Laminate Components Research Articles

On the use of double‐double design philosophy in the redesign of composite fuselage barrel frame components

AbstractThe use of optimization procedures can provide a valuable contribution in optimizing the laminate design of composite components for mass minimization and mechanical performance maximization. Design for weight and strength requirements of composite structures can be efficiently provided with the newly developed double‐double laminates concept, which allows to overcome the conventional 0, 90, and ±45° ply orientations and symmetry requirements in laminates. In the double‐double designed components, composite laminates are made up stacking thin sub‐laminates with four [±Φ, ±Ψ] oriented plies without symmetry requirements. In the present paper, the lay‐up and thickness profile of the composite frames in a fuselage section have been redesigned according to the double‐double design concept taking into account the operating loads. The starting quad configuration has been replaced by an optimized double‐double configuration with suitable lay‐up and thickness profile for each of the frames, while achieving a reduction in the total components mass.Highlights Double‐double laminates offer a novel approach to composite laminate design. Double‐doubles aim to simplify design with composites as with metals. Laminate optimization performed varying plies orientations and number. Double‐double design of components optimized with respect to the acting loads. In aviation double‐doubles allow lightening of composite laminate components.

Banana/ coir biofibers and carbon/innegra fabrics and BN/MWCNT nanoparticles reinforced UV resistant polyester hybrid composites

Plant cellulose fibers are a biodegradable and acceptable alternative for fabricating balanced-strength polymer laminate components due to their higher specific strength, eco-friendliness, and renewable nature. The target of the present investigation is to manufacture banana-boron nitride-carbon fabric and coir-multi walled carbon nanotubes-Innegra fabric hybrid polyester laminates by varying different chemical treatments and determine the physical (density, water absorption, and contact angle), mechanical (tensile, flexural, interlaminar shear, impact strength, and shore D hardness) and thermal (onset, endset, glass transition temperature, and carbon residue) characteristics of fabricated laminates. The addition of chemically treated/ untreated banana/ coir fillers in the polyester matrix was affirmed morphologically and structurally from Fourier Transform Infra-Red (FTIR) spectra and scanning electron microscope (SEM). Differential scanning calorimeter (DSC) and Thermogravimetric analysis (TGA) results examined the higher thermal stability of the chemically treated banana/ coir fiber reinforced polyester hybrid laminates around 400 °C. The artificial neural network modeling was performed to select the best composite material among the fabricated laminates. The determination coefficient values were lower than 0.98 for testing, validation, and training for both laminates. The model outcomes exhibited lower root mean squared error, explaining that using the model of an exact threshold was predicted for the artificial neural network forecasting. The one way-Analysis of variance (ANOVA) technique was applied to study the significance of the difference between the chemically treated/ untreated banana and coir fillers on physical, mechanical, and thermal characteristics.

Investigations on Guided Ultrasonic Wave Dispersion Behavior in Fiber Metal Laminates Using Finite Element Eigenvalue Analysis

AbstractComposite materials such as fiber metal laminates combine the advantages of metallic materials and fiber‐reinforced polymers. Hence, these materials are of great interest for thin‐walled structures in lightweight engineering. Due to the structure of these materials, damage to fiber metal laminate components occur more frequently inside the structure than with conventional materials. Since the detection of interlaminar damage is more complicated compared to external damage, it is one of the biggest challenges in the use of fiber metal laminates. One approach to detect this kinds of damage, is the use of guided ultrasonic waves, for example Lamb waves. To be able to perform such damage detection, knowledge about the propagation behavior of this kind of waves in fiber metal laminates is fundamental. Abrupt stiffness variations across the thickness of fiber metal laminates, resulting from the different material layers, lead to the question whether the known approaches for the propagation of guided ultrasonic waves in isotropic and transversely isotropic materials are applicable here. Therefore, the objective of this work is to investigate the propagation behavior of these guided ultrasonic waves in fiber‐metal laminates over large frequency ranges. For this purpose, dispersion relations from finite element simulations are compared with experimental data and numerical solutions based on the analytical framework. The investigations are carried out using a fiber metal laminate consisting of steel and carbon fiber‐reinforced polymers. Due to the orthotropy of the laminate, wave propagation in the fiber direction and perpendicular to it is considered. For the finite element simulations a linear two dimensional eigenvalue analysis is used. This method is especially suitable because it offers a very efficient modeling approach for this kind of application. The experimental data are based on measurements contained in previous publications by the authors. The comparison of the finite element simulations with the experimental data and the data from the analytical framework show that they are in good agreement. The results shown in this work serve to validate the numerical approach presented and allow for further, more complex simulations.

Spatial and temporal averaging in the homogenisation of the elastodynamic response of periodic laminates

This paper suggests a methodology to obtain homogenised material properties from a transient dynamic numerical model. The standard Hill–Mandel Principle, based on spatial averages, is extended with time averaging. Thus, in addition to a sufficiently large Representative Volume Element (RVE) to carry out the averaging in space, a sufficiently large time window is required to carry out the time averaging. The space–time averaging procedure is validated for a periodic laminate bar subjected to a variety of boundary conditions, impedance contrasts and loading conditions. The homogenised results converge to the analytical solutions and confirm that having a higher impedance contrast between laminate components requires not only larger RVE sizes but also longer time averaging windows. The most efficient macroscopic approximation is obtained by a balanced increase in RVE size and time averaging window.

Measurement of the principal damping components of composite laminates

The prediction of material damping in composite laminate components may allow for the development of lighter component designs, and can be achieved via several techniques. One such example, the modal strain energy (MSE) technique requires a combination of effective strain energy modelling and accurate principal loss factor parameters. Measuring principal loss factors can be very challenging for lightly damped components due to parasitic or ‘extraneous’ damping sources introduced by the test set-up itself. To ensure high quality input data to the strain energy models an novel damping test procedure has been developed, which allows for mono-harmonic damping parameter extraction via free decay and logarithmic decrements, whilst minimising extraneous dissipation. Improvements over the established impact hammer testing technique could be shown during the validation of the approach.

Simplified low order composite laminate damping predictions via multi-layer homogenisation

The increased adoption of composite laminates in modern engineering requires advancement in the prediction of their dynamic behaviour. Current damping prediction techniques can be prohibitively time consuming and computationally expensive for application during early design stages, and to abstract three-dimensional geometries. A novel, lower order methodology for damping prediction is proposed, which uses a higher-level of homogenisation than established composite damping prediction techniques to provide a reasonable damping prediction without requiring a detailed model of a laminate’s internal structure. Principal loss factor components are harvested from a set of base layup specimens and used to predict the modal loss factors and frequency response of a set of geometrically abstract single layup validation specimens. A numerical study shows the low-order approach to produce approximately equivalent strain energy distributions to a well-established ‘layered’ approach at reduced computational cost and for a third of the CPU time. Furthermore, the damping and amplitude predictions produced by novel methodology are shown to closely match experimental measurements, providing scope to expand the application of this approach to more complex, multi-layup laminate components. • Low-order ‘smearing’ of properties predicts equivalent energies to existing methods. • Validation tests show low-order amplitudes/loss factor predictions to correlate well. • Approach simplifies modelling, improving computational cost with no loss of accuracy.

A comparative study on the GLARE stamp forming behavior using cured and non-cured preparation followed by hot-pressing

Demand for lightweight materials with structural integrity is necessary due to the increased global concern about air pollution and excessive fuel consumption. Fiber metal laminates (FMLs) have the potential to find the perfect balance between weight reduction and structural reliability, which includes improved damage tolerance. However, the fiber used in FMLs has limited elongation, and existing forming approaches are not qualified enough to produce small and deep laminate components, especially for mass production. In this research paper, an investigation has been carried out to understand the laminate system’s failure mode, eliminate defects, and improve drawability. A comparative study has been carried out for producing small parts made of GLARE (glass laminated-reinforced epoxy) material, using the conventional cured laminate and non-cured laminate with a hot-pressing method. The effect of these two methods on the GLARE forming behavior has been discussed. The numerical and experimental results of the new approach were compared with the conventional method. Results exhibit the positive effect of this approach on the quality of the formed cups and depth. Finally, this investigation can enhance the FMLs, and GLARE part applications compared to the conventional methods.

Deep drawing of fiber metal laminates using an innovative material design and manufacturing process

Fiber-Metal Laminates (FMLs) have gained increasing attention in the advanced industry due to their unique structural reliability, weight reduction, and improved damage tolerance. Nevertheless, the existing forming approaches are not well qualified for the high-volume manufacturing of small and complex laminate components. With the forming of FMLs, the cured fiber and resin matrix layers are deformed elastically, and the metal layers are deformed plastically. The attainable deformation is depending on the strain amount can endure by the glass fibers and by the strength of the interface among the layers. In current research work at the department of aircraft manufacturing engineering at Beihang University, a promising cost-effective approach for the automated mass production of small parts made of FMLs was proposed using new material design and manufacturing process. The new process combined an optimized inner glass fiber patches and non-cured FMLs, followed by the Hot-pressing. Results were very encouraging and exhibited that FML parts manufactured by using this new preparation and process may pave the way for industrial-scale utilization.

Characteristics of Laminates for Car Seats

Abstract In the presented research, 11 different laminates were compared, 8 of them were two-layered 3 of them were three-layered laminates. The laminates that were analyzed vary by the type of face-side textile material (knitted and nonwoven textiles), density and thickness of the foam, and specific properties (higher air permeability and low-emission foam). Depending on the different types of laminates, different laminating processes are used: hot-melt, flame, and powder laminations. The purpose of the presented research is to analyze the basic characteristics of the different laminate structures. Properties that are important for these types of laminates are the number of layers, areal density, thickness, resistance to rubbing, fire resistance, water vapor permeability, air permeability, breaking force and extension, thermal conductivity, and stratification. We found that the properties of laminates were not affected by the density and thickness of the foam. Nonwovens and other laminate components do not perform because they have lower abrasion resistance and lower tensile strength than knitted fabrics as the face layer. Knit laminates have good abrasion resistance, high air permeability, and water vapor permeability. Both are self-extinguishing to the first or second mark. Three-layered laminates have lower thermal conductivity and air permeability than two-layered laminates.

Multi-scale reliability-based design optimisation framework for fibre-reinforced composite laminates

PurposeThe purpose of this study is to enable performing reliability-based design optimisation (RBDO) for a composite component while accounting for several multi-scale uncertainties using a large representative volume element (LRVE). This is achieved using an efficient finite element analysis (FEA)-based multi-scale reliability framework and sequential optimisation strategy.Design/methodology/approachAn efficient FEA-based multi-scale reliability framework used in this study is extended and combined with a proposed sequential optimisation strategy to produce an efficient, flexible and accurate RBDO framework for fibre-reinforced composite laminate components. The proposed RBDO strategy is demonstrated by finding the optimum design solution for a composite component under the effect of multi-scale uncertainties while meeting a specific stiffness reliability requirement. Performing this using the double-loop approach is computationally expensive because of the number of uncertainties and function evaluations required to assess the reliability. Thus, a sequential optimisation concept is proposed, which starts by finding a deterministic optimum solution, then assesses the reliability and shifts the constraint limit to a safer region. This is repeated until the desired level of reliability is reached. This is followed by a final probabilistic optimisation to reduce the mass further and meet the desired level of stiffness reliability. In addition, the proposed framework uses several surrogate models to replace expensive FE function evaluations during optimisation and reliability analysis. The numerical example is also used to investigate the effect of using different sizes of LRVEs, compared with a single RVE. In future work, other problem-dependent surrogates such as Kriging will be used to allow predicting lower probability of failures with high accuracy.FindingsThe integration of the developed multi-scale reliability framework with the sequential RBDO optimisation strategy is proven computationally feasible, and it is shown that the use of LRVEs leads to less conservative designs compared with the use of single RVE, i.e. up to 3.5% weight reduction in the case of the 1 × 1 RVE optimised component. This is because the LRVE provides a representation of the spatial variability of uncertainties in a composite material while capturing a wider range of uncertainties at each iteration.Originality/valueFibre-reinforced composite laminate components designed using reliability and optimisation have been investigated before. Still, they have not previously been combined in a comprehensive multi-scale RBDO. Therefore, this study combines the probabilistic framework with an optimisation strategy to perform multi-scale RBDO and demonstrates its feasibility and efficiency for an fibre reinforced polymer component design.

Three-dimensional modelling of interlaminar normal stresses in curved laminate components

This paper presents the interlaminar normal stress distribution across the width of L-shaped composite components in bending, with special emphasis on the free edge effects and the induced loading due to boundary conditions. As L-shaped composite components are becoming more commonplace in engineering applications, it is of vital importance to understand their failure mechanisms and stress fields. An extensive literature review reveals that interlaminar delamination is the critical failure mode for curved composite components. Despite this, most literature only provides a two-dimensional analysis of the interlaminar stresses and the free edge effects and asymmetry due to induced torsion are not considered. This paper uses three-dimensional finite element modelling to address the following with respect to L-shaped laminate components in bending: (i) radial stress due to the presence of curvature, (ii) effect of lay-up on the free edge effect, (iii) determining how induced torsion affects the interlaminar normal stress distribution. The necessity of using a three-dimensional model to analyse the interlaminar normal stress across the width of a curved composite component is discussed. It was concluded that using a two-dimensional model could underpredict the interlaminar normal stresses by up to 37% for the lay-ups analysed in this research.

A new process route for the manufacturing of highly formed fiber-metal-laminates with elastomer interlayers (FMEL)

Fiber-metal-laminates (FML) provide a high variability in part properties and are often used to satisfy multiple component demands in aerospace applications. However, conventional use of hybrid laminates in the automotive sector is unrewarding due to high manufacturing costs and strongly restricted forming degrees. This paper presents an approach, which enables the manufacturing of laminate components with low bending radii for high volume applications. To separate the carbon fiber–reinforced polymers (CFRP) from the metal sheets, an elastomer layer was used, resulting in the omission of surface treatments for adhesion and corrosion prevention. The forming degrees presented in this work exceeded current approaches. Furthermore, the influence of the forming process on the mechanical properties was analyzed, thus ensuring the profitability of the presented approach for industrial applications.

The Effect of Hypervelocity Impact Loading on Explosively Welded Ti/Al/Al Plate

The aim of this paper is to investigate the ballistic properties of explosively welded Ti6Al4V/AA1050/AA2519 laminate under hypervelocity (4000 m/s) impact loading of projectile made of aluminium ball. The paper describes the influence of the projectile impact energy on the structure of the laminate components and delamination of bonds depending on its strength and presence of intermetallic phases. Observation of the failure is performed for the plate impacted for aluminium alloy side. Results revealed ductile shearing as a dominant process leading to perforation.

Detection of Delamination in Laminate Wind Turbine Blades Using One‐Dimensional Wavelet Analysis of Modal Responses

This paper demonstrates the effectiveness of a nondestructive diagnostic technique used to determine the location and size of delamination in laminated coatings of wind turbine blades. This is realized based on results of numerical and experimental investigations obtained by the use of the finite element method (FEM) and laser scanning vibrometry (LSV). The proposed method is based on the one‐dimensional continuous wavelet transform of vibration parameters of a wind turbine blade. The investigations were conducted for a 1 : 10 scaled‐down blade of a 36 m rotor wind turbine. Glass fibres and epoxy resin were used as laminate components. For numerical studies, a simple delamination model was proposed. The results obtained by the authors were used to determine the optimal set of parameters of the continuous wavelet transform. The application of high‐quality LSV for experimental measurements allowed determining the optimal conditions of measuring procedures. At the same time the capabilities and limitations, resulting from the nature of the measurement method, were identified. In order to maximize the effectiveness of the detection method, preliminary signal processing was performed. Beside base wavelets also different waveform families were tested. The results obtained by the authors showed that it is possible to identify and localize even relatively small damage.

Residual fatigue life of carbon fibre aluminium laminates

The life cycle of fibre metal laminates subjected to mechanical fatigue is commonly divided into three stages: crack initiation, crack propagation, and final failure. However for some configurations of fibre metal laminates, the composite component may keep its fatigue load carrying capabilities, even after through the thickness metal failure, whereas normally the structure was expected to fail entirely. The aim of this article was to identify and analyse the mechanisms which are the key for appearance of residual fatigue life phase of fibre metal laminates. The results show that the shape of the stress-cycles curve, as well as the static tensile strength of particular fibre metal laminate components are crucial for the presence of residual fatigue life. The study also presents a general methodology for stress-cycle curve prediction for any type of FML laminates.

Vibration Reduction Design with Hybrid Structures and Topology Optimization

Abstract The hybrid structures show excellent performance on vibration reduction for ship, aircraft and spacecraft designs. Meanwhile, the topology optimization is widely used for structure vibration reduction and weight control. The design of hybrid structures considering simultaneous materials selection and topology optimization are big challenges in theoretical study and engineering applications. In this paper, according to the proposed laminate component method (LCM) and solid isotropic microstructure with penalty (SIMP) method, the mathematical formulations are presented for concurrent materials selection and topology optimizations of hybrid structures. Thickness distributions of the plies in laminate components are defined as materials selection design variables by LCM method. Relative densities of elements in the components are defined as topology design variables by SIMP method. Design examples of hybrid 3-bar truss structures and hybrid floating raft with vibration reduction requirements verified the effectiveness of the presented optimization models.

Thickness scaled compression tests in unidirectional glass fibre reinforced composites in static and fatigue loading

Thick laminates can be found in different wind turbine blade sections, such as the root or the spar caps. However, static and fatigue design of thick laminate components is based on thin coupons tests (around 4 mm thick) and safety coefficients determined by the guidelines and standards.The aim of this work is to study the size effect in compression for unidirectional glass fibre reinforced composites. Scaled static and fatigue compression tests were performed on glass/epoxy laminates of 4 mm, 10 mm and 20 mm thick. A series of scaled coupons were designed taking into account the influence of the manufacturing process and the final testing conditions. While static tests on laminates with different thicknesses showed no significant change in the static ultimate stresses, fatigue tests showed a decrease in the fatigue life for increasing thicknesses as well as wider intervals of confidence. In addition, fatigue data were compared with the reduced fatigue capacity reported by the design guidelines showing reserve factors larger than 2.0.

Evaluation of the failure progress in the static bending of GFRP laminates reinforced with a classic plain‐woven fabric and a 3D fabric, by means of the vibrations analysis

The aim of the work is to evaluate the effectiveness of analysis of a failure progress of the glass fiber reinforced polymer laminate (classic and 3D), during static bending, with the use of high frequency vibration analysis (the order of kHz). During the tests, the instantaneous velocity of the samples' vibrations was recorded. The 3D laminate showed a more favorable course of failure (mostly fiber fracture) than the classic laminate (mostly delamination), but only in the direction transverse to the translaminar interweave strands. In the direction parallel to the interweave, it was also characterized mainly by delamination. It was stated that the vibration measurements significantly broaden and supplement the characteristics of bending, by way of revealing the local degradation changes in the examined material, especially before the initiation of the main stage of failure. The work also describes the frequency bands in which the symptoms of the occurring failures of particular laminate components were observed and where the values of the basic point parameters were estimated, which points to the occurrence of structure failure. The obtained results confirm the effectiveness of the vibration analysis as a tool for the evaluation of the course of composite material failure under static loads. POLYM. COMPOS., 38:1070–1085, 2017. © 2015 Society of Plastics Engineers

Kompozyty epoksydowe do zastosowan w przemysle lotniczym

The effect of the amount (1.0—3.0 wt %) of bentonites modified with quaternary ammonium or phosphonium salts on the properties of epoxy resin/glass fibre composites was studied. It was found that the mechanical properties and flame resistance of the laminates filled with the modified bentonites were significantly better than of laminates produced from an unfilled resin. Scanning electron microscopy (SEM) and atomic force microscope (AFM) studies were also performed to investigate the adhesion between the laminate components.

Feasibility analysis of inter-laminar toughening for improving delamination resistance

Abstract This letter discusses the effect of bonding energy on the delamination resistance of laminate composites using a ductile interleaf. The mechanism and methods for interleaf toughening are reviewed and the improvement in delamination resistance discussed. The bonding energy between the ductile interleaf polymer and the fibers as well as between the ductile interleaf polymer and the brittle matrix polymer is shown to be a limiting factor in the interleaf toughening of epoxy based laminates. A dual bonding approach, that is, melt bonding and diffusion bonding, is evaluated as a means to increase the bonding energy between the interleaf and laminate components.