Changes In Fiber Orientation Research Articles

Study on stable configurations and snap through of the rectangular VS bi-stable laminates with curvilinear fiber alignment

With advances in fiber placement technology, variable stiffness bistable laminates (VSBL) composited by curvilinear fiber format become a subject of intense interest for morphing structures due to their lower weight, adjustable stiffness and a richer range of stable configurations compared to straight fiber bistable laminate. Merely conducting research on square laminates is not enough allowing for practical application scenarios. This article investigates the influence of geometrical parameters of VSBL on the stable state configuration and static snap through actuated by MFC systematically. A quadratic variable curvature polynomial is used to fit the transverse displacement according to classical laminate theory. By means of von-Karman geometrical relationship and the Rayleigh-Ritz method, stable configurations of the VS bistable laminate are solved. By comparing with finite element results, the reliability and precision of the current results are verified. It shows that changing fiber orientation leads to significant effects on the steady state configuration and critical bifurcation points. Theoretical analysis of VS bistable laminates containing the smart piezoelectric material MFC is followed by analytical modeling. The voltage threshold required for actuating snap through of two stable states is acquired by smart material layer MFC. The specific reasons for the differences in the configurations of VS bistable laminates are illustrated by analyzing distribution of the stiffness of VSBL in the plane.

Characterization of Blow-Spun Polyurethane Scaffolds-Influence of Fiber Alignment and Fiber Diameter on Pericyte Growth.

In this study, fibrous polyurethane (PU) materials with average fiber diameter of 200, 500, and 1000 nm were produced using a solution blow spinning (SBS) process. The effects of the rotation speed of the collector (in the range of 200-25 000 rpm) on the fiber alignment and diameter were investigated. The results showed that fiber alignment was influenced by the rotation speed of the collector, and such alignment was possible when the fiber diameter was within a specific range. Homogeneously oriented fibers were obtained only for a fiber diameter ≥500 nm. Moreover, the changes in fiber orientation and fiber diameter (resulting from changes in the rotation speed of the collector) were more noticeable for materials with an average fiber diameter of 1000 nm in comparison to 500 nm, which suggests that the larger the fiber diameter, the better the controlled architectures that can be obtained. The porosity of the produced scaffolds was about 65-70%, except for materials with a fiber diameter of 1000 nm and aligned fibers, which had a higher porosity (76%). Thus, the scaffold pore size increased with increasing fiber diameter but decreased with increasing fiber alignment. The mechanical properties of fibrous materials strongly depend on the direction of stretching, whereby the fiber orientation influences the mechanical strength only for materials with a fiber diameter of 1000 nm. Furthermore, the fiber diameter and alignment affected the pericyte growth. Significant differences in cell growth were observed after 7 days of cell culture between materials with a fiber diameter of 1000 nm (cell coverage 96-99%) and those with a fiber diameter of 500 nm (cell coverage 70-90%). By appropriately setting the SBS process parameters, scaffolds can be easily adapted to the cell requirements, which is of great importance in producing complex 3D structures for guided tissue regeneration.

Study on the Influence of Runner and Overflow Area Design on Flow-Fiber Coupling in a Multi-Cavity System.

Fiber-reinforced composites (FRPs) are characterized by their lightweight nature and superior mechanical characteristics, rendering them extensively utilized across various sectors such as aerospace and automotive industries. Nevertheless, the precise mechanisms governing the interaction between the fibers present in FRPs and the polymer melt during industrial processing, particularly the manipulation of the flow-fiber coupling effect, remain incompletely elucidated. Hence, this study introduces a geometrically symmetrical 1 × 4 multi-cavity mold system, where each cavity conforms to the ASTM D638 Type V standard specimen. The research utilizes theoretical simulation analysis and experimental validation to investigate the influence of runner and overflow design on the flow-fiber coupling effect. The findings indicate that the polymer melt, directed by a geometrically symmetrical runner, results in consistent fiber orientation within each mold cavity. Furthermore, in the context of simulation analysis, the inclusion of the flow-fiber coupling effect within the system results in elevated sprue pressure levels and an expanded core layer region in comparison to systems lacking this coupling effect. This observation aligns well with the existing literature on the subject. Moreover, analysis of fiber orientation in different flow field areas reveals that the addition of an overflow area alters the flow field, leading to a significant delay in the flow-fiber coupling effect. To demonstrate the impact of overflow area design on the flow-fiber effect, the integration of fiber orientation distribution analysis highlights a transformation in fiber arrangement from the flow direction to cross-flow and thickness directions near the end-of-fill region in the injected part. Additionally, examination of the geometric dimensions of the injected part reveals asymmetrical geometric shrinkage between upstream and downstream areas in the end-of-fill region, consistent with microscopic fiber orientation changes influenced by the delayed flow-fiber coupling effect guided by the overflow area. In brief, the introduction of the overflow area extends the duration in which the polymer melt exerts control in the flow direction, consequently prolonging the period in which the fiber orientation governs in the flow direction (A11). This leads to the impact of fiber orientation on the flow of the polymer melt, with the flow reciprocally affecting the fibers. Subsequently, the interaction between these two elements persists until a state of equilibrium is achieved, known as the flow-fiber coupling effect, which is delayed.

Anisotropy of the R1/T2* value dependent on white matter fiber orientation with respect to the B0 field

The R1 (1/T1) map divided by the T2* map (R1/T2* map) draws attention as a high-resolution myelin-related map. However, both R1 and R2* (1/T2*) values demonstrate anisotropy dependent on the white matter (WM) fiber orientation with respect to the static magnetic (B0) field. Therefore, this study primarily aimed to investigate the comprehensive impact of these angular-dependent anisotropies on the R1/T2* value.This study enrolled 10 healthy human volunteers (age = 25 ± 1.3) on the 3.0 T MRI system. For R1/T2* map calculation, whole brain R1 and T2* maps were repeatedly obtained in three head tilt positions by magnetization-prepared two rapid gradient echoes and multiple spoiled gradient echo sequences, respectively. Afterward, all maps were spatially normalized and registered to the Johns Hopkins University WM atlas. R1/T2*, R1, and R2* values were binned for fiber orientation related to the B0 field, which was estimated from diffusion-weighted echo-planar imaging data with 3° intervals, to investigate angular-dependent anisotropies in vivo.A larger change in the R1/T2* value in the global WM region as a function of fiber orientation with respect to the B0 field was observed compared to the R1 and R2* values alone. The minimum R1/T2* value at the near magic-angle range was 18.86% lower than the maximum value at the perpendicular angle range. Furthermore, R1/T2* values in the corpus callosum tract and the right and left cingulum cingulate gyrus tracts changed among the three head tilt positions due to fiber orientation changes. In conclusion, the R1/T2* value demonstrates distinctive and complicated angular-dependent anisotropy indicating the trends of both R1 and R2* values and may provide supplemental information for detecting slight changes in the microstructure of myelin and axons.

Cross-hemicord spinal fiber reorganization associates with cortical sensory and motor network expansion in the rat model of hemicontusion cervical spinal cord injury

Magnetic resonance imaging plays an important role in characterizing microstructural changes and reorganization after traumatic injuries to the nervous system. In this study, we tested the feasibility of ex-vivo spinal cord diffusion tensor imaging (DTI) in combination with in vivo brain functional MRI to characterize spinal reorganization and its supraspinal association after a hemicontusion cervical spinal cord injury (SCI). DTI parameters (fractional anisotropy [FA], mean diffusion [MD]) and fiber orientation changes related to reorganization in the contused cervical spinal cord were compared to sham specimens. Altered fiber density and fiber directions occurred across the ipsilateral and contralateral hemicords but with only ipsilateral FA and MD changes. The hemicontusion SCI resulted in ipsilateral fiber breaks, voids and vivid fiber reorientations along the injury epicenter. Fiber directional changes below the injury level were primarily inter-hemispheric, indicating prominent below-level cross-hemispheric reorganization. In vivo resting state functional connectivity of the brain from the respective rats before obtaining the spinal cord samples indicated spatial expansion and increased connectivity strength across both the sensory and motor networks after SCI. The consistency of the neuroplastic changes along the neuraxis (both brain and spinal cord) at the single-subject level, indicates that distinctive reorganizational relationships exist between the spinal cord and the brain post-SCI.

Fiber alignment in 3D collagen networks as a biophysical marker for cell contractility

Cells cultured in 3D fibrous biopolymer matrices exert traction forces on their environment that induce deformations and remodeling of the fiber network. By measuring these deformations, the traction forces can be reconstructed if the mechanical properties of the matrix and the force-free matrix configuration are known. These requirements limit the applicability of traction force reconstruction in practice. In this study, we test whether force-induced matrix remodeling can instead be used as a proxy for cellular traction forces. We measure the traction forces of hepatic stellate cells and different glioblastoma cell lines and quantify matrix remodeling by measuring the fiber orientation and fiber density around these cells. In agreement with simulated fiber networks, we demonstrate that changes in local fiber orientation and density are directly related to cell forces. By resolving Rho-kinase (ROCK) inhibitor-induced changes of traction forces, fiber alignment, and fiber density in hepatic stellate cells, we show that the method is suitable for drug screening assays. We conclude that differences in local fiber orientation and density, which are easily measurable, can be used as a qualitative proxy for changes in traction forces. The method is available as an open-source Python package with a graphical user interface.

Effect of Wall Thickness and Flow Distance behind an Obstacle on the Weldline Strength of Thermoplastic Composites

The strength of the weldline behind an obstacle in injection molded thermoplastic composites was investigated in this study. The effects of part thickness, glass-fiber length, and concentration on the weldline strength at different positions behind the obstacle were examined. The results showed that the mechanical properties of the specimen containing weldline were much lower as the fiber length and content increased. Considering the effect of part thickness on the weldline strength, it was observed that the weldline strength decreased as the part thickness increased. This was due to the fiber orientation and the void generation within the molded parts. The results obtained for the weldline strength at various positions along the weldline indicated that the weldline strength tended to increase with the increase of flow distance, especially for polypropylene containing 40 wt% long-glass-fibers. The explanation for this could be associated with the change in fiber orientation during the flow development.

Synchrotron micro-CT in kink-band formation of UD-CFRP laminates with microdefects

This paper presents the first synchrotron micro-Computed Tomography (micro-CT) study on in-situ pure compressive kink-band failure in Uni-Directional Carbon Fibre-Reinforced Polymer composites (UD-CFRPs) with a notch. The study compares the failure behaviour of baseline samples under standard conditions with defect-rich samples containing micro-defects such as voids and fibre misalignment. Quantitative image-based analysis using the structure tensor technique and Digital Volume Correlation (DVC) reveals changes in fibre orientation and localised strain, respectively, at each increment load. A large 400 μm kink-band inclined at 30° with a half-cosine wave fibre orientation is observed in the baseline samples, while the defect-rich samples form narrower conjugate kink bands (ranging from 77 μm 25 μm) inclined at 45°. Development of kink-band formations/failure of both samples is discussed and compared with literature, providing key implications for the design and safe use of this type of composite layup.

A Comprehensive Study on Measurement Accuracy of Distributed Fiber Optic Sensors Embedded within Capillaries of Solid Structures.

Embedding fiber optic sensors (FOSs) within parts for strain measurement is attracting widespread interest due to its great potential in the field of structural health monitoring (SHM). This work proposes a novel method of embedding FOSs using capillaries within solid structures and investigates fiber positions and orientation uncertainties within capillaries of different sizes and their influences on strain measurement accuracies. To investigate how the fiber positions and orientation variations influence strain measurement accuracy, both analytical and numerical models are utilized to predict strain distributions along embedded fibers at different positions and with different orientations within the specimen. To verify the predictions, a group of specimens made of Aluminum 6082 was prepared, and the specimens in each group had capillaries of 2 mm, 4 mm, and 6 mm diameters, respectively. Fibers were embedded within each specimen using the capillaries. Four-point bending static tests were conducted for each specimen with embedded FOSs, performing in situ strain measurement. Subsequently, the specimens were partitioned into several pieces, and the cross sections were observed to know the real positions of the embedded fiber. Finally, the strain predictions at the real locations of the fiber were compared with the measured strain from the embedded FOSs. The predicted strain distributions as a function of the fiber positions alone and as a function of both the fiber positions and orientations were compared to assess the influence of fiber orientation change. The results from a combination of analytical, numerical, and experimental techniques suggest that the fiber position from the capillary center is the main factor that can influence strain measurement accuracies of embedded FOSs, and potential fiber misalignments within the capillary had a negligible influence. The fiber position-induced measured error increases from 10.5% to 18.5% as the capillary diameter increases from 2 mm to 6 mm. A 2 mm capillary diameter is able to lead to the lowest measurement error in this study and maintains ease of embedding. In addition, it is found that the measured strain always lies within a strain window defined by the strain distribution along capillary boundaries when there are no cracks. This can be further studied for crack detection.

Added Value of MRI Knee Cartigram in Assessment of Anterior Knee Pain in Comparison to Conventional Standard MRI

Background Osteoarthritis (OA) is a multi-tissue, multi-factorial disease and worldwide a major cause of disability resulting from reduced joint mobility and function. Progressive loss of hyaline cartilage is one of the hallmark features of osteoarthritis, initiated by a loss of proteoglycans and an increase in water content, followed by a loss of type II collagen and a change in collagen fiber orientation. Objective To evaluate the role of T2 mapping in detection of degenerative changes in articular cartilage of knee joint as compared to standard clinical magnetic resonance imaging (MRI) at 1.5T. Patients and Methods From April 2020 to November 2020, this prospective Study was done to use T2 mapping to visualize the articular cartilage of the knee on 1.5 T MR Scanner using special software to evaluate the efficiency Of T2 mapping to detect cartilage lesions. The material of this study included 380 patients. The study includes all of them come complaining of knee pain and 2 of them had previous minor knee trauma, each patient had a single MRI exanimation including conventional MRI routine protocol and added a single complementary T2 mapping. Results there were significant differences between T2 mapping and conventional MRI sequence in the ability to detect cartilage degeneration as T2 mapping was capable of detecting all lesions that were visible on the clinical MRI. Moreover, T2 mapping showed more cartilage lesions than clinical MRI T2 mapping showed more cartilage lesions than clinical MRI, and in T2 maps the lesions appeared generally wider. This proposes that T2 mapping is feasible in the clinical setting and may reveal cartilage lesions not seen on the standard knee MRI. Conclusion Our results suggest that T2 mapping is an interesting MRI sequence for the exploration of patients articular cartilage in and should be included in the routine protocol if cartilage pathology is suspecting as it may improve the diagnostic accuracy of MRI for focal chondral lesions, and should help decide whether and MR-arthrography or CT-arthrography is necessary.

Unraveling the biomechanical properties of collagenous tissues pathologies using synchrotron-based phase-contrast microtomography with deep learning

Mechanical stimuli are regulators not only in cells but also of the extracellular matrix activity, with special reference to collagen bundles composition, amount and distribution. Synchrotron-based phase-contrast computed tomography was widely demonstrated to resolve collagen bundles in 3D in several body districts and in both pre-clinical and clinical contexts. In this perspective study we hypothesized, supporting the rationale with synchrotron imaging experimental examples, that deep learning semantic image segmentation can better identify and classify collagen bundles compared to common thresholding segmentation techniques. Indeed, with the support of neural networks and deep learning, it is possible to quantify structures in synchrotron phase-contrast images that were not distinguishable before. In particular, collagen bundles can be identified by their orientation and not only by their physical densities, as was made possible using conventional thresholding segmentation techniques. Indeed, localised changes in fiber orientation, curvature and strain may involve changes in regional strain transfer and mechanical function (e.g., tissue compliance), with consequent pathophysiological implications, including developmental of defects, fibrosis, inflammatory diseases, tumor growth and metastasis. Thus, the comprehension of these kinetics processes can foster and accelerate the discovery of therapeutic approaches for the maintaining or re-establishment of correct tissue tensions, as a key to successful and regulated tissues remodeling/repairing and wound healing.

Fiber Orientation Quantification for Large Area Additively Manufactured Parts Using SEM Imaging.

Polymer-based additively manufactured parts are increasing in popularity for industrial applications due to their ease of manufacturing and design form freedom, but their structural and thermal performances are often limited to those of the base polymer system. These limitations can be mitigated by the addition of carbon fiber reinforcements to the polymer matrix, which enhances both the structural performance and the dimensional stability during cooling. The local fiber orientation within the processed beads directly impacts the mechanical and thermal performances, and correlating the orientation to processing parameter variations would lead to better part quality. This study presents a novel approach for analyzing the spatially varying fiber orientation through the use of scanning electron microscopy (SEM). This paper presents the sample preparation procedure including SEM image acquisition and analysis methods to quantify the internal fiber orientation of additively manufactured carbon fiber-reinforced composites. Large area additively manufactured beads with 13% by weight large aspect ratio carbon fiber-reinforced acrylonitrile butadiene styrene (ABS) pellets are the feedstock used in this study. Fiber orientation is quantified using the method of ellipses (MoE), and the spatial change in fiber orientation across the deposited bead cross-section is studied as a function of process parameters including extrusion speed, raster height, and extrusion temperature zones. The results in the present paper show the results from the novel use of SEM to obtain the local fiber orientation, and results show the variation in alignment within the individual processed bead as well as an overall aligned orientation state along the direction of deposition.

Effect of fibre orientation and thermal exposure on the post‐fire mechanical behaviour of carbon fibre reinforced polymer material

AbstractThis study investigates the influence of fibre orientation and heat flux on the post‐fire (residual) load‐bearing properties of carbon fibre‐reinforced polymer (CFRP) laminates. As a result, a deep insight into the post‐fire load‐bearing response is gained, which is necessary to fully understand and assess the advantages of CFRP laminates containing different fibre orientations for use in load‐bearing structures. Specimens were produced from three CFRP laminates containing different fibre orientations, exposed to varying heat fluxes up to 40 and then loaded in either tension or three‐point bending at ambient room temperature. The study's results have shown that the post‐fire behaviour of CFRP specimens is sensitive to changes in fibre orientation and heat flux. For example, specimens with an anisotropic fibre orientation in tension had the highest tensile load‐bearing capacity, whereas those with bidirectional and multi‐directional fibre orientations demonstrated lower tensile load‐bearing capacities. In bending, however, specimens containing bidirectional and multidirectional fibre orientations had higher load‐bearing capacities than specimens with an anisotropic fibre orientation. Furthermore, the data also shows that exposure to a heat flux reduces the load‐bearing capacity in both the bending and tensile specimens.

Lignin-facilitated growth of Ag/CuNPs on surface-activated polyacryloamidoxime nanofibers for superior antibacterial activity with improved biocompatibility

IntroductionNanofibers are one of the role-playing innovations of nanotechnology. Their high surface-to-volume ratio allows them to be actively functionalized with a wide range of materials for a variety of applications. The functionalization of nanofibers with different metal nanoparticles (NPs) has been studied widely to fabricate antibacterial substrates to battle antibiotic-resistant bacteria. However, metal NPs show cytotoxicity to living cells, thereby restricting their application in biomedicine. ObjectivesTo minimize the cytotoxicity of NPs, biomacromolecule lignin was employed as both a reducing and capping agent to green synthesize silver (Ag) and copper (Cu) NPs on the surface of highly activated polyacryloamidoxime nanofibers. The activation of polyacrylonitrile (PAN) nanofibers via amidoximation was employed for enhanced loading of NPs to achieve superior antibacterial activity. MethodologyAt first, electrospun PAN nanofibers (PANNM) were activated to produce polyacryloamidoxime nanofibers (AO-PANNM) by immersing PANNM in a solution of Hydroxylamine hydrochloride (HH) and Na2CO3 under controlled conditions. Later, Ag and Cu ions were loaded by immersing AO-PANNM in different molar concentrations of AgNO3 and CuSO4 solutions in a stepwise manner. The reduction of Ag and Cu ions into NPs to fabricate bimetal-coated PANNM (BM-PANNM) was carried out via alkali lignin at 37 °C for 3 h in a shaking incubator with ultrasonication every 1 h. ResultsAO-APNNM and BM-PANNM hold their nano-morphology except for some changes in fiber orientation. XRD analysis demonstrated the formation of Ag and CuNPs as evident from their respective spectral band. Maximum 8.46 ± 0.14 wt% and 0.98 ± 0.04 wt% Ag and Cu species were loaded on AO-PANNM, respectively as revealed by ICP spectrometric analysis. The hydrophobic PANNM turned into super hydrophilic, having WCA of 14 ± 3.32° after amidoximation which further reduced to 0° for BM-PANNM. However, the swelling ratio of PANNM reduced from 13.19 ± 0.18 g/g to 3.72 ± 0.20 g/g for AO-PANNM. Even at the third cycle test against S. aureus strains, 0.1Ag/Cu-PANNM, 0.3Ag/Cu-PANNM, and 0.5Ag/Cu-PANNM displayed bacterial reduction of 71.3 ± 1.64 %, 75.2 ± 1.91 %, and 77.24 ± 1.25 %, respectively. On 3rd cycle test against E. coli, above 82 % bacterial reduction was noticed for all BM-PANNM. Amidoximation increased COS-7 cell viability up to 82 %. The cell viability of 0.1Ag/Cu-PANNM, 0.3Ag/Cu-PANNM, and 0.5Ag/Cu-PANNM was found to be ∼68 %, ∼62, and 54 %, respectively. In LDH assay, almost no release of LDH was detected, suggesting the compatibility of the cell membrane in contact with BM-PANNM. The improved biocompatibility of BM-PANNM even at higher loading (%) of NPs must be ascribed to the controlled release of metal species in the early stage, antioxidant, and biocompatible lignin capping of NPs. ConclusionsBM-PANNM displayed superior antibacterial activity against E. coli and S. aureus bacterial strains and acceptable biocompatibility of COS-7 cells even at higher loading (%) of Ag/CuNPs. Our findings suggest that BM-PANNM can be used as a potential antibacterial wound dressing and other antibacterial applications where sustained antibacterial activity is needed.

Static and dynamic control of smart damaged variable stiffness laminated composite plate with piezoelectric layers

The aim of the present study is to investigate the static and dynamic responses of damaged curved fiber laminated plates embedded with piezoelectric sensor/actuator. The damage characterized by anisotropic damage formulation is incorporated into the FE model to represent the damaged part of the structure. It is observed that continuous change of fiber orientation in lamina makes VSCL plates less affected by this type of damage and the reduction in natural frequencies can be minimized by adjustment of fiber orientation. Further, an active feedback control approach is adopted to damp out the vibration of the smart damaged VSCL plates.

A novel method based on eddy‐current equilibrium for improving the sensitivity of fiber orientation detection

AbstractFiber orientation deviation is a typical defect type in carbon fiber reinforced polymer composites (CFRPs) manufacturing process. Unlike other defect types, fiber orientation deviation has minimal influence on the local conductivity of CFRPs, so it is difficult to be detected by eddy current (EC) detection methods. Based on the principle of eddy‐current equilibrium, a new method is proposed in this paper to improve the sensitivity of fiber orientation detection. In this method, an EC field with eddy‐current equilibrium distribution inside the specimen is excited by means of a special double D‐shaped probe. When there is a deviation from the fiber orientation, the eddy‐current equilibrium state is broken, resulting in a rapid increase in the intensity and distribution range of the induced EC inside the specimen, and finally lead to a drastic change in the probe signal. The experimental results show that the double D‐shaped probe with an eddy‐current equilibrium effect can detect the fiber orientation of CFRPs, and the changes in fiber orientation can cause up to a 423.1% variation in the probe signal. Compared with the traditional rectangular probe, the designed probe is more sensitive than the former to small changes in fiber orientation in the range of −20° to 20° under high frequency excitation above 3 MHz. In addition, the proposed method can also be used for rapidly identifying fiber waviness with a deviation angle of 7.4° inside unidirectional CFRPs, which can be achieved effectively and intuitively through defect imaging.

The Effects of Downhill Running and Maturation on Histological and Morphological Properties of Tendon and Enthesis in Mice.

To date, it remains unclear how overuse affects the tendons and entheses at different stages of maturation. Therefore, we evaluated histological and morphological changes in the tendons and entheses in adolescent (4-week-old) and adult mice (8-week-old) by performing flat-land and downhill running exercises. The mice were divided into the Sedentary, High Flat (flat-land high-speed running; concentric-contraction exercise), Low Down (downhill low-speed running; eccentric-contraction exercise), and High Down (downhill high-speed running; eccentric-contraction exercise) groups. Histological changes and inflammatory factor expressions were compared in the entheses and tendons after 4 weeks of exercise. Downhill, but not flat-land high-speed running, induced muscle-tendon complex hypertrophy in both adolescent and adult mice. Histological enthesis changes were induced in both groups during downhill running but were less pronounced in adult mice. Conversely, no significant cell aggregation or fiber orientation changes were observed in the tendon, but increased inflammatory factors were observed in both groups, with significantly higher expression in the tendons of adult mice. Downhill running induced histological and morphological enthesis changes and inflammatory factor increase in the tendons, regardless of running speed variations. These results may help elucidate the pathogenesis of enthesopathy and tendinopathy, which have different pathophysiologies despite having the same pathogenetic factors.

Effect of short carbon fibers orientation on the tensile property and wear behavior of Cf(Ni)-ZrC/2024Al composite

The short carbon fiber orientation changes with the pressure direction during the sintering process, which strongly influences the mechanical and wear performance of short carbon fiber and ZrC strengthened 2024Al matrix composites (Cf(Ni)-ZrC/2024Al). The Cf(Ni)-ZrC/2024Al composite parallel to the carbon fiber plane (Cf(Ni)-ZrC/2024Al-P) shows higher elastic modulus, tensile strength, and strain, which has 17.1 %, 21.58 %, and 25.42 % increases respectively compared with the Cf(Ni)-ZrC/2024Al composite vertical to the carbon fiber plane (Cf(Ni)-ZrC/2024Al-V). In Cf(Ni)-ZrC/2024Al-P, the carbon fibers mainly fail by pulled-out behaviors, which can expend more fracture energy and lengthen the propagation path of cracks compared with the primary debonding behavior of the carbon fibers in Cf(Ni)-ZrC/2024Al-V. The wear rates of the Cf(Ni)-ZrC/2024Al-P and Cf(Ni)-ZrC/2024Al-V are improved with the load, while the coefficient of friction shows the contrary tendency. The Cf(Ni)-ZrC/2024Al-V is more wear resistance but less anti-friction than that of Cf(Ni)-ZrC/2024Al-P. In Cf(Ni)-ZrC/2024Al-P, the carbon fiber plane is parallel to the worn surface, which leads the carbon fiber to be swept out easily as a whole owing to the absence of the gripped aluminum matrix and the parallel plane between the friction force and interface. It causes the cracks to propagate along the interface easily and hardly form a steady MML.

Mathematical modeling of electric and hydraulic resistances of reconstructed carbon felt electrodes using micro-computed tomography

Redox flow batteries of various chemistries are potential electrochemical energy storages for residential accumulation and grid stabilization. Decoupled power and capacity represent the main advantages of the technology. The key component of the battery, the carbon felt electrode, does not participate in the electrochemical reaction directly, but it provides active sites for the electrochemical reaction of electroactive ions. In addition, the electrode contributes to the battery stack polarization through the charge transfer, ohmic and mass transport resistances and increases the hydraulic resistance of the battery stack and resulting pumping losses associated with the electrolyte circulation.In this contribution, a mathematical model was developed to evaluate geometrical parameters and simulate the effective electric conductivity and hydraulic resistance of two commercially available carbon felt electrodes using their micro-tomography images. These were preprocessed and binarized into a reconstructed computation domain. Geometric descriptors, such as porosity, specific surface area and fiber spatial orientation, were calculated using in-house developed algorithms. The area specific resistance and hydraulic resistance were then estimated and validated against our own experimental data, which were measured for both felts under six different relative compressions.The results of the fiber spatial orientation showed a change in the orientation of the carbon felt fiber with increasing compression rate. As the result of increasing compression, the electrical resistance decreases, whereas the hydraulic resistance increases. Interestingly, due to a change in spatial fiber orientation, Carman-Kozeny constant is also decreasing with increasing compression. The developed model can be further used to optimize the textural properties of 3D fibrous electrodes from hydraulic and ohmic point of view, within the development of flow electrochemical reactors.

A Tractable, Transferable, and Empirically Consistent Fibrous Biomaterial Model

Stochastic modeling is a useful approach for modeling fibrous materials that attempts to recreate fibrous materials’ structure using statistical data. However, several issues remain to be resolved in the stochastic modeling of fibrous materials—for example, estimating 3D fiber orientation distributions from 2D data, achieving the desired fiber tortuosity distributions, and dealing with fiber–fiber penetration. This work proposes innovative methods to (1) create a mapping from 2D fiber orientation data to 3D fiber orientation probability distributions, and vice versa; and (2) provide a means to select parameters de novo for random walks employing the popularized von Mises–Fisher distribution given that the desired tortuosity of the path is known. The proposed methods are incorporated alongside previously developed stochastic modeling techniques to simulate fiber network structures. First, fiber orientation distributions vary significantly depending on how a fibrous material is formed, and projection distortion affects the measurement of fiber orientation distributions when reported as 2D data such as histograms or polar plots. Relationships are developed to estimate 3D fiber orientation distributions from 2D data, accounting for projection distortion and the variety of orientation distributions observed in fibrous materials. We show that without correcting for projection distortion, fiber orientation distribution parameters could have errors of up to 100%. Second, in stochastic modeling, fiber tortuosity is usually treated with random walks, but no relationship is available for choosing random walk inputs to generate a desired fiber tortuosity. Relationships are also developed to relate the input parameters of von Mises–Fisher random walks to the expected tortuosity of the generated path—a necessary link to modeling fiber tortuosity distributions tractably and with empirical consistency. Using the developed relationships, we show that modeling of tortuous fibers from a distribution could be sped up by ~1200-fold and the uncertainty of selecting appropriate parameters could be eliminated. Third, randomly placing fibers in a simulation domain inevitably results in fiber–fiber penetration, and correcting this issue requires changes to the simulated fibrous material structure through non-penetration conditions. No thorough remedy can be offered here, but we statistically quantify the effects of enforcing non-penetration conditions on the fiber shape and orientation changes as well as the overall fibrous material model. This work offers tractable and transferable methods for treating fiber orientation and tortuosity that allow for empirical consistency in the stochastic modeling of fibrous materials.