Fiber Cross-section Research Articles

An Investigation of Age-related Neuropathophysiology in Autism Spectrum Disorder Using Fixel-based Analysis of Corpus Callosum White Matter Micro- and Macrostructure

Fixel-based analysis was used to probe age-related changes in white matter micro- and macrostructure of the corpus callosum between participants with (N = 54) and without (N = 50) autism spectrum disorder (ASD). Data were obtained from the Autism Brain Imaging Data Exchange-II (ABIDE-II). Compared to age-matched controls, young adolescents with ASD (11.19 ± 7.54 years) showed reduced macroscopic fiber cross-section (logFC) and combined fiber-density and cross-section (FDC). Reduced fiber-density (FD) and FDC was noted in a marginally older (13.87 ± 3.15 years) ASD cohort. Among the oldest ASD cohort (17.07 ± 3.56 years), a non-significant trend indicative of reduced FD was noted. White matter aberration appears greatest and most widespread among younger ASD cohorts. This supports the suggestion that some early neuropathophysiological indicators in ASD may dissipate with age.

Application of image processing technology on testing blending ratio and blending irregularity of blended yarns

The blending ratio and blending irregularity of the blended yarn determine its property and quality. In this article, the image processing method was introduced to accurately and conveniently measure the blending ratio and blending irregularity of blended yarn by using images of the blended yarn cross sections. The Euclidean distance peeling method was applied to segment the adhered fibers to make them individual. Then, the fibers were classified according to characteristic parameters of fiber cross section such as color, shape, and area. The experiments were implemented to verify the accuracy and applicability of the image processing method to test the irregularity of blended bundles, slivers, and yarns by different fibers including polyester, viscose, and wool. The results show that the fiber identification error rate of the image processing method for blended bundles, compared with the designed, is less than 2%; the blending irregularity difference rate between image processing method and the manual counting method is less than 5% for blended sliver by sliver blending; the difference rate of the blending ratio of polyester/viscose blended yarn between designed and measured by image processing method is less than 5%, while manual counting method is less than 10%. The findings mean that the image processing method proposed in this article can greatly save labor and time on identifying and counting fibers, and it is a more accurate, convenient, and reliable method to test blending irregularity.

Strain and Strain Rate Tensor Mapping of Medial Gastrocnemius at Submaximal Isometric Contraction and Three Ankle Angles.

The aim of this study is to analyze the muscle kinematics of the medial gastrocnemius (MG) during submaximal isometric contractions and to explore the relationship between deformation and force generated at plantarflexed (PF), neutral (N) and dorsiflexed (DF) ankle angles. Strain and Strain Rate (SR) tensors were calculated from velocity-encoded magnetic resonance phase-contrast images in six young men acquired during 25% and 50% Maximum Voluntary Contraction (MVC). Strain and SR indices as well as force normalized values were statistically analyzed using two-way repeated measures ANOVA for differences with force level and ankle angle. An exploratory analysis of differences between absolute values of longitudinal compressive strain (Eλ1) and radial expansion strains (Eλ2) and maximum shear strain (Emax) based on paired t-test was also performed for each ankle angle. Compressive strains/SRs were significantly lower at 25%MVC. Normalized strains/SR were significantly different between %MVC and ankle angles with lowest values for DF. Absolute values of Eλ2 and Emax were significantly higher than Eλ1 for DF suggesting higher deformation asymmetry and higher shear strain, respectively. In addition to the known optimum muscle fiber length, the study identified two potential new causes of increased force generation at dorsiflexion ankle angle, higher fiber cross-section deformation asymmetry and higher shear strains.

Distinguishing yak and cashmere fibers from each other to prohibit mislabeling through microscopic and spectroscopic analysis

Since yak and cashmere fibers show very similar properties and yak fibers are considerably cheaper than cashmere, it is an important issue that yak is used instead of cashmere in the industry and the final product is sold as cashmere with misleading labelling. Therefore, researchers have been working on developing a method for differentiating these two fibers for many years. In the studies carried out in literature to date, no definitive method has been found which can distinguish these fibers from each other. Accurate results can only be obtained with DNA analysis, and this method is difficult and expensive to apply. On the other hand, when the literature was examined, it was seen that various fiber properties were investigated to distinguish yak and cashmere fibers. However, fibers having the same color were not systematically used together in these studies. In this study, both white and brown fibers from cashmere and yak origin were examined and thus, whether any method would be useful or not to distinguish yak and cashmere fibers in general or white cashmere from white yak and brown cashmere from brown yak in particular was presented. Within the scope of present work, it was aimed to find a way of distinguishing these fibers from each other by making various microscopic and spectroscopic analysis. For this aim fiber cross-section and longitudinal appearance analysis by light microscopy; scale morphology (scale structure, scale shape, scale pattern), scale height (thickness), scale length and scale frequency analysis by scanning electron microscopy; color (CIE L*a*b* color coordinates) analysis with spectrophotometer, fiber functional group analysis by Fourier transform infrared spectroscopy and fiber combustion behavior analysis with thermogravimetric analysis were conducted.

Investigation of the effects of hollow yarn structure and woven fabric construction on fabric performance: mechanical properties

The appearance and performance properties of textile products are affected by the fibre, yarn, and fabric structure and the finishing processes. The number of fibres in cross-section, fibre disposition, fibre alignment, the position of the fibres in the strands, binding in, overall structure, and twist are the main factors affecting yarn characteristics. Woven fabric properties are affected by fibre, yarn, and fabric characteristics. This study aims to improve the properties of 100% cotton fabric and obtain softer fabrics. For this purpose, the effect of woven fabric construction and hollow weft yarn structure, on the mechanical properties (weft-warp density, fabric weight, fabric strength, abrasion resistance) of woven fabrics were investigated. The effect of fabric construction on fabric weight and fabric construction was found statistically significant. It is observed that the hollow yarn structure does not negatively affect the fabric tensile strength and elongation values.

Individual differences in procedural learning are associated with fiber specific white matter microstructure of the superior cerebellar peduncles in healthy adults

Functional neuroimaging has consistently implicated the fronto-basal ganglia-cerebellar circuit in procedural learning-defined as the incidental acquisition of sequence information through repetition. Limited work has probed the role of white matter fiber pathways that connect the regions in this network, such as the superior cerebellar peduncles (SCP) and the striatal premotor tracts (STPMT), in explaining individual differences in procedural learning. High angular diffusion weighted imaging was acquired from 20 healthy adults aged 18-45 years. Fixel-based analysis was performed to extract specific measures of white matter microstructure (fiber density; FD) and macrostructure (fiber cross-section; FC), from the SCP and STPMT. These fixel metrics were correlated with performance on the serial reaction time (SRT) task, and sensitivity to the sequence was indexed by the difference in reaction time between the final block of sequence trials and the randomized block (namely, the 'rebound effect'). Analyses revealed a significant positive relationship between FD and the rebound effect in segments of both the left and right SCP (pFWE < .05). That is, increased FD in these tracts was associated with greater sensitivity to the sequence on the SRT task. No significant associations were detected between fixel metrics in the STPMT and the rebound effect. Our results support the likely role of white matter organization in the basal ganglia-cerebellar circuit in explaining individual differences in procedural learning.

The Influence of Fibre Cross Section Shape and Fibre Surface Roughness on Composite Micromechanics

Many of the carbon and natural fibres used in composite reinforcement have a non-circular cross section. Recently non-circular, or flat, cross section glass fibre products have become commercially available. This paper explores the potential effects that such non-circular fibre cross section shapes may have on the micromechanics of stress transfer at the composite fibre–matrix interface and the resulting changes in composite strength performance. Analytical modelling is used to show how the critical fibre length in composites with non-circular fibres is always less when compared to circular fibres with an equal cross-sectional area. This can result in significant changes to the strength performance of discontinuous fibre reinforced composites. Additionally, it is shown that the surface roughness found on natural and carbon fibres, many of which are also non-circular in cross section, can decrease the critical fibre length still further. These effects have important consequences for the use of single fibre micromechanical tests used for the characterisation of interfacial strength.

Flat glass fibres: The influence of fibre cross section shape on composite micromechanics and composite strength

Many of the fibres used in composite reinforcement have a non-circular cross section and recently non-circular glass fibre products have become commercially available. This paper explores the potential effects that such non-circular fibre shapes may have on the micro-mechanics of stress transfer at the fibre–matrix interface and the resulting changes in composite strength performance. Analytical modelling is used to show how the critical fibre length in composites with non-circular fibres is always less when compared to circular fibres with an equal cross sectional area. This can result in significant changes to the strength performance of discontinuous fibre reinforced composites. Additionally it is shown that non-circularity in fibre cross section can have important consequences for the use of single fibre micromechanical tests in the characterisation of interfacial strength.

Nicotinamide Phosphoribosyltransferase-elevated NAD+ biosynthesis prevents muscle disuse atrophy by reversing mitochondrial dysfunction.

It is well known that muscle disuse atrophy is associated with mitochondrial dysfunction, which is implicated in reduced nicotinamide adenine dinucleotide (NAD+ ) levels. Nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme in NAD+ biosynthesis, may serve as a novel strategy to treat muscle disuse atrophy by reversing mitochondrial dysfunction. To investigate the effects of NAMPT on the prevention of disuse atrophy of skeletal muscles predominantly composed of slow-twitch (type I) or fast-twitch (type II) fibres, rabbit models of rotator cuff tear-induced supraspinatus muscle atrophy and anterior cruciate ligament (ACL) transection-induced extensor digitorum longus (EDL) atrophy were established and then administered NAMPT therapy. Muscle mass, fibre cross-sectional area (CSA), fibre type, fatty infiltration, western blot, and mitochondrial function were assayed to analyse the effects and molecular mechanisms of NAMPT in preventing muscle disuse atrophy. Acute disuse of the supraspinatus muscle exhibited significant loss of mass (8.86±0.25 to 5.10±0.79g; P<0.001) and decreased fibre CSA (3939.6±136.1 to 2773.4±217.6μm2 , P<0.001), which were reversed by NAMPT (muscle mass 6.17±0.54g, P=0.0033; fibre CSA, 3219.8±289.4μm2 , P=0.0018). Disuse-induced impairment of mitochondrial function were significantly improved by NAMPT, including citrate synthase activity (40.8±6.3 to 50.5±5.6nmol/min/mg, P=0.0043), and NAD+ biosynthesis (279.9±48.7 to 392.2±43.2pmol/mg, P=0.0023). Western blot revealed that NAMPT increases NAD+ levels by activating NAMPT-dependent NAD+ salvage synthesis pathway. In supraspinatus muscle atrophy due to chronic disuse, a combination of NAMPT injection and repair surgery was more effective than repair in reversing muscle atrophy. Although the predominant composition of EDL muscle is fast-twitch (type II) fibre type that differ from supraspinatus muscle, its mitochondrial function and NAD+ levels are also susceptible to disuse. Similar to the supraspinatus muscle, NAMPT-elevated NAD+ biosynthesis was also efficient in preventing EDL disuse atrophy by reversing mitochondrial dysfunction. NAMPT-elevated NAD+ biosynthesis can prevent disuse atrophy of skeletal muscles that predominantly composed with either slow-twitch (type I) or fast-twitch (type II) fibres by reversing mitochondrial dysfunction.

Optimum Design of Glass–Air Disordered Optical Fiber with Two Different Element Sizes

This paper presents a detailed study investigating the effect of the material refractive index distribution at the local position of a glass–air disordered optical fiber (G-DOF) on its localized beam radius. It was found that the larger the proportion of the glass material, the smaller its localized beam radius, which means that the transverse Anderson localization (TAL) effect would be stronger. Accordingly, we propose a novel G-DOF with large-size glass elements doped in the fiber cross-section. The simulation results show that the doped large-size glass elements can reduce the localized beam radius in the doped region and has a very tiny effect on the undoped region, thus contributing to reducing the average localized beam radius of G-DOF.

A nonlinear fibre beam-column model for partially encased composite columns incorporating local buckling effect

Partially encased composite (PEC) columns are being widely used as vertical load carrying members in high-rise building structures. The complex structural behaviour of PEC columns at ultimate and failure states, related to local buckling of steel section and confinement effect of concrete, has posed significant difficulties and computational costs for accurate analysis of these members. To address this issue, this paper presents a nonlinear fibre beam-column (FBC) model for efficient and accurate analysis of PEC columns. A 2D Euler-Bernoulli beam element based on geometrically exact beam theory is employed, which has fibre cross sections accounting for the material nonlinearity of steel and concrete. A generalised effective width method (GEWM) is developed and integrated in the FBC model to simulate the stress redistribution in the steel section due to the progression of local and post-local buckling. Numerical examples demonstrate that the proposed FBC model can reasonably predict the behaviour of short PEC columns under concentric and eccentric compression, as well as the global buckling behaviour of long PEC columns. The computational cost of the proposed FBC model is considerably lower than that of 3D finite element analysis. The numerical examples also show that the incorporation of the local buckling effect (GEWM) leads to decreases in the ultimate and post-peak loads predicted by the FBC model. The effect of local buckling becomes insignificant for long PEC columns with length-to-depth ratios greater than 15.

A Low-Flow Fiber-Optic Flowmeter Based on Bending Measuring Using a Cladding Fiber Bragg Grating

A low-flow flowmeter based on the bending measurement of a cladding fiber Bragg grating (CLFBG) has been proposed and demonstrated. The CLFBG is fixed in a cantilever beam structure composed of a spring and a circular target. A femtosecond laser side-illumination technique was utilized to ensure that the grating inscription remains close to the core–cladding interface of the multi-cladding fiber (MCLF). The cladding resonance presents fiber bending dependence because of the asymmetrical distribution of the CLFBG along the fiber cross section. The force exerted on the circular target by the slow flow rate of the fluid on the order of mm/s bends the fiber, which changes the peak intensity of the cladding mode. The experimental results show that the sensor responds in the range of 0–87 mm/s and has extremely low-temperature cross-sensitivity. The proposed sensor has potential application prospects in high-precision, low-start flow measurement and can be applied to oil pipelines, downhole, and other fields.

Changes in White Matter Microstructure Over 3 Years in People With and Without Stroke.

Cerebral white matter health can be estimated by MRI-derived indices of microstructure. White matter dysfunction is increasingly recognized as a contributor to neurodegenerative disorders affecting cognition and to functional outcomes after stroke. Reduced indices of white matter microstructure have been demonstrated cross-sectionally in stroke survivors compared with stroke-free participants, but longitudinal changes in the structure of white matter after stroke remain largely unexplored. We aimed to characterize white matter micro- and macrostructure over 3 years after stroke and study associations with white matter metrics and cognitive functions. Patients with first-ever or recurrent ischemic stroke of any etiology in any vascular territory were compared with stroke-free age- and sex-matched controls. Those diagnosed with hemorrhagic stroke, TIA, venous infarction, or significant medical comorbidities, psychiatric and neurodegenerative disorders, substance abuse, or history of dementia were excluded. Diffusion-weighted MRI data at 3, 12, and 36 months were analyzed using a longitudinal fixel-based analysis, sensitive to fiber tract-specific differences within a voxel. It was used to examine whole-brain white matter degeneration in stroke compared with control participants. We studied microstructural differences in fiber density and macrostructural changes in fiber-bundle cross-section, in relation to cognitive performance. Analyses were performed controlling for age, intracranial volume, and education (family-wise error-corrected p < 0.05, nonparametric testing over 5,000 permutations). We included 71 participants with stroke (age 66 ± 12 years, 22 women) and 36 controls (age 69 ± 5 years, 13 women). We observed extensive white matter structural degeneration across the whole brain, particularly affecting the thalamic, cerebellar, striatal, and superior longitudinal tracts and corpus callosum. Importantly, follow-up regression analyses in 72 predefined tracts showed that the decline in fiber density and cross-section from 3 months to 3 years was associated with worse cognitive performance at 3 years after stroke, especially affecting visuospatial processing, processing speed, language, and recognition memory. We conclude that white matter neurodegeneration in ipsi- and contralesional thalamic, striatal, and cerebellar tracts continues to be greater in stroke survivors compared with stroke-free controls. White matter degeneration persists even years after stroke and is associated with poststroke cognitive impairment. ClinicalTrails.gov NCT02205424.

Effects of fiber cross-section shape on thermal comfort properties of polyester interlock fabrics

In this study, some dimensional and thermal comfort properties, i.e. thermal resistance, water vapor permeability, and air permeability properties of interlock fabrics knitted from different cross-section shaped polyester fibers were investigated. Four polyester yarns of different fiber cross-section shapes (hollow-round, round, triangular, and W-shape) were used to produce the samples. From the results, it was found that the triangular and W-type fibers had higher fabric density values due to the denser and closer fiber settlement. The highest bursting strength value belonged to the sample knitted from hollow-round yarn, which had also the highest yarn-breaking load value. The samples knitted from both round cross-section polyester yarns had significantly higher air permeability and thermal resistance values than the other samples due to the lower fabric density values of these fabrics. On the other hand, the water vapor permeability values of the fabrics from triangular and W-type fibers were slightly higher than the others because of their lower thicknesses.

Hybridization Engineering of Oxyfluoride Aluminosilicate Glass for Construction of Dual-Phase Optical Ceramics.

The construction of transparent ceramics under mild conditionsand standard atmospheric pressure has great scientific and technological potential; however, it remains difficult to achieve when conventional ceramic sintering techniques are used. Herein, a mild strategy for constructing dual-phase optical ceramics with high crystallinity (>90%) based on the stepped dual-phase crystallization of hybridized aluminosilicate glass is presented. Theoretical and experimental studies reveal that the hybridization of the glass system enables a new balance between the glass-forming ability and crystallization and can overcome the uncontrolled devitrification phenomenon during the dense crystallization of glass. Transparent hybridized oxide-fluoride ceramics with fiber geometry and dual-phase microstructures are also successfully fabricated. The generality of the strategy is confirmed, and transparent ceramics with various chemical compositions and phase combinations are prepared. Additionally, the cross-section of the ceramic fibers can be easily tuned into a circle, square, trapezoid, or even a triangle. Furthermore, the practical applications of optical ceramics for lighting and X-ray imaging are demonstrated. The findings described here suggest a major step toward expanding the scope of optical ceramics.

Mechanical anisotropy of hair affected by genetic diseases highlights structural information related to differential crosslinking in keratins.

Previous work with Atomic Force Microscope (AFM) nanoindentation, on longitudinal and cross-sections of the human hair fibre, allowed for the derivation of a model for the mechanical behaviour of human hair, called the Anisotropic Index. Expanding that research further, and by applying this model, the nanomechanical behaviour of hairs from patients with the disease Trichothiodystrophy (TTD) has been examined and structural insights, gained from combining the AFM results with Differential Scanning Calorimetry (DSC) experiments and tensile measurements, suggests that TTD-affected hairs have a relatively increased amount of Keratin Intermediate Filaments, contained in compartments of differing crosslinking extent. The associated calculations of axial and transverse Young's Moduli deliver values in good agreement with the measured fibre mechanics. Furthermore, comparing these findings with the results previously obtained from the study of hairs from patients with the disease Monilethrix, it is shown that the Anisotropic Index correlates well with the known deficiencies in both hair types obtained from such patients and allows for discerning between the Control hair and from those affected by the two diseases. AFM nanoindentation along and across the fibre axis and the Anisotropic Index thus appear to reveal structural details of hair not otherwise acquirable, whilst DSC may offer a quick and simple method for distinguishing between different severities of TTD.

Analysis of physical and mechanical characteristics of tropical natural fibers for their use in civil engineering applications

ABSTRACT Natural fibers investigated in this study are mainly waste from agro industry. The importance of natural fibers in building composites is increasing, as they partially replace nonrenewable natural resources acting as reinforcement in composite materials such as concrete, mortar and earth bricks. Their recycling requires a detailed analysis of the physical, chemical, and mechanical characteristics of the fibers. In this study, tropical natural fibers i.e., palm oil flower fibers (POFL), palm oil fruit fibers (POFR), sugarcane bagasse (Sc), coconut coir (Cn), and banana spine (Bs) were investigated, and their characteristics such as cross-section, density, water absorption, thermogravimetry, chemical composition, and tensile strength of fibers were determined. The area of these fibers ranges from 0.03 mm2 to 0.07 mm2. POFL fibers have highest density (1.36 g/cm3), while Cn fibers have lowest density (0.79 g/cm3). Chemical composition of fibers shows that cellulose content of tropical fibers ranges from 37–54%, followed by hemicellulose 5–27%, and lignin and cutins content 5–25%. Mechanical characteristics of tropical fibers show that tensile strength of these fibers fluctuates between 119–347 MPa. Tensile load-deflection behavior of Cn, Bs, POFL, and POFR fibers is elastoplastic with hardening, while the behavior of Sc fibers is pseudo elastic.

Cerebellar and basal ganglia structural connections in humans: Effect of aging and relation with memory and learning.

The cerebellum and basal ganglia were initially considered anatomically distinct regions, each connected via thalamic relays which project to the same cerebral cortical targets, such as the motor cortex. In the last two decades, transneuronal viral transport studies in non-human primates showed bidirectional connections between the cerebellum and basal ganglia at the subcortical level, without involving the cerebral cortical motor areas. These findings have significant implications for our understanding of neurodevelopmental and neurodegenerative diseases. While these subcortical connections were established in smaller studies on humans, their evolution with natural aging is less understood. In this study, we validated and expanded the previous findings of the structural connectivity within the cerebellum-basal ganglia subcortical network, in a larger dataset of 64 subjects, across different age ranges. Tractography and fixel-based analysis were performed on the 3 T diffusion-weighted dataset using Mrtrix3 software, considering fiber density and cross-section as indicators of axonal integrity. Tractography of the well-established cerebello-thalamo-cortical tract was conducted as a control. We tested the relationship between the structural white matter integrity of these connections with aging and with the performance in different domains of Addenbrooke's Cognitive Examination. Tractography analysis isolated connections from the dentate nucleus to the contralateral putamen via the thalamus, and reciprocal tracts from the subthalamic nucleus to the contralateral cerebellar cortex via the pontine nuclei. Control tracts of cerebello-thalamo-cortical tracts were also isolated, including associative cerebello-prefrontal tracts. A negative linear relationship was found between the fiber density of both the ascending and descending cerebellum-basal ganglia tracts and age. Considering the cognitive assessments, the fiber density values of cerebello-thalamo-putaminal tracts correlated with the registration/learning domain scores. In addition, the fiber density values of cerebello-frontal and subthalamo-cerebellar (Crus II) tracts correlated with the cognitive assessment scores from the memory domain. We validated the structural connectivity within the cerebellum-basal ganglia reciprocal network, in a larger dataset of human subjects, across wider age range. The structural features of the subcortical cerebello-basal ganglia tracts in human subjects display age-related neurodegeneration. Individual morphological variability of cerebellar tracts to the striatum and prefrontal cortex was associated with different cognitive functions, suggesting a functional contribution of cerebellar tracts to cognitive decline with aging. This study offers new perspectives to consider the functional role of these pathways in motor learning and the pathophysiology of movement disorders involving the cerebellum and striatum.

Eco-Friendly Fibers Embedded Yarn Structure in High-Performance Fabrics to Improve Moisture Absorption and Drying Properties.

This study examined the perspiration absorption and drying characteristics of eco-friendly fiber-embedded fabrics with different yarn structures. The wicking and drying rates of fifteen fabrics made from quadrilobal PET, Lyocell, and bamboo fibers were measured using two evaluation methods and compared with the pore diameter and hygroscopic characteristics of the constituent fibers in the yarns. The sheath/core yarn structure played a vital role in improving the moisture absorption and drying properties of the eco-friendly fibers embedded in high-performance fabrics, which was partly affected by the hygroscopicity and non-circular cross-section of constituent fibers in the yarns. Superior perspiration absorption and drying properties among the various eco-friendly high-performance fabrics were observed in the quadrilobal PET/Lyocell sheath/core and quadrilobal PET/bamboo spun yarn fabrics. By contrast, the PET/Lyocell Siro-fil, bamboo spun, and hi-multi PET yarn fabrics exhibited inferior moisture absorption and drying properties. In particular, the evaluated results between transverse and vertical wicking measuring methods in absorption property showed a similar trend. In contrast, the drying property measured between the drying rate (min) at a steady state and the drying rate (g) at a transient state showed a different trend. Multiple regression analysis showed that the wicking property of the eco-friendly fiber-embedded fabrics was mainly related to the pore diameter, cross-sectional shape, and absorption property of the fibers in the yarns, and it was also highly associated with the drying characteristics of the fabrics. The market application of the sheath/core yarn structure using Lyocell and bamboo fibers with quadrilobal PET is available for producing eco-friendly fabrics that can contribute to environmental improvement and wear comfort related to the moisture absorption and fast-drying properties of the woven fabrics.

Mineral-impregnated carbon-fiber (MCF) composites made with differently sized fly-ash geopolymers for durable light weight and high temperature applications

For a wide application of carbon-fiber reinforcement in large-scaled, lightweight construction, mineral-impregnated carbon-fiber (MCF) composites provide a promising alternative to rebar or reinforcement made of non-metallic fibers and polymer matrix. The penetration ability of the aluminosilicate particles is a key factor for a stable, reproducible impregnation and the maximal reinforcing efficiency of continuous fiber geopolymer composites.The work at hand focuses on the influence of the particle sizes of geopolymer precursors on the processing quality, microstructural development and final composite performance regarding the flexural, tensile and pullout behavior. Three differently sized fly ash (FA) sources were used to impregnate a carbon fiber heavy tow before curing at 75 °C. FA particles in the same size range as the filament diameter proved to be the most efficient, enhancing both mechanical properties of MCF and its bond to concrete matrix, well beyond the effects induced by other, coarser precursors. The results of the microscopic investigation, μCT, thermal gravimetric analyzes and mercury intrusion porosimetry measurements show that the use of this particle fraction resulted in the best fiber-matrix distribution over the cross-section, densest microstructure and highest fiber volume fraction in the impregnated yarn. Furthermore, the geopolymerization kinetics of all FAs at ambient temperature and at 75 °C were determined by isothermal calorimeter, showing an increase in the reaction rate with elevated curing temperature and higher particle finesse.