Properties Of Fiber Metal Laminates Research Articles

Tensile behavior of fiber metal laminates with multiple holes at different temperature conditions

In this paper, the tensile properties of fiber metal laminates (FMLs) at 25°C ∼ 180°C temperature conditions and different hole arrangements are researched mainly by means of experiments, theoretical model, and numerical simulation. The stress–strain curves of FMLs are obtained by extensive tensile tests and are analyzed and compared. The fracture morphology of the specimens under different temperature conditions is observed using scanning electron microscopy (SEM). Finally, a progressive damage model on the basis of the subroutine Abaqus-VUMAT is developed to analyze the damage evolution process and failure mode of FMLs. Combined with the numerical simulation results, the damage evolution process, equivalent plastic strain, and interlaminar damage of FMLs under different hole arrangements are investigated and found to be in good agreement. The phenomena such as tough nest fracture, matrix fragmentation, fiber debonding, and fiber pullout at different temperatures are observed and analyzed by SEM. The failure modes of FMLs with multiple holes at different temperatures are discussed in this paper, which provides a solution for the application of FMLs in practical engineering.

Role of stacking sequence, metal sheets, and nano particle on strength and toughness of FMLs

The effect of nano particle inclusion and the stacking sequence/metal volume fraction on the tensile strength and energy absorption properties of Fiber Metal Laminates (FML) is investigated. The FML structure is composed of lightweight thin sheets of aerospace grade aluminum alloy 7075 and unidirectional glass fiber composite sheets with Araldite LY5052 thermoset epoxy system as the matrix. The volume fraction of aluminum sheets in the FML structure was varied by increasing the number of aluminum sheets from 2 to maximum 4. In the second batch, the epoxy matrix is reinforced with of multi-walled carbon nano tubes and nano diamond particles together, each with 0.15 wt%. The purpose is to enhance the properties of the epoxy matrix to facilitate higher inter-laminate adhesion (FRP and aluminum). The results of the tensile testing show that with the increase of the metal volume fraction, the tensile strength as well energy absorbing capability (toughness) both are increased. The inclusion of the nano-reinforcements has increased the tensile strength and the toughness of the FML structure as compared to that of the FMLs without nano particles. The strength-to-weight ratio of FML structures is also increased after the inclusion of nano reinforced as desired for aerospace applications.

Enhancing carbon fiber reinforced aluminum laminates with cellulose paper interlayers: experimental characterization of tensile, flexural, and interlaminar fracture toughness

ABSTRACT The mechanical properties of fiber metal laminates (FML) are influenced by several various factors. Interface adhesion plays a particularly crucial role in interlaminar strength. Enhancing the interlaminar strength of carbon fiber reinforced aluminum laminate (CARALL) composites present a persistent challenge due to inherent weaknesses between metal and composite elements. Therefore, this study focuses on improving the interlaminar performance of CARALL composites by introducing cellulose paper interlayer at the metal/composite interface. The cellulose paper interlayer offers the advantage of being cost-effective and sustainable. Cellulose paper-interleaved CARALL composites were fabricated by vacuum bagging method and exhibited noteworthy improvements in mechanical properties. Comparative analysis with pristine samples revealed substantial enhancements, including a 15% increase in tensile strength, a remarkable 42% improvement in flexural strength, and a significant enhancement in mode-I fracture toughness by 65%. Furthermore, the cellulose paper interleaving played a crucial role in stabilizing fracture formation at the fiber-matrix interface, with mode II fracture toughness witnessing a 3% increase. Visual examination revealed the underlying toughening processes occurring in the interfacial area. This innovative approach of interleaving laminated composites with cellulose paper emerges as a sustainable and effective strategy, demonstrating the potential to fortify and toughen the interlaminar zones of CARALL composites.

Achieving strong interfacial bonding of CFRP and magnesium alloy by modifying magnesium alloy surface via alkaline etching with EDTA addition

The interfacial properties of fibre metal laminates are closely related to the surface microstructure of metals. Herein, a hitherto unreported honeycomb-like micro/nano-porous structure was successfully fabricated on an AZ31B Mg alloy surface by incorporation of ethylenediaminetetraacetic acid disodium (EDTA-2Na) into an alkaline solution and achieved excellent interfacial bonding property between AZ31B and carbon fibre-reinforced plastic. The addition of EDTA-2Na can promote the formation of etched pores. The growing nano-scale etched pores join together to produce micro-scale pores and ultimately lead to the formation of a micro/nano-porous structure. The 60 min etched AZ31B/carbon fibre-reinforced plastic laminate exhibits a bonding strength of 25.87 MPa, which is an increase of 350.7% compared to that of the untreated sample. The significant increase in bonding strength is mostly ascribed to composite mechanical interlocking by the micro/nano-porous structure and chemical bonding through the formation of MgCO3 and MgO1+X. In addition, the characteristics of micro-pores also affect the bonding strength.

The effect of thermal and cryogenic environments on the impact performance of aluminum-glass fibers/epoxy laminated composites

In this research work, the effect of various environments on the impact properties of fiber metal laminates was investigated. To do so, in the first step, the 2024 aluminum layers were surface modified with the etching method. Then, the various glass fibers/epoxy composites with the configurations of (0°/0°/0°/0°, 90°/90°/90°/90°, +45°/−45°/−45°/+45° and 0°/90°/90°/0°) were sandwiched between two aluminum sheets. In the following, these samples were aged under thermal cycling (between 25 and 100 °C), isothermal aging at the temperature of 100°C, cryogenic cycling (between −196 and 25 °C), and cryogenic isothermal aging at the temperature of −196°C. To understand the effect of various aging methods on the mechanical features of these structures, the Charpy impact test was performed. Also, the failure mechanisms and related phenomena were assessed by visual observations and microstructural investigations. In the first steps of thermal aging, the impact strength of FMLs was improved, which the highest of that being 46.9%. In the higher cycles or exposing times, the impact strength showed reducing trends, due to thermal degradations of the epoxy matrix. The cryogenic cycling in the high cycles reduced the impact strength of FMLs. But in the cryogenic isothermal condition, in some cases, the improvement in the impact strength was seen, which the highest of that being about 43.4%.

Enhancing the mechanical properties of fiber metal laminate by surface treatment

AbstractFiber‐metal laminates with high toughness and high strength have become an important direction for the development of new materials in the future. During the production and service process of fiber‐metal laminates, brittle fracture and interlaminate damage are easily caused by low load, which leads to the instability and damage to the overall structure. This article mainly studies the effects of surface treatment process, and material combination on the mechanical properties of glass fiber/polypropylene (PP)/stainless steel mesh (SSM) composite laminates. It is shown that the adhesion force of the phosphating SSM sample is 1.73 times that of the etched sample, and the bonding effect with organic substances is relatively better. The laminate with the structure of “unetched SSM + maleic anhydride grafted polypropylene + aminosilane glass fiber fabric” had the best tensile load. The etched and phosphatized SSM enhanced the interface adhesive effect with PP‐g‐MAH, thereby improving the overall structural strength of the laminate.

The experimental assessment of carbon nanotubes incorporation on the tensile and impact properties of fiber metal laminate fabricated by jute/basalt fabrics-aluminum layers: As hybrid structures

In this work, the simultaneous effect of different stacking sequences of basalt/jute fibers and adding the various weight fractions of carbon nanotubes (CNTs) on the mechanical features of fiber metal laminates (FMLs) under the tensile and impact conditions was assessed. According to the results, the FML had the highest performance under the mechanical tests, when the jute layers were sandwiched by the basalt fibers. In contrast, by sandwiching the basalt fibers with the jute fibers, the FML showed the weakest performance just under the tensile test. This configuration had the moderate performance under the impact test. Incorporating 0.3 wt.% CNTs in all configurations caused to reach the highest improvement in the tensile strength, elastic modulus and impact energy, which were 301 MPa, 50.9 GPa, and 12.3 J, respectively. Reinforcing an adhesion between skin/core and enhancing the mechanical properties of composite core were the effective factors for improving the tensile properties. The delamination of layers, fibrillation of jute fibers, creation of imprint phenomenon, and pull out the basalt fibers were the characterized wasting mechanisms under the impact conditions.

Fire Properties of Hybrid Composites

Thermal conductivity of a components subjected to high temperature is an important property to be considered in a materials to be used in automobile and aerospace fire designated zones; likewise, it is availability, cost, stiffness, resistant to corrosion, and its strength. The main aim of the study is to investigate the fire behavioural properties of fibre metal laminates (FML) composite of a metal, synthetic, natural and polymer matrix. The composites were fabricated in a mould using hand lay-up method and allow to cured before test.. The fire property test was carried out using the standard properties test equipment as ISO 2685 propane burner thermocouples and heat flux meter. The result of the properties test shows a remarkable increase in the properties of only natural fibre metal laminate composites, with a slight decrease in the properties of pure synthetic fibre metal laminates. Flax composite has a high percentage of 21.43% of thermal conductivity and withstand the flame temperature for 15 minutes using an ISO 2685 standard while kenaf composite fail at 10 minutes 30 seconds, Conclusively, the composites can be used as the component in fire designated zones of automotive, aerospace and other machines.

The Interlaminar Mechanical and Impact Properties of Fibre Metal Laminates Reinforced with Graphene

The Interlaminar Mechanical and Impact Properties of Fibre Metal Laminates Reinforced with Graphene

Effect of chemically grafted CNTs onto carbon fiber on the mechanical properties of fiber metal laminates

This study explores the influence of the chemical grafting of CNTs on the surface of carbon fibers (CFs) on the mechanical properties of Ti/CFRP laminates. After grafting CNTs onto oxidized CFs, Ti/CFRP laminates were prepared through vacuum-assisted resin-transfer molding (VARTM). Then, the bending performance, interlayer shear performance, static press-through, and impact resistance of the modified laminates were systematically studied. Compared with the original laminates, the bending strength and interlaminar shear strength were all remarkably improved. The static press-through tests showed a linear relationship between the energy absorption and laminate thickness, and the maximum failure load was slightly lower than that of the original specimen. The introduction of CNTs improved the deformation resistance of the laminate by increasing the critical fracture energy. Under a certain impact energy, the damaged area of the modified laminates decreased by a quarter without matrix or fiber delamination.

Evaluation of tensile properties of fiber metal laminates under different strain rates

There has been an ever-going need for materials containing excellent mechanical properties, lower density, and improved fuel efficiency in the aerospace industry. To date, Fiber Metal Laminates (FMLs) are a prime choice for aerospace applications. The components of aircraft are subjected to various mechanical loadings under operating conditions; therefore, an in-depth understanding of material behavior under expected loading conditions is imperative for the meticulous design and manufacturing of these components. To evaluate the tensile behavior of the FMLs containing Aluminum 7075-T6 sheets as a metallic phase was the primary aim of this study. Furthermore, the manufactured composites were treated with the processes including surface de-greasing, mechanical abrasion, and anodizing. In order to perform mechanical characterization, uniaxial tensile tests were conducted at various strain rates 2×10−4 s−1, 5×10−4 s−1 and 8×10−4 s−1. The FMLs were fabricated through vacuum-assisted resin transfer molding (VARTM) process. The results revealed that FMLs based different combinations of the fiber and metal constituents exhibited a low degree of strain rate-sensitivity. In the case of CARALL, 1.7% increase in tensile strength was observed, and, its tensile strength was increased from 741 MPa to 754 MPa. Whereas, ARALL and GLARE laminates exhibited high degree of strain rate-sensitivity. When the strain rate is increased from 2×10−4 s−1, 5×10−4 s−1 and 8×10−4 s−1 the values are increased in the following patterns: 389 MPa, 411 MPa, and 475 MPa for GLARE laminates, and 253 MPa, 298 MPa 352 MPa for ARALL laminates. Thus, 39% and 22% increase in the tensile strengths were noted for ARALL and GLARE laminates, respectively.

Effect of coupling agent quantity on composite interface structure and properties of fiber metal laminates

AbstractEpoxy silane coupling agent A‐187 and amine silane coupling agent A‐1387 were used to modify the interface of carbon‐reinforced aluminum laminates (CARE), respectively. The effects of the type and content of coupling agent on the microstructure and mechanical properties of CARE were investigated. Results show that with the increase in the content of two coupling agents, the wettability first increases and then decreases. When the mass fraction of the two coupling agents is 1%, good wetting property is obtained, and the interlaminar shear and flexural strengths of the CARE plate are the best. Compared with epoxy coupling agent A‐187, amine coupling agent A‐1387 had better wettability to aluminum alloy surface and highly contributed to the improvement of interface structure and properties, which then increased the interlaminar shear and flexural strengths by 19.1% and 8.9%, respectively.

Experimental and numerical investigations on the quasi-static structural properties of fibre metal laminates processed by thermoforming

Recently, increasing development efforts of components made of fibre metal laminates (FMLs), with thermoplastics due to their numerous advantages are remarkable. One-step adhesion and forming approach is an innovative solution to process such laminates reducing the cycle time and delivering failure-free components simultaneously. Hat shaped sections were the chosen geometry in this paper. This process is described considering the temperature, pressure and time progress in addition to the temperature distribution inside the FMLs in different locations. In order to describe the structural behaviour of the hat profiles, top-hat crashboxes were produced and tested via quasi-static three-point bending tests. The investigations were carried out by experimental and finite element simulation. Several parameters are discussed in detail, the top layer (steel and aluminium), the core layer thickness (0.5 and 1.0 mm) and glass fibre orientations (0°/90° and ±45°). The results revealed that by doubling the core thickness, the forming forces and accordingly the absorbed deformation energy were doubled at reduced weight increase. Comparing the experimental and numerical results for the Al-based FMLs, a good agreement regarding the energy absorption deformation mode and the force–displacement progress was reached.

Available Relevant Study on Stress Analysis and Static Strength Prediction of Fiber Metal Laminates.

Fiber metal laminates (FMLs) are a novel type of structural material that has been extensively applied in the aerospace field. These laminates are sandwich-type composite materials that comprise alternate metal and fiber-reinforced resin layers. Because of the structural characteristics of the material, it has high-impact resistance from the metal layer and increased fracture toughness and excellent fatigue and damage tolerance properties from the fiber layer. To further develop and apply this new composite material, it is essential to understand the research status on the stress analysis of each component in FMLs and the tensile strength properties of FMLs. Therefore, in this study, the current research status on the residual stress and applied stress of the component materials in FMLs and the tensile strength of the laminates is summarized. The relationship between the applied stress of each layer and the remote stress of laminates and the relationship between the tensile properties of laminates and the component material properties in laminates are clarified. Additionally, the theoretical basis and direction of development of the related models are analyzed and studied. Consequently, all of the above are aimed at laying a foundation for further investigations of the laminate theory and for the improvement of the theoretical research system.

The fracture properties of fiber metal laminates based on a 3D printed glass fiber composite

Fiber Metal Laminates (FML) are structures that contain a sequential arrangement of metal and composite materials, which are of great interest to the aerospace sector due to the superior mechanical performance. The traditional manufacturing process for FML involves considerable investment in manufacturing resources depending on the design complexity of the desired components. To mitigate such limitations, 3D printing enables direct digital manufacturing to create FML with customized configurations. In this work, a preliminary mechanical characterization of additively-manufacturing-enabled FML has been investigated. A series of continuous glass fiber-reinforced composites were printed with a Markforged system and placed between layers of aluminum alloy to manufacture hybrid laminate structures. The laminates were subjected to tensile, interfacial fracture toughness, and both low-velocity and high-velocity impact tests. The results showed that the FMLs appear to have a good degree of adhesion at the metal-composite interface, although a limited intralaminar performance was recorded. It was also observed that the low and high-velocity impact performance of the FMLs was improved by 9–13% relative to that of the constituent elements. The impact performance of the FML appeared to be related to the fiber fracture, out of plane perforation and interfacial delamination within the laminates. The present study can provide an initial research foundation for considering 3D printing in the production of hybrid laminates for static and dynamic applications.

The Mechanical Properties of Fiber Metal Laminates Based on 3D Printed Composites.

The production and mechanical properties of fiber metal laminates (FMLs) based on 3D printed composites have been investigated in this study. FMLs are structures constituting an alternating arrangement of metal and composite materials that are used in the aerospace sector due to their unique mechanical performance. 3D printing technology in FMLs could allow the production of structures with customized configuration and performance. A series of continuous carbon fiber reinforced composites were printed on a Markforged system and placed between layers of aluminum alloy to manufacture a novel breed of FMLs in this study. These laminates were subjected to tensile, low velocity and high velocity impact tests. The results show that the tensile strength of the FMLs falls between the strength of their constituent materials, while the low and high velocity impact performance of the FMLs is superior to those observed for the plain aluminum and the composite material. This mechanism is related to the energy absorption process displayed by the plastic deformation, and interfacial delamination within the laminates. The present work expects to provide an initial research platform for considering 3D printing in the manufacturing process of hybrid laminates.

Mechanical characterisation of kenaf/PALF reinforced composite-metal laminates: Effects of hybridisation and weaving architectures

Fibre metal laminates are advanced sandwich materials that offer various outstanding properties over conventional metallic alloys and composites. This research study intends to investigate the effects of weaving architectures and stacking configurations on the mechanical properties of fibre metal laminates based on kenaf/pineapple leaf fibre. Fibre metal laminates were fabricated through the hot moulding compression technique. Mechanical tests were performed on the kenaf/pineapple leaf fibre-based fibre metal laminates. In accordance with the findings obtained, hybridisation had led to the improvement in the mechanical properties of fibre metal laminates in comparison with [K/K/K] fibre metal laminates. Overall, twill woven-ply [P/P/P] fibre metal laminates showed the highest tensile and flexural strength, which was 14.53% and 33.50% higher than twill woven-ply [K/K/K] fibre metal laminates, respectively. Besides, the twill woven-ply [P/P/P] fibre metal laminates also displayed the highest impact strength and indentation properties compared to other non-hybrid and hybrid fibre metal laminates. When comparing the fibre metal laminates with different weaving architectures, twill woven-ply fibre metal laminates were shown to have higher mechanical properties over those of plain woven-ply fibre metal laminates.

Chemically Grafting Carbon Nanotubes onto Carbon Fibers for Enhancing Interfacial Properties of Fiber Metal Laminate.

This paper primarily investigates the effects of chemically grafted modified carbon fibers on the bonding properties of fiber metal laminates (FMLs). Relative elemental content on the carbon fibers’ surface was performed via X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was utilized to observe the material microstructure. The effect of chemically grafted carbon fibers on the bond strengths of FMLs was experimentally investigated through lap joint testing. The carbon nanotubes (CNTs) grafting concentration and curing conditions of the samples were also investigated. The test results demonstrate that grafting concentrations of 0.1, 0.2, and 0.3 mg/mL CNT solution increased the bond strength of the cured samples under vacuum conditions by 63.51%, 87.16%, and 71.56%, respectively. In addition, the bond strengths of vacuum-cured samples were also increased.

The effect of graphene nanoplatelets on the flexural properties of fiber metal laminates under marine environmental conditions

In this research, the effects of adding graphene nanoplatelets (GNPs) on the flexural properties of fiber metal laminates (FMLs) under marine environmental conditions were investigated. The FMLs were fabricated with alternating layers of Al6061 and glass fiber reinforced epoxy (GFRE) with different concentrations of GNPs (0.25, 0.5, and 1.0 wt%). The samples were immersed in the 3.5 wt% NaCl solution for different immersion times (7, 14, and 28 days) at room temperature. The addition of GNPs led to decreasing the water absorption of samples after immersion in the 3.5 wt% NaCl solution; the lowest absorbed water was for the samples with 0.25 wt% GNPs. Although the flexural properties of samples decreased by increasing the immersion time, the lowest reduction in flexural properties was obtained for the sample with 0.25 wt% GNPs. Results showed that by adding GNPs and immersing the specimens in the 3.5 wt% NaCl solution for 28 days, the flexural strength and modulus, and strain values of specimens containing 0.25 wt% GNPs were respectively about 128%, 63%, and 1.85 times higher than those of samples without GNPs. Also, the reduction of the flexural properties caused by immersion in NaCl solution was lower than that of samples without GNPs. Moreover, the water uptake of samples with 0.25, 0.5, and 1.0 wt% GNPs was about 38%, 31%, and 37% lower than that of samples without GNPs after 28 days of immersion. Microstructural analyses revealed that the improvements in the metal/polymer adhesion and mechanical properties of the polymeric part of FMLs resulting from various mechanisms were the main reasons for the improved performance of samples with GNPs under marine conditions.

Lay-up optimisation of fibre–metal laminates panels for maximum impact absorption

This paper introduces a methodology utilising a ply-ply damage Finite Element models with Genetic algorithm optimisation procedure to investigate the effect of lay-up configuration on the impact absorption properties of fibre metal laminates (FMLs). The methodology was carried out in two steps. In the first step, a pseudo-2D model was used to explore the vast design space to identify potential optimised layup-configurations. In the second step, the optimised configurations were studied in full 3 D, with high fidelity simulations, verifying the results obtained from the optimisation process. The design variables used include thickness and material (including fibre orientation) of each ply. The results produced an optimised configuration consisting of a metallic ply on the impacted side followed by a cross-ply composite lay-up. The results also suggest that the first composite ply (second ply of the FML) should be about 3 times thicker than the other plies.