechanisms for the effect of a single overload on the crack growth rates and the delamination growth rates were identified. An equivalent closure model for predicting crack-growth in FRMLs under variable amplitude loading and spectrum loading was presented. All the models presented in this paper were verified by applying to GLARE under constant amplitude loading and Mini-transport aircraft wing structures (TWIST) load sequence. The predicted crack growth rates are in good agreement with test results.

Notched tensile strength of various fibre reinforced metal laminates

Modifications in Whitney-Nuismer (WN) fracture models known as the point stress criterion and the average stress criterion are proposed for notched strength estimations of laminates. Applicability of the proposed procedure is examined by considering the residual strength data on carbon fibre reinforced metal laminates, aramid reinforced aluminium laminates and glass fibre reinforced aluminium laminates having saw-cuts and circular holes of various sizes. The analytical results obtained in the present study are close to the test results. This study confirms that the present modification in WN fracture models for fibre reinforced composites can be used for notched strength evaluation of FRMLs.