Ply Layup Research Articles

An Enhanced Jig-Shape Approach to Lifting Propeller Design

The jig-shape approach decouples the design process of aeroelastic structures. During structural sizing, elastic deformations are subtracted from the initial shape to achieve a desirable flying shape under loads at one specific design point. However, due to nonlinear loads, stiffness, and deformations, there is a disparity between intended rigid and actual elastic propeller performance at off-design points. Propellers lifting air taxis or large cargo drones are particularly susceptible to such variances due to their slender design. This paper presents an enhanced jig-shape approach to minimize these discrepancies by inducing additional coupling effects counteracting elastic deformations. Beyond the traditional single-point predeflection analysis, the improved strategy employs geometric and structural modifications to mitigate errors at off-design points. Comparing the aeroelastic performance of propellers sized according to the traditional and the enhanced procedure illustrates the effectiveness of the modifications. The enhanced approach remains computationally efficient due to its decoupled nature. A novel finite beam element that accurately captures the relevant structural coupling effects of lifting propellers is derived. Applying unbalanced ply layups inducing extension–twist coupling is limited in effectiveness and increases weight. Modifying the coning angle of a straight blade affects loads and stresses but does not allow the adjustment of aeroelastic performance. Combining the coning angle with a swept planform enables the flexible correction of aeroelastic performance within limits at minimal weight increase.

An adaptive metastructure concept using bistable composite laminates

Concepts involving adaptive and morphing structures offer us the possibility to realise shape transformation with each shape imparting an individual functionality. There is an increased demand in the design of structural components that are suitable for diverse operational conditions rather than limited to a unique one. However, most concepts of shape adaptive structures require a “holding force” or a continuous supply of energy to maintain a targeted 3D shape. As a result, structures that can lead to desired shape transformation with self-locking capabilities are more desirable.In this work, the concept of multistability is employed to demonstrate a novel class of metastructures that can tackle this challenge. The metastructure is constructed with a periodic arrangement of bistable unit cells made of highly anisotropic composite laminates. Each unit cell comprises multi-sectioned rectangular composite plates exhibiting bistable behaviour due to the thermal residual stresses engendered during the cool-down process from curing to room temperature. To analyse the proposed metastructure, a finite element model has been developed at three hierarchical levels: a plate level, a unit cell level, and a lattice level. At the plate level, a corresponding semi-analytical model using the Rayleigh–Ritz method has also been formulated to validate the finite element models. By carefully tuning the size and spacing of the unit cell, a desired response of the metastructure can be achieved. Additionally, by changing the ply layup and the fibre orientation of each layer of constituent composite plates, conflicting requirements, including load-carrying, shape-adaptive and lightweight, at the same time can be addressed simultaneously. From an extensive parametric study, few designs have been selected for its application in a load-carrying morphing structure.

Effect of nanoscale interface modification on residual stress evolution during composite processing

The interface characteristics of the matrix and fibers significantly influence the evolution of residual stress in composite materials. In this study, we provide a methodology for reducing the residual stress in laminated composites by modifying the thermomechanical properties at the fiber–matrix interface. A hydrothermal chemical growth method was used to grow Zinc Oxide nanowires on the carbon fibers. We then utilized a novel digital image correlation approach to evaluate strains and residual stresses, in situ, throughout the autoclave curing of composites. We find that interface modification results in the reduction of residual stress and an increase in laminate strength and stiffness. Upon growing ZnO NWs on the carbon fibers, the maximum in situ in-plane strain components were reduced by approximately 55% and 31%, respectively, while the corresponding maximum residual stresses were decreased by 50.8% and 49.33% for the cross-play laminate [0°/90°] layup in the x and y directions, respectively. For the [45°/-45°] angle ply layup in the x-direction, the strain was decreased by 27.3%, and the maximum residual stress was reduced by 41.5%, whereas in the y-direction, the strain was decreased by 166.3%, and the maximum residual stress was reduced by 17.8%. Furthermore, mechanical testing revealed that the tensile strength for the [45°/-45°] and [0°/90°] laminates increased by 130% and 20%, respectively, with the interface modification.

Numerical simulation of inductive heating in thermoplastic unidirectional cross-ply laminates

Thermoplastic Composites can be re-melted allowing them to be joined via welding. This is an attractive alternative to conventional methods that are used to join thermoset composite parts such as mechanical fastening and adhesive bonding. In this work the inductive heating of uni-directional (UD) plies of thermoplastic carbon fiber reinforced polymer (CFRP) laminates is investigated. The focus is on developing a numerical electromagnetic and thermal simulation model that captures the main processes involved in eddy current generation and heat generation, in particular in the interface areas of the UD plies. A measurement technique has been developed to obtain the electric properties of the ply material. Furthermore, to support the modelling of both the induction heating equipment and work piece a field measurement of the magnetic field surrounding the coil and work piece has been developed. Inductive heating experiments were carried out on several thick composite laminate plates with different ply lay-ups to compare and validate the electro-magnetic-thermal simulation model. The measured surface temperatures were compared with the results from the simulation model. The results of this work can be used to support the design of UD-ply laminates to improve their ability to be welded via inductive heating. In addition, the results of this work can be used to assist in pre-determining induction welding equipment settings and heating times.

A global-to-local sub modelling approach to investigate the effect of lubrication during double diaphragm forming of multi-ply biaxial non-crimp fabric preforms

The forming behaviour of preforms constructed from multiple plies of Non-Crimp Fabric (NCF) has been investigated for manufacturing a complex double-curved geometry using Double Diaphragm Forming (DDF). An established multi-resolution finite element forming simulation has been employed to investigate the effect of the ply layup sequence on the formation of fabric wrinkles. FE simulations are shown to be in good agreement with experiments performed using the same geometry, in terms of the location and number of fabric wrinkles, for layups containing single or multi-ply orientations. Simulation results indicate that the convex double-curved features on the tool surface induce fabric over-shearing, coupled with fabric bridging, leading to wrinkles. In addition, the dissimilar inter-ply shear deformations in multi-ply preforms result in local fibre compression causing additional wrinkles. Experiments confirm the feasibility of using liquid resin as an inter-ply lubricant to mitigate out-of-plane wrinkles, but this is found to compromise the stability of the fibre architecture in local convex regions, causing additional in-plane fibre misalignment.

Examining slow crack growth metrics and competing failure modes in IM7/5320-1 carbon fiber reinforced polymer laminates with pre-existing damage states

The growing use of composites in aircraft structures has necessitated a slow growth criteria to assess the life of these materials and an appropriate similitude parameter. Due to the simplified stress state and inherent interactions of intralaminar and interlaminar damage progression in multi-directional ply layups, there have been questions about the applicability of double cantilever beam specimens to aerospace applications. This study examines these interconnected damage growth mechanisms in [±453]s and [±452/902]s layups via compact tension specimen geometries, with and without pre-existing damage, in order to examine the efficacy of proposed similitude parameters in capturing slow crack growth. The change in stored potential strain energy per cycle provided the most unified results across the 18 tests under different loading and pre-existing damage conditions. Via microscopy of the specimens after damage progression, the similitude parameters were connected to overall trends in the damage mechanisms. The fatigue results, coupled with the microscopy of the interactions amongst the complex damage mechanisms, demonstrates the need to analyze proposed similitude parameters across various sample geometries and stress states, which will be more enable an understanding of composite material fatigue performance in aerospace applications.

The performance characterization of carbon fiber–reinforced plastic for space applications

In this paper, the excellent dimensional stability and vacuum outgassing of high-performance carbon fiber–reinforced plastic (CFRP) were discussed. First, the high-performance resin matrix was obtained by modifying cyanate resin, and the modified cyanate ester was used to make prepreg and laminates. Then, the mechanical property retention rate of laminates reached 90.79% under proton and electron irradiation. The average values of total mass loss and collected volatile condensable material of high-performance CFRP were 0.116% and 0.008%, respectively. Finally, the candidate tube and frame were fabricated based on the ply lay-up design. The candidate tube and frame were subjected to a series of experiments of thermal deformation and hygroscopic deformation to verify the dimensional stability. The thermal deformations of the tube and frame reached 0.468 μm/m and 4.579 μm/m, respectively, with a temperature variation of 4°C. The measured hygroscopic deformation of the tube reached 8.16 μm/m in nearly 3 months. The experimental results show that the high-performance CFRP can be used for precision optical structures of space telescopes.

Thermal and Mechanical Analysis of Bimodular Beam

"The paper demonstrates the analysis of cantilever beam having dissimilar modularity in tensile and compressive tests liable with thermal and mechanical loading. The prime objective is to evaluate the governing differential equations to determine the displacements of the bimodular beam under combined loading of force and temperature. Also, the impact of ply lay-up and influence of residual thermal stresses and elastic loading on the cantilever bimodulus beam has been computed. Stress and flux analyses of beam made up of laminated Fiber Reinforced Polymeric (FRP) composite are computed with the help of Finite Element Analysis. The results show that the stresses and flux is increases with the advancement in bond length.

Effect of hygrothermal environment on tensile properties of carbon fiber epoxy resin composites

[0]16, [90]16, [±45]4s and [+45/0/0/-45/-45/0/0/+45]s were fabricated to study the influence of the different ply lay-up on the moisture absorption and tensile properties of TG800/E207 carbon fiber epoxy resin composite laminates at a hygrothermal environment of 80℃ and 90%RH. Moisture absorption curves, damage morphology after moisture absorption, fracture morphology, load-displacement curves and strength degradation were analyzed. The results show that the moisture absorption curves of TG800/E207 composite laminates present multi-stage phenomenon. The moisture adsorption reached equilibrium at a moisture absorption time of 1 608 hours. The equilibrium moisture content of [90]16 is the lowest and its saturated moisture content is only 0.806%; the equilibrium moisture content of [+45/0/0/-45/-45/0/0/+45]s is the highest and its saturated moisture absorption rate is 0.876%. The failure load of [0]16, [90]16, [±45]4s and [+45/0/0/-45/-45/0/0/+45]s samples decreased by 13.8%, 27.36%, 10.7% and 25.6%, respectively. The saturated moisture absorption of [90]16 is the lowest, but its tensile strength degradation is the most serious.

A cooperative mobile robot and manipulator system (Co-MRMS) for transport and lay-up of fibre plies in modern composite material manufacture

Composite materials are widely used in industry due to their light weight and specific performance. Currently, composite manufacturing mainly relies on manual labour and individual skills, especially in transport and lay-up processes, which are time consuming and prone to errors. As part of a preliminary investigation into the feasibility of deploying autonomous robotics for composite manufacturing, this paper presents a case study that investigates a cooperative mobile robot and manipulator system (Co-MRMS) for material transport and composite lay-up, which mainly comprises a mobile robot, a fixed-base manipulator and a machine vision sub-system. In the proposed system, marker-based and Fourier transform-based machine vision approaches are used to achieve high accuracy capability in localisation and fibre orientation detection respectively. Moreover, a particle-based approach is adopted to model material deformation during manipulation within robotic simulations. As a case study, a vacuum suction-based end-effector model is developed to deal with sagging effects and to quickly evaluate different gripper designs, comprising of an array of multiple suction cups. Comprehensive simulations and physical experiments, conducted with a 6-DOF serial manipulator and a two-wheeled differential drive mobile robot, demonstrate the efficient interaction and high performance of the Co-MRMS for autonomous material transportation, material localisation, fibre orientation detection and grasping of deformable material. Additionally, the experimental results verify that the presented machine vision approach achieves high accuracy in localisation (the root mean square error is 4.04 mm) and fibre orientation detection (the root mean square error is 1.84∘) and enables dealing with uncertainties such as the shape and size of fibre plies.

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.

Investigation into the effects of inter-ply sliding during double diaphragm forming for multi-layered biaxial non-crimp fabrics

The effect of inter-ply sliding was investigated for multi-ply Non-Crimp Fabric (NCF) preforms during the Double Diaphragm Forming (DDF) process. A Finite Element (FE) model was employed to investigate the influence of the ply layup sequence and the coefficient of friction between fabric-fabric and fabric-diaphragm interfaces. Simulation results indicate that in-plane fibre compression, caused by dissimilar shear deformation between adjacent plies, can lead to out-of-plane wrinkles, where the wrinkle length is a function of the relative fibre angle at the ply-ply contact interface. The most severe wrinkles occurred when the inter-ply angle was 45° for a multi-ply biaxial NCF preform with a pillar stitch at 45° to the primary yarns. A second parametric study was conducted by incrementally reducing the coefficient of friction at the ply-ply interface. Experiments confirmed that out-of-plane wrinkles are sensitive to the friction resistance between NCF plies and therefore lubricating the fibres can minimise wrinkling defects caused by dissimilar inter-ply deformation.

Weight minimization of fiber laminated composite beam for aircraft wing construction using exhaustive enumeration algorithm and numerical modeling

PurposeThis paper aims to focus on calculating the number of layers of composite laminates required to take the applied load made up of graphite/epoxy (AS4/3501-6) which can be used in many industrial applications. Optimization for minimization of weight by variation in the mechanical properties is possible by using different combinations of fiber angle, number of plies and their stacking sequence.Design/methodology/approachLots of research studies have been put forth by aerospace industry experts to improve the performance of aircraft wings with weight constraints. The orthotropic nature of the laminated composites and their ability to characterize as per various performance requirements of aerospace industry make them the most suitable material. This leads to necessity of implementing most appropriate optimization technique for selecting appropriate parameter sets and material configurations.FindingsIn this work, exhaustive enumeration algorithm has been applied for weight minimization of fiber laminated composite beam subjected to two different loading conditions by computing overall possible stacking sequences and material properties using classical laminate theory. This combinatorial type optimization technique enumerates all possible solutions with an assurance of getting global optimum solution. Stacking sequences are filtered through Tsai-Wu failure criteria.Originality/valueFinally, through the outcome of this optimization framework, eight different combinations of stacking sequences and 24-ply symmetric layup have been obtained. Furthermore, this 24-ply layup weighing 0.468 kg has been validated using finite element solver for given boundary conditions. Interlaminar stresses at top and bottom of the optimized ply layup were validated with Autodesk’s Helius composites solver.

Failure Mode Analysis of Carbon Fiber Composite Laminates by Acoustic Emission Signals

Composite laminates have complex failure modes. In order to investigate the evolution of failure in the composite laminates, this paper performed an experimental study on four laminates with different layups using acoustic emission (AE) technique. Two different kinds of defects are imposed on the laminates, including a hole and a crack in the center. Tensile and bending tests are performed on the defective laminates and real‐time AE signals are collected. By analyzing the spectrograms of the obtained AE signals and integrating with the dispersion curves, the evolution of failure modes for different laminates can be observed. The tests show that the defects cause multiple failure modes, which change gradually during the experiments. It is also revealed that laminates with different layups have different failure modes. More specifically, the stacking order of different plies has a greater impact on the occurrence of delamination and fiber fracture than matrix crack. The tentative research shows that there is great potential for improving the performance of the composite laminates by careful selection of ply layups.

COMPARATIVE ANALYSIS OF METHODS FOR DETERMINING THE MASS OF THE SHAFT OF A SPORTS AND AEROBATIC AIRCRAFT, MADE OF TITANIUM AND COMPOSITE MATERIAL

Comparative analysis of an acrobatic aircraft's weight and shaft which is made of a titanium alloy and composite materials. The article contained requirements and specificities of an acrobatic aircraft's landing gear shaft design. The article describes prediction method of an acrobatic aircraft’s weight fraction of shaft which is allows to take into account shaft mass on wing loading upon condition that composite materials will be used in construction. Research objectives include: –Documentation of an acrobatic aircraft’s shaft design. – Analytic dependence conclusions on shaft mass by applying energy absorption of landing impact. – To quantify the algorithm of shaft mass based on strength prediction of shaft construction. –To quantify the mass and construction of shaft based on patterns that are made of titanium and composite materials. – Comparative analysis and references to practical using these methods to quantify shaft’s mass. –To quantify how shaft mass influenced by wing loading. –Designing shaft construction that is made of titanium alloy VT22 and composite material VKU26 by taking into account quantity and ply layup. Comparative analysis shaft mass which is made by different variety of composite materials. The constructive analysis is distinguished for decreasing the shaft mass that is made by composite material and references on ply layup.

Experimental Study of the Probabilistic Fatigue Residual Strength of a Carbon Fiber-Reinforced Polymer Matrix Composite

Degradation of the mechanical properties of fiber-reinforced polymer matrix composites (PMCs) subjected to cyclic loading is crucial to the long-term load-carrying capability of PMC structures in practice. This paper reports the experimental study of fatigue residual tensile strength and its probabilistic distribution in a carbon fiber-reinforced PMC laminate made of unidirectional (UD) carbon-fiber/epoxy prepregs (Hexcel T2G190/F263) with the ply layup [0/±45/90]S after certain cycles of cyclic loading. The residual tensile strengths of the PMC laminates after cyclic loading of 1 (quasistatic), 2000, and 10,000 cycles were determined. Statistical analysis of the experimental data shows that the fatigue residual tensile strength of the PMC laminate follows a two-parameter Weibull distribution model with the credibility ≥ 95%. With increasing fatigue cycles, the mean value of the fatigue residual strength of the PMC specimens decreased while its deviation increased. A free-edge stress model is further adopted to explain the fatigue failure initiation of the composite laminate. The present experimental study is valuable for understanding the fatigue durability of PMC laminates as well as reliable design and performance prediction of composite structures.

Mechanical performance of carbon-glass hybrid composite joints in quasi-static tension and tension-tension fatigue

The ever increasing size of wind turbines has given rise to a need for robust glass to carbon joint designs. This study investigates the effect of different ply layups on the static and fatigue behaviour of hybrid glass/carbon fibre composite joints. Uni-directional carbon fibre prepreg was co-cured to 8H glass prepreg using an overlap to thickness ratio of 20:1, where four joint designs were examined: scarf, interleaving and two forms of double scarf. The joints were tested statically in uniaxial tension and dynamically in tension-tension fatigue. Finite element analysis has been performed to provide insight into stress distributions within each joint. The double scarf joint (with glass on the outside) was found to perform best in fatigue and static tension, while the interleaving joint performed second best in fatigue in static tension but poorest in fatigue. For joint designs that will be used under highly stressed cyclic loading conditions, the current study indicates that static tests alone are a poor indicator of the joint performance and fatigue tests are required.

Process induced deformations in composite sandwich panels using an in-homogeneous layup design

This work presents an experimental and numerical study of process-induced deformation (PID) in flat sandwich panels with in-homogeneous ply layups. An over-expanded Nomex honeycomb core and aerospace-grade prepreg was used to manufacture sandwich panels using the autoclave technique. Process-induced spring-in and warpage at different locations were measured. A 3D FE analysis was performed for the full cure cycle. The FE model successfully captured the shrinkage due to cure, anisotropic and thermo-physical properties of the sandwich structure and tool-part interactions. The computed maximum spring-in values obtained from the FE model were in good agreement with average spring-in values measured experimentally. An overall error of less than 2% was found in the PID of the sandwich panel. The effect of tooling material and core material on PID was also investigated. The numerical results suggest that an aluminum tool and an aluminum core could potentially reduce warpage in the sandwich panel studied.

Out-Of-Plane Permeability Evaluation of Carbon Fiber Preforms by Ultrasonic Wave Propagation.

Out-of-plane permeability of reinforcement preforms is of crucial importance in the infusion of large and thick composite panels, but so far, there are no standard experimental methods for its determination. In this work, an experimental set-up for the measurement of unsaturated through thickness permeability based on the ultrasonic wave propagation in pulse echo mode is presented. A single ultrasonic transducer, working both as emitter and receiver of ultrasonic waves, was used to monitor the through thickness flow front during a vacuum assisted resin infusion experiment. The set-up was tested on three thick carbon fiber preforms, obtained by stacking thermal bonding of balanced or unidirectional plies either by automated fiber placement either by hand lay-up of unidirectional plies. The ultrasonic data were used to calculate unsaturated out-of-plane permeability using Darcy’s law. The permeability results were compared with saturated out-of-plane permeability, determined by a traditional gravimetric method, and validated by some analytical models. The results demonstrated the feasibility and potential of the proposed set-up for permeability measurements thanks to its noninvasive character and the one-side access.

Feasibility of ultrasonic guided waves for detecting surface-breaking cracks in laminated composite plate structures

Ultrasonic guided waves are attractive for rapid inspection of laminated composite structures, where the cracks developed transverse to the loading direction are the serious type of damage. In this context, the paper presents studies of guided wave interaction with transverse cracks in symmetric and non-symmetric cross-ply composite laminates. In view of this, a two-dimensional finite element approach is used to gain physical insight into the reflection regime. Reflection ratios for GFRP/CFRP cross-ply laminates with various surface-breaking/transverse crack sizes are calculated, and results are presented in frequency spectrum, which shows that the minimum crack depth of 0.0093 of the operating wavelength has been successfully detected. Effect of different ply layup orientations is also considered. This work will be useful for practical guided wave-based inspection of composite plate structures. These points have been added at the abstract section of the revised manuscript.