Fiber Metal Laminates Research Articles

Damage failure prediction study of carbon fiber metal laminates in hot stamping process

In addressing the difficulty of forming Fiber Metal Laminates (FMLs), a laminate composed of a 0.1 mm-thick 304 Stainless Steel Foil (SSF) and Carbon Fiber Reinforced Plastics (CFRP) as the base material is prepared using a specific process. Subsequently, forming limit diagrams are obtained through hemispherical bulge forming experiments to investigate the forming performance of FMLs laminates. The damage phenomena of various forming specimens during the thermal stamping process are analyzed. Based on different damage forms, corresponding theoretical models are established to simulate and predict the forming damage modes of FMLs through simulation. The research results indicate that the stamping formability of FMLs is influenced by the damage tolerance of the thin stainless steel foil. During the thermal stamping process, FMLs may experience delamination, fracture/crack of the thin stainless steel foil, and rupture/tearing/wrinkling of the prepreg. To address these issues, cohesive elements, GTN-M-K damage, and Hashin damage models are established, providing a reasonable simulation prediction of the stamping damage phenomena of FMLs.

An experimental investigation of the effect of carbon nanotubes addition and shot peening process on the ballistic limit of fiber-metal laminates

The present research has experimentally investigated the effect of adding multi-walled carbon nanotubes (MWCNTs) and shot peening operations on the ballistic behavior of fiber-metal laminates (FMLs). The unreinforced and reinforced FMLs with 0.2 wt.%, 0.4 wt.%, and 0.6 wt.%. of MWCNTs were manufactured by hand lay-up method and subjected to shot peening operations. Finally, the specimens were exposed to the ballistic impact test using a cylindrical projectile with a conical head. The best result was obtained for 0.4 wt.% of MWCNTs, in which the ballistic limit and absorbed energy increased by 6.80% and 13.75% for non-shotted and by 8.50% and 17.45% for shotted samples, respectively. This demonstrates the positive effect of shot peening in increasing the ballistic limit through a combination of work hardening and compressive residual stresses in the aluminum layers. However, mechanical performance decreased in samples containing 0.6 wt.% of MWCNTs due to nanoparticle agglomeration. The fracture surfaces of the samples were also analyzed by scanning electron microscopy, and the results indicated an improvement in the adhesion properties at the interface between the fibers and matrix in the reinforced samples, achieved through mechanisms such as crack bridging and MWCNTs pull-out.

Numerical and experimental validation of fiber metal laminate structure for lithium-ion battery protection subjected to high-velocity impact loading

A novel structural protection based on fiber metal laminate (FML) was developed for a lithium-ion battery module to address ground impact issues in electric vehicles (EVs). To verify the battery structural protection and for experimental validation, a new high-velocity impact test methodology was proposed. FML was selected for its high strength-to-weight ratio. The design implemented was the optimum configuration identified in a prior study. Finite element models comprising FML and lithium iron phosphate batteries were developed. The numerical simulation results, which correlated well with the experiments, enabled observation of the perforation process and failure modes of the FML. In the experiment, the safety valve of the center battery in the module experienced a compression of 3.28 mm. Despite this deformation, the FML effectively protected the lithium-ion batteries, as evidenced by the stable battery voltage during the high-velocity impact test.

Investigation of structure–flexural response relations in thermoplastic carbon/glass fiber‐metal laminates

AbstractIn the current work, fiber‐metal laminates (FMLs) consisting of alternated continuous fiber‐reinforced thermoplastic composite layers and aluminum alloy sheets were proposed by the hot‐pressing method. Carbon fiber‐reinforced polyamide 6 (PA6/CF) and glass fiber‐reinforced polypropylene (PP/GF) prepregs were selected as composite layers. The effect of the assembly method between composite prepreg and aluminum sheets as well as the stacking configurations on the flexural response of FMLs were investigated. Meanwhile, the macro and micro‐structural observations were performed to characterize failure mechanisms in these structures. Experimental results revealed that the strength and stiffness of hybrid FLMs depended on the material property on the surface layer. With the stacking sequence of aluminum sandwiched by PA6/CF achieved the highest flexural strength of 535.3 MPa and modulus of 63.6 GPa in the series of FMLs, which could achieve satisfied lightweight and strength‐stiffness properties. The ductile deformation of aluminum sheets and fracturing and pulling out of the fibers were the main characterized failure mechanisms of thermoplastic FMLs. For glass fiber‐metal laminates, stacking configurations of three aluminum sheets alternation with four PP/GF intermediate layers achieved a favorable flexural property. Above all, the proposed thermoplastic FMLs have great potential in civil applications especially in the automobile industry as structural parts.Highlights Thermoplastic fiber‐metal laminates are designed and fabricated. The assembly method and stacking sequences influence the flexural property. FMLs with PA6/CF and aluminum achieve satisfied strength stiffness. PP/GF prepreg and aluminum layer display ductile deformation mode.

GLARE deformation in low-restraint state: Tensile and bending behavior

Fiber metal laminates (FMLs) possess a better weight reduction effect than traditional metal materials due to the coupling properties of heterogeneous materials, showing promise in the areas of aviation and aerospace. At present, the research on FMLs mainly focuses on the deformation properties after curing while the mechanical properties in the low-restraint state, i.e. the laminates are temporarily not cured and are formed under lower constraint stresses, are not studied in detail. Herein, the low-restraint GLARE is taken as a research object and its deformation characteristics and failure mode are studied using uniaxial tensile, bending experiments and numerical simulation in this paper. Moreover, the influence of key parameters, such as temperature, laminate structure and span length, is investigated, as well as the tensile and bending deformation behavior of GLARE in a low-restraint state is obtained. In addition, based on experimental observations, it is found that the low-restraint GLARE produces the phenomenon of interlayer slip, and the interlaminar residual stress is much smaller than the cured laminate, whereas the deformation limit and performance are improved. This paper provides theoretical bases for the in-depth analysis of deformation properties and forming laws of low-restraint GLARE, guiding further applications of laminates.

Life cycle assessment of fibre metal laminates: An ecodesign approach

Despite the extensive research on renewable resources (RR) and their potential applications in composite materials and sandwich structures, there remains a significant dearth of life cycle assessment (LCA) studies that comprehensively evaluate the efficacy of RR in mitigating environmental impacts (EI). To bridge this gap, the present study aims to investigate twelve different designs of sandwich panels, specifically referred to as Fibre Metal Laminates (FML). These FML combine aluminium skins (2024-T3 and 1200-H14), polymer matrices (Epoxy, Polyester, and Castor oil Bio-PU), natural fibres (Sisal, Coir, and Cynodon spp.), surface treatments for aluminium skins (sanding, NaOH, and Washprimer), and treatments for natural fibres (Ground, NaOH-treatment and untreated). A cradle-to-gate LCA is conducted, and the inventories are modelled using the OpenLCA 1.6.3 and ecoinvent 3.9 cut-off regionalized database. EI are evaluated in twelve categories, including climate change, fossil and nuclear energy use, freshwater (acidification, ecotoxicity and eutrophication), human toxicity (cancer and non-cancer), mineral resources use, ozone layer depletion, particulate matter formation, photochemical oxidant formation, and terrestrial acidification. Impact World+ method for Latin America version 1.251 is employed to calculate EI. Nine Eco-efficiency indicators and trade-off analyses are evaluated to gain insights into design decision outcomes. Among the various panels considered, FML12, manufactured with aluminium alloy 1200-H14 treated only with sanding, castor oil biopolymer and untreated coir fibres, present the most consistent eco-efficiency indicators. The reference scenario considers the average characteristics of FML (both environmental and mechanical) for trade-off analysis. Despite the fifty percent chance of better performance, FML12 is the only panel that shows higher mechanical performance and lower EI compared to the reference scenario. The importance of this article lies in the novel results obtained using the proposed eco-efficiency indicators, which can be expanded in further studies on the topic.

Vibration Characteristics of FML Cylindrical Shell Bonded by Thin Piezoelectric Actuator and Sensor Layer with and Without Fluid–Structure Interaction Resting on Pasternak Elastic Foundation

The present study investigates the vibration analysis of cylindrical shells composed of fiber metal laminate (FML) with embedded piezoelectric layers, undergoing fluid-structure interaction (FSI) and resting on a Pasternak elastic foundation based on the principles of three-dimensional elasticity theory. Using the state space approach, the equations of motion were derived under simply supported boundary conditions. The natural frequencies of the FML cylindrical shell, accounting for the presence of a moving fluid, were computed by solving the eigenfrequency equations. The study examined the influence of various parameters, including boundary conditions, length-to-radius ratio, fluid type, fluid velocity, circumferential wave number, and radius-to-thickness ratio, on glass-reinforced aluminum laminate (GLARE), aramid-reinforced aluminum laminate (ARALL), and carbon-reinforced aluminum laminate (CARALL). A constant composite/metal volume ratio was assumed. The results obtained were validated by comparing with natural frequency values from the existing literature, confirming the agreement and convergence with previous studies. The results confirm that the highest natural frequency values are assigned to the CARALL, ARALL and GRALE structures in descending order. Furthermore, an increase in fluid flow velocity through the cylindrical shell correlates with a reduction in natural frequency.

Improved mechanical properties of environmentally friendly jute fibre reinforced metal laminate sandwich composite through enhanced interface

Natural plant based fibres are being increasingly used in sustainable fibre reinforced composite applications in order to meet the demand of using environmentally friendly materials for composites. Fibre metal laminates (FMLs) are used in aerospace, automobile, marine and civil engineering applications, due to their excellent mechanical behaviors compared to traditional metals and their alloys. This study describes a novel fabrication of jute fibre reinforced aluminum metal laminates, using different jute fibre architectures (plain and twill fabric structures), wherein jute fibres were used in the skins and aluminum in the core layers. Jute fibres and aluminum sheets were chemically treated to enhance the compatibility and interfacial bonding at fibre-metals-matrix interfaces. FMLs were manufactured by hot pressing technique, after the application of wet lay-up process for the resin impregnation and they were further tested under tensile, flexural and impact loading conditions. While comparing results, the twill architecture showed improved tensile and flexural properties compared to plain fabric based FMLs. Chemical treatments on twill jute fibres and metal sheets further exceptionally enhanced the flexural properties (151 MPa flexural strength and 21.3 GPa modulus and they were increased by 186.5 % and 722.7 % respectively compared to the untreated jute fibre counterparts) of the laminates due to a significant improvement in the adhesion between the jute fibre and aluminum sheet after alkali treatment applied. Therefore, with these enhanced properties, jute based FML laminates can be used as sustainable composite materials in many structural applications.

Procena karakteristika obrade i habanja alata tokom bušenja ugljenika / aluminijum-aluminijum

In the past few decades, fibre metal laminate (FML) machining has been facing critical challenges in quality control and tool wear monitoring due to the material's intrinsic heterogeneity and abrasiveness. Different drill tools have been used to investigate the effect of process parameters on machining performances. Composite holes and tool wear was studied for drilling forces and surface roughness. An emphasis was made on examining the tool morphologies and wear processes that influence the drilling of CARALL composites. The drilling responses obtained from both the drill bits were optimized using a decision-making approach viz; Combined Compromise Solution Analysis (CoCoSo). The SEM investigation of the machined samples was used to examine the hole quality and surface finish. A lower point angle drill with a longer chip flute length produced the best results for drilling CARALL composites up to a specific point with minimum flank wear and chip adhesion.

Experimental evaluation of inter laminate shear stress of CAJRAL type fibre metal laminates prepared with surface treated aluminium sheet by sobbing technique

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Mechanical characterization of 3/2 fibre metal laminate materials

Development of lightweight materials onto vehicle bodies, especially in the automotive sector is seen as one of the best alternative solutions in order to reduce fuel consumption and decrease harmful emissions produced by the emission. Reducing in weight of a vehicle can improve fuel efficiency with no prejudice to safety strength requirements. Fibre metal laminate (FML) is hybrid composite structure based on thin sheet of metal alloys and plies of fibre reinforced polymeric materials which offer the ability of superior mechanical properties such as lightweight, high fatigue growth resistance and high strength and stiffness. Multi-material auto bodies will allow optimal material selection in structural components for higher performance and lower cost. This study aims to fabricate and investigate the failure behaviour of a 3/2 layer fibre metal laminate subjected to the quasi-static indentation test. The FML is constructed from aluminium 2024-T3 and layered with composite materials CFRP, GFRP and SRPP. The crosshead speed test analysis ran in different parameters on 1 mm/min, 5 mm/min, 10 mm/min and 50 mm/min, respectively in quasi-static indentation test. The experimental performances of each specimen were compared to predict the behaviour and performance of the FML composite. The test indicates that varying crosshead speeds have influenced the affected region of the FML, causing debonding on the laminate as a result of continued loading.

Improving fatigue initiation life of open-hole fibre metal laminates by laser shock peening

Although drilling open holes in fibre metal laminates reduces weight, it brings potential crack initiation sites. This paper investigates the effect of laser shock peening (LSP) on fatigue performance of open-hole titanium-based carbon-fibre/epoxy laminates (Ti-CF FMLs). A method based on multi-step simulation was proposed for the reconstruction of LSP induced residual stress field in open-hole Ti-CF FMLs. The results show that the fatigue initiation life of open-hole Ti-CF FMLs is improved by 22.1 %–81.0 % after LSP, depending on the structure of FMLs and the applied fatigue load. The improved fatigue crack initiation life attributes to compressive residual stress generated throughout the entire depth of the hole wall in outer titanium layer in Ti-CF FMLs after LSP. However, LSP leads to the formation of tensile residual stress far from the hole edge, resulting in accelerated propagation of fatigue crack. The fatigue initiation lives of open-hole Ti-CF FMLs before and after LSP were calculated by finite element simulation and theoretical method, showing good consistency.

A novel active hydroforming & curing process to manufacture GLARE laminates: Numerical and experimental investigations

Fiber Metal Laminates (FMLs) are preferable thin-walled structures in several fields for their exceptional mechanical properties. However, how to manufacture thin-walled FMLs structures with complex shapes and guarantee the high mechanical properties is still a challenge. To address these, this paper proposes an innovative hybrid forming method, referred to as active warm hydroforming and curing, to enhance the formability and performance of FMLs in GLARE form by combining the forming and curing process into a single step. The hybrid method was verified on a box-shaped part as a proof-of-concept to assess the feasibility and parameter influence. Online curing was utilized to enhance efficiency and quality. The outcomes revealed that the new method increases the ultimate tensile stress by 12.1 % and reduces curing deformation from 3.1 mm to 1.3 mm compared to the vacuum bagging method. Furthermore, the critical parameters in forming of thin-walled structures, including blank holder force (BHF), pressure rate (PR), maximum pressure (MP), and forming temperature (FT), were identified using experimental, mathematical, and numerical approaches. Four defects in the formed thin-walled structures were observed and successfully eliminated through the control of these parameters. The method and results presented in this paper also provide direct guidance for optimizing the process parameters of FMLs warm hydroforming.

Study of the dynamic response and damage evolution of carbon fiber/ultra-thin stainless-steel strip fiber metal laminates under low-velocity impact

Two configurations of carbon fiber/ultra-thin stainless-steel strip fiber metal laminates (CUSFML) with differing metal volume contents (35.3% and 18.2%) and carbon fiber-reinforced polymer (CFRP) composite laminates were selected for tests. The impact response and the effect of metal volume content on the impact resistance of CUSFML were assessed via experiment and FEM. Inducing damage by drop-weight test within the impact energy range of 18.60–46.23 J, two types of CUSFML and CFRP composite laminates were compared. In particular, the bearing capacity, impact deflection, failure modes, and energy dissipation were considered. The impact modeling using the VUMAT subroutine refines the relationship between energy-dissipating mechanism and damage evolution. The results indicate that CUSFML are characterized by higher impact resistance than CFRP composite laminates under low-velocity impact. The effect of metal volume content on the impact resistance increases gradually with impact energy increasing. Under 46.23 J impact, the CUSFML with higher metal volume content exhibits more concentrated damaged area with severe penetration failure, which is more dominated by metal failure features with a higher proportion of plastic energy dissipation. For CUSFML with lower metal volume content, extensive delamination and damage expansion occurs under the dominance of fiber damage behaviors.

ANN MODELING AND OPTIMIZING THE DRILLING PROCESS PARAMETERS FOR AA5052-GLASS FIBER METAL LAMINATE USING GREY-FUZZY LOGIC APPROACH

The exterior layer of the fuselage skin structure is made of Glass-Reinforced Fiber Metal Laminates (GLARE-FMLs). Hole quality is impacted by various force components during the drilling process. The process variables of drilling are optimized to obtain quality holes by controlling such force components. Because of the very limited works on optimizing the significant input process variables in getting quality drilled holes on FML plates, the present investigation is aimed to analyze the impact of varying the significant drilling process variables referred from the literature study and the wt.% of Layered Double Hydroxide (LDH) mixed with the epoxy, on the force components generated during the drilling process. The FML plates proposed in the study have been drilled based on the test plan prepared by Taguchi’s DOE. Grey Relational Analysis has been used for discovering the best combination of process variables leading to good quality holes. Further, grey-fuzzy modeling technique has been employed to check the results of GRA. From the results, it is identified that 1000 rpm spindle speed, 20 mm/min feed rate and 4 wt.% inclusion of LDH to the epoxy resin combination within the considered range of input process variables were found to be the best input parameter combinations resulting in comparatively better output responses. Artificial Neural Network (ANN) model has been generated to bridge the input variables with the outputs measured. The fitness of the generated ANN model has been checked and reported. The effect of varying the process variables on obtaining the quality drilled holes has been revealed using Main Effect Plots (MEPs).

Multiscale modelling and experimental analysis of ultrasonic-assisted drilling of GLARE fibre metal laminates

This study aims to evaluate the effectiveness of Ultrasonic-assisted drilling (UAD) of Glass laminate aluminium reinforced epoxy (GLARE) at high cutting speeds (Spindle speeds: 3000–7500 rpm; feed rates 300–750 mm/min) by analysing the thrust force and hole quality metrics (surface roughness, hole size, and burr formations. The research also presents numerical modelling of FMLs under conventional and UAD regimes to predict thrust force using ABAQUS/SIMULIA. The thrust force and exit burrs were reduced by up to 40.83 % and 80 %, respectively. The surface roughness metrics (Ra and Rz) were slightly higher using UAD but remained within the desirable limits of surface roughness for machined aeronautical structures. The discrepancy between the simulation and experimental results was adequate and did not exceed 15 %. The current study shows that it is feasible to drill holes in GLARE using higher cutting parameters and maintain excellent hole quality, which means increased productivity and reduced costs.

Eccentric ballistic impact of fiber-metal laminates and aluminum plates supported with different boundary conditions

This article investigates the eccentric ballistic impact response of square aluminum and fiber-metal laminated plates with the ANSYS AUTODYN hydrocode. The plates are impacted by a cylindrical projectile with normal high velocity. The validation of the numerical procedure is mainly carried out through comparisons with published experimental data. The modeling procedure and the verification of numerical results are described in detail so as to provide a useful reference. The effect of impact point eccentricity and different boundary conditions on the ballistic resistance of the targets is evaluated. It is found that the ballistic limits of the considered targets can be substantially affected by the boundary conditions and the eccentricity of impact. The targets are sorted in a descending order of ballistic resistance which is found invariant to the impact position.

Experimental and simulation analysis of the effect of GNPs on the mechanical and interfacial properties of CF/PEEK-Ti fiber metal laminates

In this study, graphene nanoplatelets (GNPs) were used to improve the interfacial and mechanical properties of carbon fibre-reinforced polyetheretherketone-based titanium alloy laminates (CF/PEEK-Ti) and molecular dynamics (MD) simulations were used to investigate the mechanism by which GNPs improve CF/PEEK-Ti, collectively known as fibre reinforced metal laminates (FMLs). In addition, surface anodising of titanium (Ti) sheets was used further to enhance the interfacial bonding properties of the FMLs. The experimental results showed that the flexural and shear strengths of the anodised FMLs were increased by 77.7% and 29.5%, respectively, compared with those of the Ti plates without surface anodisation. Based on this, different levels (0–1.5 wt.%) of GNPs were added to the FMLs matrix, and test results showed that FMLs containing 0.5 wt.% GNPs had the best flexural and shear strengths, 108.9% and 130.8% higher than untreated FMLs without GNPs. In addition, an in-depth microscopic analysis was carried out to understand the enhancement mechanism of GNPs on FMLs. Finally, MD simulations were used to analyze the role and mechanism of GNPs in this system. The results show that the addition of GNPs can increase the interfacial energy of FMLs. In other words, the interfacial mechanical properties of FMLs are improved. The effect of the dispersion of GNPs on the interfacial properties of FMLs was also investigated. The polyetheretherketone (PEEK) matrix could be significantly improved by well-dispersed GNPs. These findings provide insight into designing high-performing composites for various engineering applications.

Tensile and flexural mechanical attributes of hybrid carbon/basalt fiber metal laminates under various hybridization and stacking sequences

In this work, experimental measurements and theoretical validation are adopted to examine the tensile and flexural behaviors of titanium-based carbon/basalt fiber metal laminates under various hybridization ratios and stacking sequences. Firstly, the mechanical response and damage patterns of fiber metal laminates (FMLs) subjected to different tensile and flexural loads have been explored. By observing the fracture surfaces of FMLs with various hybridization ratios and stacking sequences, scanning electron microscopy (SEM) has been used to identify the related microscopic damage patterns. The principal damage mechanism were attributed to fiber/matrix debonding, matrix microcrack, fiber pull-out, and delamination. Subsequently, to analyze the discreteness of experimental results and evaluate the theoretical flexural strength of FMLs under different conditions, the two-parameter Weibull statistics model for engineering application of FMLs was established. These results indicate that the tensile and flexural strength of FMLs can be improved by altering the hybridization ratios and stacking sequences. The thorough understanding of the mechanical behavior and failure mechanism of FMLs under various hybridization conditions can provide the basis for the design and utilization of FMLs structures.

Experimental study on the impact resistance and damage tolerance of thermoplastic FMLs

This study aimed to enhance the impact resistance of fiber metal laminates (FMLs) and achieve lightweight optimization by incorporating a new thermoplastic resin, a titanium alloy and ultra-high-molecular-weight polyethylene (UHMWPE) fiber to produce a novel type of FMLs (PEFMLs). The impact resistance of PEFMLs was analyzed through low-velocity impact tests conducted at different energy levels. Subsequently, the residual compression-after-impact (CAI) strength of the PEFMLs was evaluated through compression tests on the impacted specimens. The experimental findings revealed that PEFMLs exhibited subcritical failure when subjected to impact energies less than 35 J, with a penetration energy threshold of 55 J. Higher impact energies resulted in larger damage areas and increased plate buckling of PEFMLs, consequently leading to reduced CAI strength. The presence of metal, thermoplastic resin and UHMWPE in the PEFMLs effectively dissipated a substantial amount of impact energy while maintaining their structural integrity during both the impact and compression processes.