Fiber Angle Research Articles

Statistical assessment of natural frequency values obtained from numerical analyses in the tapered composite laminated beams

In the last years, the glass/epoxy laminated composites which are a combination of glass reinforcement and epoxy matrix are widely used in the field of automotive and aerospace due to their strength/weight ratio. The proposed study statistically evaluates the natural frequency data obtained by the numerical analysis of glass reinforced epoxy matrix beams with Taguchi method. Accordingly, numerical analyzes were performed based on L27 orthogonal array at different levels of tapered angle (0, 0.25, and 0.5), fiber orientation angle (30?, 600?, and 900?), and a/l ratio (delamination ratio) (0, 0.25, and 0.5). The obtained results were evaluated with analysis of variance (ANOVA), regression analysis, main effects, and interactions plots. Lastly, it was observed that the tapered angle changes directly with the natural frequency and inversely with a/l delamination rate, and there is a dramatic increase in the natural frequency at the 30? angle. With regression analysis, the effects of main, interaction, and squares of factors on natural frequency are predicted with a coefficient of determination of 95.63%. Finally, the optimum natural frequency is obtained at third level of the tapered angle (A = 0,5), the first level of angle (B = 30?) and a/l ratio (C = 0) as 40.091 Hz.

Investigation of Orientation Angle of Short Glass Fiber in Polyethylene Pipe Using X-ray CT

Investigation of Orientation Angle of Short Glass Fiber in Polyethylene Pipe Using X-ray CT

On the possibility of estimating myocardial fiber architecture from cardiac strains.

The myocardium is composed of a complex network of contractile myofibers that are organized in such a way as to produce efficient contraction and relaxation of the heart. The myofiber architecture in the myocardium is a key determinant of cardiac motion and the global or organ-level function of the heart. Reports of architectural remodeling in cardiac diseases, such as pulmonary hypertension and myocardial infarction, potentially contributing to cardiac dysfunction call for the inclusion of an architectural marker for an improved assessment of cardiac function. However, the in-vivo quantification of three-dimensional myo-architecture has proven challenging. In this work, we examine the sensitivity of cardiac strains to varying myofiber orientation using a multiscale finite-element model of the LV. Additionally, we present an inverse modeling approach to predict the myocardium fiber structure from cardiac strains. Our results indicate a strong correlation between fiber orientation and LV kinematics, corroborating that the fiber structure is a principal determinant of LV contractile behavior. Our inverse model was capable of accurately predicting the myocardial fiber range and regional fiber angles from strain measures. A concrete understanding of the link between LV myofiber structure and motion, and the development of non-invasive and feasible means of characterizing the myocardium architecture is expected to lead to advanced LV functional metrics and improved prognostic assessment of structural heart disease.

Effect on Strength of Different Fiber Orientation Angles of the Composite Plate Under Out of Plane Load

Composite materials obtained by combining two or more materials macroscopically; It is expressed as a new type of material with low specific gravity, high strength and high rigidity properties. Composite materials are materials that are used under different loads and can be produced in various constructions. In this study, the effects of fiber orientation angle degrees on stress and deformation in composite plates with different fiber materials were investigated using the finite element method. Graphite, glass and aramid as fiber materials; Epoxy was chosen as the matrix material. According to the analysis results, while the stress and deformation values increased as the fiber angle increased in the graphite and aramid fiber epoxy matrix composite plates, the stress and deformation values did not change at different fiber angles in the glass fiber epoxy matrix composite plate.

Analysis of Fiber Metal Composite Shear Strength Using Independent Variables of Fiber Angle Orientation and Metal Surface Roughness

Fiber Metal Laminates (FML) is a classification of metallic materials consisting of several thin layers of metal combined with composite materials. The constraint of FML is the weak bond between the layer material and the core composite. The weak bond between the layer material and the core composite can be influenced by several things, including the absence of an interlock system between the layer material and the core composite so that the strength of the FML composite decreases. In this study, a study was conducted on the shear strength of FML composites using the independent variables of surface roughness and fiber angle orientation. The highest shear strength in FML composite with fiber angle orientation of 45/45° and with a surface roughness value of 2.128 m with a shear strength value of 2.7 MPa

Manufacture and Buckling Test of a Variable-Stiffness, Variable-Thickness Composite Cylinder Under Axial Compression

Variable-angle tow (VAT) manufacturing methods significantly increase the design space for elastic tailoring of composite structures by smoothly changing fiber angle and ply thickness across a component. Rapid tow shearing (RTS) is a VAT manufacturing technique that uses in-plane shearing (rather than in-plane bending) to steer tows of dry or pre-impregnated fibers. RTS offers a number of benefits over conventional bending-driven steering processes, including tessellation of adjacent tow courses; no overlaps or gaps between tows; and no fiber wrinkling or bridging. Further to this, RTS offers an additional design variable: fiber orientation to tow thickness coupling due to the volumetric relation between tow shearing and the tow’s thickness and width. Previous computational work has shown that through a judicious choice of curvilinear fiber trajectories along a cylinder’s length and across its circumference, the imperfection sensitivity of cylindrical shells under axial compression can be reduced and load-carrying capacity increased. The present work aims to verify these predictions by manufacturing and testing two cylinders: an RTS cylinder and a straight-fiber, quasi-isotropic cylinder as a benchmark. The tow-steered manufacturing process, imperfection measurements, instrumentation, and buckling tests of both cylinders are discussed herein. The experimental tests results are compared against high-fidelity geometrically nonlinear finite element models that include measured geometric and loading imperfections before and during the tests. Finally, a discussion is provided on the outstanding challenges in designing and manufacturing RTS cylinders for primary aerostructures.

Estimating of cutting force and surface roughness in turning of GFRP composites with different orientation angles using artificial neural network

Abstract Glass fiber-reinforced polymer (GFRP) composite materials are widely used in many manufacturing industries due to their low density and high strength properties, and consequently, the need for precision machining of such composites has significantly increased. Since composite materials have an anisotropic and heterogeneous structure, the machinability of composite materials is quite different from conventional materials. In the machining of GFRP composite pipes, tool wear, cracks or delamination, a rough surface, etc., many unwanted problems may occur. Therefore, GFRP composite pipes are difficult to process. To prevent such problems, it is very crucial to select suitable process parameters, thereby achieving the maximum performance for the desired dimensional integrity. In this study, through turning of GFRP composites with different orientation angles (30°, 60°, and 90°), the effects of cutting speed (50, 100, and 150 m·min−1), feed rate (0.1, 0.2, and 03 mm·rev−1), and depth of cut (1, 2, and 3 mm) on cutting force and surface roughness were determined. Then, with the use of these machining parameters, a model of the system for determining cutting force and surface roughness was established with artificial neural networks (ANNs). The ANN was trained using Levenberg–Marquardt backpropagation algorithm. It has been observed that the results obtained with the ANN model are very close to the data found in experimental studies. In both experimental and model-based analysis, minimum cutting force (44 N) and surface roughness (2.22 µm) were achieved at low fiber orientation angle (30°), low feed rate (0.1 mm·rev−1), and depth of cut (1 mm) at high cutting speeds (150 m·min−1).

Effects of Small Deviations in Fiber Orientation on Compressive Characteristics of Plain Concrete Cylinders Confined with FRP Laminates

The effectiveness of concrete confinement by fiber-reinforced polymer (FRP) materials is highly influenced by the orientation of fibers in the FRP laminates. In general, acceptable deviation limit from the intended direction is given as 5° in most design guidelines, without solid bases and reasoning. In this paper, a numerical study using finite element modeling was conducted to assess the effects of small deviations in fiber orientation from the hoop direction on compressive behavior of concrete cylinders confined with FRP. Different fiber angles of 0°, 2°, 5°, 8°, 10° and 15° with respect to hoop direction, unconfined concrete compressive strengths of 20, 35 and 50 MPa, FRP thicknesses of 0.2, 0.5 and 1.0 mm and FRP moduli of elasticity of 50 and 200 GPa were considered. The results showed that total dissipated energy (Et), ultimate axial strain (εcu') and compressive strength (fcu') exhibited the most reduction with deviation angle. For 5° deviation in fiber orientation, the average reduction in fcu', εcu' and Et were 2.4%, 2.8% and 4.5%, respectively. Furthermore, the calculated allowable limit of deviation in fiber orientation for a 2.5% reduction in fcu', εcu' and Et were 6°, 3° and 2°, respectively, with a 95% confidence.

An Ordinary State-Based Peridynamic Model of Unidirectional Carbon Fiber Reinforced Polymer Material in the Cutting Process

Due to the complexity of the composite structure, analyzing the material failure process of carbon fiber reinforced polymers (CFRP) is fairly difficult, particularly for the machining process. Peridynamic theory, a new branch of solid mechanics, is a useful tool for dealing with discontinuities. This study presents an ordinary state-based peridynamic (OSB-PD) model for unidirectional CFRP material in the cutting process. In this model, angle tolerance is used to overcome the fiber angle limitation in a classical OSB-PD laminate method, and the short-range force approach is utilized to simulate the contact of the cutting tool and workpiece. The effectiveness of the supplied models is validated by tension and cutting tests. Finally, it can be indicated that the OSB-PD model is capable of predicting machined surface damage and cutting force, based on the comparison of simulation and experimental data.

Dynamic Analysis of Laminated Composite One-fold Plates under Thermal Load

In this research, free vibration analysis of epoxy-based laminated composite folded plate structures for thermal loads have been considered using finite element method. Eight noded isoparametric element with five degrees of freedom per node have been considered in the study. Folded plate formulation using 6 X 6 transformation matrix is applied to transform the element mass and stiffness matrices to global system matrices. Yang-Norris-Stavsky (YNS) theory along with rotary inertia have been used in the present formulation. Lamina material properties at elevated temperature have been used in the study. Parametric studies have been performed for laminated composite one-fold plate structure for various thicknesses, crank angle and fibre angle under different temperatures. Results reveal that rising thermal load reduces the stiffness of the structure considerably. As the presence of fold increases stiffness of the plate structures significantly, it can withstand increased temperature. Proper choice of fibre angle and thickness increases the stiffness of the structures thus making it more capable of resisting higher thermal load.

Stationary Random Vibration Analysis of Composite Laminated Shell Structures of Revolution in Thermal Environment

Currently, few studies are focused on the stationary random vibration for composite laminated shell structures of revolution (CLSSR), including composite laminated cylindrical shell (CLCY), composite laminated conical shells (CLCO), and composite laminated annular plates (CLAP). To fill this void corresponding to the above research in the literatures, a combination of the spectro-geometric method (SGM) and pseudo-excitation method (PEM) was developed to construct the theoretical model within the first-order shear deformation theory (FSDT). The different boundary restraints and coupling conditions were achieved by taking the appropriate stiffness values of artificial springs, and the thermal effect induced by thermal load was considered. Moreover, the Rayleigh–Ritz method was employed to deduce the governing differential equation. Further, the solution accuracy of the established model was assessed by comparing the obtained results with those from the literatures and the finite element method (FEM). Finally, the effect of specific parameters (i.e. fiber angle, temperature value and ply number) on the stationary random response of CLSSR was explored. According to the results, the proposed method proved effective for predicting the stationary random response characteristics of CLCY, CLCO, and CLAP in a thermal environment.

A new approach to optimize variable axial composite shells: A metaheuristic procedure using the finite element method

A strategy for the design of optimum fiber pattern of constant thickness variable-stiffness laminated composite plates and shells is presented and evaluated. The optimization framework employs finite element analysis and the particle swarm optimization (PSO) algorithm, but the main contribution lies in the method proposed for the parametric description of the fiber orientation. Scalar values assigned to control points distributed in advance on the structure are taken as the design variables. These values are interpolated at the nodes of the finite element mesh using a radial basis function (RBF). The fiber orientation on the surface of the structure is continuously defined by the gradient of the scalar field obtained by the interpolation of the nodal values using the finite element shape functions. This approach is applicable to flat and curved structures, ensuring fiber continuity and demanding less design variables than element-wise fiber angle optimization. The effectiveness of the proposed strategy is evaluated by the optimization of a flat plate, a shallow shell with a hole and a pressure vessel.

Fiber-dominated Soft Actuators Inspired by Plant Cell Walls and Skeletal Muscles

Morphing botanical tissues and animal muscles are all fiber-mediated composites, in which fibers play a passive and active role, respectively. Herein, inspired by the mechanism of fibers functioning in morphing botanical tissues and animal muscles, we propose two sorts of fiber-dominated composite actuators. First, inspired by the deformation of awned seeds in response to humidity change, we fabricate passive fiber-dominated actuators using non-active aligned carbon fibers via 4D printing method. The effects of process parameters, structural parameters, and fiber angles on the deformation of the printed actuators are examined. The experimental results show that the orientation degree is enhanced, resulting in a better swelling effect as the printing speed increases. Then, motivated by the actuation mechanism of skeletal muscle, we prepare active fiber-dominated actuators using active polyurethane fibers via 4D printing and pre-stretching method. The effect of fiber angle and loading on the actuation mode is experimentally analyzed. The experimental results show that the rotation angle of the actuator gradually decreases with the angle from 45° to 60°. When the fiber angle is 0° and 90°, the driver basically stops rotating while shrinking along the loading direction. Based on the above actuation mechanisms, identical contraction behaviors are realized both in passive and active fiber-dominated soft actuators. This work provides a validation method for biologically actuation mechanisms via 4D printing technique and smart materials and adds further insights to the design of bioinspired soft actuators.

A concurrent fibre orientation and topology optimisation framework for 3D-printed fibre-reinforced composites

This work proposes a novel framework able to optimise both topology and fibre angle concomitantly to minimise the compliance of a structure. Two different materials are considered, one with isotropic properties (nylon) and another one with orthotropic properties (onyx, which is nylon reinforced with chopped carbon fibres). The framework optimises, in the same particular sub-step, first the topology, and second, the fibre angle at every element throughout the domain. For the isotropic material, only topology optimisation takes place, whereas, for the orthotropic solid, both topology and fibre orientation are considered. The objective function is to minimise compliance, and this is done for three volume fractions of material inside the design domain: 30%, 40%, and 50%. Two classical benchmark cases are considered: 3-point and 4-point bending loading cases. The optimum topologies are further treated and manufactured using the fused filament fabrication (FFF) 3D printing method. Key results reveal that the absolute stiffness, density-normalised and volume-normalised stiffness values within each admissible volume are higher for onyx than for nylon, which proves the efficiency of the proposed concurrent optimisation framework. Moreover, although the objective function was to minimise compliance, it was also effective to improve the strength of all parts. The excellent quality and geometric tolerance of the 3D-printed parts are also worth mentioning.

Variable stiffness optimization algorithm for vibration optimization of variable-stiffness composite plates

A novel variable stiffness optimization (VSO) algorithm is proposed for vibration optimization of variable-stiffness composite (VSC) plates uisng linear variation fiber path function. Firstly, an independent 2D-sampling optimization method (2DSOind) is employed to generate a good initial point. Then, optimization is conducted in multiple phases, within each phase, the problem is simplified to an approximately one-dimensional linear search problem. By dividing the fiber angles into two groups, VSO algorithm designs the laminate between two fiber angle groups sequentially and iteratively, making the stiffness of VSC plate stiffened part by part. Lastly, the VSC plate is redesigned accounting for the curvature constraint. The sequential permutation search (SPS) algorithm is coupled into VSO to optimize one group of fiber angles whilst the angles of another group are fixed during the iteration. Under a variety of boundary conditions, the free vibration frequencies of VSC plates are optimized using VSO. In comparison to conventional layerwise optimization (LO) and genetic algorithm (GA), the present results demonstrate much higher efficiency and similar robustness. Moreover, the maximum fundamental frequency of VSC plates can be improved by about 10% in comparison to straight fiber laminates.

Proposal of a model for estimating the tensile strength of hardwoods depending on fiber orientation angle

Resumo Pela complexidade anatômica e variabilidade intrínseca das propriedades encontradas dentro de uma mesma espécie, a madeira tem sido tratada, pelos diversos documentos normativos, como material isotrópico, com valores de resistência e de rigidez determinados por meio de formulações advindas da resistência dos materiais. A falta de informações experimentais, aliada ao desconhecimento da utilização de critérios de resistência para materiais anisotrópicos, aumenta as incertezas na análise de falha das estruturas quanto às estimativas das propriedades de resistência e rigidez em função da orientação das fibras. Com o objetivo de solucionar este problema, modelos empíricos têm sido desenvolvidos e incorporados em diversos documentos normativos nacionais e internacionais. Tais modelos são ajustados em função de um expoente (n) que fornece o melhor ajuste, entretanto, mesmo em se tratando do mesmo modelo, ainda há divergências com relação ao uso desse expoente. Nesse contexto, esta pesquisa objetivou propor um modelo para a estimativa do valor característico de resistência à tração inclinada (ftθ,k) e compará-lo com modelos empíricos provenientes da literatura correlata (com os ajustes ótimos do expoente n), para evidenciar o melhor ajuste. Os resultados obtidos revelaram que o modelo desenvolvido na pesquisa foi o mais preciso.

Daylighting Performance of Sunlight Transmission and Concentration via Plastic Optical Fibers

The energy-saving technology of this thing is thriving. One of promising technology is the daylighting system via optical plastic fibers. It has many advantages, and its characteristics need further research. This paper analyses the transmission characteristics, attenuation rate, and incident angle of the optical fiber. The test data shows that the spectrum, color rendering index are good, and the energy efficiency is high. This shows that plastic optical fibres have excellent development prospects for daylighting.

Математическое моделирование потери устойчивости локальных расслоений, полученных в результате скоростного удара

Delamination of a composite may occur as a result of high-speed impact under the action of shock-wave unloading. Delamination could grow further under operation with the subsequent composite destruction. This paper presents analytical expressions for values characterizing the delamination critical loss of stability and describing their non-linear delaminating deformation resulting from the impact. Elastic characteristics of the thin-walled delamination of a multilayer package, elastic characteristics of separate layers included in it depending on the shear modulus, elastic moduli, Poisson ratio, thickness, and orientation angle of fibers of the unidirectional layer were determined. A technique for numerical simulation and calculation of the structural elements made of layered composite materials with allowable defects such as delamination was developed in the ANSYS Mechanical system to solve problems of the plates’ supercritical behavior.

Continuous fibre reinforced Vat photopolymerisation (CONFIB-VAT)

Additive manufacture of fibre-reinforced composites is one of the most recent technological advancements in composites production. However, research on continuous fibre-reinforced composites produced by Vat photopolymerisation is severely lacking. This paper proposed a new 3D printing process, called continuous fibre reinforced Vat photopolymerisation (CONFIB-VAT). Plain and fibre-reinforced tensile specimens were produced and systematically tested. The results showed that the mechanical properties were not affected by the printing direction. The influence of fibre volume fraction on CONFIB-VAT composites was also studied. A 10% fibre volume content embedment resulted in more than a 500% increase in ultimate tensile strength. For the first time, this study studied the effects of fibre angle placement and the shadow under fibre shielding during UV curing, resulting in incomplete curing. The use of post-curing to overcome the shadow problem was investigated and considerably improved mechanical property. Additionally, simultaneous fibre embedding in the XY and Z planes was achieved, which allowed for greater flexibility in fibre arrangement and composite design. Overall, this research establishes a robust platform for Vat photopolymerisation based composite printing with virtually no restrictions on the materials and fibres printed. CONFIB-VAT significantly expands the material palette for emerging technologies and provides guidance for the design of structural 3D printed composite components and will aid in the development of commercial Vat photopolymerisation composite 3D printing machines.

Humidity-Responsive Guar Gum Fibers by Wet Spinning.

In this study, guar gum fibers were obtained by wet spinning, in which epichlorohydrin (ECH) and calcium chloride (CaCl2) were used as the cross-linking agent and metal complexing agent, respectively. The fibers' chemical structure, morphology, crystallinity, and thermal and mechanical properties were analyzed by Fourier infrared spectroscopy, scanning electron microscopy, and so forth. The results showed that ECH reacted with guar gum and formed ether bonds. Meanwhile, ECH can effectively increase the number of cross-linking points and improve the mechanical properties of the fibers. When the ECH content was 12% (w/w), the breaking strength could reach 2.4 cN/dtex. The conductivity of MC-GG fibers varied with the relative humidity and could reach 2.845 × 10-2 S/cm at maximum. Meanwhile, the contact angle of MC-GG fibers was 33°, indicating that the fibers had good hydrophilicity and humidity response ability and had excellent potential in the field of smart fabrics.