Fiber Angle Research Articles

Quantification of collagen fiber properties in alcoholic liver fibrosis using polarization-resolved second harmonic generation microscopy

Liver fibrosis is assessed mainly by conventional staining or second harmonic generation (SHG) microscopy, which can only provide collagen content in fibrotic area. We propose to use polarization-resolved SHG (PR-SHG) microscopy to quantify liver fibrosis in terms of collagen fiber orientation and crystallization. Liver samples obtained from autopsy cases with fibrosis stage of F0–F4 were evaluated with an SHG microscope, and 12 consecutive PR-SHG images were acquired while changing the polarization azimuth angle of the irradiated laser from 0° to 165° in 15° increments using polarizer. The fiber orientation angle (φ) and degree (ρ) of collagen were estimated from the images. The SHG-positive area increased as the fibrosis stage progressed, which was well consistent with Sirius Red staining. The value of φ was random regardless of fibrosis stage. The mean value of ρ (ρ-mean), which represents collagen fiber crystallinity, varied more as fibrosis progressed to stage F3, and converged to a significantly higher value in F4 than in other stages. Spatial dispersion of ρ (ρ-entropy) also showed increased variation in the stage F3 and decreased variation in the stage F4. It was shown that PR-SHG could provide new information on the properties of collagen fibers in human liver fibrosis.

Preparation and properties of polyester fibers with polyacrylamide hydrogel grafted by UV‐irradiation

AbstractIt is widely recognized that polyester (PET) fibers with swelling properties are necessary for advanced applications of PET fibers in waterproof fabrics. This study presented the UV‐initiated methods to graft polyacrylamide (PAM) hydrogel on the surface of PET fibers. In the one‐step method, PET fibers are impregnated with a mixed solution of the photoinitiator benzophenone (BP) and the monomer acrylalkylamine (AM). Then, the PET fiber was directly exposed to UV light. In the two‐step method, PET fibers were first impregnated with a photoinitiator solution to generate BP radicals. Then, the fibers impregnated with a monomer solution before being grafted by UV light. Both two methods ultimately achieve PAM gelation‐modified PET fibers. The chemical composition and surface structure were detected by Fourier transform infrared spectroscopy and scanning electron microscope. The findings demonstrate that the PAM hydrogel was successfully grafted on the PET fibers through one‐step method or a two‐step method. In addition, the properties of the grafted PET fibers were evaluated by grafting yield, contact angle, and swelling test. The study indicated that the modified PET fibers via a two‐step method exhibited a superior grafting yield up to 29.3% (PET‐2n) and 54% (PET‐2) compared to the one‐step technique (PET‐1). It was shown that the grafting efficacy of PET fibers modified by two‐step method is better than one‐step method. The static contact angles of PET fibers by UV‐Induced were all reduced. For instance, the contact angles of PET‐2n were decreased from 115° to 62.9°; and the two‐step modified PET fiber after acetone cleaning (PET‐2) decreased from 115° to 60°. It was suggested that the hydrophilicity of the modified PET fibers significantly increased. In addition, the research shows that the gelation‐modified fibers were all possessed swelling properties.

Evolving Genetic Programming Tree Models for Predicting the Mechanical Properties of Green Fibers

Advanced modern technology and the industrial sustainability theme have contributed to the implementation of composite materials for various industrial applications. Bio-composites are among the desired alternatives for green products. However, to properly control the performance of bio-composites, predicting their constituent properties is of paramount importance. This work introduces an innovative, evolving genetic programming tree model for predicting the mechanical properties of natural fibers for the first time based upon several inherent chemical and physical properties. Cellulose, hemicellulose, lignin, and moisture contents, as well as the Microfibrillar angle of various natural fibers, were considered to establish the prediction models. A one-hold-out methodology was applied for the training/testing phases. Robust models were developed utilizing evolving genetic programming tree models to predict the tensile strength, Young’s modulus, and the elongation at break properties of the natural fibers. It was revealed that the Microfibrillar angle was dominant and capable of determining the ultimate tensile strength of the natural fibers by 44.7%, comparable to other considered properties, while the impact of cellulose content in the model was only 35.6%. This would facilitate utilizing artificial intelligence to predict the overall mechanical properties of natural fibers without exhausting experimental efforts and cost to enhance the development of better green composite materials for various industrial applications. Doi: 10.28991/ESJ-2023-07-06-02 Full Text: PDF

Tuning damping and dynamic response of smart MR cylindrical composite panels based on a higher-order shear deformation theory

This study delves into the dynamic analysis of magnetorheological elastomer composite (MREC) cylindrical panels with laminated construction. Magnetorheological elastomers (MREs) are viscoelastic materials that exhibit tunable properties when subjected to magnetic fields. By incorporating reinforcing fibers, a new class of materials, MRE Composites (MRECs), is formed, which not only inherits MRE properties but also enhances rigidity. The novelty of the present study resides in its comprehensive exploration of the vibration and damping characteristics inherent in deep laminated cylindrical shells composed of MRECs. The homogenization of this composite media is performed by employing the modified rule of mixture and Halpin-Tsai micromechanical rule. To achieve this, the Mechab theory, utilizing a high-order hyperbolic function, approximates the displacement field. The study employs the generalized Maxwell's constitutive model to describe the viscoelastic behavior of MRECs, and Hamilton's principle is used to derive the partial differential form of vastly coupled equations of motion. The 2-dimensional Chebyshev collocation method, a discretization method, is applied to solve these equations, allowing the determination of natural frequencies and loss factors. The investigation covers various parameters, including magnetic field strength, volume fraction of reinforcers, layering, and fiber angles, geometry, and boundary conditions, to understand their influence on the dynamic response of MREC cylindrical panels. The results provide valuable insights into the potential applications of these tunable materials in adjustable dynamic and damping systems, contributing to advancements in solid mechanics and materials engineering. Such knowledge opens up new possibilities for utilizing MRECs in diverse technological applications.

Fabrication and Experimental Investigation of Composite Pressure Vessel

Abstract: Composite pressure vessels are an important type of high-pressure containers that are widely used in aerospace industries. The pressure vessels develop hoop stresses that are twice the longitudinal stresses. CFRP (Carbon Fiber Reinforced Polymer) composite materials with their higher specific strength and characteristics will result in reduction of weight of the structure when compared with isotropic materials like steel. The present work is aimed in understanding the behaviour of the Composite Pressure Vessel with variation of internal pressure. In this connection, a pressure vessel using CFRP (Carbon Fiber Reinforced Polymer) is fabricated which can hold liquids or gases under pressure and is tested at various pressures. The FEA tool ANSYS 14.5 is used to determine better fiber angle required for liquid storage, when the conventional low carbon steel cylinder is replaced with CFRP Pressure Vessel.

Damage-induced buckling characteristics of thermally loaded variable angle tow laminated plates under uncertain environment

The prime focus of the current study is to shed light on the deterioration in thermal buckling performance of variable angle tow laminated (VATL) plates induced by the existence of damages (internal flaws) amid uncertainties in various composite and damage characteristics. In a finite element (FE) framework, the work is carried out using improved first-order shear deformation theory (IFSDT), which has accountability for the shear stress distribution pattern. Parametric examination with various fiber orientation angles considering two types of VATL plates is performed to observe the damage effect. The presence of damage is made over two different locations, namely mid and corner, with three distinct damage ratios. To circumvent the enormous sample and time requirements of Monte-Carlo simulations (MCS) for stochastic investigation, a highly efficient RBFN-based surrogate model is used. The uncertainty in the analysis is introduced first with composite properties. The investigation disclosed that the presence of damage reduces the sensitivity of composite properties to the buckling response. The probabilistic failure estimation is then carried out as a crucial step in thorough stochastic observation. Later, the potential of variability in damage parameters is considered, revealing a distinctive pattern of buckling response to the uncertain composite properties.

Performance and failure analysis of perforated CFRP/aluminum alloy bonding and self-piercing riveting hybrid joints

This paper explores the new hybrid hole-drilled bonding and self-piercing riveting (HH-BR) connection technique to enhance the strength and overall performance of carbon fiber reinforced polymer (CFRP) and dissimilar metal materials at joint interfaces. The forming quality, mechanical performance, failure modes, and fracture characteristics of the CFRP and aluminum alloy joints utilizing the HH-BR procedure were analyzed in detail and compared with the joints of the hole-less adhesive-bonding self-piercing riveting (H-BR) and self-piercing riveting (SPR). At the same time, the effects of different rivet performance levels, overlap lengths, and various fiber orientation angles on joint performance were discussed. The results show that joints made by the HH-BR technique have a substantial advantage in terms of achieving superior mechanical performance and interlocking value. Firstly, HH-BR joints with bent rivets and torn fibers have connection strengths that are noticeably higher than those with CFRP laminate delamination or rivet pullout failure. The use of the HH-BR technique for joining CFRP/aluminum alloy culminated in reduced strength loss and higher energy absorption than H-BR and SPR joints, improving the joint's overall strength. Secondly, the interlock value between the rivet and the plate, is what essentially determines the strength of HH-BR joints, especially evident in connections with 0°/90° fiber orientation and more overlap lengths. The results also show that there is a strong relationship between the height of the rivet head and the joint's mode of failure, and the height of the rivet head is affected by the rivet force. Furthermore, the interlock value's magnitude, the joint's remaining bottom thickness, and the metal material's capacity for plastic deformation are all directly correlated.

Experimental validation study on snap through and coiling up of deployable composite shells

AbstractBistable reeled composite shells (BRCS) have been widely used in deployable space structures due to advanced properties of light weight and large volume reduction. A finite element simulation and experimental validation to study the transition of BRCS between their two stable states are performed. In this article, multiscale representative volume element (RVE) modeling is used to compute the equivalent mechanical properties of carbon/epoxy plain woven fabrics that were utilized to construct the deployable composite laminates, followed by experimental verification. The deformation characteristics and strain energy distribution of the deployable composite shell (DCS) during snap through and coiling up are investigated using finite element analysis (FEA) and verified by strain‐gauge and digital image correlation (DIC) tests. The results show that the strain energy distribution in the snap through and coiling up of the carbon/epoxy plain woven BRCS with laminate stacking sequence of [+45/−45] is approximately symmetric. Additionally, an offset phenomena is observed during the coiling up of the BRCS in the finite element modeling. A parametric analysis is complemented to investigate effects of fiber angles on the deformation characteristics and strain energy distribution of the shell structures during snap through and coiling up.Highlights Shell deformation during snap through and coiling up was investigated. DIC test was performed to capture the shell deformation. Strain energy distribution of the deployable composite shell was discussed. Offset phenomena are observed during the coiling up.

Impact Energy Dissipation and Quantitative Models of Injection Molded Short Fiber-Reinforced Thermoplastics

Glass short fiber-reinforced thermoplastics (SGFRTP) are used to reduce carbon dioxide emissions from transportation equipment, especially household vehicles. The mechanical properties required for SGFRTP include flexural strength, impact resistance, etc. In particular, impact resistance is an important indicator of the use of SGFRTP. For this study, a mechanical model was developed to explain the notched impact strength of SGFRTP injection molded products in terms of their interfacial shear strength. The values obtained from the model show good agreement with the experimentally obtained results (R2 > 0.95). Results also suggest that the model applies to different fiber orientation angle and a range of fiber lengths in the molded product that are sufficiently shorter than the critical fiber length.

Effect of 3 Weeks of Strict Head‑Down Tilt Bed Rest on Human Muscle Fuction and Architecture

The aim of this study was to first, experimentally measure in vivo changes in the length, fiber angle and thickness of the medial gastrocnemius muscle (MG) in young men in response to changes in foot position and joint moment during isometric plantar flexion and, in secondly, to compare the changes in the above characteristics of the muscular architecture that occur during the transition from a state of rest to a given isometric intensity during plantar flexion. The internal architecture of the MG was determined after 21-day of strict head‑down tilt bed rest (HDT). MG scanning was performed using ultrasound at rest at ankle joint angles of –15° (dorsiflexion), 0° (neutral), +15° and +30° (plantar flexion). Additional ultrasounds were performed during maximal voluntary contraction (MVC) and additionally at 80, 60, 40, and 20% of the MVC with the ankle in neutral position. In each position, longitudinal ultrasound images of the MG were obtained in a relaxed (passive) state with the determination of the length (Lf) and angles of fascicles (Θf) relative to the aponeurosis. After HDT, the thickness of the MG during graduated isometric force up to 80% of the MVC in the neutral position of the ankle joint remained constant. Various Lf and Θf and their changes after HDT can be a limiting factor in the generation of muscle contractile functions. The results of the study show that the change in muscle structure during contraction compared to rest, as measured by changes in muscle architecture, can be used to assess muscle mechanical output.

Buckling stability of variable stiffness composite cylinder shell based on automated fiber placement technology

Automated fiber placement technology (AFP) is the key technology to realize variable-stiffness design that have fiber orientation variation across its in-plane. However, defects such as fiber angle deviation and overlap are inevitable during AFP manufacturing. A finite element model has been developed for variable-stiffness cylinder shell that can investigate the effect of the overlap areas and fiber angle deviation on the buckling stability of variable stiffness cylinder shell. Furthermore, the influence of the design parameters of the curved fiber path and the process parameters such as the tow width, the number of tow feeding, and the overlapping strategies on the buckling performance of the structure was studied by parametric analysis. The results showed under the condition of compression-bending coupling, the buckling performance is improved by the variable stiffness design in which the fiber angle varies along the circumferential direction, the maximum critical buckling load factor of optimal variable-stiffness design [0 /〈30|80〉/ 90 /−〈30|80〉] s is 10771, which is 21.1% higher than that of the optimal normal stiffness design. It is found that increasing the course width reduces the buckling performance of the variable stiffness structure, when the tow width is kept constant. When the course width is kept constant, the buckling performance of the variable stiffness structure increases with the increase of the tow width.

Frequency veering and nonlinear coupled vibration analysis of variable stiffness composite plates with curvilinear fiber paths

The coupling forced vibration behaviors of a variable stiffness plate with curvilinear fiber paths at mode veering regions caused by variations of fiber angle have been rarely found in previous papers, especially in the presence of considering the complex material nonlinearity of composite materials. In this paper, the variable stiffness plate of carbon fiber reinforced composites (CFRC) with curvilinear fiber paths is taken as the research object, and the influence of curvilinear fiber paths on its natural characteristics and vibration responses are studied in detail on the basis of considering the material nonlinearity of CFRC. Firstly, it is found that the variations of curvilinear fiber paths can cause complex frequency veering behavior of the variable stiffness plate, and lead to the appearance of irregular modal shapes formed by modal interaction. Then, the forced vibration response of the variable stiffness plate in the frequency veering region is analyzed methodically, and the variation rules of the vibration response under modal interaction is obtained. After analyzing the nonlinear vibration response of the variable stiffness plate under the combined influence of modal interaction and CFRC material nonlinearity, the mechanism of complex nonlinear dynamic behavior of variable stiffness plate in frequency veering region is further investigated.

Buckling optimization of variable-stiffness composite plates via variable stiffness optimization algorithm

A variable stiffness optimization (VSO) algorithm is presented for optimizing variable-stiffness composite (VSC) plates with linear fiber path functions. A new definition of lamination parameters characterizing the distances between stacking configurations of VSC plates is presented. Using the inherent sensitivity of bending stiffness of composite laminates, the concept of “through thickness design” is introduced. The first step is to determine a good initial point for the VSC plates using three-dimensional sampling optimization (3DSO). The fiber angle design variables are then categorized into three groups. By optimizing the three groups' design variables sequentially and iteratively, the stiffness of the VSC plates is stiffened part by part until an optimum is reached. Lastly, the obtained optimum is redesigned accounting for the curvature constraint. The finite element method (FEM) is developed for the buckling analysis of VSC plates, and both Q4 and Q8 elements are employed to verify the accuracy and convergence of the FEM. Under a variety of boundary conditions and loading cases, FEM and VSO algorithm are used to maximize the buckling load of square and rectangular symmetrical VSC plates. Optimal results are compared with those available in the literature, demonstrating the effectiveness, robustness, and efficiency of the VSO algorithm.

Influence of realistic microscopic fiber misalignments on compressive damage mechanisms of 3D angle-interlock woven composites: In-situ measurements and numerical simulations

Stochastic fiber misalignments have been proven to have a significant impact on the compressive strength of traditional unidirectional laminates. However, these inherent manufacturing defects are rarely considered when dealing with 3D woven composites, due to the difficulty in characterizing the misalignment angles of individual fibers within all yarns. The current work provides the first in-situ measurements of fiber misalignments in 3D angle-interlock woven composites (3DAWCs) at the microscale, where the continuous fibers inside the warp, weft, and binder yarns are systematically examined using a high-resolution optical microscope. Statistical analysis reveals that the microscopic fiber misalignments follow a normal distribution, and the magnitude of the misalignment angle increases slightly with the degree of yarn fluctuation. Through a developed user subroutine, SDVINI, the obtained misalignment distributions are initialized in the corresponding yarns that belong to the constructed high-fidelity model. In comparison to the idealized one, the model introducing realistic fiber misalignments can effectively correct the overestimated predictions, and exhibits better agreement with the performed experiments. Furthermore, the influence of fiber misalignments on compressive damage mechanisms, particularly kinking failure, is also parametrically studied by incorporating different misalignment distributions.

Study of Tensile and Impact Properties for 0<sup>0</sup> and 45<sup>0</sup> Fiber Directional Orientation of Polyester Resin Composites with Woven Ramie Reinforced

The current technological need is the use of eco-friendly and biodegradable composites. It seeks to increase the use of natural resources to engineer composite materials to be better than before. This study aims to analyze the effect of ramie fiber orientation for ramie composites (in this study 450 and 00) on tensile strength and impact strength and find the best orientation angle with higher power and impact value than the other fiber angles on ramie composite. The fiber used in this study was ramie fiber, and the matrix used was Yukalac 157 BQTN-EX polyester resin. This research method uses the experimental process of conducting experiments and testing. The results showed that the 00 angle direction composite achieved the highest average tensile strength value of 54.3 N/mm2, and the impact strength showed the highest average impact strength value of 0.0168 J/mm2, performed by the 00 composites.

Numerical Analysis of Lamb Wave Propagation in Composite Plate with Different Fiber Orientation Angles – Acoustic Emission Approach

Numerical Analysis of Lamb Wave Propagation in Composite Plate with Different Fiber Orientation Angles – Acoustic Emission Approach

Mesoscale numerical investigation of dynamic spalling fracture in toughness concrete

This study presents a two-phase mesoscale numerical model to investigate the dynamic spalling fracture behaviour of hybrid fibre ultra-high toughness cementitious composites (UHTCC). The model simulated the presence of random steel fibres and ductile UHTCC independently, and accurately incorporated the fibre-matrix bond-slip relationship, with carefully considering the influence of the inclination angle of the steel fibres on the pullout behaviour. Validation of the numerical model involved a meticulous comparison between numerical outcomes and results from spallation tests, encompassing strain-time and velocity-time histories, failure modes, and locations of cracking or fracture. Subsequently, the developed model was employed to analyse the impact of fibre inclination, stress wave amplitude, and waveform (based on the impulse equivalence principle) on the dynamic spalling fracture behaviour of hybrid fibre UHTCC. Evaluation of spalling fracture performance was based on both maximum velocity and pullback velocity of resulting fragments or free surfaces. Findings revealed that fibres parallel to the stress wave propagation direction exhibited optimum performance. It was also observed that stress waveforms with rectangular and sinusoidal shapes presented the highest risk of spalling fracture, while exponentially attenuated waves were comparatively safer. Additionally, stress waveforms with either rise time or duration at maximum pressure were deemed hazardous. Further, the hybrid fibre UHTCC demonstrated multiple spalling cracking/fracture behaviours under all stress waves except rectangular ones. This comprehensive exploration provided insights for the utilization of hybrid fibre UHTCC in impact engineering.

Optimizing buckling load of sandwich plates with cutouts using artificial neural networks and genetic algorithms

In this research, the optimization of the geometric parameters of a 3-layer composite plate with an elliptical cutout in the center was investigated utilizing an artificial neural network and genetic algorithm for the first time to obtain the minimum ratio of linear buckling load to weight and the ratio of the diameters of the ellipse. After completing 294 simulations in Abaqus finite element software and forming an artificial neural network with two hidden layers, the function obtained in the artificial neural network was used as the objective function in the genetic algorithm, and the optimal values for the angle of the ellipse with the horizon axis, the diameter ratio of ellipses as well as the fiber angle of the middle layer of the composite were obtained. using artificial neural networks, three algorithms, Levenberg-Marquardt, Bayesian regularization; and scaled conjugate gradient backpropagation, were compared and the number of neurons in each algorithm was compared. The results showed that Levenberg-Marquardt’s algorithm is more accurate compared to other algorithms. In the end, the optimal values for the angle of the ellipse with the horizontal axis; as the fiber angle of the middle layer of the composite and, the ratio of the oval diameters as α = 12.3001 degree , θ = 5.9481 degree and D = 1.5690 .

Sea water exposure and erosion impact on multifunctional ABS-based thermoplastic hybrid composites

In the present work, acrylonitrile-butadiene-styrene (ABS)/glass fiber (varying fiber orientation angle) and with different % of carbon black (CB) particles-based hybrid composites are fabricated by hot press compression molding technique. Prepared composites were examined under marine conditions in sea water medium and erosion behavior under erodent particles entrained in gas fluid and found reduced impact. Morphological studies are studied through scanning electron microscope. Material removal mechanism is found to be micro-cracking at the impingement angle of 90°. Additionally, numerical analysis for the composite material with respect to single particle impact for erosion was conducted using LS-DYNA.

ANN-based structure peciliaties evaluation of polymer composite reinforced with unidirectional carbon fiber

At the moment, there is a growing interest in composite materials with matrices based on thermoplastic polymers; these materials are superior to traditional carbon fiber plastics due to higher fracture toughness and impact strength, low smoke generation during combustion, and high thermal and chemical resistance. The deformation behavior of such composite materials due to the high plastic deformation of the matrix differs from the behavior of traditional composites, which must be considered when performing calculations. In our study, as a model object, the features of the microstructure of single carbon thread impregnated with polysulfone were studied in order to evaluate the distribution of misorientation angles of elementary fibers, the degree of their damage, the thickness of the polymer matrix interlayers between elementary fibers in threads impregnated with more viscous thermoplastic binders. Statistical analysis of a large array of micrographs was carried out using specially developed algorithms for computer processing of electron microscopic images of a composite material. Algorithms for processing arrays of images using machine vision algorithms are proposed. Based on the analysis of the data array, the distributions of carbon fibers impregnated with polysulfone were plotted over the misorientation angle of the filaments and over the interfilament distance in the longitudinal and cross sections of the fiber. Using the machine learning method, an algorithm for detecting violations of the filament structure was implemented. The data obtained can be used to refine the calculations of the strength and deformation characteristics of composite materials with thermoplastic matrices.