Fiber Reinforced Aluminum Laminates Research Articles

Performance Analysis of Helical Milling and Drilling Operations While Machining Carbon Fiber-Reinforced Aluminum Laminates

Being a difficult-to-cut material, Fiber Metal Laminates (FML) often pose challenges during conventional drilling and require judicious selection of machining parameters to ensure defect-free laminates that can serve reliably during their service lifetime. Helical milling is a promising technique for producing good-quality holes and is preferred over conventional drilling. The paper compares conventional drilling with the helical milling technique for producing holes in carbon fiber-reinforced aluminum laminates. The effect of machining parameters, such as cutting speed and axial feed, on the magnitude of cutting force and the machining temperature during conventional drilling as well as helical milling is studied. It was observed that the thrust force produced during machining reduces considerably during helical milling in comparison to conventional drilling at a constant axial feed rate. The highest machining temperature recorded for helical milling was much lower in comparison to the highest machining temperature measured during conventional drilling. The machining temperatures recorded during helical milling were well below the glass transition temperature of the epoxy used in carbon fiber prepreg, hence protecting the prepreg from thermal degradation during the hole-making process. The surface roughness of the holes produced by both techniques is measured, and the surface morphology of the drilled holes is analyzed using a scanning electron microscope. The surface roughness of the helical-milled holes was lower than that for holes produced by conventional drilling. Scanning electron microscope images provided insights into the interaction of the hole surface with the chips during the chip evacuation stage under different speeds and feed rates. The microhardness of the aluminum layers increased after processing holes using drilling and helical milling operations. The axial feed/axial pitch had minimal influence on the microhardness increase in comparison to the cutting speed.

Effect of boundary conditions on the low‐velocity impact damage mechanism of fiber metal laminate

AbstractThe boundary condition is a very important factor when characterizing the impact performance of a material or a structure. However, its effect on fiber metal laminate (FML) has been rarely mentioned. In the present investigation, three levels of low‐velocity impact tests were conducted on the glass fiber reinforced aluminum laminate (Glare) under two different boundary conditions, one was that defined in ASTM D7136 and another one was self‐designed that has the same constraint area but different constraint degree. One basis of the experiments, finite element analyses were performed to gain a deeper understanding of the different damage mechanisms. With which another three boundary conditions were investigated for further considering the effect of constraint areas on both the impact and non‐impact sides, including that defined in another commonly used standard ASTM D5628 and two self‐designed cases. It was indicated that the boundary conditions influenced less the force and energy responses of Glare laminate, regardless of the impact damage levels, and hardly on the damage behavior as well when perforation was encountered. However, influences were obtained under lower and intermediate damage levels, and it was the constraint area on the rear side and constraint degree that played the dominant roles, respectively. The results achieved can provide suggestions for reasonably evaluating the low‐velocity impact performance of FML.Highlights Comparisons were made between the low‐velocity impact behavior of Glare laminates under five different boundary conditions. Boundary conditions influenced hardly on maximum impact force and energy absorbed ratio, but evidently on damage behavior. Constraint area and constraint degree governed damage mechanism under lower and intermediate impact energies, respectively. Influence of boundary conditions on damage behavior disappeared when the impact energy was enough to perforate Glare laminate.

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.

Study on bending properties and damage mechanism of carbon fiber reinforced aluminum laminates

Study on bending properties and damage mechanism of carbon fiber reinforced aluminum laminates

Numerical investigation on dynamic behavior and damage mechanisms of fiber metal laminates subjected to combined explosion and fragments loading

Fiber metal laminates (FMLs) are widely applied as protective structures in various high-tech industries owing to their excellent impact resistance. This paper presents an explicit finite element (FE) simulation to investigate the dynamic damage behavior of carbon fiber-reinforced aluminum laminates (CRALLs) under combined explosion and fragment loading. Johnson-Cook model is utilized to capture the damage response of aluminum material; 3D Hashin failure criteria are applied to predict the damage evolution of fiber composite material considering the high strain rate effect; cohesive elements are incorporated to simulate the inter-laminar delamination phenomena. The effectiveness of the proposed numerical model is verified through a comparison with available experimental data in ballistic impact conditions. In addition, a thorough analysis of the dynamic behavior and damage mechanism of FMLs is conducted, and the impact performance is extensively discussed in terms of the influences of explosion distance and explosion mass. This work serves as a valuable reference for future numerical studies on the explosive impact resistance of other FMLs structures.

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

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

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

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

Theoretical analysis on carbon fiber reinforced aluminum laminate under off-center impact

Carbon fiber reinforced aluminum laminate (CARALL) composed of multi-layer CFRP and aluminum has better toughness and impact resistance than composite laminates due to the existence of metal. This work investigates the energy absorption mechanism and creatively proposes a theoretical analysis model to predict the dynamic response of CARALL under off-center impact. Firstly, based on a simplified ideal rigid-plastic material model, a unified yield criterion and its simplified method for hybrid plastic hinges are proposed. Then, the analytical solution for maximum transverse displacement and impact force of CARALL under off-center impact is established. Finally, it is verified by the simulation and discussed in detail. The results show that the established theoretical method can predict the structural response under low-velocity impact.

Molding preparation and tensile properties test of carbon fiber reinforced aluminum laminates

Molding preparation and tensile properties test of carbon fiber reinforced aluminum laminates

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

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

Energy dissipation mechanism of fiber metal laminate under low-velocity impact

Identification of the energy dissipation behavior of fiber metal laminate under low-velocity impact is necessary for understanding its impact response and damage mechanism, as the impact scenario is typical for energy conversion. In this paper, the glass fiber reinforced aluminum laminate (Glare) was tested under different impact energy to achieve typical low-velocity impact responses and damage patterns. By which the finite element model was built and verified to be effective, by employing the Johnson–Cook model for aluminum, Hashin’s criteria and exponential damage evolution law based VUMAT subroutine for GFRP, and bi-linear traction–separation cohesive zone model for their interface. Based on the history energy outputs on internal energy, elastic strain energy, plastic deformation dissipated energy, and damage dissipated energy in the finite element model. The contributions of the constituents in the energy absorption aspect of Glare were firstly revealed. Furthermore, how the energy was dissipated by the laminate and by the constituents, i.e., the distributions of energy evolutions in laminate and constituent levels, were clarified. Finally, damage evolutions of individual layers and the failure sequence of the entire laminate were elaborated. The results achieved have specified the energy dissipation mechanism and its association with the impact response of Glare.

Study on off-center impact behavior and damage characterization of carbon fiber reinforced aluminum laminate

This paper aims to explore the off-center low-velocity impact response and damage characteristics of carbon fiber reinforced aluminum laminate (CARALL). Progressive damage finite element models of CARALL considering the stiffness degradation and damage evolution of carbon fiber reinforced plastic (CFRP) were established using a user subroutine and verified by off-center impact tests with different impact energies. The motion propagation, damage, and spatial distribution of dynamic responses of CARALL impacted in different locations are studied. The results indicate that increase in impact distance from center dissipates more energy due to the more severe damage and failure of CFRP, while the off-center impact have a negative effect on the plastic energy absorption of metal compared with center impact. A quantitative expression is proposed to describe the spatial distribution of the maximum transverse displacement.

Progressive Damage Behaviour Analysis and Comparison with 2D/3D Hashin Failure Models on Carbon Fibre-Reinforced Aluminium Laminates.

It is known that carbon fibre–reinforced aluminium laminate is the third generation of fibre metal materials. This study investigates the response of carbon fibre–reinforced aluminium laminates (CARALL) under tensile loading and three-point bending tests, which evaluate the damage initiation and propagation mechanism. The 2D Hashin and 3D Hashin VUMAT models are used to analyse and compare each composite layer for finite element modelling. A bilinear cohesive contact model is modelled for the interface failure, and the Johnson cook model describes the aluminium layer. The mechanical response and failure analysis of CARALL were evaluated using load versus deflection curves, and the scanning electron microscope was adopted. The results revealed that the failure modes of CARALL were mainly observed in the aluminium layer fracture, fibre pull-out, fracture, and matrix tensile fracture under tensile and flexural loading conditions. The 2D Hashin and 3D Hashin models were similar in predicting tensile properties, flexural properties, mechanical response before peak load points, and final failure modes. It is highlighted that the 3D Hashin model can accurately reveal the failure mechanism and failure propagation mechanism of CARALL.

Impact resistant basalt fiber-reinforced aluminum laminate with Janus helical structures inspired by lobster and mantis shrimp

Fiber metal laminate (FML) is an extremely strong and light material that is widely applied in the structural components of aircraft for weight reduction and improving mechanical properties. However, the effective integration of excellent structural failure tolerance property and superior stress dissipation capacity into one FML material remains a huge challenge. Herein, inspired by the non-linear helical structure of lobster and the linear helical structure of mantis shrimp, a novel bioinspired FML with Janus helical structure was designed and manufactured through the method of hot press forming. Afterwards, low velocity impact tests were carried out to evaluate the impact resistant property. Remarkably, the peak impact force of the bioinspired Janus FML (BJFML) at the impact energy of 40 J was 8216.36 N, which increased by 10.22% compared with the 7454.52 N of traditional cross-ply FML (CPFML). Moreover, the dent depth of the BJFML (5.95 mm) decreased by 28.23% compared with that of CPFML (8.29 mm). Finally, the finite element simulation was conducted systematically. In fact, the non-linear helical arrangement greatly hindered crack propagation and the periodic linear structure improved its load homogenizing ability for impact forces, thus improving structural failure tolerance, strengthening stress dissipation, and synergistically enhancing the impact resistance.

Impact Properties of Novel Natural Fibre Metal Laminated Composite Materials

Fibre metal laminates (FMLs) are lightweight structures with high structural performance and are suitable for many industrial applications. This work describes the impact behaviour of novel sisal fibre-reinforced aluminium laminates (SiRAL) and their dependence upon the orientations of the fibres, the composite core used and the surface treatment of the metal skins. A cold-pressing technique is used to produce SiRALs in six configurations. The FMLs here also have treated or untreated aluminium skins (2024 T3) and three different types of core materials (0°/90° fabric, ±45° fabric and random matt). The ±45° core treated SiRAL provides the highest energy absorption and deflection properties. The pre-treatment of aluminium skins using sandpaper, deep cleaning and primer significantly affects the delamination of the panels under bending impact. The findings reveal that the SiRAL concept is a promising multifunctional FML suitable for different applications that require lightweight, bending and impact performance, together with sustainability characteristics.

Deterministic and probabilistic buckling response of fiber–metal laminate panels under uniaxial compression

PurposeThe purpose of this paper is to study the deterministic elastic buckling behavior of cylindrical fiber–metal laminate panels subjected to uniaxial compressive loading and the investigation of GLAss fiber-REinforced aluminum laminate (GLARE) panels using probabilistic finite element method (FEM) analysis.Design/methodology/approachThe FEM in combination with the eigenvalue buckling analysis is used for the construction of buckling coefficient–curvature parameter diagrams of seven fiber–metal laminate grades, three glass-fiber composites and monolithic 2024-T3 aluminum. The influences of uncertainties concerning material properties and laminate dimensions on the buckling load are studied with sensitivity analyses.FindingsIt is found that aluminum has a stronger impact on the buckling behavior of the fiber–metal laminate panels than their constituent uni-directional or woven composites. For the classical simply supported boundary conditions, it is found that there is an approximately linear relation between the buckling coefficient and the curvature parameter when the diagrams are plotted in double logarithmic scale. The probabilistic calculations demonstrate that there is a considerable probability to overestimate the buckling load of GLARE panels with deterministic calculations.Originality/valueIn this study, the deterministic and probabilistic buckling response of fiber metal laminate panels is investigated. It is shown that realistic structural uncertainties could substantially affect the buckling strength of aerospace components.

Comprehensive experimental investigation on drilling multi-material carbon fiber reinforced aluminium laminates

The amalgamation of metallic alloys and fiber-reinforced composites has helped Fiber Metal Laminates (FMLs) like Carbon fiber reinforced aluminum laminates (CARALL), and Glasslaminatealuminum-reinforced epoxy (GLARE) overcome the limitations of standalone metals and composites. As a result, they have found increasing applications in the aircraft and defense industries. Moreover, the inhomogeneous nature and poor machinability of the materials make hole drilling challenging. Therefore, to enhance drilling performance, the paper reports a systematic analysis of the effect of spindle speed and axial feed on key performance measures, including thrust force, machining temperature, surface roughness, hole size, burr size, and chip morphology. Experimental outcomes indicate a significant reduction in the thrust force while utilizing higher spindle speed (4000 rev/min) and lower axial feed (0.1 mm/rev), while the surface finishes improved under high feed conditions (0.4 mm/rev). The analysis revealed that machining temperature increased with the employment of higher spindle speed and lower axial feed. Higher spindle speeds and axial feeds are desirable from the perspective of hole accuracy as they help produce holes within H9 diameter tolerance. Burr size was verified to be larger at the hole exit compared to the hole entry, with the size of the burr increasing with an increase in spindle speed and axial feed. The results show that the axial feed was the significant variable affecting chip size, followed by spindle speed. Higher axial feed (0.4 mm/rev) and spindle speed (4000 rev/min) helped improve the chip breakability, thus helping improve chip evacuation.

The experimental assessment of the various surface modifications on the tensile and fatigue behaviors of laminated aluminum/aramid fibers-epoxy composites

Fiber metal laminates (FMLs) are introduced as the kind of advanced hybrid composites consisting of the metals and composite layers, which the adhesion between those has an important role on the static and dynamic mechanical properties of these structures. To do so, the mechanical abrading, alkaline etching, forest products laboratory (FPL) and anodizing surface modification methods were performed on the 2024 aluminum for fabricating aramid fiber-reinforced aluminum laminate (ARALL). After that, by using tensile and fatigue tests as well as micro/macro-structural investigations, the static and dynamic mechanical properties of ARALL structures were studied. Based on the fatigue results at the stress level of 90%, the mechanical surface modification caused that the fatigue cycles reached to 2155 cycles, which was the highest fatigue cycles. Whereas in the stress level of 45%, the anodizing surface modification with the 34,420 fatigue cycles had the highest improvement. Given up the tensile results, the FPL and anodizing surface modified FMLs had the highest tensile strength, which were 317 and 319 MPa, respectively. The microstructural investigations showed that by using the various surface modification methods, the absorbing energy mechanisms of fatigue loadings by aramid fibers changed. Also, changes in the number and diameter of formed dimples in the aluminum skins were seen.

Interlaminar shear strength (ILSS) characterization of fiber metal laminates (FMLs) manufactured through VARTM process

The aircraft industry is always seeking materials with excellent mechanical properties and good strength to weight ratio. Fiber metal laminates (FMLs) are the emerging class of hybrid composite materials consisting of fiber-reinforced polymers (FRP) plies and metal sheets. Aircraft parts are subjected to different types of mechanical loading during operation. Combining the properties of FRPs and metals provides excellent resistance to impact as well as improves the fatigue performance of the aircraft. In this study, aluminum 7075-T6 sheets were used to fabricate FMLs with varying fiber reinforcements. These sheets were treated with different surface and chemical treatment processes. The short beam shear test is utilized in this work that gives practical information on interlaminar shear strength (ILSS) and it can also be employed in real design applications. The results indicated that the ILSS of carbon fiber reinforced aluminum laminates (CARALL) was higher than glass-reinforced aluminum laminates (GLARE) and aramid-reinforced aluminum laminates (ARALL) at all displacement rates. The reason for the higher ILSS of CARALL is due to the stifness of carbon fiber and the strong adhesion of carbon with aluminum metal. However, ILSS for all three types of FMLs did not change significantly which shows that it is independent of displacement rates.

Experimental and analytical assessment of the hypervelocity impact damage of GLAss fiber REinforced aluminum

This article addresses the response of GLAss fiber REinforced aluminum to hypervelocity impacts of micrometeoroid analogs at impact velocities of 7 km/s and beyond. In relation, the damage modes of different GLAss fiber REinforced aluminum configurations have been exemplified. The GLAss fiber REinforced aluminum configurations comprised six to twelve variably thick aluminum layers and up to four plies of glass fiber reinforced epoxy per composite laminate. Hypervelocity impact experiments have been conducted with the help of a two-stage light-gas gun, wherein aluminum- and stainless steel projectiles were launched at velocities up to 7.15 km/s. Visual inspection of the damage area suggested the dissipation of impact energy in elastic-plastic deformation, petalling, delamination, debonding, tensile failure of fibers, and pyrolysis of epoxy. A prevailing damage mode was not apparent albeit. The quasi-isotropic ply orientation of S2-glass/FM94-epoxy laminates promoted the interference of shock- and rarefaction waves and suppressed the damage area of GLAss fiber REinforced aluminum. To discriminate between the impact performance of different GLAss fiber REinforced aluminum configurations, the energy dissipated in different damage modes of GLAss fiber REinforced aluminum has been assessed quantitatively. In terms of normalized energy, the cross-ply GLAss fiber REinforced aluminum dissipated higher energy in petal formation than in other primary damage modes. The normalized petalling energy was found to decline with the increase of impact energy. The outcomes of this study will help to optimize the GLAss fiber REinforced aluminum laminate, which will be employed as a bumper shield to prevent the fatal damage and the unzipping of a spacecraft pressure bulkhead.