Fiber Angle Research Articles

Improving fatigue characteristics of ply drop-off in composite laminate with ply curving termination

Ply drop-off is a weak point of a tapered composite laminate, where stress concentration occurs and delamination initiates. By suppressing delamination from the ply drop-off, more optimized structural design and further weight reduction are possible. Ply Curving Termination (PCT), which locally changes the fiber direction at the edge of the dropped ply, is one of the promising delamination suppression mechanisms. To improve the technical maturity of PCT, this study conducted tensile fatigue tests using asymmetric taper configuration. Damage initiation, delamination propagation, and final failure were evaluated in detail by changing the PCT fiber angle and loading level, confirming that large PCT angles are effective in improving the fatigue properties of tapered laminates and that controlling the location of initial damage is necessary to maximize the effectiveness of PCT. Based on the findings, an effective design guideline for tapered laminates with PCT was presented.

Flexural performance of nature-inspired 3D-printed strain-hardening cementitious composites (3DP-SHCC) with Bouligand structures

Inspired by nature, this study employed the Bouligand structures, as observed in the dactyl club of mantis shrimp, to enhance the performance of 3D-printed Strain-Hardening Cementitious Composites (3DP-SHCC). Twenty sets of printed and mold-cast specimens were prepared to investigate the effects of Bouligand structures on the flexural performance of 3DP-SHCC. Three printing patterns (parallel, cross, and Bouligand printing) and five pitch angles (15°, 30°, 45°, 60°, 75°) were used for the Bouligand printing pattern. The results showed that the flexural performance of parallel-printed SHCC exhibited significant directionality. The flexural strength and toughness of parallel-printed SHCC in the X direction were 1.28 times and 3.27 times greater than the mold-cast SHCC. However, the flexural strength and toughness in the Y direction were 0.58 times and 0.25 times those of the mold-cast SHCC. The cross-printed and Bouligand-printed SHCC alleviated the directionality. The flexural performance of cross-printed SHCC was lower than that of the mold-cast SHCC. Compared to parallel-printed SHCC, the flexural strength and toughness of Bouligand-printed SHCC increased by 1.25 to 1.73 times and 3.48 to 5.10 times, respectively, in the Y direction. Bouligand-printing twisted the fiber angles, enabling effective crack bridging across multiple directions and endowing the SHCC with uniform mechanical properties in various directions. The Bouligand structures provided valuable inspiration for optimizing 3DP-SHCC structures.

In-situ monitoring of carbon fiber/epoxy composite with FBG sensors under curing and thermal cycling conditions

Residual strains from curing process as well as thermal expansion behaviors in application process are critical to structural design of composites. Here we demonstrate the applicability of fiber Bragg grating (FBG) sensors for in-situ measurements of strain evolution in epoxy resin and unidirectional (UD) laminate under curing and thermal cycling conditions. The validity of the FBG sensors was verified by the TMA tests. From the data recorded by the sensors, the information about real-time gel point, strain/temperature evolution and residual strains during curing can be obtained. The epoxy resin and UD laminates have distinct curing histories and characteristics under the same curing conditions because of the exothermic reaction. During thermal cycling, we found that the coefficient of thermal expansion (CTE) of the UD laminate is directional dependent as is the residual strain, i.e., it increases with fiber orientation angle. In addition, the relaxation of partial residual strains, attributed to the mismatch in CTE between the specimen and the mold, was captured by FBG sensors around the glass transition temperature during the first thermal cycle.

Effect of the filling pattern in 3D-printed polylactic acid scaffolds on mechanical properties and cell proliferation for bone tissue regeneration

3D printing technology can control the shape and filling pattern of the scaffold very well and has been widely used in the preparation of bone repair scaffolds. Modifying the filling pattern of scaffolds to alter their mechanical properties and cellular adhesion holds immense significance. In this study, 3D-printed polylactic acid (PLA) scaffolds with different fibre angles (15°-90°) were prepared. The 90° scaffold showed the best mechanical properties and was suitable for repairing long bones. The 60° scaffold has balanced mechanical properties and is suitable for maxillofacial bone repair. The scaffold with a 30° angle was the best for cell adhesion and proliferation and was suitable for cancellous bone repair.

Formulation and free vibration analysis of spinning Timoshenko composite beams using nonlinear geometrically exact theory

AbstractIn this study, a set of generalized nonlinear equations of motion for Timoshenko composite shafts is derived using the geometrically exact approach. These partial differential equations of motion are discretized by Galerkin method and the free vibration of an orthotropic spinning shaft with hinged‐hinged boundary conditions is investigated using the multiple‐scale method. We find that in the case of two mode discretization, composite couplings can have significant linear and nonlinear effects on the behavior of the shaft and that these effects were not predictable in the classical model. Also, in the investigating of composite layering we find that the effects of the fibers angle as well as the composite couplings can be noticeable, and these effects are greater in the case of the asymmetrical layering.

Buckling variability analysis in damaged composite laminates subjected to thermally varying environment

The present study investigates the effect of internal defects on the composite laminated (CL) plates comprised of two distinct graphite-epoxy materials (AS4/3501-6 and T300/5208). The centrally damaged laminates stacked in two distinct lamination sequences are exposed in thermally varying environments. The CL plates are considered to experience damage in two different combinations of damage parameters. The improved first-order shear deformation theory (IFSDT) based finite element (FE) model is employed to estimate the thermal buckling of CL plates comprised of multiple fiber orientation angles and constrained to C-S-C-S and S-C-S-C boundary restrictions. The implementation of a Radial basis function network (RBFN) surrogate model has demonstrated its potential as a feasible substitute for the computationally demanding Monte-Carlo simulations (MCS) in the context of stochastic exploration. The present investigation scrutinizes the probabilistic properties of diverse materials and their associated damage characteristics. Subsequently, the RBFN-based surrogate model is employed to evaluate the likelihood of failure.

Structural parameters defining distribution of collagen fiber directions in human carotid arteries

Collagen fiber arrangement is decisive for constitutive description of anisotropic mechanical response of arterial wall. In this study, their orientation in human common carotid artery was investigated using polarized light microscopy and an automated algorithm giving more than 4·106 fiber angles per slice. In total 113 slices acquired from 18 arteries taken from 14 cadavers were used for fiber orientation in the circumferential-axial plane. All histograms were approximated with unimodal von Mises distribution to evaluate dominant direction of fibers and their concentration parameter. 10 specimens were analyzed also in circumferential-radial and axial-radial planes (2-4 slices per specimen in each plane); the portion of radially oriented fibers was found insignificant. In the circumferential-axial plane, most specimens showed a pronounced unimodal distribution with angle to circumferential direction μ = 0.7° ± 9.4° and concentration parameter b = 3.4 ± 1.9. Suitability of the unimodal fit was confirmed by high values of coefficient of determination (mean R2 = 0.97, median R2 = 0.99). Differences between media and adventitia layers were not found statistically significant. The results are directly applicable as structural parameters in the GOH constitutive model of arterial wall if the postulated two fiber families are unified into one with circumferential orientation.

Optimization of infill density, fiber angle, carbon fiber layer position in 3D printed continuous carbon-fiber reinforced nylon composite

Composite materials have gained much attention in various industries, such as aerospace, automotive, sports, marine, and construction, as these sectors rely on high-performance, durable, and cost-effective materials. Such materials offer high strength, stiffness and heat resistance. However, the influence of printing parameters especially the position of carbon fiber layer on such material is rarely found in literature. The current study focuses on optimizing different printing and testing parameters such as carbon fiber layer position, infill density, fiber angle, and strain rate in 3D printed carbon-fiber reinforced nylon composite. The study also recommended the optimal combination of these parameters for maximizing the mechanical strength and energy absorption of related 3D printed parts. The investigation revealed that the most optimum condition was 80% infill density, fiber angle of 0°, carbon fiber layer position of 12–13, and strain rate of 10 mm/min. It has been found in the study that fiber angle was the most dominant input parameter with a contribution of 54.13%, whereas infill density was the second dominant parameter with a contribution of 16.25%. The study also found that the position of the carbon fiber layer has comparatively less effect on the final mechanical properties of 3D printed parts, with a contribution of 10.12%. To facilitate the optimization, the outcomes will be helpful for designing and manufacturing 3D printed carbon-fiber reinforced nylon composite parts.

Tensile properties of banana fiber reinforced recycled high‐density polyethylene composites: An experimental investigation

AbstractNatural fiber‐reinforced polymer composites (NFRCs) are increasingly favored over synthetic fiber‐reinforced alternatives due to their beneficial properties and environmental sustainability. Mechanical properties of composites are critical to ensure optimized utilization of NFRCs. Here, this research explores the effects of different fiber parameters on the tensile strength of high‐density polymer composites reinforced with banana fiber and utilizes the Taguchi method for both experimental and statistical analysis of the outcomes. Three different parameters are considered here: weight fractions, fiber orientation angle, and plasma treatment to fabricate the composites using the compression molding process. Taguchi analysis revealed that fiber orientation angle has the greatest influence among the three variables, with plasma treatment and weight fraction following in impact on tensile strength. The composite that exhibited the highest tensile strength was determined to have a weight fraction of 10%, a fiber orientation angle of 90°, and a plasma treatment period of 5 min. This combination yielded a strength of 30.351 MPa. The analysis of the interaction between any two factors was done using contour plots. In order to compare the experimental tensile strength values with the anticipated values derived from the regression equation, regression analysis was carried out.Highlights Composites were made up of recycled HDPE (rHDPE) from plastic bottles using a compression molding technique. The Taguchi method is applied to achieve an experimental design employing an L4 orthogonal array. Contour plot analysis is conducted to identify points of minimum and maximum responses, as anticipated from the results. Tensile strength was optimized to a maximum of 30.351 MPa.

Grey wolf optimizer based-natural frequency optimization of laminated composite shells carrying distributed mass

In this study, a grey wolf optimizer is proposed to find the optimum stacking sequence to maximize the fundamental frequency of shells. The vibration analysis of the shells is done using first-order shear deformation theory and a nine-node isoparametric element with five degrees of freedom per node. A mass lumping scheme with rotary inertia is considered in the finite element formulation to include the rotary inertia effect. The design variable considered is the fiber angle orientation of the shells. The present approaches are compared with previously published results using layerwise optimization theory, the Ritz method, and classical lamination theory. A comparison study is also performed, comparing the GWO-based finite element model against six different metaheuristic approaches, and it demonstrates that the Grey Wolf Optimizer consistently outperforms these competing algorithms. The optimum fiber angle orientation of shells carrying distributed mass for various boundary conditions and shell types is analyzed for the first time, to the best of the author’s knowledge. This novel discovery will benefit future studies.

Numerical investigation on orthogonal cutting and damage response of CFRP/Ti6Al4V stacks

CFRP/Ti6Al4V stacks are widely employed in aerospace, automotive and marine applications owing to their superior properties. However, machining these stacked structures pose challenges due to the intrinsic difference in the mechanical properties of CFRP and Ti6Al4V. Such difference can induce distinct failure mechanisms and chip formation processes compared to those observed in individual materials. This paper presents an explicit finite element (FE) modeling to predict the cutting forces and analyze the induced damage during the orthogonal cutting process. The proposed FE model is validated using available experimental data for separate CFRP and Ti6Al4V conditions before being applied to simulate the cutting behavior of CFRP/Ti6Al4V stacks. The effects of fiber angles, cutting sequences and cutting parameters on the cutting performance and damage mechanism of CFRP/Ti6Al4V stacks are investigated in detail. This work provides insights into the cutting behavior of CFRP/Ti6Al4V stacks and facilitates the optimization of machining process for such composite system.

Mechanically enhanced battery separator prepared by hot‐pressing electrospun polyvinylidene fluoride@polymethyl methacrylate membranes with different fiber orientations in adjacent layers

AbstractCompared with commercial polyolefin membranes, electrospun polymeric membranes have the advantages of higher porosity and better electrolyte wettability, but their poor mechanical performance limits their industrial use as battery separators. In this work, a layer‐to‐layer electrospinning is used for fabrication of PVdF@PMMA membranes, in which fibers in adjacent layers are arranged at a certain angle (0°, 30°, 60°, 90°). The as‐electrospun membranes are further hot‐pressed to boost their mechanical strength. Various techniques are employed to evaluate the membranes, such as scanning electron microscopy, differential scanning calorimetry, contact angle measurement, electrochemical impedance spectroscopy, and linear sweep voltammetry. The results show that polymethyl methacrylate partially melts during the hot‐pressing treatment, causing adjacent fibers in the membranes to bridge. The obtained membranes show different tensile strength values with the various angles between fibers. When the angle is 30°, the tensile strength can reach 22.09 MPa and higher porosity (74.68%), greater liquid electrolyte absorption (612.36%) than that of commercial polyolefin membrane are harvested. The lithium‐ion cell assembly with the membrane separator exhibits a discharge capacity reaching 142 mAh g−1 and an excellent capacity retention of 90.7%. This present study provides an innovative and promising approach for the fabrication of high‐performance battery separator by electrospinning.Highlights PVdF@PMMA membranes are prepared by a layer‐to‐layer electrospinning. In the membranes, fiber orientation in adjacent layers is kept at a certain angle. Hot‐pressing further boosts mechanical performance of the membranes. Membranes with different angle of fibers show various mechanical strengths.

Comprehensive evaluation of energy absorption characteristics of Al‐CFRP hybrid tube under radial impacts

AbstractThis paper aimed to investigate the energy absorption characteristics and damage mechanism of carbon fiber reinforced plastics/aluminum (Al‐CFRP) under radial impact. In this study, the damage mode of the hybrid tube is analyzed by falling hammer impact experiments, and the correctness of the finite element model is verified by comparing the experimental and numerical simulation results. Then, the damage mechanism of the hybrid tube under impact loading and the effects of the increase of the fiber angle, the wall thickness of Aluminum, and the number of outer CFRP layers on the impact resistance were analyzed according to the model. The comprehensive performance model of the hybrid tube was established by using the complex scale comprehensive evaluation method, and the genetic algorithm was used to optimize the hybrid tube and determine its optimal performance under radial impact load. The results show that the Al‐CFRP hybrid tube's overall stiffness and deformation resistance under radial impact is improved with the increase of the fiber angle, the wall thickness of the Al tube, and the number of outer CFRP layers. Combined with the parametric analysis of the numerical simulation results, a comprehensive performance evaluation model based on the complex proportionality assessment method (COPRAS) was developed and a genetic algorithm (GA) under back propagation (BP) neural network prediction was used. The optimal hybrid tube form with the best overall performance under radial impact was obtained using GA with BP neural network prediction.Highlights The energy absorption characteristics of hybrid tubes under radial impact are investigated A comprehensive performance evaluation model of hybrid pipe based on the complex proportional assessment method (COPRAS) is developed The failure process and energy absorption mechanism of the hybrid pipe under radial impact are analyzed A genetic algorithm (GA) with backpropagation (BP) neural network prediction was used to obtain the hybrid pipe form with the best overall performance under radial impact

ENERGY ABSORPTION AND DEFORMATION PATTERN OF CIRCULAR HYBRID CRASH BOX SUBJECTED TO FRONTAL LOAD

Crashworthiness is related to the ability of a structure to reduce the effects of a collision risk of injury to passengers and the risk of damage to vital parts of the vehicle. Geometry design of crash box is one important parameter to increase crashworthiness performance by increasing energy absorption through progressive deformation. In previous studies, circular crash box absorbed higher energy than other geometry design. Besides that, another parameter is material design. In other studies, the hybrid model absorbs more energy with a less increasing mass. Hybrid crash box combine low-density and high-strength of composite materials with aluminium materials are affordable and ductile to increase energy absorption. This study aims to develop circular hybrid crash box by variating fibre orientation angle of composite and hybrid material configuration. Crash box design is investigated by using computer simulation with ANSYS Workbench. The crash box materials used are Carbon Toray T300 – Epoxy Resin (CCE) and Aluminium Alloy 6063 (AA6063). Eight of circular hybrid crash box models subjected to axial loading with a speed of 10 m/s. The frontal loading is modelled by setting impactor with mass of 100 kg. Energy absorption and deformation pattern were observed. The results showed that the Al-Ko45 model with orientation angle [45/- 45,-45/45]5 and hybrid material configuration of composite inside has highest energy absorption of 8.24 kJ. The deformation pattern in the aluminium part is mixed of concertina at the first stage then continued by diamond pattern, The deformation composite part is dominated by local buckling with transverse shearing. The fractions or folds of composite is functions like foam-filled filling folds of aluminium deformation to initiate progressive crushing folding that can increase the crashworthiness characteristic as the energy absorption.

Study of self-heating and local strain rate in polyamide-6 and short fibre glass/polyamide-6 under tension through synchronised full-field strain and temperature measurements

This paper studies thermomechanical coupling during room-temperature tensile testing of polyamide-6 (PA6) and 50 wt% short glass fibre/PA6. The tests were performed for different fibre angles (0°, 45°, 90°), moisture contents (dry, 50%RH), and strain rates (10−4, 10−2, 10−1s−1). Digital image correlation (DIC) was coupled with infrared thermography. The contribution of the local strains, strain rates and temperatures to the global mechanical behaviour was investigated throughout deformation. The initial thermoelastic response was used to estimate the coefficient of thermal expansion. In PA6, neck development caused significant self-heating at high strain rates, differently between dry and 50%RH. In glass/PA6, however, temperature rises were always small (<+3 °C) despite local strain rate peaks in the fracture zone. This was ascribed to limited plastic deformation, as confirmed by post-mortem microscopy. The full-field data can be highly valuable for the development of advanced constitutive models for both pure polymer and short fibre composite.

Generation of Tow Paths on a Curved Shell in Three-Dimensional Space for Fiber Steering

A multimesh framework to optimize two-dimensional, flat-steered fiber laminates for a given loading condition is extended to include complex curved laminates in three-dimensional (3D) space. The optimal fiber angle distribution solution is used by a tow path planner to generate (steered) tow paths in curved laminates in 3D space. The framework utilizes two meshes in the optimization step: i) a coarse quadrilateral element-based manufacturing mesh (MM) used to discretize the fiber angle distributions with nodal values; and ii) a fine triangular element-based stress mesh used in the finite-element-based stress analysis to ensure a converged solution. Lagrangian interpolation functions are used to determine the fiber angles at the centroid of each finite element analysis (FEA) mesh element within a given MM. The number of design variables is minimized without jeopardizing the accuracy of the FEA solution. A third mesh, the tessellation mesh, is used to project the generated tow paths onto the curved laminates in 3D space accurately. This paper presents all the steps needed to go from optimized fiber angles to tow paths. In conclusion, a methodology is proposed and implemented to optimize variable-stiffness laminates on complex curved structures.

3D micromechanical modeling of orthogonal hole saw cutting on CFRP composites

In the interest of developing a comprehensive understanding of the drilling process using the hole saw tool, this article aims to build a three-dimensional (3D) micromechanical model representing the orthogonal cutting of CFRP using one tooth of the hole saw tool. For this purpose, a finite element model is developed using Abaqus Explicit code. The influence of various drilling parameters like rake angle, inclination angle and cutting-edge radius on the drilling quality is explored. Especially, chip formation mechanisms, cutting force and lateral damage are analyzed. Through finite element simulations and computational analyses, it is found that these outputs results are highly influenced by drilling parameters. When the fiber orientation angle is set to 0°, increasing the rake angle results in a change in the chip formation mechanism from buckling to bending. In contrast, with a fiber orientation angle of 90°, bending and shear governs the chip formation process, irrespective of the rake angle. In both cases, whether the fiber orientation angle is 0° or 90°, chips tend to fragment more favorably with increasing the inclination angle. Regarding the cutting-edge radius, when the fiber orientation angle is 0°, an increase in the cutting-edge radius leads to a transition in the chip-forming mechanism from buckling to bending. However, for a fiber orientation angle of 90°, the chip formation remains governed by bending even as the cutting-edge radius changes. Decreasing the rake angle, the inclination angle, and the cutting-edge radius contribute to a reduction of the cutting force. As the inclination angle and the cutting-edge radius increase, the lateral damage increases, while the rake angle has showed a negligible impact on the damage. These results provide a guidance on the appropriate hole saw tool parameters for a good drilling quality namely, a rake angle of 20°, an inclination angle of 5° and a cutting-edge radius of 0.03 mm.

A refined analytical model for reconstruction problems in diffuse reflectance spectroscopy

A refined analytical model of spatially resolved diffuse reflectance with small source-detector separations (SDSs) for the in vivo skin studies is proposed. Compared to the conventional model developed by Farrell et al., it accounts for the limited acceptance angle of the detector fiber. The refined model is validated in the wide range of optical parameters by Monte Carlo simulations of skin diffuse reflectance at SDSs of units of mm. Cases of uniform dermis and two-layered epidermis-dermis structures are studied. Higher accuracy of the refined model compared to the conventional one is demonstrated in the separate, constraint-free reconstruction of absorption and reduced scattering spectra of uniform dermis from the Monte Carlo simulated data. In the case of epidermis-dermis geometry, the recovered values of reduced scattering in dermis are overestimated and the recovered values of absorption are underestimated for both analytical models. Presumably, in the presence of a thin mismatched topical layer, only the effective attenuation coefficient of the bottom layer can be accurately recovered using a diffusion theory-based analytical model while separate reconstruction of absorption and reduced scattering fails due to the inapplicability of the method of images. These findings require implementation of more sophisticated models of light transfer in inhomogeneous media in the recovery algorithms.

Investigation of patch application failure behaviors according to fiber orientation difference at notched composite plates

In this study, the damage behaviors of different type notched composite plates bonded with external composite patches were investigated experimentally under static tensile test. Eight-layer woven glass fiber reinforced epoxy resin matrix composite plates and epoxy based adhesive were used as materials. Notch type, fiber orientation angle, double side repair and single side repair were used as parameter. Effects of fiber orientation angle was investigated for 0 ° , 15 ° , 30 ° and 45 ° . Radial notch in the center (Type I), semicircular notch on the plate edge (Type II), a circular hole in the plate center (Type III) and U notch at the edges (Type IV) have been examined for 4 different notch types. The outstanding feature of this study is that many parameters were compared for many samples under the same experimental conditions. The composite plates and patches were used from same materials. Reducing of the damage loads has been observed for all notch types depending upon the increasing of fiber orientation angle significantly. In addition, that patch application to different fiber orientation plates is quite effective on damage loads. The extension was changed depending on the notch geometry at unrepaired composite. The load increasing rate is between + % 24 and + % 189 for one-sided bonded repair; + % 60 and + % 349 for two-sided bonded repair compared to the unrepaired samples. The results of this work can serve as a guide for workers to improve repair quality and durability in an understandable way.

Flutter investigation and deep learning prediction of FG composite wing reinforced with carbon nanotube

Abstract The flutter of a composite wing reinforced with functionally graded carbon nanotubes (CNTs) has been investigated. A rectangular plate models a supersonic wing with cantilever boundary conditions. To determine displacement fields of a moderately thick plate, shear deformation theory is used. Using the Hamilton principle, a first-order piston theory was used to simulate supersonic airflow. This study examines four types of CNT thickness. Also, four different CNT distribution patterns are investigated. In a two-layer asymmetric composite, the effects of patch mass, mass distribution, fiber orientation angle, and distribution of CNTs were examined. Moreover, the results are compared and verified with other studies. A greater mass ratio led to a smaller flutter boundary, while a longer added mass increased the flutter boundary. A variation in the distribution pattern in CNT fiber orientation results in a distinct behavior of the flutter boundary for asymmetric composites with increasing orientation angles. The artificial neural network is utilized to predict the damping ratio, and the results showed great accuracy compared to the study results. Hyperparameter tuning is employed for better optimizing the predictive models.