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GLARE is a type of laminate material made up of layers of aluminum and fiberglass used in automotive, and aircraft structures like fuselage panels, control surfaces, and wing skins due to their superior specific strength, fatigue, and damage tolerance. The inclusion of nanoclay filler was reported to improve the mechanical properties of the GLARE laminates. However, it is important to investigate the machinability of such laminates to extend their applicability in the industry. The current work optimizes the process parameters of the Abrasive Water Jet Machining (AWJM) process to cut the nanoclay-modified Fiber Metal Laminates (FMLs). The experiments were designed by following Taguchi’s L9 orthogonal array. The influence of factors like the velocity of waterjet, mass flow rate, and stand-off distance of the nozzle against the response such as cutting time and sub-surface delamination of layers were studied. The delamination was measured using the variation in thickness before and after the cutting process. The changes in the cutting surface were analyzed using macroscopic analysis. The study also developed the regression model and conducted ANOVA on generated data. Grey Relational Analysis (GRA) was used to identify the optimum values of input process parameters against multiple responses such as cutting time and delamination. The results revealed that the jet velocity significantly affected the cutting time, whereas the stand-off distance and mass flow rate affected the delamination thickness of the laminates. A slight plastic deformation was noted on the metal surfaces along with irregularities and fiber exposure was observed in the GFRP layers of laminates exhibited low cutting performance. [ABSTRACT FROM AUTHOR]

Purpose: Fiber Metal Laminates (FML) are cutting-edge materials that combine the strength of fibers with the versatility of metals. This study prepared FML plates with different compositions, including glass fiber, epoxy resin, multi-walled carbon nano tubes (MWCNT), Layered double hydroxide (LDH), and nano clay. These materials are increasingly used in the aircraft industry for their high performance. Our research, which includes free vibration analysis, is crucial for the design process of such structures, offering practical insights for engineers and researchers in the field. Methods: The bending natural frequencies for the free-free, cantilevered, and clamp-clamped boundary conditions of the FML plates were ascertained using experimental and numerical analysis. The experimental and numerical analysis vibration analysis of FML plates was carried out using the Fast Fourier Transform (FFT) analyzer and Finite Element Analysis software, i.e., ANSYS, respectively. Results: In this study, the bending natural frequencies for the free-free, cantilevered, and clamp-clamped boundary conditions were investigated experimentally and numerically. Firstly, numerical results were obtained using Finite Element Analysis software, and then these results were compared with the experimental results. The bending natural frequencies predicted by means of the experimental and numerical analysis were observed to be in good agreement. Conclusion: It was identified that the natural frequency of the FML composite plates increased with the inclusion of nanofillers, according to the results of both the experimental and numerical investigations. It was discovered that the clamped-clamped boundary condition specimens have a greater natural frequency than the cantilevered boundary condition specimens for similar setups. It was also discovered that the free-free boundary condition specimens behaved as rigid bodies up to the first six modes. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

Delamination is a typical flaw in fiber-metal laminated composite structures that, when hidden from view, can significantly lower structural stiffness and alter a structure's ability to respond dynamically to forces like natural frequencies. Delamination is undoubtedly an important topic as it causes the performance of the Fiber Metal Laminate structures in the service to worsen. Delamination detection and severity analysis are essential in the aerospace industry for both safety and cost reasons. Although natural frequencies do not directly reveal the location or extent of damage, they are the most dependable metrics for damage detection. Frequency shifts in various modes are used to solve the inverse problem to pinpoint the damage location and extent. The bending natural frequencies shift brought on by delamination is utilized as an input to predict the delamination parameters. This study used an approach based on machine learning and a regression model to find the delamination parameters, i.e., locations and severity, in fiber metal laminated cantilever beams. FEA simulations using ANSYS were used to get the dataset pertaining to the position, severity, and eigen values (or bending natural frequencies) of the delamination. The results of this study indicate that the delamination locations and severity predictions developed using machine learning and regression models are reasonably accurate and demonstrate good agreement with the observed data. [ABSTRACT FROM AUTHOR]

The design of structures using advanced composite materials such as fiber metal laminate requires an in‐depth understanding of their deformation behavior and response to the discontinuities in the structures. In the present study, a GLARE kind of fiber metal laminate in 2/1 configuration was fabricated in the form of conical frustum. Three cut‐outs of two different shapes such as circular and square were intentionally made at the center of the frustum at an angular distance of 120°. The quasi‐static compression test was conducted to determine the crashworthiness characteristics of laminate frustums with cut‐out and the results were compared with perfect frustum. The study showed that the laminate with cut‐out undergone for inward buckling near the discontinuities. Apart from that, the delamination and outward buckling were noted in the edges of the cut‐outs. The energy absorption of laminate frustum with circular cut‐outs was observed to be better than square cut‐outs. The performance of laminate frustums with cut‐outs was ranked using Technique for Order Preference by Similarity to an Ideal Solution technique. A finite element analysis was carried out to simulate the deformation behavior of laminate frustum with cut‐outs and the numerical results of deformation mode closely represented the experimental results. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FML) are used in outer covering of the fuselage skin structure. The thrust force and the torque generated during drilling process affect the quality of the holes on the structure. The magnitude of cutting forces is controlled by optimizing the drilling process parameters. In this study, the influence of drilling parameters such as spindle speed, feed rate and the weight percentage of layered double hydroxides (LDH) in the binder epoxy on the thrust force and torque during drilling operation was studied. The experiments were designed based on Taguchi's L9 orthogonal array. The Gray Relational Analysis was used as multi-objective optimization tool for finding the optimal combination of process parameters. The spindle speed was identified as the most influencing process parameter to affect the drill quality in the FMLs. SEM images taken on the drilled specimens for the best and worst input parameter settings were compared and discussed. The regression models were generated to predict the output response values within the range of actual experiments. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FMLs) belong to a class of composite materials comprising layers of metal sheets and fiber-reinforced polymers (FRP), configured in a specific sequence. This study investigates the tensile strength of FML specimens joined by riveted joints. FML plates were fabricated using AA5052 aluminium alloy, E-glass fibers, epoxy resin, and layered double hydroxide (LDH) via a hand layup process. The experimental parameters included the pattern of rivets, type of rivet materials, and rivet size. Tensile strength, the output response, was evaluated using Taguchi’s L9 orthogonal array design, followed by testing on a universal testing machine. The main effect plot and 3D surface plots were employed to analyze the tensile test results. Maximum tensile strength was held by the test specimen which was connected by the rivets made up of mild steel. From the ANOVA results presented in Table 6, it was inferred that the number of rivets used for joining the FML specimens (pattern) played a major role in deciding the tensile strength of the specimens (57.25%). A regression equation, derived from Design Expert software, established the relationship between input variables and the tensile strength of FML specimens. ANOVA was conducted to assess the impact of each process variable on achieving optimal tensile strength.This research contributes novelty by integrating LDH into FML fabrication and demonstrates practical significance through systematic optimization of riveting parameters to enhance tensile strength. Quantitative and qualitative analyses underscore the effectiveness of the proposed FML configuration, validating its potential for structural applications. [ABSTRACT FROM AUTHOR]

Fiber Metal Laminates (FML) are hybrid composites comprising metals and Fiber Reinforced Plastics (FRP). FMLs are the most widely used in aerospace, defence and automotive sectors due to their superior qualities like light weight, tensile, compression, flexural, excellent fatigue and impact resistance. The properties like strength-to-weight ratio, susceptibility to corrosion and good heat conduction of FML make it suitable for subsea applications. Commonly, FML with a combination of aluminium (Al), titanium (Ti), stainless steel (SS) alloys and FRP are widely used for ocean applications. Compared to other FML, the SS alloy-based FML is typically used in subsea applications as it has more creep and excellent corrosion resistance. In India, under the Ocean Acoustics programme of the National Institute of Ocean Technology (NIOT), an autonomous underwater Ambient Noise Measurement System (ANMS) has been developed and deployed in the shallow waters of Indian seas for the past 12 years to study the background noise prevailing in the sea. To accommodate electronics and power packs for the measurement of ambient noise at an ocean depth of 100 m, subsea housing with stainless steel 316L (SS316L) material for a pressure rating of 1 MPa has been developed. The objective of this study is to develop the FML with SS316L and FRP for reducing the weight of the housing. Based on the literature studies and Classical Laminate Theory (CLT), the FML has been fabricated as a 0.45 m (450 mm) panel with a sequence of SS316L as outer layers and E-glass fibre and carbon as the inner layers. The total thickness of the laminates is 0.006 m (6 mm). The developed FMLs are processed with water jet cutting machines to carry out various testing such as tensile, compression and flexural, which are relevant to the characterization of FML and the experimental results are described in the paper. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FMLs) are a super hybrid material that provides the combined advantages of metals and composites and offers significant potential as an ultralight structural material in the aerospace industry. Consequently, there has been increased research attention on FML mass production processes. The recent developments in FML component production and FML sheet preparation are the main topics of this review. First, a general overview of the development history, fabrication process, and properties of FMLs and their production process is presented in this paper. With a focus on combined die forming, such as stamping and hydroforming, which is the most promising method for the mass manufacture of complex curve-shaped FML components, several other forming technologies are also discussed in depth. Afterward, the FMLs' forming limitations and challenges, which have been observed in previous research, are also mentioned thoroughly. The defect and deformation modes that can develop during the forming processes of FMLs are addressed. Furthermore, considering all the relevant factors, the future scope of study and development has also been evaluated. [ABSTRACT FROM AUTHOR]

The current study investigated the influence of incorporation of graphene nanoplatelets (GNPs) on quasi-static behavior of composite and fiber metal laminate (FML) panels. The unmodified and modified composite specimens and FML panels with 2/1 configuration were fabricated using a hand lay-up method and investigated through a quasi-static punch and indentation testing. The two sets of tests were conducted with a flat-ended indenter and the loading conditions were the same for all samples, except support spans which were varied. Following experimental testing, possible damages at the punch region were closely investigated and localized and global damages were observed. The results revealed that adding 0.2 wt% GNPs improved the strength and fracture toughness of specimens by delaying the failure modes. On the contrary, GNPs made the bonding between the aluminum and composite interface to weaken. [ABSTRACT FROM AUTHOR]

Although fiber metal laminates (FMLs) were invented a few decades ago, large-scale manufacturing, especially the forming process of small and complex-shaped products, has not been matured yet. The forming difficulty comes with the limited strain rate of the fiber layers compared to the metallic layers. As a result, the conventional approaches to form FML parts are not very suitable. Understanding the material behavior during the forming process is critical to find a new technique for relatively intricate and smaller FML parts. The blank holder gap (BHG) is one of the effective parameters to control the material flow in the deep drawing process, but in the case of the FMLs, the situation is completely different due to the laminate constituent. The compression of the fiberglass and thermo-plastique resin to the blank holder force (BHF) is not the same as the metals. The resin acts like a rubber, which decreases the thickness of the laminate and affects the friction between the laminate layers, especially when forming semi-cured laminates, which makes it hard to define an ideal BHF. This paper presents the results of numerical and experimental investigation of the effect of the BHG on the hydromechanical deep drawing (HDD) of a cylindrical cup made with 2/1 Glare sheets. It is found that the optimized BHF and cavity pressure (CP) with a BHG of 1.1 mm, smaller than the laminate's initial thickness of 1.2 mm, resulted in a good part with a significant depth improvement of 35 mm. Results also exhibited that FML parts manufactured by considering the BHG can enhance its applications and lead to a reduction of time and effort spent in mass production. [ABSTRACT FROM AUTHOR]

It is known that fiber metal laminates as one of hybrid materials with thin metal sheets and fiber/resin layers have limited formability in conventional forming methods. This paper presents an experimental and numerical study for drawability of glass fiber-reinforced aluminum laminates under hydromechanical drawing technique. Fiber metal laminates comprised of a layer of woven glass fiber-reinforced prepreg, sandwiched between two layers of aluminum alloy. In order to produce fiber metal laminates, the laminates were subjected to a sufficient squeezing pressure under a controlled heating time and temperature by using a hydraulic hot press. A hydromechanical tooling equipped with blank-holder force and fluid pressure control system was used to form the initial circular fiber metal laminate blank. Finally, the effect of parameters such as pre-bulging pressure, final chamber pressure, and drawing ratio on process variables was evaluated. Also, the characteristic curve of hydromechanical drawing of fiber metal laminate i.e. chamber pressure in terms of drawing ratio was achieved by means of experimental tests and numerical simulations. The results showed that the maximum drawing ratio of defect-free fiber metal laminates, namely without any tearing, wrinkling, and delamination was obtained at pre-bulging and chamber pressure of 35 and 80 bar, respectively. [ABSTRACT FROM AUTHOR]

Fibre metal laminates are high strength materials made up of alternating layers of metal alloy and composite materials. Commercially available fibre metal laminates include CARALL, ARALL and GLARE. Other than the commercially available fibre metal laminates, number of researches have been performed with the alternate metal alloys such as stainless steel, Ti, Mg alloys and polymer matrices based on polypropylene, polyimide, polyester, etc. In this study, various factors affecting the mechanical properties of fibre metal laminates have been addressed along with the different types of failure modes observed by various researchers in their experiments. Hygrothermal conditioning which involves the subjection of fibre metal laminates to moisture and temperature (80℃ and 90% humidity as per ASTM standard 5229), their behaviour and influence on mechanical properties has also been reported in this study based on the results from the various researchers. [ABSTRACT FROM AUTHOR]

Fiber metal laminates (FMLs) are a type of hybrid materials interlacing composites and metals. In the present work, FMLs with aluminum alloy 6061 as the skin and E-glass fiber-reinforced polypropylene (PP) as the core material are fabricated and formed by the creep age forming (CAF) process. The effects of time and temperature as the process parameters and thickness and stacking sequences of composites layers as the FML parameters are evaluated on the springback of glass-reinforced aluminum laminates (GLARE) FMLs. After the CAF process, the springback of creep age-formed FMLs is calculated. The results show that the FMLs can be successfully formed with the CAF process by considering appropriate time and temperature. In addition, the stacking sequence of composite layers can affect the springback behavior of FMLs significantly. [ABSTRACT FROM AUTHOR]