Lay-up Pattern Research Articles

Effects of species, adhesive, and structural configurations on compression parallel to the grain of laminated bamboo

This study investigated the compressive performance of 24 three-layered laminated bamboo specimens made with four different parameters, primarily bamboo species, adhesive type, lay-up pattern, and arrangement of laminated bamboo. The goal for this study was to investigate the compression parallel to the grain performance of laminated bamboo. A total of 288 laminated bamboo specimens were tested. Modulus of elasticity (MOE) and compressive strength were conducted to simulate the utilization of this material into construction material. The laminated bamboo produced were comparable to wood strength group A to B for vertical and horizontal arrangements and SG D for mixed arrangements. Laminated bamboo was produced based on Gigantochloa scortechinii and Gigantochloa levis and bonded with phenol resorcinol formaldehyde (PRF) and one-component polyurethane (PUR) adhesive. Four failure types were classified. All specimens experienced the elastic stage at the beginning of the loading process and then changed to elastic-plastic stage. There was a significant difference in the parallel and perpendicular lay-up for vertical, horizontal, and mixed arrangements.

Optimizing performance of hybrid fiber reinforced overwrapped pressure vessel

Composite overwrapped pressure vessels (COPVs) offer significant weight advantages over traditional all-metal vessels particularly in industries like aerospace, automotive and pharmaceutical, but pose unique challenges in mechanical design, fabrication, and testing. Despite their benefits, COPVs are susceptible to stress rupture failure, which can lead to catastrophic consequences during operation. This failure mode is not fully understood, with burst pressure-induced extreme stress concentrations and dynamic loading primarily contributing to rapid deformation and strain. To address these concerns, a comprehensive investigation was conducted, focusing on optimizing and examining the effects of optimum winding angle and lay-up pattern configuration on burst pressure in vessels under internal pressure. Finite element modeling analyzed the burst pressure behavior of COPVs with a 4 mm thick aluminum core cylinder and varying layers of carbon/fiber epoxy, each with a constant thickness. ABAQUS composite modeler generated 18 COPV models with carbon fiber/epoxy plies, ensuring uniform thicknesses while exploring different fiber orientations. The effects of ply stacking sequence were analyzed through finite element analysis for all models, comprising varying layers with uniform thicknesses. Attention was paid to failure criteria, methodically evaluating the burst strength of the Al/CFRPC COPVs This exhaustive analysis yielded an optimal COPV design profile characterized by a precisely calibrated ply stacking sequence of [24.50, −24.50] PP winding pattern and six (6) arranged layers. The stress-strain distribution analysis of the Composite Overwrapped Pressure Vessel (COPV) revealed both a uniform distribution of stress across its surface and extreme stress concentration, particularly peaking towards the polar boss region. This concentration is discernible due to variations in ply thickness induced by the overwrapped fiber orientation. This investigation provides valuable insights for optimizing COPV design and enhancing its performance and reliability in various applications.

Deformation processes of polymer composites with stress concentrators under different reinforcement schemes

This paper is dedicated to an experimental investigation of an effect of a stress concentrator orientation on a mechanical behavior of polymer composites with various reinforcement schemes. Composite specimens have been made of layered carbon fiber reinforced polymer (CFRP) with lay-up patterns of [±45]16 and [0/90]16. The stress concentrators have been cut in a form of a rectangle (with rounded corners) orientated at angles of 0°, 45°, and 90° to a loading axis. The novel data about the composite’s mechanical behavior has been obtained by the digital image correlation (DIC) method, the acoustic emission (AE) method and the optical microscopy. Quasistatic tests have been carried out taking into account recommendations of the ASTM D5766, ASTM D3039, ASTM D3518. The effect of the stress concentrator orientation on the composite’s strength has been evaluated. It has been found that the stress concentrator does not affect the strength of the composite with the [±45]16 lay-up pattern. This peculiarity has been explained by the absence of the layers preventing the fibers system turning in the direction of the load application. The DIC method has allowed to study the evolution of inhomogeneous strain fields on the specimens’ surfaces. Computational simulations have been carried out within the elasticity stage. The results have shown that the strain fields obtained by both the DIC method and the numerical simulation were similar for the composites with the [0/90]16 reinforcement pattern. However, significant differences have been found for the [±45]16 reinforcement pattern, which have been explained by the development of inelastic zones near the stress concentrator even if the elastic stage is realized at the macrolevel. The using of the AE method and the optical microscopy has allowed to reveal typical mechanisms of the structural damage and to study their occurrence during the tests. It has been concluded that the orientation of the stress concentrator significantly influences the deformation processes of the CFRP with various reinforcement patterns.

An investigation of vibration responses for bolted composite flanged-cylindrical shells considering material and joint nonlinearity

In this paper, a thorough investigation into the vibration response of bolted composite flanged-cylindrical shell structures, considering the material nonlinearity of carbon fiber-reinforced polymer composites (CFRP) and the joint nonlinearity of bolt connections, is presented. Firstly, a general semi-analytical modeling method for bolted composite flanged-cylindrical shell is developed based on the first-order shear deformation theory (FSDT) and the energy method. In this method, material nonlinearity is introduced by accounting for the frequency-strain dependency of material parameters. A joint model with non-uniform distribution parameters and dynamic boundaries is proposed to simulate the interface pressure distribution and nonlinear mechanical behavior of bolted joints. Then, for the general numerical model that incorporates both types of nonlinearities, the ability to accurately predict the nonlinear vibration behavior of a bolted composite flanged-cylindrical shell is demonstrated through experimental testing. Finally, an in-depth discussion is conducted on the influence of fiber layup patterns and bolt numbers on the nonlinear vibration response of the bolted composite flanged-cylindrical shells. The conducted analysis indicates that the proposed method can offer utility to designers, empowering them with the insights necessary for the dynamic optimization of such structures.

Crashworthiness analysis and optimization design of special-shaped thin-walled tubes by experiments and numerical simulation

Thin-walled structures are widely used as typical high-efficiency energy-absorbing structures in crash safety protection. This paper aims to combine the characteristic of the square tube which concentrates energy dissipation through angle elements with the stable fold deformation of the circular tube, and innovatively propose a special-shaped thin-walled tube that contains both angle elements and arc elements. The failure behavior and energy absorption characteristics of the special-shaped tube were investigated by compression test and numerical simulation. The simulation results showed that the special-shaped thin-walled tubes have a significant advantage in energy absorption, and the specific energy absorption of the special-shaped tubes is 31.57% and 75.2% higher than that of the equal-mass circular and square tubes, respectively. Next, through finite element analysis, the effects of various parameters and initial imperfections on the crashworthiness of the special-shaped tubes were compared. The results indicated that adjustments to geometrical parameters significantly impact the energy absorption properties and crushing behavior of thin-walled tubes. Moreover, the tube with induced circular holes exhibited an optimal deformation mode. Further, a multi-objective optimal design of the metal special-shaped tube was carried out to obtain the best parameter configuration of the metal special-shaped tube. Finally, the special-shaped structure was extended to CFRP/AL hybrid thin-walled tubes. The failure behavior and energy absorption enhancement mechanism of the hybrid special-shaped tubes were investigated with experiments, and the absorbed energy of the hybrid tube was about 20% higher than the sum of the absorbed energy of the single constituent tubes. The effect of the CFRP lay-up pattern on the crashworthiness of the hybrid tube was investigated by numerical simulation, and it was found that the energy absorption capacity of the hybrid tube could be improved by appropriately increasing the number of layers and the proportion of axial fibers.

Underwater Implosion and Energy Mitigation of Hybrid Glass-Carbon Composite Shells

Experiments were conducted to investigate the dynamic buckling behavior of underwater hybrid composite tubes. The study focused on roll-wrapped hybrid layered glass-carbon fiber epoxy composite shells with a six-layer quasi-isotropic layup configuration. In addition to control specimens consisting of fully glass fiber-reinforced polymer and carbon fiber-reinforced polymer, four different hybrid layup patterns were examined. These specimens fitted with custom endcaps were placed inside a 7-kiloliter pressure vessel and subjected to increasing hydrostatic pressure until dynamic implosion occurred. High-speed cameras captured the failure event, and the resulting images were analyzed using Digital Image Correlation (DIC) techniques to obtain full-field displacement data. Additionally, tourmaline pressure transducers positioned around the specimens recorded local dynamic pressure histories. The results revealed that the contribution of each ply location varied in the overall failure behavior of the structures. The thickness of the internal plies played a dominant role in enhancing the structural performance, while the stiffness of the outer plies greatly influenced the bending stiffness. The energy released during the collapse was highly dependent on the failure mechanism of the internal plies. Specifically, for the considered geometries, tubes with glass fiber internal plies exhibited significantly lower energy emissions compared to carbon fiber inner plies.

Optimization Design and Nonlinear Bending of Bio-Inspired Helicoidal Composite Laminated Plates

Inspired by the bionic Bouligand structure, helicoidal carbon fiber-reinforced polymer composite (CFRPC) laminates have been proven to own outstanding out-of-plane mechanical properties. This work aims to further explore the excellent bending characteristics of helicoidal CFRPC laminated plates and find out the optimal helicoidal layup patterns. The optimization design of laminated plates stacked with single-form and combination-form helicoidal layup sequences are carried out by using the finite element method (FEM) and adaptive simulated annealing (ASA) optimization algorithm on the Isight platform. Then, the nonlinear bending responses of optimal helicoidal CFRPC laminated plates are investigated via the FEM for the first time. The helicoidal CFRPC laminated plates under three different types of boundary conditions subjected to transverse uniformly distributed load are considered. The numerical results reveal that the combination-form helicoidal layup sequences can decrease the dimensionless bending deflection of laminated plates by more than 5% compared with the quasi-isotropic plate and enhance the out-of-plane bending characteristics of CFRPC laminated plates effectively. The boundary conditions can significantly influence the nonlinear bending responses of helicoidal CFRPC laminated plates.

Energy dissipation theory performance of different layup patterns CFRP/aluminium alloy hat-shaped hybrid beams under three-point bending conditions

This study investigates the bending failure behaviour of CFRP-reinforced aluminium alloy hat-shaped hybrid beams under three-point bending conditions. Firstly, three-point-bending experiments are conducted for four kinds of hybrid beams with different layup directions of CFRP. It is found that the layup direction has a more significant impact on the maximum loads. The load carrying capacity of the hybrid beam tends to stabilise around a certain load after decreasing from the maximum value of load. Subsequently, FE models of hybrid beams with inner, external and concurrent reinforced patterns are established to analysis the effect of locations of reinforced structure on the bending characteristics. It is found that the effect of reinforced structure location is influenced by the relative relationship between the thicknesses of aluminium alloy and the CFRP parts. Finally, a theoretical model of hybrid beams under three-point bending condition is proposed to predict the bending characteristics.

Experimental study of GFRP stiffened plates with and without large opening under combined axial and pressure loading

GFRP stiffened panels forms the basic component of ship hulls, decks, submarines, offshore oil platforms etc., GFRP stiffened panels used in ship hulls and decks are subjected to axial loading due to buoyancy and pressure loading due to cargo. GFRP stiffened plate dimensions considered in this study are the scaled down dimensions of a cargo ship. Aluminium moulds with and without opening are fabricated for casting GFRP stiffened panels. GFRP stiffened panels with integral stiffeners are manufactured using hand lay-up process. A unique lay-up pattern was adopted to achieve the monolithic behaviour of stiffeners and plate. Fabrication of GFRP stiffened panels by manual hand layup process leads to formation of indentations. These imperfections are determined using the LVDTs attached to imperfection measurement setup. The measured imperfections are compared with the allowable imperfection values available for steel in BS 5400, because limiting imperfection values are not available for FRP. Openings are necessary for access and maintenance in ship hulls, decks etc. The presence of openings can lead to loss in strength and stiffness of the GFRP stiffened panels. In this study, GFRP stiffened panels with and without opening are tested for different combinations of axial and pressure loading. Axial loads are applied using two hydraulic jacks and measured using two load cells which are fabricated to prevent eccentricity while applying axial load. Pressure loads are applied using inflatable air balloons with and without opening fabricated for this study. Load capacity, failure strain, failure patterns of GFRP stiffened panels under different load combinations are presented. Failure locations of GFRP stiffened panels with and without opening various load combinations are discussed. Reduction in load capacity, span to deflection ratio and loss in stiffness due to opening is calculated.

Effects of Adhesive Types and Structural Configurations on Shear Performance of Laminated Board from Two Gigantochloa Bamboos

Semantan (Gigantochloa scortechinii) and beting (Gigantochloa levis) bamboo are the two Malaysian bamboo that are suitable to be converted into laminated bamboo boards. One of the main criteria for laminated board is its good bondability, which is determined by shear performance. The shear performance of laminated board is influenced by several factors such as the species used, adhesive types and lamination configurations. Therefore, in this study, laminated bamboo boards were produced using Semantan and Beting bamboo bonded with phenol–resorcinol–formaldehyde (PRF) and polyurethane (PUR) adhesives. Different configurations (lay-up patterns and strip arrangements) were used during the consolidation of the laminated boards. The bamboo strips were arranged in three different arrangements, namely vertical, horizontal and mixed, and then assembled into a three-layered structure with two lay-up patterns, which are perpendicular and parallel. Shear performances, such as shear strength, bamboo failure and delamination of the boards, were evaluated. The results revealed that the adhesive type and lay-up pattern were the most influential factors on the shear performance. PRF-bonded laminated bamboo boards outperformed PUR-bonded laminated bamboo boards in terms of shear strength and bamboo failure but PUR bonding had better bond durability as indicated by its low delamination. Boards laminated parallelly significantly outperformed those bonded perpendicularly. As for strip arrangement, PRF-bonded laminated boards were less influenced by it compared to PUR-bonded laminated boards. The results suggested that PRF is a better adhesive for bamboo lamination due to its higher shear performance and more consistent performance across structural configurations (lay-up patterns and strip arrangements).

Experimental and numerical studies on bending characteristics of woven CFRP reinforced aluminum thin-walled automotive structures

Metal/composite hybrid thin-walled structure is the most preferential approach to achieve dual contradictive objectives of high crashworthiness and lightweight of auto body. Its collapse with regard to different fiber layup patterns is one of the governing mechanisms of energy dissipation, which is yet to be explored. Especially, the effect of different fiber layup angles and layup sequences on bending collapse, which is one of the most significant performance indicators, has received little attention. To this gap, this study investigates experimentally and numerically the bending characteristics of aluminum/carbon fiber reinforced plastic (Al/CFRP) hybrid structures with different layup angles and layup sequences. To start with, three-point bending tests are carried out on specimens to derive the bending failure behavior and crashworthiness, and the internal section damage is observed by CT scan. Finite element model is then constructed and benchmarked against the test results to be proficient. On this basis, the effects of Al thickness, number of CFRP layers and CFRP wrapping range on the bending performance of hybrid tube are analyzed numerically. The simulation results show that layup angle has greater effect on the bending performance than layup sequence. Increasing Al thickness and the number of CFRP layers can effectively improve the bending resistance of structure, and appropriate partial wrapping of CFRP can increase the specific energy absorption (SEA) by 10.92% compared with that of complete wrapping. The revelation from this study provides sound reference for the crashworthiness design of metal/composite hybrid thin-walled structure.

Modelling and Analysis of Thermal Vibrations of Coated Fiber-Reinforced Composite Cylindrical Thin Shells

The thermal vibration characteristics of fiber-reinforced composite (FRC) cylindrical thin shells (FRCCTSs) coated with functionally graded porous graphene platelet (FGPGP) are investigated in this work, which is based on a theoretical model constructed by a mixed analytical and finite element method. Firstly, the porosity distributions of the FGPGP coating are assumed to be uniform or nonuniform along thickness direction with four porous forms of coating being taken into account. Next, the displacement field functions along with the axial, circumferential, and transverse directions are assumed on the basis of Love’s first-order approximation theory. Furthermore, this coated thin shell is discretized by the four-node shell element method to calculate the mass and stiffness matrices, with the artificial spring technology being adopted to simulate arbitrary boundary conditions. After the frequency parameters and dynamic responses are successfully solved, the proposed model with and without coating material is roughly validated by comparing with literature results at different boundary conditions without considering the temperature effect. Meanwhile, by utilizing the natural frequencies and vibration responses measured via a thermal vibration experiment bench, the comprehensive verification is performed within a temperature range of 20–200∘C. Finally, parametric studies are undertaken to study the influences of boundary condition, porosity distribution of coating, fiber layup pattern, the predefined thickness ratio, and elastic modulus ratio on the corresponding thermal vibration properties.

Structural design optimization of a wind turbine blade using the genetic algorithm

With the increasing size of wind turbines in terms of their dimensions and capacity, structural design optimization for their blades is becoming all the more important. This study suggests an improved optimization framework. Blade optimization is performed in two stages: the ply lay-up pattern of the spar cap in the initial blade configuration based on the existing configuration, followed by the cross-sectional design optimization at several spanwise locations. The genetic algorithm is adopted and, in terms of the structural integrity evaluation, the final configuration results are found to be safe; in addition, the number of plies in the spar cap rapidly decreases through the two-stage design optimization procedure. As a result, the blade is lighter, and the lighter blade also reduces the applied load on the wind turbine. This will have an excellent effect that leads to a reduction in the weight of the entire turbine system.

Quasi-static indentation and sound-absorbing properties of 3D printed sandwich core panels

The use of 3D printing to produce acoustic panels with good mechanical and acoustic properties was investigated in this paper. Various fiber layups of the fiberglass face sheet and core designs were fabricated and tested for their indentation resistance and acoustic absorption performance. It was found that the bidirectional face sheet layup exhibited the best indentation energy absorption recording 4.2 J, which is 37% more than the 45-degree layout and 66% more than the quasi-isotropic layup. The specific energy absorption of the hybrid honeycomb core is the best among the three core designs recording 404 J/kg, which is 56% higher than the corrugated triangle with horizontal beam core (359 J/kg) and 20% higher than double ellipse core (335 J/kg). Computed-Tomography (CT) scan was used to study the fracture behavior of the sandwich structures. It was found that the bidirectional layup exhibited a different failure mode as compared to the 45-degree and quasi-isotropic layup. In terms of the acoustic properties, the face sheets with various layup patterns have a low acoustic absorption coefficient with minimal differences from each other at low frequencies (500 Hz–3000 Hz) and have higher absorption coefficients with greater differences from each other at frequencies between 3000 Hz–6500 Hz. The absorption curve was significantly affected by the design of the core. The orientation of the core also comes into play if the core is asymmetrical. The hybrid honeycomb sandwich structure was the optimal structure among the three designs for balanced indentation resistance and acoustic insulation.

The Effect of Landmarks With Their Color on Learning Basketball Lay-Up in Beginners

The purpose of this study was to determine the effect of landmarks on learning basketball lay-up in beginners. Twenty-seven females (age = 20.30 ± 0.24 years, height = 164.37 ± 0.53 cm) participated in this study. They were assigned to three groups: no landmark group, colored landmark group, and black and white landmark group. All participants performed basketball lay-up for six sessions. The colored group and black and white group trained with the landmarks on the ground while the no landmark group trained without any landmarks based on a trainer instruction. Posttest was performed at the end of the last session of training and also in the retention test following 72 hr. All trials were assessed through 5-point Likert scales, ranging from 1 (very poor) to 5 (very good). The results showed that using landmarks significantly changed the lay-up pattern; however, these changes were not significant for color and lay-up shot accuracy.

Comparison of laminate thickness on the low velocity impact behaviors for Z-pinned composite laminates

The Z-pinning technique can enhance the delamination resistance for composite laminates effectively. In this paper, the effect of laminate thickness on the low velocity impact responses of Z-pinned laminates with [02/902]2S, [02/902]4S, and [02/902]6S layup patterns was explored. These laminates had nominal thickness of 2.1 mm, 4.5 mm and 6.9 mm, respectively. The impact energy was set to 5 J, 10 J, 20 J and 30 J, and the mechanical curves during the experiment were recorded. Afterwards, ultrasonic C-scanner, scanning electron microscope (SEM) and X-ray micro-computed tomography (μCT) were used to detect the impact-induced damage. The theoretical models for predicting the delamination initiation threshold and related threshold impact energy were consistent with the experimental data. The results showed that Z-pins had almost no effect on the delamination initiation, but Z-pinning became significant for delamination suppression as the impact energy exceeded the threshold impact energy. In addition, due to the improved penetration resistance, the maximum central displacements were suppressed with Z-pin implantation as the noticeable fiber breakage occurred. Due to the fact that the dominant failure mode changed from fiber breakage to delamination with the increase of the laminate thickness, the delamination damage and internal defect suppression for thin laminate was inferior to that for the intermediate-thickness laminate. However, the suppression effectiveness became weak for the thick laminate at the same impact energy due to the smaller bridging force with slight Z-pin pull-out.

Effect of Honeycomb Core on Free Vibration Analysis of Fiber Metal Laminate (FML) Beams Compared to Conventional Composites

According to the different higher-order deformation beam theories, the current survey is related to the fundamental frequency analysis of composite beams using the Rayleigh-Ritz method. Different types of materials, including isotropic, fiber-reinforced orthotropic composites, and FML hybrid composites in the presence and the absence of honeycomb core, have been selected. In this theory, the material property as well as the thickness of each layer can be changed, and the effect of various boundary conditions, lay-up configurations, and slenderness ratios of the beams have been discussed. To verify the obtained theoretical results, the FML beam with [Al/0/90/90/0/Al] lay-up pattern was fabricated by hand lay-up technique and subjected to Clamped-Free boundary condition. Accordingly, the free vibration experimental data confirmed the results which were obtained by the different theories. The results show that by changing the reinforced composite beam to the FML beam, the natural frequencies experience a drop by 37%, 43%, and 43% for slenderness ratios of 5, 20, and 100, respectively. This level of descent for transferring from reinforced composite sandwich beam to the FML sandwich beam is about 24%, 37%, and 37.5%, respectively.

Selection and justification of polymer composite wing load-bearing elements design parameters with material anisotropy and airload

The rapidly developing aviation industry is looking for new design solutions in the field of designing modern passenger airliners. To ensure reliability and increase the service life of developed products can help polymer composite materials, which are already successfully used in the construction of a number of aircraft. This work is devoted to the urgent task of determining and optimizing the structural parameters of the carbon fiber wing load-bearing elements, taking into account rational reinforcement schemes. The wall thicknesses, layup patterns of unidirectional layers, the safety margins of the wing structural elements, taking into account the current operational loads for several angles of attack corresponding to different flight modes. The work is part of the methodology for designing a wing of polymer composite materials.

Shear strengthening of RC beams using GFRP sheets

This paper presents an experimental investigation on the shear behaviour of RC beams strengthened with externally bonded glass fibre reinforced polymer (GFRP) sheets. The externally applied GFRP technique is significantly effective to enhance the ultimate load carrying capacity of RC beams. Two beams without GFRP and nine beams wrapped in different lay-up patterns with one/two layers of GFRP sheets have been tested for shear under two-point loading. Loads at first crack of beam/delaminating of GFRP, tearing point of GFRP and ultimate failure of the beam has been noted and types of failure have also been observed. Thereafter, a critical discussion is made with respect to increase in the strength of retrofitted beams with respect to the beam without GFRP in order to explore the optimal use of GFRP for strengthening the RC beams. The comparison is also made between the shear strength obtained from experimental results and that predicted from different design proposals available in the literature.

Imperfection sensitivity analysis for a composite bowed-out shell under axial compression

In this article, we present a systematic work to investigate the imperfection sensitivity of composite bowed-out shells with different layup patterns under axial compression. Two types of geometric imperfections, including eigenmode-shaped imperfections (produced by a first-order eigenmode imperfection approach and an N-order eigenmode imperfection approach) and dimple-shaped imperfections (produced by a single perturbation load approach and a multiple perturbation load approach), are introduced into the finite element model to predict their knock-down factors. For the eigenmode-shaped imperfections, we show that the knock-down factors predicted by the first-order eigenmode imperfection approach are riskier than the ones predicted by the N-order eigenmode imperfection approach. When adopting the single perturbation load approach, we reveal that the direction of a dimple on the shell makes a negligible effect on axial pressure bearing capacity, while the amplitude of a dimple on the shell plays a significant role in affecting the knock-down factors. Using the multiple perturbation load approach as an extension of the single perturbation load approach, we uncover that the knock-down factors predicted by the multiple perturbation load approach are more conservative than these achieved by the single perturbation load approach. In addition, we also find that the composite bowed-out shells are more sensitive to dimple-shaped imperfection than eigenmode-shaped imperfections. This work provides helpful findings for designing an airplane body and marine risers.