Lay-up Orientations Research Articles

Investigation of Mode I and II Interlaminar Fracture Toughness of Nylon/Glass Fiber Laminates with Various Layup Orientations

Investigation of Mode I and II Interlaminar Fracture Toughness of Nylon/Glass Fiber Laminates with Various Layup Orientations

Effect of temperature aging of thermoset UD prepregs on inter‐ply friction behavior and formability in prepreg compression molding process

AbstractLimited material out‐life of thermoset prepregs is unavoidable attributed to the slow crosslinking reaction between molecules and curing agents. Previous studies have explored the effects of temperature aging on the final mechanical properties of composites, but have been limited by the processing mismatch in compression molding. The research primarily focuses on the effects of forming temperature and ply angle of prepreg on inter‐ply friction behavior at various aging levels. The importance of inter‐ply friction on the forming quality is further discussed through the L‐shaped specimens forming with prepreg compression molding (PCM) process. Firstly, a comprehensive influence of aging on the properties of resin including cure kinetics, gel point, glass transition temperature (Tg) and viscosity of UD prepreg are characterized and discussed. And then, the influence of factors including resin aging, forming temperature and prepreg ply orientation on the inter‐ply friction are discussed. It can be found that the aging of prepreg reduce 26.47% of inter‐ply friction resistance under room temperature, and the increase of temperature can reduce inter‐ply friction resistance by 79.31%. Finally, the effect of aging on the forming quality is researched by PCM formed L‐shaped components. Results indicated that fresh prepreg with 20°C and prepreg with an aging level of 0.4 performed at 95°C exhibited poor formability, while prepreg with aging level of 0.2 at 95°C exhibited the best forming property. In general, this study provides a basic explain and a practical suggestion to the reuse of room temperature aging thermoset prepregs in PCM process.Highlights A comprehensive of basic properties of aged resin were characterized, as the basic principle for inter‐ply friction behavior analysis. The gel point and final mechanical properties of prepreg were tested, for judging the aged materials whether could be used continuously. The inter‐ply friction behaviors of aged prepregs under various forming temperatures were investigated. The influence of layup orientations on the inter‐ply frictional performance with various aging levels were explored. The effect of aging and forming temperature on the PCM formability were studied and a practical suggestion to the reuse of aged thermoset prepregs in PCM process was given.

Assessment of tensile damage mechanism of open‐hole GLARE laminates based on acoustic emission and digital image correlation techniques

AbstractGLARE laminates have emerged as a favored option for the construction of fuselage and wing skins in large airliners, owing to their exceptional mechanical characteristics. Nevertheless, the incorporation of open‐hole designs poses a challenge as it disrupts the continuity of the laminates, resulting in stress concentration and subsequent damage. To investigate the impact of various layup orientations and hole sizes on the tensile properties of open‐hole GLARE laminates, this study conducted axial tensile tests. Additionally, the tensile damage process was monitored using DIC and AE techniques, enabling the identification of damage patterns and the analysis of their evolution. The results demonstrate a noteworthy decline in the ultimate strength and failure strain as the size of the opening increases. Moreover, the retention rate of failure strain displays a marked sensitivity to the layup orientation. In conjunction with observations made through DIC and SEM, the k‐means++ algorithm successfully clustered peak frequencies, thereby revealing distinct damage patterns and their corresponding frequency ranges as aluminum alloy damage [0–90 kHz], matrix cracking [104–174 kHz], fiber/matrix debonding [175–224 kHz], interlaminar delamination [234–300 kHz], and fiber fracture [304–469 kHz]. AE cumulative counts were utilized to evaluate the progression of individual damage modes. The results emphasize that matrix cracking demonstrates the most substantial cumulative counts, whereas damage to the fibers and aluminum alloy noticeably affects the load‐carrying capability of the laminate. Furthermore, the fibers/matrix debonding and interlaminar delamination, exhibit heightened susceptibility to layup orientation and hole size.Highlights The tensile performance evaluation of GLARE laminates with open‐hole varying layup orientations and hole sizes was investigated. A combination of DIC and AE techniques was used to monitor the tensile damage process. Damage pattern was identified based on the observations of DIC and SEM. An approach based on Pearson's correlation coefficient and k‐means++ clustering algorithm was used for damage pattern recognition in GLARE laminates. AE cumulative counts were employed to assess the evolution of each damage mode.

A Lay-up-Oriented CFRP-Substrate Metamaterial Absorber with High Insensitivity to Polarization

Metamaterial absorbers with carbon fiber reinforced polymer (CFRP) substrates, which are called meta-CFRPs, have recently gained recognition for their excellent mechanical and electromagnetic performance. Different from traditional metamaterial absorbers with an isotropic substrate, meta-CFRPs with a highly anisotropic CFRP substrate are facing challenges in acquiring polarization-insensitive absorption. Here, a lay-up-oriented structure design method is proposed to solve this problem. Considering the lay-up configuration of CFRP laminates, metallic patterns are designed under corresponding polarization angles and then united together to form an integral structure. A meta-CFRP with a typical CFRP lay-up configuration([0°/45°/90°/−45°]3s ) is designed and tested. The experimental results exhibit over 99% microwave absorptivity at 2.44 GHz for all polarization angles. The maximum shift among the resonance peaks of the curves at all polarization angles is only 0.021 GHz. Further studies show that when there are cross-ply laminates in the first few layers of the CFRP substrate, the lay-up-oriented design method can be effectively simplified by ignoring the subsequent lay-up orientations after the first cross-ply layers. Our method can not only provide an effective way for acquiring polarization-insensitive microwave response on meta-CFRPs but also be expected to be promoted to metamaterial absorbers with other anisotropic materials.

Study on vibro-acoustic performance of composite laminates under transient impact excitation

With the widespread use of composite structures in ship superstructures, their vibro-acoustic response under transient impact loads is of increasing concern. This paper studies the vibro-acoustic behavior of a carbon fibre reinforced composite laminate under transient impact excitation based on the time-domain hybrid FEM/BEM method. Firstly, the numerical method is verified through the model test of a homogeneous plate. Subsequently, the vibration and sound radiation characteristics of composite laminates are studied. It was found that the impact noise energy mainly concentrated in the low-frequency range of 10~200Hz, and the peak noise spectrum was 9dB lower than that of the steel plate. The variation of lay-up orientations causes differences in the structural properties of the laminates, resulting in differences in their vibro-acoustic radiation performance. In this study, the laminate with the [0°/90°]5s orthogonal lay-up scheme has better acoustic radiation performance under the impact load.

The influence of the fiber–matrix microstructure on the energy release rate of off-axis tunnel cracks in laminates

Microstructural effects on the energy release rate and the mode mixity for tunneling cracks are investigated. A detailed microstructure is based on scanning electron microscopy of a real laminate. Based on a newly developed two-dimensional off-axis finite element formulation, the dependency of the Mode I, Mode II, and Mode III energy release rates on a range of different layup orientations are investigated. First, the influence of the fiber–matrix microstructures on the energy release rates is assessed and compared to results from homogenized models that exclude explicit representation of the microstructure. A finite element-based homogenization is found to provide consistent and accurate predictions, whereas analytical homogenization methods yield greater discrepancies with respect to a basic stress-based validation case and are thus not recommended in the context of tunneling crack modeling. Secondly, realistic non-straight crack shapes are included in the model resulting in similar energy release rates as for straight cracks in the corresponding fully homogenized models. However, modeling the realistic non-straight cracks without accounting for the specific microstructure provides too low energy release rates when compared to the realistic cases with microstructures.

Study of air-backed and water-backed carbon fiber composite plates subjected to underwater shock loading

A collection of experimental and numerical studies was conducted for laminated carbon fiber composite plates of different layup orientations to investigate their response and failure when subjected to underwater shock loading. The composite plates were clamped within a rigid fixture and submerged within an anechoic water tank while having either an air-back or water-back supporting condition. Plastic bottles partially filled with liquid nitrogen were used to generate shock pressures whose characteristics were closer to that resulting from the pulsation of a gas bubble rather than the detonation of an explosive. A multiphysics model based on fluid–structure interaction was considered for the numerical study. A multiscale approach was also used for the numerical study to predict failure based on the constituent material level (i.e., fiber and matrix material level). Both experimental and numerical results agreed well, indicating that the water-backed carbon fiber plate had a very localized failure while the air-backed composite plate showed global failure. The critical stand-off distance for the failure of the water-backed carbon fiber composite was approximately half of that for the air-backed composite plate of the same layup orientation. In other words, the water-backed carbon fiber composite plate had greater damage tolerance than the air-backed plates.

Thermal characterization of short carbon fiber reinforced high temperature polymer material produced using the fused filament fabrication process

The objective of this research is to perform the thermal analysis on high-temperature polymer (polycarbonate) based composite material reinforced with short carbon fiber (SCF) produced by utilizing the fused filament fabrication (FFF) process. Different percentages of SCF (by vol.), i.e., pure (0 %), 3 %, 5 %, and 10 %, were taken to fabricate the additively manufactured part for thermal analysis. The entire part manufacturing process was described, starting with material mixture generation, composite filament fabrication with different SCF percentages, and finally, FFF printing. Micrography analysis was performed to observe the fiber behavior, including fiber-matrix adhesion, fiber orientation, and fiber distribution. The thermal behavior was investigated by determining the thermal degradation temperature, viscoelastic properties like loss modulus, storage modulus, and creep behavior at high temperature (100 °C) by varying the SCF percentage. Due to the anisotropic nature of the FFF-made parts, thermal conductivity was analyzed on 0° layup and 90° layup orientations in the X-Y plane to observe the behavior of thermal properties in different directions. The results of the study indicated that the addition of fibers has maintained or improved the thermal properties of PC. The incorporation of SCF has enhanced the degradation temperature and viscoelastic properties of the 3D printed composite parts. Thermal conductivity results also showed a significant improvement with the increase in SCF amount. In summary, PC-based composites with SCF incorporation were found to execute well with FFF technology and allow the fabrication of electronic products and heat exchangers with satisfactory thermal performance.

A comprehensive damping study of variable stiffness composite rectangular/skew laminates reinforcement with curvilinear fibers by higher-order shear flexible model

In this work, a comprehensive investigation of curvilinear fiber reinforcement on damping of rectangular and skew composite plates is computationally estimated using higher-order shear flexible model. A set of governing equilibrium equations developed here in form of eigenvalue analysis is solved by adopting the Q-R algorithm. The damping factors associated with different vibrational modes are evaluated from the complex eigenvalues. The proposed model is validated against the available analytical and experimental results. The damping capability of laminated rectangular/skew composite plates is thoroughly analyzed by varying the curvilinear fiber path angles in the layers, lay-up orientations, structural boundary conditions, skew angle of the laminate, and nature of the material. Results reveal that the damping pretending to the curvilinear fibers plate is better than the conventional composite laminate; it varies significantly according to the variation in center and edge of the curvilinear fiber angles. It is also noted that the damping increases with the skew angle of the plate. The study conducted here shows the suitability of such variable stiffness composite structure for safe design under dynamic/impact loading situation.

Failure Criteria for Brittle Notched Specimens

Abstract Recently, new failure criteria were proposed for brittle materials to predict their failure loads regardless of the shapes of a notch or a crack in the material. This paper is to further evaluate the failure criteria for different shapes of notches and different materials. A circular hole, elliptical hole, or crack-like slit with a different angle with respect to the loading direction were considered. Double circular holes were also studied. The materials studied were an isotropic material such as polymethyl methacrylate (PMMA) as well as laminated carbon fiber composites. Both cross-ply and quasi-isotropic layup orientations were examined. The lamination theory was used for the composite materials so that they can be modeled as an anisotropic and homogeneous material. The test results were compared to the theoretical predictions using the finite element analysis with two-dimensional plane stress models. Both theoretical failure stresses agreed well with the experimental data for the materials and notch geometries studied herein.

Free vibration analysis of perforated composite cylindrical shell and panel using multi-domain generalized differential quadrature (GDQ) method

Free vibration behavior of a composite shell/panel with and without a central square cutout has been studied using Multi-domain Generalized Differential Quadrature (GDQ) method. A physical domain is decomposed into several elements in such a way that all the elements have uniform thickness and material properties, as well as continuous loading and boundary conditions at their edges. The governing equations are derived based on the first-order shear deformation theory. They are formulated in a general form and can be converted to Donnell’s, Love’s, and Sanders’ theories. In addition, compatibility conditions are considered at the interface boundaries of adjacent elements as well as proper boundary conditions on other elements edges. The GDQ method is employed to discretize these equations in both longitudinal and circumferential directions. By assembling these discretized relations, a system of algebraic equations will be generated. These equations can be solved throughan eigenvalue solution to compute the natural frequencies of the whole shell/panel. Numerical results obtained by the presented method are compared with ABAQUS results and those available in the literature. After verifying the accuracy and precision of the proposed method, it is employed to study the effect of an opening on the vibrational behavior of composite shells and panels through a parametric study. The influence of the presence of a cutout and its size is investigated on shells/panels with various material properties, layup orientations, thicknesses, dimensions, and boundary conditions. The obtained results can be used as a benchmark for further researches.

Dynamic stability optimization of laminated composite plates: An isogeometric HSDT formulation and PSO algorithm

An isogeometric analysis framework based on the non-uniform rational B-spline (NURBS) and the higher-order shear deformation theory (HSDT) is developed to study the geometry-accurate dynamic instability behavior of the shear-sensitive generally laminated composite plates. The developed approach is combined with the particle swarm optimization (PSO) technique to modify the layup orientations of the laminate corresponding to the minimum dynamic instability opening (DIOI) value. Based on the accuracy assessment results, the convergence rate of the developed method is higher than the classical finite element method. Moreover, the frequency accuracy of cubic NURBS is stabilized for high degrees of freedom denoting their high computational efficiency. The optimization procedure reveals that the mode shapes of the plates with optimal layups are more complex than their non-optimal case. The optimal ply angles are mostly oriented along the maximum-curvature path, perpendicular to the loading direction, and parallel to the supported edges. The mixed-type supports leads to lower DIOI values for optimal layups concerning the homogeneous supports. The pure compressive force expands the fundamental dynamic instability region (DIRI) for the generally laminated plates and leads to wide-range frequency instabilities. However, the combination of compressive force with lateral or shear force increases the lower bound of the DIRI for optimal layups. The minimization of DIOI value does not necessarily increase the lower bound of DIRI for optimal layups.

Novel Carbon Fibre Composite Centrifugal Impeller Design, Numerical Analysis, Manufacturing and Experimental Evaluations.

This paper presents an experimental investigation on using high strength-to-weight composite materials to reduce the mass of a centrifugal compressor impeller by 600%. By reducing the blades number from 17 to 7 and by doubling their thickness, the compression ratio and efficiency were maintained close to the reference metallic impeller. Using autoclave technology, seven composite blades were manufactured individually and assembled to form the impeller. After manufacturing, small deviations were found at the blade’s tip. As these deviations were found to be symmetrical, impeller balancing was successfully performed removing a total of 45 g of mass, followed by an experimental test on a dedicated test bench. Experimental testing identified the resonant frequencies of the composite centrifugal impeller at 13.43 Hz 805 rot/min and at 77 Hz with a 0.1 mm/s amplitude at 4400 rot/min, highlighting feasibility and the advantage of a composite compressor impeller design with application in centrifugal compressors and rotating machine assemblies and sub-assemblies. As there are numerous numerical investigations performed on the strength analysis and on the lay-up orientations mechanical behaviour for polymer composite materials with respect to the design of centrifugal impellers, no experimental evaluations in relevant working conditions have been performed to date. As the paper contains relevant experimental data on the subject, the outcome of the paper may aid the oil and gas or aviation industries.

Design and discrete optimization of hybrid aluminum/composite drive shafts for automotive industry

Fiber reinforced composites have been widely used in automotive industry since they offer significant weight reduction, low manufacturing and tooling cost, and better integration of parts compared to metal counterparts. In this study, design optimization of a hybrid aluminum/composite drive shaft subjected to torsion was carried out using ANSYS Workbench with ACP module. The numerical validation of finite element (FE) model was carried out by means of theoretical, experimental, and numerical studies in the literature. The ply material, lay-up orientations, and thickness of aluminum layer were considered as design variables. The geometric parameters in design were the length and inner diameter of the drive shaft. Two important design constraints, the minimum first mode natural frequency and design torque, were considered to satisfy the design requirements of a rear-wheel drive shaft used in automotive industry. The optimum design variables were determined by using screening method. The optimum design parameters (length, inner diameter, ply angle, and material) were presented in tabular form. Compared to nonoptimized scenario, the optimized solution reduced the cost of the hybrid composite drive shaft about 30% without ignoring the design requirements.

Analysis of the crushing behaviors of woven carbon fiber reinforced plastic hat section component under dynamic bending and axial crushing loading

In current work, the crashworthiness of woven carbon fiber reinforced plastic (CFRP) hat section component is investigated under two types of loading experimentally and numerically, i.e., axial crushing and dynamic three-point bending. The crushing characteristics of woven CFRP hat section sample are evaluated at various impact velocities and layup orientations which exhibit different effects under two types of loading. With impact velocity/energy increasing, the bending behaviors illustrate different evolutions with distinct stages which are affected by the damage development. Layup orientation shows a little effect on the bending behaviors, while it exerts remarkable effects on the axial crushing which leads to different crushing modes and thus different energy absorption capabilities. The finite element model with multiple layers of thick shell element and cohesive element is shown to capture the crushing behaviors reasonably well in both axial crushing and dynamic bending. The corresponding damage evolutions are also analyzed with simulations to explain the crushing behaviors.

Experimental and numerical failure analysis of horizontal axis water turbine carbon fiber-reinforced composite blade

High-performance composites are used in many applications due to their design flexibility, corrosion resistance, high strength-to-weight ratio, and many other excellent mechanical properties. In this study, the location and magnitude of failure initiation in horizontal axis water turbine carbon fiber reinforced polymer (CFRP) blades with different lay-up orientations were investigated. Unidirectional [0°]4 and cross-ply [0°/90°]S layups were selected to study the effect of the buildup direction on the failure of the composite water turbine blades. A finite element analysis (FEA) model was generated to examine the stresses along blade span under both flexural and hydrodynamic loads. Flexural destructive tests were conducted to validate the results obtained from the numerical simulations. In addition, a blade element momentum theory model was created to calculate the hydrodynamic forces acting along the span to determine the maximum loading radial location, which was used for the fixture design and FEA simulation input. Both unidirectional and cross-ply composite blades were tested for failure. There was a general agreement between the experiments and simulations, which validated the results. Moreover, FEA simulations were performed to apply the load to the samples with different pitch angles (−10°, −5°, 0°, 5°, and 10°). Even though the unidirectional CFRP composite blades showed higher strength at 0° pitch angle than the cross-ply blades, the strength of the unidirectional blade dropped significantly when the load was applied with different pitch angles other than 0°, while the strength of the cross-ply blades was less responsive to this pitch angle variation.

In Situ Investigation of the Kinematics of Ply Interfaces During Composite Manufacturing

Abstract The kinematics of composite ply interfaces critically affects both the manufacturing processes and deformation mechanisms and is often responsible for the formation of defects such as wrinkles and delamination. In the present work, processing-induced defects in a carbon fiber prepreg composite are evaluated by devising a novel in situ experimental approach. Carbon fiber prepreg laminates are cured in a specially designed autoclave with viewports with plies laid up on a mold with cylindrical tooling set up to maximize the ply-movement. Four-ply layup orientations of [90/90]s, [90/0]s, [90/45]s, and [90/−45]s and three-mold configurations with cylindrical tools of diameter 9.5 mm (3/8 in.), 12.7 mm (1/2 in.), and 15.9 mm (5/8 in.) are used for the parametric study. Strains, ply-movement, and formation of defects are observed in situ using digital image correlation (DIC) during the autoclave cure cycle, through the viewports. The processing-induced defects in the composite are further characterized by X-ray micro-computed tomography (micro-CT). We observed that the mold with the larger radius of curvature (15.9 mm cylinder) leads to higher strains in both in-plane directions and higher displacement in out of plane directions. The maximum average out-of-plane ply movement, as well as the largest wrinkle, are observed for [90/−45]s layup on the mold with the highest radius of curvature.

Effect of tufting technique on sound insulation of multi-layer glass woven fabrics

A new idea to influence the sound insulation property of multi-layered woven fabric by the embedded tufting yarns is presented in this paper. The effect of layer number, layer orientation, tufting density and tufting pattern is investigated respectively, in the basis of sound transmission loss (STL) analysis measured by an impedance tube. The experimental results show that the sound insulation can be enhanced by increasing the number of layers or maintaining the same lay-up orientations. Moreover, the effect of tufting yarns on sound insulation is more sensitive in the low-middle frequency range and relatively more complicated. The obtained results can be applied in the part design, the preform engineering, and the positioning of tufting process.

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.

Crushing behaviors of unidirectional carbon fiber reinforced plastic composites under dynamic bending and axial crushing loading

The dynamic crushing characteristics of unidirectional carbon fiber reinforced plastic composites under two loading types, dynamic three-point bending and axial crushing, are investigated by experiment and finite element simulation. Hat section samples with two different layup orientations are tested at various impact velocities to investigate its effects. The experiment results show that delamination plays a critical role in dynamic bending deformation. Different layup orientations lead to similar crushing bending behaviors, but remarkable variations in delamination pattern evolutions. In contrast, layup orientation exerts more significant effects on failure modes and energy absorption in axial crushing. A finite element model with multiple layers of thick shell element and cohesive element is established, and simulations are performed for both dynamic three-point bending and axial crushing. The model can capture the crushing behaviors in the two loading types reasonably well. The damage evolution and energy absorption through various mechanisms at different loading conditions are discussed.