Lay-up Schemes Research Articles

Deflection and stress characteristics of single lap joint (adhesively bonded) theoretical analysis and experimental verification

The adhesively bonded single-lap joint strength is computed numerically and verified with the experiment. An ABAQUS model is prepared to analyze by adding the primary information, i.e., geometry, material properties, element, and solution type, including the boundary conditions. The model accuracy has been verified through two-step comparisons with published numerical deflection data and in-house experiments. The validated model is used to compute the energy-absorbing capacity better to understand lap joint strength. Further, the statistical analysis (variance-based sensitivity analysis) is conducted to measure the model output variability with the model input parameter. Additionally, the influences of geometry and property-dependent design parameters (layup schemes, loading position, adherend thickness ratio (L/t), and adhesive thickness ratio: (a/h), including the overlapping length (25, 30, 35, and 40 mm) are examined through several examples. The conclusions on the overlap length in bonded joints are that an increase in intact/lap length improves the joint stiffness and decreases the deflection. Similarly, a few insights on layer sequence (angle-ply) and shear stress thickness ratio are discussed in detail.

First-Ply Failure Analysis of Helicoidal/Bouligand Bio-Inspired Laminated Composite Plates

Among the first, the present paper focuses on studying the first-ply failure load for bio-inspired helicoidal laminated composite plates. Five different layup schemes, namely, helicoidal recursive, helicoidal semicircular, helicoidal exponential, Fibonacci helicoidal, and linear helicoidal, were studied. The performance of the five helicoidal layups was compared with the commonly used cross-ply and quasi-isotropic lamination schemes. Maximum stress, maximum strain, Tsai–Hill, Tsai-Wu, and Hoffman failure theories were employed in the framework of the recently proposed finite-element-based higher-order zigzag theory to determine the first-ply failure load. It was observed that the maximum strain theory predicted the lowest value of the first-ply failure load, whereas Tsai–Wu predicted the highest one. For some cases, Tsai–Hill and Tsai–Wu theories were not able to predict the first-ply failure load. For plates having free edges, the bio-inspired plates exhibited the first-ply failure load compared to the conventional layup sequences.

Numerical study on the influence of liner geometry and lay-up sequence on the fatigue life of composite hydrogen storage vessel

This study focuses on the effect of liner geometry and lay-up sequence on the fatigue life of composite hydrogen storage vessel (CHSV). The ellipsoidal ratio and the maximum thickness of boundary section are selected as the independent variables for liner geometry and a sequence is determined that can make the vessel have higher fatigue life from 12 different lay-up schemes. The difference of the stress condition of the liner is the decisive factor that leads to the change of the fatigue life of CHSV, and this paper summarizes the influence law of the von Mises stress of liner on the lifetime of the vessel. The results show that stress concentrations in the dome section and excessive amplitude of alternating stress in the cylinder section should be avoided. Finally, a reasonable combination of parameters is determined, which can be a reference for the design of type III CHSV.

A semi-analytical method for vibro-acoustic characteristics of orthogonal stiffened laminated cylindrical shells

This paper presents a semi-analytical model for vibro-acoustic characteristics of submerged orthogonal stiffened laminated cylindrical shells strengthened with orthogonal stiffeners. The first-order shear deformation theory (FSDT) combined with the Lekhnitsky smeared stiffener technique is adopted to describe the displacement field, and the spectral boundary element method is utilized to model the sound field. For modeling of a complex stiffened shell, the shell is divided into several main structures with the additional stiffness and mass of the smeared stiffeners. Then, the main structure is separated into sub-segments that match the boundary elements to ensure high accuracy of acoustic calculations. The continuous boundary conditions between sub-segments are simulated by using the artificial spring technique. The Fourier series and Legendre orthogonal polynomials are selected as admissible functions to describe the displacement field and the sound field. The vibration governing equations and Helmholtz integral equation are coupled with each other and solved simultaneously. High accuracy is demonstrated by comparing the results of the developed model with the literature. In numerical investigations, the influences of different external fluids, layup schemes, quantities and shapes of stiffeners (width and height) on vibro-acoustic characteristics of orthogonal stiffened laminated cylindrical shells (OSLCS) are investigated.

Buckling and free vibration analysis of bio-inspired laminated sandwich plates with helicoidal/Bouligand face sheets containing softcore

Helicoidal laminates inspired by mantis shrimp crustacean can sustain higher loads compared to conventional laminated structures. However, there is still a lack of bending studies on the plates inspired by these helicoidal structures. The buckling and free vibration studies have been undertaken in the present work on the laminated composite and sandwich plates inspired by the helicoidal structures of the biological characters. Investigations are carried out using higher-order zigzag theory. For sandwich plates, the top and bottom face sheets are assumed to be made up of helicoidal layup schemes. Different kinds of helicoidal schemes, namely, recursive, exponential, semicircular, Fibonacci, and linear helicoidal are considered during the analysis. The buckling and free vibration behavior of helicoidal-based laminated sandwich plates are compared with the conventional laminated sandwich plates such as uniform distribution and cross-ply configurations. The influence of the number of layers, helicoidal schemes, geometric properties, and end conditions on the buckling and free vibration analysis of bio-inspired helicoidal laminated composite and sandwich plates is carried out in detail.

Properties of Plywood Panels Composed of Thermally Densified and Non-Densified Alder and Birch Veneers

Ukrainian companies mainly use birch in the manufacture of plywood, but species, such as black alder, are not yet widely used in the manufacture of plywood due to their poorer properties. It is well known that thermal compression is often used to improve the properties of solid wood. Good lay-up schemes of veneer can maximize the advantages and minimize the disadvantages of these wood species, and generally improve the utility value of the plywood. This research aimed to develop plywood panels with two wood species and two types of veneer treatments in order to evaluate the influences of different lay-up schemes on the properties of the plywood. Five-layer plywood panels were formed with 16 different lay-up schemes using birch (Betula verrucosa Ehrh.) (B) and black alder (Alnus glutinosa L.) (A) veneers, which were non-densified (N) and thermally densified (D). The different lay-up schemes were used to identify opportunities to improve the mechanical and physical properties of the plywood by replacing the birch veneer in the plywood structure with an alternative alder veneer. The veneer sheets were thermally densified in a laboratory hot press at a temperature of 180 °C and pressure of 2 MPa for 3 min. The conducted study showed that the bending strength, modulus of elasticity and shear strength of mixed-species plywood (BD–AN–AN–AN–BD) increased by up to 31.5%, 34.4% and 16.8%, respectively, in comparison to those properties of alder plywood from non-densified veneer (AN–AN–AN–AN–AN), by positioning alder non-densified veneers in the core layers and birch densified veneers in the outer layers. Moreover, the surface roughness of plywood panels with outer layers of birch veneer was lower than that of panels with outer layers of alder veneer. It was shown that non-treated alder veneer, despite exhibiting somewhat lower strength properties than birch veneer, could be successfully used with proper lay-up schemes in the veneer-based products industry.

Progressive failure analysis and burst mode study of type IV composite vessels

ABSTRACT The lightweight high-pressure hydrogen storage vessels composed of polymer liner and composite reinforced layers have attracted more and more attention. In this research, a 2D axisymmetric finite element model was proposed to predict the damage evolution, failure strength and failure mode of the composite overwrapped pressure vessels, in which a user subroutine UMAT based on Hashin failure criteria was introduced to simulate the progressive damage properties of the composite material. The FE models are validated by comparison with the experimental results, and the error between the numerical simulation results and the experimental results was within 10%. It is found that vessels with different lay-up schemes might burst in different locations. Parametric studies are performed to obtain a critical ratio of hoop and helical layers to keep the vessel burst in safe mode.

Study on formability and failure modes of steel/CFRP based FMLs consisting of carbon fiber reinforced polymer prepreg and steel sheet

Due to the potential application need of the automotive and transportation industry for Fiber metal laminate parts made of steel sheets and carbon fiber reinforced polymer (i.e., Steel/CFRP based FML parts), the related combined forming process of FML parts has attracted extensive attention in the last decades. In order to design and fabricate the qualified Steel/CFRP based FML auto parts with various plane stress states, it is vital to thoroughly understand the formability and failure modes of Steel/CFRP based FMLs under various forming states and process conditions. Accordingly, in the present work, a series of deep drawing experiments were designed and conducted on Steel/CFRP based FML specimens with various width to embody their special forming features under different stress states. By considering the limit drawing height at fracture for the evaluation indicator of the forming limit of FMLs, authors studied systematically the influence of key process conditions such as lay-up scheme, stamping speed and the number of plies in the carbon fiber reinforced polymer prepreg (i.e.,CFRP prepreg) core on the formability and failure modes of FML specimens with various forming states. The research results are expected to provide a reliable data source for establishing the accurate forming limit criterion of FMLs and optimizing lay-up schemes.

Design of Laminated Composite Plates with Carbon Nanotube Inclusions against Buckling: Waviness and Agglomeration Effects.

In the present study, a buckling analysis of laminated composite rectangular plates reinforced with multiwalled carbon nanotube (MWCNT) inclusions is carried out using the finite element method (FEM). The rule of mixtures and the Halpin–Tsai model are employed to calculate the elastic modulus of the nanocomposite matrix. The effects of three critical factors, including random dispersion, waviness, and agglomeration of MWCNTs in the polymer matrix, on the material properties of the nanocomposite are analyzed. Then, the critical buckling loads of the composite plates are numerically determined for different design parameters, such as plate side-to-thickness ratio, elastic modulus ratio, boundary conditions, layup schemes, and fiber orientation angles. The influence of carbon nanotube fillers on the critical buckling load of a nanocomposite rectangular plate, considering the modified Halpin–Tsai micromechanical model, is demonstrated. The results are in good agreement with experimental and other theoretical data available in the open literature.

Natural frequency analysis of sigmoid functionally graded sandwich beams in the framework of high order shear deformation theory

The current study aims to analyze the natural frequencies of sigmoid functionally graded (FG) sandwich beams having various configurations employing the high-order shear deformation theory. To do this, three diverse types of sandwich layup schemes have been constructed. The material characteristics of FG components of sandwich beams are presumed to vary continuously along the thickness direction, as indicated by the volume fraction of constituents specified with sigmoid law distribution, whilst the other components are assumed to be isotropic ceramic/metal. The governing equations are derived for higher-order shear deformation theory, i.e., hyperbolic shear deformation theory (HSDT). Navier's method is used to solve the governing differential equations analytically for simply supported boundary conditions at both ends. To show the efficiency of the current theory, the numerical results are obtained not only for HSDT but also for first-order shear deformation theory (FSDT), in the special case. Similarly, power law distributions of FG sandwich beams are also presented for emphasizing the effectiveness of sigmoid law distribution. Detailed comparisons are performed with available results of open literature to confirm the current formulation. Finally, the effects of the HSDT, variations of material properties, layup schemes, and geometrical characteristics of sandwich beams on the non-dimensional natural frequencies are discussed.

Effect of compression and tension types of concentrated edge loads on buckling and vibration behavior of interlaminar hybrid fibre metal laminates

The present study deals with the numerical investigation on the buckling and vibration behaviour of interlayer hybrid fibre metal laminates (HFMLs) subjected to different types of concentrated edge compression and tension loads. The term interlayer hybrid represents carbon and glass fibre laminates are sandwiched in between aluminum face sheets. Totally six different hybrid configurations are taken into consideration separately for cross-ply and angle-ply layup schemes. To serve this purpose a finite element code using MATLAB is developed to examine the effects of hybrid configuration, aspect ratio, fiber orientation, type of loading and boundary conditions have been considered to study the buckling responses of HFMLs. The plate is modelled by using 9-noded heterosis elements by considering the effect of shear deformation and rotary inertia. It is revealed from the investigation that the hybrid configurations and loading conditions significantly affect the buckling and vibration characteristics of HFMLs.

Investigation on failure behaviors of 70 MPa Type IV carbon fiber overwound hydrogen storage vessels

In this paper various lay-up schemes were designed for a 70 MPa Type IV hydrogen storage vessel to evaluate the effects of different stacking sequences on the ultimate strength. The netting theory was here used to calculate the laminate thickness and twelve lay-up schemes were selected. The user subroutine UMAT provided by the general software ABAQUS was then introduced to define the composite material properties. The progressive damage model using the Hashin failure theory was created to predict the burst pressure of the vessel. The three lay-up schemes were used to manufacture the prototyped hydrogen vessels for their hydrostatic tests. The results showed that the error between the numerical simulation results and the experimental results were within 10% and the lay-up comprises about 15% of the effect on the burst pressure. It was also indicated that the lay-up model with separated hoop and helical layers can improve the burst pressure, and the helical winding angle distributed from large to small can also improve the burst pressure. The tested results of the fiber volume fraction and porosity demonstrated that lay-up model with alternated hoop and helical layers had a lower porosity than that with separated hoop and helical layers; this is mainly triggered by the cross effect of the helical winding in terms of the elevated fiber and the enriched resin which results in high porosity and low burst pressure.

Buckling behavior of interlaminar hybrid fiber metal laminate (HFMLs) subjected to uniaxial compressive loading

The aerospace industry witnessed the rapid increase in the usage of Fiber Metal Laminate (FMLs) for its higher load carrying capacity and many other advantages. The core material of FMLs made up of either glass or carbon fibers based on the type of application. One can achieve superior material property and economic in design by combining glass and carbon interlayer as a core material and the top and bottom by aluminum sheets, which forms a hybrid fibre metal laminates (HFMLs). In this investigation, the effect of different hybrid combinations on the vibration and buckling behavior of interlayer HFMLs have been studied by developing finite element formulation. The 9-noded heterosis plate element has been used to model the plate by incorporating the effect of shear deformation and rotary inertia. Sixteen different hybrid combinations have been considered to investigate the effect of ply orientation, boundary condition and aspect ratios of HFMLs. In each combination cross-ply, angle-ply and quasi isotropic layup schemes are considered to investigate the different parameters in detail and the results are discussed below.

Effect of position of partial load on buckling and vibration characteristics of composite panels with circular cutouts

Abstract In this, the effect of different positions of partial ledge loads on buckling behavior of laminated panels with the centrally placed circular cutout is studied by developing finite element formulation using 9 - noded heterosis element. The formulation includes the effect of shear deformation and rotary inertia. The effect of various parameter such as cutout size, ply-orientation and thickness of the panel included in this work to study the buckling behavior of each parameter in detail. It is observed that the buckling resistance of the panel decreases with the increase in cutouts size irrespective of position of partial load. However, the position of partial load at extreme ends show higher buckling resistance as compared to that of centrally placed edge loads, irrespective of cutout size. Further, cross-ply symmetric laminates show extremely higher and least buckling resistance, when partial load acting at the extreme edges and at the center of the partial edges respectively, as compared to all other layup schemes.

A nonlinear dynamical model for rotating composite thin-walled beams subjected to hygrothermal effects

A rotating composite thin-walled beam structure usually works in environment with strong hygrothermal characteristics. Temperature variation and moisture absorption can influence physical properties of composite, and furthermore change mechanical behavior of the structure. Hygrothermal influences depend on composite, layup scheme, geometry and nonlinearity of the beam. However, a comprehensive analytical model including these factors is lacking. This work aims to establish such a model for rotating composite thin-walled beams subjected to hygrothermal effects so that relevant problems can be solved analytically, which can aid numerical simulation and experimental test. Many important factors including hygrothermal effects, nonlinearity, mode coupling, arbitrary layup schemes, rotation, external forces, transverse shear, non-uniformity of cross section, constrained torsion, warping, setting angle and pretwist angle are considered. Governing equations of the coupled vibration are established by using the generalized Hamiltonian principle. Reduction verification, simplification principles and reduced models are discussed. The solution of the model is illustrated and some examples are given. Finally, the influences of temperature, moisture absorption and ply angle on hygrothermal internal forces of constrained thin-walled beams with CUS and CAS configurations are analyzed.

Effect of Different Hardwood Species and Lay-Up Schemes on the Mechanical Properties of Plywood

In Estonia, hardwoods form approximately 50% of all forest area, where the main species are birch (30%), gray alder (9%), aspen (6%) and black alder (4%). Birch has been extensively used by the veneer-based industry, but species like black alder, gray alder and aspen have not been commonly used by the veneer-based products industry due to the lower quality of this resource. The aim of this research is to determine the effect of different lay-up schemes and usages of gray alder, black alder and aspen on the mechanical properties of plywood, by replacing birch veneer in the plywood core with alternative wood species. The main veneer and plywood characteristics will be evaluated according to the current standards, e.g., veneer strength perpendicular to grain, plywood bonding and bending strength, and modulus of elasticity. All processing parameters will be kept similar to those used generally by birch plywood manufacturers. The results showed that birch and black alder plywood panels had generally the highest bending strength properties, followed by grey alder and aspen. It was also found that, for proper gluing, birch veneers had the lowest glue consumption, 152 g/m2, and aspen had the highest glue consumption, 179 g/m2. It was found that when lower density wood was used in the plywood, the product density increased. Low density wood veneers had higher glue consumption, and also higher compaction in thickness than birch veneers under the same pressure. Overall, it was shown that the wood species used in this study have slightly lower strength properties, but with proper lay-up schemes, these wood species could be successfully used by the veneer-based products industry.

LASER-ULTRASONIC METHOD OF ACOUSTIC IMPEDANCE MEASUREMENT FOR QUANTITATIVE POROSITY ESTIMATION OF CROSS-PLY CARBON FIBER REINFORCED PLASTIC MATERIALS

A method of measuring the acoustic impedance of carbon fiber plastics based on the laser optoacoustic effect is proposed and experimentally realized. Measurement of the acoustic impedance of the studied composite is made by the value of the antiderivative of ultrasonic pulse reflected from the interface between the immersion liquid and the sample. A method for determining the porosity of a material by the measured value of the acoustic impedance, based on the dependence of the material density and the velocity of propagation of longitudinal acoustic waves in it on its porosity, is presented. Porous samples of crossply reinforced carbon plastics with three types of carbon fiber lay-up schemes were studied. It was found that the studied carbon fiber plastics have a non-uniform distribution of local porosity in the plane of carbon fabric stacking. It is also shown that the variation of the local porosity in the sample depends on the fiber laying scheme. It is shown that the porosity value obtained by X-ray computed tomography coincides with the results of laser-ultrasonic measurements. The advantage of the proposed method is the possibility of rapid diagnosis of porosity with one-way access to the object under study without measuring its dimensions and mass, which can be used for composite structures of complex shape.

Effect of fibre direction and stacking sequence on dynamic impact performance of composite bicycle frame

ABSTRACTLightweight and safety performance are two important factors for bicycle design. For a composite bicycle frame with given geometry size, the material design is a new method to improve its dynamic impact performance. Since different levels of impact are generated among different parts, different parts with different fibre directions and stacking sequences are considered for each part. In this study, the effect of fibre direction and stacking sequence on dynamic impact performance of composite bicycle frame has been discussed. A three-dimensional solid model of bicycle frame is constructed and the low-velocity impact finite element simulations for the CFRP bicycle frame are performed via ANSYS/LS-DYNA. In addition, the energy absorption capabilities and dynamic response characteristics of the CFRP bicycle frame are investigated. It can be found from results of the finite element simulations that, three relatively optimal lay-up schemes with minimal permanent deformation are obtained and the corresponding bicycle frame specimens are manufactured. Through impact experiments and finite element analysis, finally, the optimal lay-up scheme (Case 1, stacking A:[(±45°)4], stacking B:[(±45°)2/0°]) with minimal permanent deformation is obtained. The stacking sequence has little effect on dynamic impact performance. Furthermore, proportion of layers with different fibre directions has an obvious effect on impact performance, and a higher proportion of layers with ±45° fibre directions improve the impact performance.

Vibration and lateral buckling optimisation of thin-walled laminated composite channel-section beams

This study presents vibration and lateral buckling optimisation of thin-walled laminated composite beams with channel sections. While flanges’ width, web’s height, and fibre orientation are simultaneously treated as design variables, the objective function involves maximising the fundamental frequency and critical buckling moment. Based on the classical beam theory, the beam element with seven degrees of freedom at each node is developed to solve the problem. Micro Genetic Algorithm (micro-GA) is then employed as an optimisation tool to obtain optimal results. A number of composite channel-section beams with different types of boundary conditions, span-to-height ratios, and lay-up schemes are investigated for the optimum design. The outcomes reveal that geometric parameters severely govern the optimal solution rather than the fibre orientation and it is considerably effective to use micro-GA compared with regular GA in term of optimal solution and convergence rate.

Post-buckling and Large Amplitude Free Vibration Analysis of Composite Beams: Simple Intuitive Formulation

Post-buckling and large amplitude free vibration analysis of composite beams with axially immovable ends is investigated in the present study using a simple intuitive formulation. Geometric nonlinearity of Von-Karman type is considered in the analysis which accounts for mid-plane stretching action of the beam. Intuitive formulation uses only two parameters: the critical bifurcation point and the axial stretching force developed due to membrane stretching action of the beam. Hinged–hinged, clamped–clamped and clamped–hinged boundary conditions are considered. Numerical accuracy of the proposed analytical closed-form solutions obtained from the intuitive formulation are compared to available finite element solutions for symmetric and asymmetric layup schemes of laminated composite beam which indicates the confidence gained on the present formulation.