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In this paper, the effect of different environmental conditions on the impact properties of fiber metal laminates hybridized with nanoclay is studied. For this purpose, the fiber metal laminates were first laminated by aluminum alloy sheets, glass fiber, pure epoxy resin and modified resin with nanoclay using hand lay-up process. The influence of different types of environmental conditions including cryogenic aging (at temperature of -196 °C in LN2), high-temperature aging (at temperature of 130°C in dry air), and hygrothermal aging (at temperature of 90 °C in distilled water) on the impact properties of the specimens made with pure epoxy resin and modified resin was investigated using response surface method in various levels. A suitable model was developed to predict the effect of aging type and nanoparticle content on the impact strength of specimens. The results obtained suggest that the cryogenic aging has a most effective role reduction of the impact properties of the specimens. While htgrothermal aging has a less effective role in decreasing the impact properties of fiber metal laminates. Additionally, the result of main effects analysis showed that the detrimental role of different types of aging in reducing the impact properties is more effective than the positive role of nanoparticles in improving the impact properties of fiber metal laminates. [ABSTRACT FROM AUTHOR]

In this study, grit blasting with different abrasive particle sizes was carried out on magnesium alloy sheets, then the carbon fiber reinforced polymer (CFRP)/magnesium alloys laminates were prepared using a hot-press process. The surface characteristics of magnesium alloy, and the interlaminar strength of CFRP/Mg laminates were examined, in order to investigate comprehensively the effect of surface roughness on interlaminar strength of laminates under peel and shear loading conditions. The results show that the rougher surface significantly improves the peel strength of laminates, while the shear strength of laminates increases only slightly with increasing surface roughness. Hence, the rougher surface exhibits a good overall interlaminar strength under peel and shear loading when compared to the smoother surfaces. [ABSTRACT FROM AUTHOR]

A study on new materials usage to produce fiber metal laminates is presented in this work. Amorphous polyvinyl chloride thermoplastic and aluminum 3550 sheets are used to fabricate the fiber metal laminates. Different surface treatments were carried out on the aluminum sheets and the fiber metal laminates were produced using the film stacking procedure. Flexural strength and modulus of the products and also shear strength of bonding were measured using three-point bending test, and their failure mechanisms were evaluated using optical microscope images. Also, the effects of aluminum layer and aluminum/composite laminates bonding on the dynamic properties of the fiber metal laminates were studied using Dynamic Mechanical Thermal Analysis. It was concluded that mechanical roughening of the aluminum sheet has the maximum effect on the aluminum/matrix bonding strength such that simultaneous fracture of composite laminates and aluminum layer in the bending condition was observed in the produced fiber metal laminates without any delamination. [ABSTRACT FROM AUTHOR]

In this study the theory and experimental validation of a novel continuum damage modeling framework for highly predictive strength and fatigue analyses of mechanical joints in fiber-reinforced polymer (FRP) composites with local metal hybridization is presented. In contrast to existing damage modeling approaches for mechanical joints in fiber metal laminates (FML), the herein presented framework is able to predict the joint's failure mode both under static and fatigue loading, which is an indispensable feature for the identification of damage tolerant lightweight joint designs. For this purpose, the laminate's constituent materials (i.e. the metallic inlays and the FRP plies) are simulated individually by physically motivated static-fatigue continuum damage models. Here, the elastic and plastic mechanical strain energy is utilized to compute the materials' damage parameters. In this way, the models are (i) able to suppress any mesh-dependence during material softening, (ii) able to account for damage initiation and growth, and (iii) applicable both in the low- and high-cycle fatigue regime. The algorithms are implemented as user-material (UMAT) subroutine for the commercial finite element software ABAQUS. The damage modeling framework is validated for open hole tension and T-bolt joint setups both under static and fatigue loading. [ABSTRACT FROM AUTHOR]

The application of plant fiber-reinforced composite (PFRC) is limited due to its relatively low mechanical properties. The hybridization of a thin metal layer with plant fiber into a fiber metal laminate can largely improve the mechanical performance and the brittle fracture behavior of PFRC. However, both plant fiber and metal have difficulty bonding with the polymer matrix. In this paper, several different surface treatment methods were applied on Al alloy sheets, and the influence of surface treatments on the surface morphology and nano-mechanical properties of Al alloy were studied using an atomic force microscope (AFM). After the preparation of flax fiber−metal laminates (FFMLs) with a vacuum-assisted resin transfer molding (VARTM) technique, the nanomechanical properties of different modified FFMLs were also evaluated with an AFM. It was found that the surface treatment combination of the sulfuric acid-ferric sulfate-based treatment (P2 etching) and the silane coupling agent provided the best adhesion force and modulus for Al alloy sheets at nanoscale resolution, which contributed to the surface energy increasing and strong covalent bonds between metal and polymer matrix. The resulting manufactured FFMLs also exhibited the highest nano-mechanical properties due to the great improvement of interfacial properties between metal and matrix, which was caused by mechanical interlocking mechanism and covalent bonds between metal/fiber and resin. Macromechanical performance, including tensile and flexural properties of these modified FFMLs, was also investigated. Comparison of the modulus at the nanoscale and macroscale showed reasonable agreement, and it revealed the tough interlaminar mechanisms of these types of FFMLs.

In the one-step manufacturing process for fiber metal laminate parts, the so-called in situ hybridization process, the fabrics are interacting with metal blanks. During deep drawing, the liquid matrix is injected between the metal sheets through the woven fiber layers. The metal blanks can be in contact with dry or with infiltrated fibers. The formability of the blanks is influenced by the variation of the starting time of injection. The reason for that is that, due to high contact forces, the fibers are able to deform the metal surface locally, so that movement and the strain of the blanks is inhibited. To investigate the influence of different fibers on the formability of metals, Nakazima tests are performed. In these tests, two metal blanks are formed with an interlayer of fibers. The results are compared with the formability of two blanks without any interlayer. It is shown that in with fibers between sheets, the formability decreases compared to the formability of two metal blanks without interlayers. Based on a simplified numerical model for different types of fibers, the interactions of the fibers with the metal blank are analyzed. It could be shown that the friction due to contact has more influence than the friction due to the form fit caused by the imprints.

This paper investigates the influence of multiple surface treatment, including chemical etching and plasma treatments, on the mode I inter-laminar fracture toughness ( G 1 C ) of aluminum/fiberglass fiber-metal laminates. Laser technology was employed to further enhance aluminum substrate surface morphology to promote micro-mechanical interlocks (MMI) with non-crimp [0°/−45°/90°/+45°] fiberglass/epoxy resin. A vacuum assisted resin transfer molding technique was used to produce the hybrid laminates. Five surface pre-treatments were compared; N 2 plasma, O 2 plasma, alkaline etch, laser, and laser+N 2 plasma. Alkaline etched specimens absorbed the highest energy (237.8%) whereas laser+N 2 plasma treated specimens exhibited the highest G 1 C (73.2%). In addition, when MMI is promoted, the mechanical locks acted as localized obstacles resisting the propagating crack and caused transition of failure mode from adhesive to adhesive-cohesive mixed mode. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FMLs) are new hybrid materials which are widely used in aircraft industry due to their higher mechanical properties compared to monolithic metal and epoxy based composites. In this work, mechanical behavior of the FML is investigated by experiment and simulation. The FML used in this study is made of two layers of aluminum 2024 and a layer of glass-fiber reinforced epoxy (GFRE). The experiments showed nonlinear elastic behavior for GFRE layer. This behavior is due to damage evolution and material degradation. Therefore, a simple nonlinear damage is presented to improve the results of the proposed material model. Mechanical properties of the layers are measured by uniaxial tensile test. Numerical simulations are performed by implementing the material model into the user subroutine of MSC MARC FE code. The results of the proposed model showed a reasonable agreement with the experiments. The agreement confirms the nonlinear damage behavior of the FMLs observed in the experiments. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FMLs) consist of layers of thin metallic sheets and fiber reinforced composite layers bonded together. In the present study, the tensile response of FMLs consisting of aluminum 2024-T3 (Al) sheets of thicknesses 0.2, 0.4, and 0.6 mm and uni-directional glass-fiber reinforced composite layers are investigated. FMLs having three different stacking sequences, all having the same total metal layer thickness were prepared using the hand layup process. The results of the tensile tests indicated that the layup sequence did not have any influence on the initial modulus of the FMLs. However, the ultimate strength and the post ultimate strength behavior of the FMLs are significantly affected by the layup sequence. In order to gain more insight into the sequence of damage evolution, a detailed finite element analysis (FEA) of the tests was also carried using the commercial software ABAQUS. The Hashin failure criterion was used to model failure of composite layers and cohesive surface interaction was used to capture inter-layer delamination. [ABSTRACT FROM AUTHOR]

In this work, three different surface modification techniques, including grit blasting, micro-arc oxidation (MAO) and laser ablation, were respectively carried out on magnesium alloy sheets, and then the treated surfaces were evaluated for surface topography and surface roughness characteristics. Besides, the interlaminar strength and the interface failure characteristics of the CFRP/Mg laminates were examined, in order to comprehensively analyze the effects of the various pre-treatment techniques on interlaminar strength and fracture mechanisms of the CFRP/Mg laminates under Mode I (peel) and Mode II (shear) loading. The results show that the MAO treatment resulted in a slight increase of shear strength when compared with grit blasted surfaces, yet it yields worse peel strength outcome due to the weak MAO coating/Mg substrate interface. The laser ablation effectively enhances the overall interlaminar strength of the CFRP/Mg laminates under peel and shear loading. [ABSTRACT FROM AUTHOR]

CARALL and GLARE type multidirectional fiber metal laminates were subjected to interlaminar fracture toughness tests by End Notched Flexure method. The critical strain energy release rates were calculated based on authors developed methodology of recent analytical Enhanced Beam Theory, and then verified by standardized experimental Compliance Calibration method. With increase of fiber orientation angle (0°, 45°, 90°) at the metal-composite interface, the determined critical strain energy release rate significantly decreased. Simultaneously, the growing contribution of mode I in resulting mode mixity ratio at the crack tip was revealed. Performed experimental tests were supported by Finite Element Analysis by Cohesive Zone Method. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FMLs) are a family of hybrid materials consisting of alternating thin coatings of aluminum alloy and fiber-reinforced epoxy layers. In contrast to aluminum alloys， the presence of notches in FMLs causes significant strength reduction. To evaluate the residual strength of fiber metal laminates with circular open hole， mechanical testing was performed to determine the un-notched tensile properties and notched strength of FMLs. The influence of ply structure on residual strength of FMLs was investigated. The stress failure model was introduced to predict the residual strength of FMLs with an open hole. Failure modes， damage initiation and progression of notched FMLs were also characterized and discussed. The results show that the presence of a hole in GLARE3 laminates gives a strength reduction about 40%. It can be seen that the characteristic length increase and notch sensitivity tends to decrease with the increase of ply number. The damage initiated at the hole edge when the residual strength is 90%. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FMLs) intended for blast and ballistic resistance applications need to contain ballistic grade plies like aramid (Kevlar®), ultra-high molecular weight polyethylene (Spectra®) as supporting plies in addition to the metallic layers. The order of stacking varies depending on the functional grading of plies. In the current work, five sequences of fiber metal laminates made of AA6061-T6, aramid, ultra-high molecular weight polyethylene, and paperboard have been developed. The novelty of the work is the basis of the layering based on functional grading by the shock impedance of the respective plies. The FML sequences were subjected to mechanical characterization comprising flexural and tensile tests, as well as damping characterization for vibration characteristics. The key metrics of areal density, storage modulus, natural frequency, damping coefficient, tensile strength, tensile modulus, tensile strain-to-failure, flexural strength, flexural modulus, flexural strain-to-failure were considered for comparing the different layups of the FMLs. From the experimental studies, placing a low-impedance ply (paperboard layer) as the penultimate layer before the AA6061-T6 rear skin led to the best mechanical and damping performance as seen in the FML sequences BRSP-II and BRSP-IV. • Fiber metal laminates comprising ballistic fabrics and low shock impedance ply for armor materials. • Ply based shock impedance used for functional grading of layers. • Damping characterization using impact hammer setup, damping coefficient, natural frequency and storage modulus analyzed. • Mechanical characterization composed of tensile and flexural three-point bending. [ABSTRACT FROM AUTHOR]

This paper mainly investigates the initial low-velocity impact behavior and the residual tension performance of FMLs with different composite layer directions through experimental and numerical methods. First, the detailed studies for the impact response and failure behavior of FMLs under different impact loadings are carried out experimentally, including various impact energies and impact numbers. Then, the post-impact tension behavior of FMLs with various impacted damage are further characterized through tension tests. Meanwhile, an integrated numerical model in virtue of VUMAT subroutine in ABAQUS is developed to simulate the impact and post-impact tension behavior of FMLs. The Hashin and Yeh failure criteria are employed to predict the complex failure modes of composite laminates, and the cohesive model is utilized to simulate the delamination damage between metal alloy and composite laminates. The reliability and accuracy of the integrated model can be demonstrated through comparison with the experimental results. Subsequently, the progressive damage evolution process of FMLs during the loading can be characterized in detail from the numerical predictions. It can be demonstrated that the aluminum alloy plays a decision role in the protection of structure perforation, while the composite laminates mainly dissipate the impact energy through the complex failure modes. • Experimental characterization of the various impact behavior and residual tension performance of FMLs. • Different impact loads are implemented on FMLs to further explore the damage evolution and energy absorption characteristics. • An integrated numerical model for impact and residual tension simulation is developed. • Residual ultimate tension strength of FMLs with different layer directions are compared and analyzed. [ABSTRACT FROM AUTHOR]

Damage caused by random impact incidents can greatly reduce the load bearing capacity of composite structural components. In this study, numerical simulations were performed to investigate the influence of impact damage on the buckling and post-buckling performance of carbon fiber reinforced polymer (CFRP)/aluminum laminate (CARALL) channel-section profiles. Low-velocity impact experiments and simulations were performed first on CARALL panel with the exact stacking configuration of the profiles to characterize the possible failure mechanisms for such hybrid components. Then, the dynamic responses of the channel-section profiles with the corner, web and flange impacted respectively, and the corresponding residual properties under axial compression were numerically revealed. Results showed that the residual deformation of specimens after impact was the dominate factor concerning its residual buckling load, and the post-buckling strength was mainly determined by the material damage propagation in the post-buckling stage. The specimens with corner impacted exhibited the highest residual axial buckling load and the lowest failure load compared with the ones with web or flange impacted. This work intended to provide insight into developing novel fiber reinforced polymer/metal hybrid structural components with high impact resistance. • 3D progressive damage model based on the Hashin and Puck criterion was proposed and used in the simulation. • The Effects of impact locations on the low-velocity impact behavior was analyzed through simulation. • The residual compressive behavior and damage propagation features of the pre-impacted profiles were discussed. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FMLs) provide a reliable approach for achieving lightweight in high-speed aerospace vehicles. However, the weak interfacial properties between metals and composites could significantly affect the deformation and failure modes of FMLs. In this paper, the low-velocity impact responses and damage mechanisms of CF/PEEK-Ti hybrid laminates with nano-interfacial enhancement by multi-walled carbon nanotubes (CNTs) were characterized and analyzed. The post-impact residual tensile strengths (RTS) were investigated experimentally using quasi-static uniaxial tests combined with digital image correlation, and were evaluated theoretically by developing an analytical prediction model that considers the internal thermal stress and dent geometry. Results show that the initial delamination thresholds of force and displacement during impact can be effectively increased via interfacial enhancement of CNT network. By using a 5% decrease in RTS retention rate as a criterion for damage tolerance, a significant strength decrease starts to appear at 3 J for the sandblasted-only laminates, which is improved to 10 J for the laminates with nano-interfacial enhancement. The proposed unified constitutive model can yield an acceptable prediction for RTS and failure strain of the hybrid laminate after impact, providing a guidance for the structural design and engineering applications of FMLs. [Display omitted] • Delamination threshold in force is effectively increased by interfacial enhancement. • Damage tolerance on RTS of impacted laminate is improved. • A unified constitutive model considering internal thermal stress and dent geometry is proposed. • The proposed model is in good agreement with experiments for RTS and failure strain. [ABSTRACT FROM AUTHOR]

A reliable strategy to enhance the bonding ability in hybrid titanium carbon laminates (HTCLs) is proposed, which is based on the pinning effect produced by bionic micro texture etched by laser on titanium and multi-walled carbon nanotubes (MWCNTs) introduced into adhesive layer. The characteristic of bionic micro texture is determined, and the strengthening mechanism of bonding interfaces is revealed. The HTCLs samples with various micro texture groove widths, laser scanning times and MWCNTs content are fabricated via an autoclave process. The micro texture morphologies, surface wettability, interlayer bonding properties under different conditions are studied. Results show that the recast layers formed on titanium during etching are beneficial to improve the interfacial bonding properties. Compared with no micro texture, the contact angle with micro texture can be reduced by 68.4%. Both micro texture and MWCNTs can reduce the defects at the interlayer interfaces and improve the interfacial adhesion. In this work, the maximum tensile shear strength (TSS) and interlaminar shear strength (ILSS) can be obtained with the micro texture groove width of 30 μm, the laser scanning of 30 times and the MWCNTs content of 0.4 wt%, which are 56.39% and 32.84% higher than that without any treatment, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

The present paper gives details of the structural response of titanium-based fiber metal laminates (TFML) subjected to high velocity impact. Dynamic perforation behavior of two different sample configurations, TFML-2/1 and 3/2 are presented. The behavior of the metal and composite layer is defined using two independent appropriate constitutive material models. Both experimental and numerically predicted residual velocity follows the Recht-Ipson model variation with impact velocity. Being larger in thickness, residual velocity, peak contact force and total energy absorbed were found to be larger for TFML-3/2 than 2/1. However, the contact duration was rather insignificantly affected. Having similar metal volume fraction (MVF), energy dissipated by means of plastic deformation of metal layers was found to be constant for both TFML configurations that were considered. The axisymmetric loading, boundary conditions and having balanced material property distribution along the principle axes resulted in doubly symmetric damage surfaces, both layer-wise and overall. The developed finite element (FE) model adequately simulated the contact behavior and all of the experimentally realized damage modes in the metal and composite layers and confirmed its reliability. Having limited experimental information, the obtained numerical information allows one to briefly understand the dynamic perforation behavior of TFML laminates.

While an ultralight sandwich construction with cellular core can be tailored to exhibit superior load-bearing capability and blast resistance, its ballistic performance is typically inferior to its equivalent monolithic counterpart. To improve the projectile penetration resistance while maintaining the capability of load bearing and blast mitigation, this work proposed a multifunctional sandwich plate with ultra-high molecular weight polyethylene (UHMWPE) fiber metal laminate (FML) skins and aluminum honeycomb core. A combined experimental and numerical approach was employed to quantify the ballistic performance, assess the penetration process, and reveal the underlying mechanisms of the novel sandwich construction. In addition to ballistic resistance, its performance under three-point bending as well as impulsive shock loading was also assessed for multifunctional applications. Relative to all-metallic honeycomb sandwich plate having identical areal density, incorporating UHMWPE composite layers into the skin improved significantly the penetration resistance: the failure mode of the laminate skin was changed from local shear-plugging to global dishing and cracking, enabling enhanced energy absorption of the thin metallic (titanium) layers. Moreover, the use of UHMWPE FML skin for sandwich construction led to not only significantly enhanced bending capacity but also reduced maximum deflection under impulsive shock loading. Hence, the proposed cellular sandwich plate with UHMWPE FML skins can be designed as ultralight multifunctional structure with simultaneous load-bearing and blast/ballistic resistant capabilities. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FML) are composite structures consisting of metals and fiber reinforced plastics (FRP) which have experienced an increasing interest as the choice of materials in aerospace and automobile industries. Due to a sophisticated built up of the material, not only the design and production of such structures is challenging but also its damage detection. This research work focuses on damage identification in FML with guided ultrasonic waves (GUW) through an inverse approach based on the Bayesian paradigm. As the Bayesian inference approach involves multiple queries of the underlying system, a parameterized reduced-order model (ROM) is used to closely approximate the solution with considerably less computational cost. The signals measured by the embedded sensors and the ROM forecasts are employed for the localization and characterization of damage in FML. In this paper, a Markov Chain Monte-Carlo (MCMC) based Metropolis–Hastings (MH) algorithm and an Ensemble Kalman filtering (EnKF) technique are deployed to identify the damage. Numerical tests illustrate the approaches and the results are compared in regard to accuracy and efficiency. It is found that both methods are successful in multivariate characterization of the damage with a high accuracy and were also able to quantify their associated uncertainties. The EnKF distinguishes itself with the MCMC-MH algorithm in the matter of computational efficiency. In this application of identifying the damage, the EnKF is approximately thrice faster than the MCMC-MH. [ABSTRACT FROM AUTHOR]

A structural lithium ion battery is a material that can carry load and simultaneously be used to store electrical energy. We propose for the first time the fabrication of structural batteries based on modified fiber metal laminates with integrated energy storage function. The metal sheets act as both an impact resisting layer and current collectors. With the successful fabrication of solid polymer electrolyte membrane of high ionic conductivity, metal sheets supported solid state battery core can be integrated with fiber reinforced polymer composites (FRP) by layer stacking and subsequent co-curing to produce lightweight fiber metal laminated structural battery (FMLSB), which has outstanding impact resistance and can still operate a LED when subjected to 30 J impact energy. Further analysis indicates the underlying mechanism lies in low energy adsorption for FRP incorporated with metal sheets supported solid state battery core, which only brings about divergent in-plane cracks to FMLSB, in contrast to through-thickness penetration of FRP. To prove the concept of the as-fabricated FMLSB in electric vehicle industry, we successfully fabricated an 11 mAh FMLSB-type chassis which can be self-powered for over 20 min. This study shows that fiber metal laminates combined with solid state battery represents a promising path to mechanically strong structural batteries. Based on the multifunctionality of metal sheets (outstanding electrical conductivity and high impact resistance), multifunctional fiber metal laminated structural batteries have been developed through incorporating pouch-free solid state energy storage units into fiber laminates, which can still power a LED when subjected to 30 J impact energy. Underlying mechanism behind the outstanding impact properties is the low absorbed energy (15.34 J) due to the optimized prepreg layup angles. For demonstration purpose, a FMLSB-based chassis has been self-powered for over 20 min, which presents the high potential of the newly developed FMLSB in automobile industry. [Display omitted] • A multifunctional fiber metal laminated structural battery (FMLSB) is for the first time proposed. • The potential of FMLSB has been demonstrated through a self-powered chassis over 20 min. • Underlying mechanisms behind the superior impact resistance of FMLSB to FRP has been clarified. • The effect of fiber laminate stacking angles on the amount of absorbed energy has been found out. • Effect of lithium salt on the electrochemical properties of SPEs has been investigated based on Li/LFP batteries. [ABSTRACT FROM AUTHOR]

The effect of adhesive quantity on the failure behavior and mechanical properties of fiber metal laminates based on the aluminum–lithium alloys (NFMLs) was investigated to optimize the manufacture process and further recognize the interface interaction. The NFMLs with different adhesive quantities (0 g/m 2 , 20 g/m 2 , 40 g/m 2 , 60 g/m 2 ) were prepared primarily. Then, the influence of adhesive quantity on the interlaminar, tensile, flexural and fatigue properties of NFMLs was studied respectively. Also, the failure behaviors of NFMLs under different loading conditions were revealed. The results indicated that the adhesive layers significantly enhanced the interlaminar properties of the NFMLs within the investigated quantities. Moreover, the reasonable adhesive quantity also greatly improved the mechanical properties of the laminates, while an excessive amount deteriorated the performance. For the different properties, the peak values appeared under different adhesive quantities. Besides, the changing mechanical properties followed with the variation of failure mode. From the engineering perspective, the adhesive quantity of 40 g/m 2 is optimal to achieve the excellent performance of NFMLs. [ABSTRACT FROM AUTHOR]

The rise in cutting temperatures during the machining process can influence the final quality of the machined part. The impact of cutting temperatures is more critical when machining composite-metal stacks and fiber metal laminates due to the stacking nature of those hybrids which subjects the composite to heat from direct contact with metallic part of the stack and the evacuated hot chips. In this paper, the workpiece surface temperature of two grades of fiber metal laminates commercially know as GLARE is investigated. An experimental study was carried out using thermocouples and infrared thermography to determine the emissivity of the upper, lower and side surfaces of GLARE laminates. In addition, infrared thermography was used to determine the maximum temperature of the bottom surface of machined holes during drilling GLARE under dry and minimum quantity lubrication (MQL) cooling conditions under different cutting parameters. The results showed that during the machining process, the workpiece surface temperature increased with the increase in feed rate and fiber orientation influenced the developed temperature in the laminate. [ABSTRACT FROM AUTHOR]

In this manuscript, integral method was used for the approximation of residual stresses field in fiber-metal laminates (FMLs). Initially, calibration coefficients matrix for the integral method were determined numerically by the finite element program using ANSYS software. The calibration coefficients were used to relate the measured strains relaxation field with the existing residual stresses prior to the IHD process. Subsequently, FML specimens with symmetric stacking sequence of [ AL / 0 2 ° / 90 2 ° ] S were manufactured. Next, the IHD experiment by high speed drilling machine were performed and released strains caused by the change in hole-geometry have been obtained. Finally, experimental results from IHD experiment were compared with the theoretical predictions from classical lamination theory. Very good agreements with the experimental and theoretical results show that, the IHD technique can be successfully applied for measuring residual stresses in FML composites. [ABSTRACT FROM AUTHOR]

The fiber metal laminates (FML), consisting of carbon fiber reinforced polymer prepregs and magnesium alloys sheets, were introduced, and the Mode I (peel) and Mode II (shear) interlaminar fracture toughness of the FMLs were investigated. The results show that the Mode I interlaminar toughness (0.23 kJ/m2) of the FMLs is much lower than the Mode II interlaminar toughness (5.81 kJ/m2), due to the fact that the effects of mechanical interlock to hinder crack propagates is smaller under Mode I loading conditions than under Mode II. The FMLs mainly show adhesive failure and interfacial failure under Mode I loading conditions, while for Mode II loading, it exhibits a degree of epoxy cohesive failure except the adhesive failure and interfacial failure. [ABSTRACT FROM PUBLISHER]

Fiber-metal laminates (FMLs) composed of metal lamina and reinforcing fibers exhibit an improved crack growth resistance as compared to conventional aircraft materials. The crack resistance of a hybrid FML composite consisting of LY12M aluminum alloy lamina and prepreg layers of HS2 glass fibers and T700 carbon fibers has been experimentally investigated on tensile specimens at stress ratios R = - 1, 0.1, and 0.5. The crack growth rate data at positive stress ratios demonstrate a significant scatter and a large difference between specimen's back and front surfaces formed by 1-mm thick outer aluminum layers. This violation of the test standard requirements for metal materials in the performed FML tests presents a problem of determining a proper failure criterion for the engineering applications of FMLs. Based on the comparative analysis of FML crack resistance results obtained, some qualitative conclusions are drawn on solving this problem. [ABSTRACT FROM AUTHOR]

Being light weight and superior in characteristics, hybrid materials such as fiber metal laminate (FMLs) and functionally graded structures (FGS) are becoming increasingly popular in aeronautical, automobile and military industries. In the present work, an innovative methodology which hereafter will be named as '3A method' has been proposed to replace complex shaped, monolithic, metallic sheet parts with hybrid parts. This method is based on simultaneous forming of any number of multiple metallic blanks in required shape by applying hydroforming (HF) technology. Based on numerical simulations, forming limit diagrams (FLDs) are established for three types of blanks forming hemispherical shaped parts using Barlat 2000 yield criteria/DYNA Form/LS Dyna. To validate the simulation results, experimental study is accomplished and optimal process parameters are determined by varying the cavity pressure under constant die-binder gap. Effects of number of layers and thickness of blanks on thinning, wrinkling and punch force have been well studied for three types of blanks and a comparative analysis is made to investigate various failure modes. To achieve a composite layered structure, post forming procedure has been devised and implemented to get a final hybrid part. Furthermore, limitations of the 3A method in terms of final shape of parts are discussed. Good agreement can be found between numerical and experimental research. The new methodology is capable of employing any types of resins and composite materials at any required place in parts for desired characteristics. Elimination of repeated heating and solidification of blank assembly as well as precise punch force and speed requirements make this multilayer blank forming method more efficient, economical and user friendly for manufacturing of FMLs and FGSs at commercial scales. [ABSTRACT FROM AUTHOR]

An experimental investigation focusing on the hygrothermal aging-structural degradation-mechanical property relationship of GLARE 4A laminates was conducted. Water immersion conditioning at 80 °C for up to 4 months was carried out on GLARE 4A laminates. It was found that although the outer aluminum layers effectively protected the glass/epoxy composite layers from hygrothermal attack, the composite layers absorbed moisture through the edges. Consequently, significant decrease in both, the tensile strength and fatigue life of the GLARE 4A laminates, was observed although no structural defects were apparently identifiable in the microstructures of the conditioned laminates. Detailed experimental investigation was conducted to study the mechanism of mechanical property decay due to hygrothermal aging. It is proposed that the strength of the S2-glass fibers was not fully realized due to the weakening of the fiber/matrix interface and the deterioration of the sizing, which consequently led to the reduction in the tensile strength and fatigue life of the GLARE 4A laminates. The stiffness degradation characteristics of GLARE 4A laminates under cyclic loading were also investigated. [ABSTRACT FROM AUTHOR]

A nano-scale electrochemical sculpture (NES) method has been developed to enhance the bonding strength of fiber metal laminates (denoted as FMLs-NES). The influence of NES surface treatments on the low velocity impact response and static mechanical behavior of FMLs was systematically investigated and compared with traditional surface treatments such as mechanical polishing and NaTESi anodizing (denoted respectively as FMLs-PS and FMLs-NaTESi). The examination of the damage area and energy absorption under different impact energy levels revealed that the FMLs-NES specimen exhibited the smallest damage area and energy absorption while maintaining the structural integrity after impact. Finite element simulations were conducted to inform the impact damage progression and failure mechanisms, the results indicate that the interfacial failure mainly occurred between the middle titanium sheet and the bottom 90° fiber layer and propagated from the long edge to the center of FMLs. The experimentally validated finite element model can also be employed to optimize the stacking sequence of FMLs and to predict the residual strength after impact, where the FMLs-NES showed the highest residual strength. [Display omitted] [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FMLs) have been regarded as an important structural material in aerospace and are getting more attention from the fields of automobile, rail transportation and other industries, owing to their excellent fatigue and high damage tolerance. Based on the introduction of the development of FMLs, this paper focuses on the research status of novel GLARE with aluminum-lithium alloy, titanium sheets and carbon-fibre reinforced PEEK laminates (Ti/Cf/PEEK), and novel FMLs with carbon fibre reinforced polyimide(Ti/Cf/PMR). Subsequently, the importance of further recognizing their damage mechanism and performance prediction through computer simulation is reviewed, considering the complicated failure behaviors of FMLs and the lack of reasonable evaluation methods on some mechanical properties. Moreover, conventional forming technologies of FMLs, including the roll bending and the self-forming, are summarized. Finally, the shot peen forming and the hydro-forming to be used in the manufacture of complicated FML components are discussed. [ABSTRACT FROM AUTHOR]

Delamination extension and fatigue crack growth behaviors under single overloads were investigated for GLARE 2-2/1-0.3 with fiber direction of 00/00. The results indicate that the stress intensity factor at the crack tip in metal layer while overload applied, K tip,ol is a key controlling variable which influences fatigue crack growth and delamination behaviors. When K tip,ol becomes bigger and exceeds a critical value, an obvious kink in the delamination shape is observed nearby the location of overload applied. Crack growth rate after application of overload could not return to its original level even the crack grows beyond the overload plastic zone. The reduction magnitude of the crack growth rate becomes bigger with the overload ratio (intrinsically K tip,ol ) increasing. These new results for the crack growth behavior have never been reported before, which can be well explained by the delamination extension behavior observed after overload applied. [ABSTRACT FROM AUTHOR]

In this paper, the incremental hole-drilling method is used to measure experimentally with accuracy non-uniform residual stresses in each ply of fiber metal laminate (FML) composites. Integral method was used for the approximation of residual stress. This method is considered a constant and uniform residual stress analysis at each hole-drilling depth increment. First, finite element method is used to calculate the calibration coefficients matrix of the incremental hole drilling process. The calibration coefficients matrix determined by finite element analysis can be used directly in the experiment. Calibration coefficients matrix is used to relate the measured strain relaxation field with the existing residual stresses prior to the hole-drilling process. Also, for the experimental determination, released strains induced by high speed drilling process on FML composites with a stacking sequence of [AL/02 ° /902 °]S have been quantified. Finally, the experimental measurements are compared with the theoretical predictions of the classical laminate theory. Good agreement between the experimental data and theoretical prediction show that, incremental hole-drilling technique can be proved to be successfully applied for measuring non-uniform residual stresses in FML composites. [ABSTRACT FROM AUTHOR]

The rate-sensitivity of a range of fiber metal laminates (FMLs) has been investigated though split Hopkinson bar, quasi-static perforation and low velocity impact tests. Initial attention focused on assessing the rate-sensitivity of the constituent materials, that is the glass fiber reinforced epoxy and the three aluminum alloys. This was followed by a series of perforation tests on multilayer configurations. It has been shown that both the composite and the aluminum substrates exhibit a low degree of rate-sensitivity, with both the tensile strength and the perforation energy increasing slightly in passing from quasi-static to dynamic rates of loading. Similarly, FMLs based on combinations of the composite and metal constituents exhibit a low degree of rate-sensitivity, with the impact perforation energy and the maximum impact force being only ten to fifteen percent higher than their quasi-static values. An examination of the cross-sections of the failed laminates indicated that the failure processes were similar at both quasi-static and dynamic rates of strain. Also, similar levels of plastic deformation, fiber fracture and delamination were observed at both rates. Finally, it has been shown that the energy to perforate the various FMLs is directly related to the aggregated perforation energies of their constituent parts. [ABSTRACT FROM AUTHOR]

In this study, scaling effects on fiber metal laminates under tensile and three-point bending tests were investigated numerically and experimentally. The fiber metal laminate specimens were made of aluminum 1050 and unidirectional glass–epoxy. Two scaled sizes of specimens were prepared based on [A1n,0n∘/90n∘]s. Some specified mechanical properties of these samples were investigated and results showed that fiber metal laminates obey scaling law under quasi-static loading. Explicit finite element code LS-DYNA was utilized for numerical simulation. After validating numerical simulation with experiments, scaling law was studied numerically for four different sample sizes. Finite element analysis demonstrated that scaling law is valid for fiber metal laminates. In final part, hole size effect in FML specimen was investigated numerically. [ABSTRACT FROM PUBLISHER]

Glass laminate aluminium reinforced epoxy (GLARE) is an advanced aircraft material because of its excellent fatigue crack resistance, high impact strength, high strength-to-weight ratio and high stiffness-to-weight ratio. While drilling on composite/metal stacks has been investigated, the drilling of GLARE, which consists of several alternate thin layers of aluminium and composites, has not been addressed separately in the open literature. The focus of present experimental work is to understand the cutting mechanism and relative effect of cutting parameters and tool geometry on the delamination and burr formation during drilling of GLARE. Thrust force, torque and acoustic emission (AE) signals were acquired for analyzing the cutting mechanism, burr and delamination formation. Also, several measurements of burrs, delamination and hole size were taken in order to understand the hole quality. It has been observed that, 2-fluted drill is the best out of four different geometries used, giving zero delamination and acceptable burr formation followed by the 4-faceted drills. The conventional 3-fluted and 8-faceted drills that are otherwise superior for drilling of fiber reinforced plastics (FRP) composites, performed poorly in drilling of the GLARE laminates. Analyzing the processing parameters, feed again has a dominant role in controlling delamination and burr formation than speed. [ABSTRACT FROM AUTHOR]

This paper presents a numerical analysis of Fiber Metal Laminate thin-walled column behaviour under dynamic pulse loading. Structural resistance to dynamic pulse loading was assessed by applying two types of criteria: dynamic stability and failure criteria. The FE model was created to take into consideration delamination failure between laminate layers. Contact elements were implemented to solve this problem within the frame of a three-dimensional model. Therefore, it was possible to analyse the FML column dynamic stability by considering all failure mechanisms at the meso -mechanical level, i.e. aluminium yielding, fiber and matrix failure modes, and layer debonding. [ABSTRACT FROM AUTHOR]