Single-fiber Tension Research Articles

Effects of Aging and Fatigue on Human Skeletal Muscle Cellular Contractile Function

Aging is associated with a reduction in skeletal muscle mass and function, known as sarcopenia. While reductions in contractile force are typically explained by loss in muscle cellular cross sectional area (CSA) loss of contractile power during high velocity contractions exceed reductions in force and cannot be solely explained by loss of muscle size and are observed at the single fiber within the same myosin heavy chain isoform (MHC). These phenomenon may be explained by myosin binding protein C (MyBP-C), which is known to modulate contractile force and velocity in a phosphorylation-dependent manner in both cardiac and skeletal muscle. Few studies have investigated the inherent contractile performance of single fibers between old and young adults, and none have explored the effects of altered MyBP-C phosphorylation on single fiber function. Therefore, the PURPOSE of this study was to investigate the effects of age and fatigue-induced MyBP-C phosphorylation on single fiber contractile performance. We HYPOTHESIZED that isometric tension will be enhanced in older adults but velocity and power will be reduced, and fatigue will enhance velocity and power in single fibers. To test this hypothesis, we recruited 4 young (18-35) and 3 older (65-80) adult males to perform a single bout of unilateral knee extensions at 30% maximal voluntary isometric contraction (MVIC) until task failure. Immediately following, a bilateral biopsy of the vastus lateralis (VL) muscle was performed on the fatigued and non-fatigued control limbs. Tissue was either flash frozen for western blot or prepared for mechanical analysis of single fiber tension (Tmax), velocity (Vmax), and power (Pmax) under optimal intracellular metabolic conditions. Our analyses were limited to MHC IIA due to differences in fiber type distribution between the groups. Our RESULTS showed that neither age nor fatigue had an effect on contractile performance in MHC IIA fibers. However, independent analysis of fatigue within age groups suggest trends towards an increase in velocity (p=0.055) in young (MHC IIA) and reduction in tension (p=0.085) in old (MHC I) adult fibers. We CONCLUDE that fatigue may modulate contractile function in the single fiber in an age- and fiber-type dependent manner. Future studies will be aimed at collecting multiple fiber types and investigating the role of biological sex. Wu Tsai Human Performance Alliance. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A pre-screening of the solvolysis recycling process for CFRPs based on the mechanical properties of the recovered fibers.

Over the past few decades, composite materials, and specifically carbon fiber reinforced plastics (CFRPs), are finding increasing use in the automotive, aerospace, and aeronautics industries. As a result, the production of CFRPs has been significantly increased, thus leading to a corresponding increase in waste production. In the near future, landfill and incineration disposal of waste will likely be prevented due to legislation, thereby bringing forward the need to develop efficient recycling processes for CFRPs. However, recycling of CFRPs is very challenging, mainly due to the difficulty in removing the thermosetting matrix. This paper reports a pre-screening of the solvolysis recycling process for CFRPs on the basis of the mechanical properties of the recovered fibers. To this end, solvolysis tests were conducted on unidirectional CFRP samples under supercritical and subcritical conditions using acetone and water. The solvolysis tests were conducted for various conditions of temperature, pressure, and reaction time. The efficiency of the recycling processes has been evaluated by means of single-fiber tension tests on the recovered fibers, which were conducted according to the ASTM C 1557-14 standard. In most cases, the decomposition efficiency of the epoxy resin in the CFRP, measured in terms of mass, ranged between 90 and 100%. Moreover, the mechanical tests showed that the recovered fibers retained more than 58% of their initial Young’s modulus and tensile strength.

A Preliminary Investigation on a Water- and Acetone-Based Solvolysis Recycling Process for CFRPs.

Composites, and especially carbon-fiber-reinforced plastics (CFRPs), are increasingly used in the automotive, aerospace, and aviation industries, and as a result, CFRP production has increased dramatically, leading to a corresponding increase in waste. Landfills and the incineration of waste are likely to be restricted as a result of legislation, thus highlighting the need for efficient recycling methods for CFRPs. However, the recycling of CFRPs is very challenging, mainly due to the difficulty of removing their thermosetting matrix. This study reports a pre-screening of the solvolysis recycling process for CFRPs based on the mechanical properties of the recovered fibers. To this end, solvolysis tests were conducted on unidirectional CFRP samples under supercritical and subcritical conditions using acetone and water. The solvolysis tests were conducted for various conditions of temperature, pressure, and reaction time, without the use of any catalyst. Also, the loading rate (volume of solvent/volume of reactor) was constant. The efficiency of the recycling processes has been evaluated through a morphological and a mechanical characterization of the recovered fibers. In most cases, the decomposition efficiency of the epoxy resin, measured in terms of mass, ranged between 90 and 100%. Moreover, the scanning electron microscopy images of the recovered fibers showed negligible traces of resin residues and no detectable signs of physical damage or any changes in morphology with regard to diameter. Finally, the single-fiber tension tests revealed that that the recovered fibers retained more than 61% of their initial Young's modulus and 70% of their tensile strength.

Effect of electrophoretic deposition of micro-quartz on the microstructural and mechanical properties of carbon fibers and their bond performance toward cement

An electrophoretic deposition (EPD) process of micro-quartz (MQ) powder is applied to carbon fibers (CFs) with the aim to enhance their interfacial bond to cementitious matrices and to investigate its influence on the microstructural and mechanical properties of the CFs itself. The electrophoretic mobility of the MQ particles with negative charge in aqueous media was confirmed by potential sweep experiments and zeta-potential measurements. High amounts of MQ were successfully deposited onto the fiber surface, as proven by scanning electron microscopy. Single-fiber tension tests and thermogravimetric analysis showed that EPD treatment had little impact on the tensile properties and thermal stability of the modified fibers. However, storing the CFs in cement pore solution impaired temperature stability of untreated and modified fibers. X-ray diffraction and Raman spectroscopy reveal specific changes of CF's microstructure upon EPD treatment and immersion in pore solution. Single-fiber pullout tests showed that the pullout resistance of MQ-modified CFs was enhanced, relative to untreated CFs. This augmentation can be explained by an enhanced interlocking mechanisms between CF and matrix due to the deposited quartz particles on the CF surface.

Electrochemical oxidation of recycled carbon fibers for an improved interaction toward alkali-activated composites

In this study, recycled carbon fibers (rCF) obtained from pyrolysis are utilized as reinforcements in fly ash-GGBS alkali-activated composites. Since the bond between the fiber and matrix is relatively poor, anodic oxidation was conducted by applying various voltages to enhance the interfacial interactions. Cyclic voltammetry (CV) was performed to investigate the chemical reaction process during the electrochemical fiber modification. Scanning electron microscopy showed the removal of contaminations and impurities from the fiber surfaces by anodization. Thermogravimetric analysis (TGA) analysis was performed to compare the heat resistance properties of the CF reinforced composites and single-fiber tension tests were carried out to evaluate the influence of the electrochemical treatment on the fiber's properties. Single fiber pullout tests and energy dispersive X-ray mapping indicated a remarkable improvement of compatibility between the modified fibers and the matrix, since chemical bonds are formed between oxygen-related functional groups from the anodized fiber surfaces and the alkali-activated matrix. With the addition of 1 wt.% rCFs compressive and flexural strengths have been enhanced by up to 25% and 19%, respectively, compared to the plain composites. The results reveal that electrochemical surface treatment of rCFs is beneficial for enhancing the flexural behavior of rCF-reinforced composite owing to enhanced interfacial bonding. However, this method also provokes a slight increase of porosity compared with untreated fiber-reinforced samples, as proved by mercury intrusion porosimetry (MIP). This study provides a promising utilization of rCF in the production of waste-based fiber-reinforced alkali-activated composites, promoting the management of carbon fiber-reinforced plastic waste.

Material response and failure of highly deformable carbon fiber composite shells

Very thin carbon fiber composite shells can withstand large bending curvatures without failure. The resulting high tensile and compressive strains require accurate modeling of the fiber-dominated non-linear effects to predict the mechanical response. To date, no universal modeling technique can precisely capture the behavior of such structures. In this work, successful representation of composite’s response was achieved by utilizing single fiber tension and compression experimental data, implemented to extend a basal-plane-realignment based non-linear carbon fiber material model. Numerical techniques were adopted to model the bending behavior of unidirectional carbon fiber composites that was recorded in a comprehensive experimental campaign. Observations show that high material non-linearity leads to a non-negligible neutral-axis shift and drastic reduction of bending modulus due to compressive softening. Tensile fiber failure is the driving mechanism in thin shells flexure allowing for elastic compressive strains of up to 3% without micro-buckling. As a result, a remarkable flexibility in thin shells is realized. With increasing thickness, the elastic flexibility is reduced as the failure-driving mode switches to compressive micro-buckling.

Extraction and Characterization of Natural Fibers from Citrullus lanatus Climber

ABSTRACT The growing environmental awareness toward the replacement of non-biodegradable materials with biodegradable materials has led many researchers for looking at many bio-based materials to suit various applications. This study objective to evaluate the morphology and properties of fibers extracted from Citrullus lanatus climber. The physical-chemical, thermal, mechanical, crystalline, morphological characteristics of Citrullus lanatus climber fibers were examined by Fourier transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), single fiber tension test, X-ray diffraction (XRD), and scanning electron microscope (SEM). The test results showed cellulose content (53.7 wt. %), density (1227 kg/m3), crystallinity index (33.33%) which prove that Citrullus lanatus climber fibers can be used as reinforcement for light-weight medium load applications.

Large Hypertrophy but Unmodified Specific Tension of Single Fibers of Body Builders

IntroductionMuscle hypertrophy is the main outcome of training for body building. Previous studies showed a discrepancy between the functional (force/tension) and structural (cross‐sectional area, CSA) proprieties of leg extensor muscles measured in vivo and the corresponding parameters measured in single muscle fibers [1] [2]. In particular, a puzzling finding from these studies was that of a lower specific tension of skinned fibers of body builders (BB) compared to a control (C) population.In this study we aimed to investigate the possible reasons behind the alleged lower specific tension in single fibers of a strictly diet‐and‐training‐controlled BB population.MethodsFive male body builders (26±4.7 yr; 87.2±9.7 kg; 178.4±7.5 cm) with a training history of at least 5 years were recruited for this study. Five age‐matched recreationally active males (24.6±3.6 yr; 84.4±14.9 kg; 186.4±4.4 cm) were recruited as controls. After ethical approval, biopsies from the vastus lateralis (VL) muscle were collected together with in‐vivo quadriceps maximum isometric voluntary contraction (MVC) and architecture and CSA. Data analysis included (i) single skinned fiber mechanics (n=200 fibers; maximum force, CSA, specific tension and calcium diffusion), (ii) single fiber myosin quantification (n=100 fibers), (iii) slow and fast fiber CSA via histological section analysis. In addition, swelling ratio (skinned fibers CSA/histological CSA) was calculated for each fiber type and for each subject. A general linear mixed model was used to assess statistically significant differences.ResultsQuadriceps MVC and CSA were 64% and 33% higher in BB than C (p<0.05), VL pennation angle (PA) and thickness (MT) were 16% and 15% higher in BB than C (p<0.05). Quadriceps specific force was 25% higher in BB than C (n.s.). Single skinned type 2 CSA and force were 48% and 28% higher in BB than C (p<0.05), while specific tension was 19% lower (p<0.05). Type 1 fibers specific tension was 32% higher in BB than C (p<0.05). Myosin content and calcium diffusion were similar among populations. CSA determined in histological sections was 10% and 27% higher in BB than C (p<0.05) for type1 and 2 fibers, respectively. When type 1 and type 2 fiber tensions were corrected for individual swelling ratio, the difference between BB and C disappeared.ConclusionsAlthough at first sight these findings seem to confirm that in type 2 skinned fibers of BB specific tension is lower than in C, once accounting for fiber swelling, this difference disappears. This is further confirmed by the lack of difference in myosin concentration and calcium diffusion kinetics.In contrast, the results point to the existence of a differential swelling response to the skinning process by BB and C fibers, possibly due to adaptations of the fiber cytoskeleton proteins or specific permeability of the membrane of slow and fast fibers.

Electrochemical modification of carbon fiber yarns in cementitious pore solution for an enhanced interaction towards concrete matrices

Carbon fibers (CFs) and yarns are modified by a novel approach to improve their interfacial interaction with cementitious matrices to efficiently enhance the bond and herewith mechanical performance of carbon fiber-reinforced, cement-based composites. Anodic oxidation in cement pore solution is performed by applying different voltages and treatment times. Both parameters contributed to production of a significant quantity of crystalline products, confirmed by scanning electron microscopy. X-ray diffraction (XRD) and energy dispersive x-ray analysis (EDX) confirmed the presence of oxygen-containing calcium species on the fiber surface, supporting strongly the presence of calcite. Moreover, the thermal stability of the modified CFs was studied by thermogravimetric analysis, indicating a temperature-stable coating but also a degradation of the CFs when higher voltages had been applied. Single-fiber tension tests documented the influence of various treatment times and voltages on the tensile strength of the CFs. Additionally, single-fiber pullout tests were performed to examine the bond behavior of a single fiber embedded in a cementitious matrix. The results proved an enhancement of the bonding between modified fibers and cement-based matrix.

Effect of fiber properties and matrix composition on the tensile behavior of strain-hardening cement-based composites (SHCCs) subject to impact loading

The article at hand describes the behavior of high-strength and normal-strength strain-hardening cement-based composites (SHCCs) made of fine-grained matrix and high-density polyethylene fibers under quasi-static and impact tensile loading. The dynamic tension testing of unnotched and notched cylinders was performed using the Hopkinson bar at strain rates of around 150s−1. The responses of the materials under dynamic and quasi-static tensile loading were compared to the corresponding results for normal-strength SHCC made of polyvinyl-alcohol fibers as obtained in previous investigations. To explain the pronounced differences in rate effects on the material performance of various SHCC compositions, cracking pattern and fracture surface conditions were studied. Additionally, strain rate dependent changes in the mechanical behavior of individual fibers and in the fiber–matrix interfacial properties were deduced from single-fiber tension tests and fiber pullout tests, respectively. Altogether, the results obtained provide clear indications as to the decisive parameters for a purposeful material design of impact resistant types of SHCC for use in structural elements or protective overlays.

Effect of annealing and silylation on the strength of melt-spun Ni–Mn–Ga fibres and their adhesion to epoxy

Single crystals of ferromagnetic Ni–Mn–Ga shape memory alloys show magnetic-field and stress induced twinning, leading to shape memory. Adaptive composites can thus be produced by embedding single crystalline particles or bamboo-structured Ni–Mn–Ga fibres into a polymer matrix. To guarantee a durable performance of these composites, adhesion between reinforcement phase and matrix should be quantified and optimised. The influence of annealing and surface treatment with an aminosilane of melt-spun Ni–Mn–Ga fibres on their strength and adhesion to an epoxy matrix was investigated using single fibre tension and fragmentation tests. Annealing of the melt-spun Ni–Mn–Ga fibres changed the surface from a “pimpled” to a smooth microstructure. This resulted in a reduced adhesion of the annealed fibres in comparison to the as-spun fibres embedded in an epoxy matrix. As-spun fibres exhibited an interfacial shear strength (IFSS) comparable to the shear strength of the epoxy matrix so that the silylation did not change the adhesion significantly. For the annealed fibres, the silane treatment improved the IFSS by 67%. Furthermore, the silylation increased the fracture strength of the Ni–Mn–Ga fibres due to surface flaw healing or forming of a protective surface coating.

Study on the Ultraviolet Aging of APMOC Fiber

An ultraviolet aging test of APMOC fiber is carried out with the irradiation of xenon lamp, in which the effects of ultraviolet aging on APMOC fiber were studied by single fiber tension and FTIR. The result shows that the tensile strength, the modulus of elasticity and the elongation rate of APMOC fiber would have a change, among which the tensile strength increases by 13.7% after 6 hours UV irradiation and decreases by 2.1% after 36 hours. The C-N in amide of the APMOC fiber is broken; while the hydrogen bond combination ability and crystallinity increase by FTIR. It can, therefore, be concluded that short time UV irradiation can cause two contradictory effects on APMOC fiber.

Resistance training alters skeletal muscle structure and function in human heart failure: effects at the tissue, cellular and molecular levels

Reduced skeletal muscle function in heart failure (HF) patients may be partially explained by altered myofilament protein content and function. Resistance training increases muscle function, although whether these improvements are achieved by correction of myofilament deficits is not known. To address this question, we examined 10 HF patients and 14 controls prior to and following an 18 week high-intensity resistance training programme. Evaluations of whole muscle size and strength, single muscle fibre size, ultrastructure and tension and myosin-actin cross-bridge mechanics and kinetics were performed. Training improved whole muscle isometric torque in both groups, although there were no alterations in whole muscle size or single fibre cross-sectional area or isometric tension.Unexpectedly, training reduced the myofibril fractional area of muscle fibres in both groups. This structural change manifested functionally as a reduction in the number of strongly bound myosin-actin cross-bridges during Ca²⁺ activation. When post-training single fibre tension data were corrected for the loss of myofibril fractional area, we observed an increase in tension with resistance training. Additionally, training corrected alterations in cross-bridge kinetics (e.g. myosin attachment time) in HF patients back to levels observed in untrained controls. Collectively, our results indicate that improvements in myofilament function in sedentary elderly with and without HF may contribute to increased whole muscle function with resistance training. More broadly, these data highlight novel cellular and molecular adaptations in muscle structure and function that contribute to the resistance-trained phenotype.

Rippling of polymer nanofibers

This paper studies the evolution mechanism of surface rippling in polymer nanofibers under axial stretching. This rippling phenomenon has been detected in as-electrospun polyacrylonitrile in recent single-fiber tension tests, and in electrospun polyimide nanofibers after imidization. We herein propose a one-dimensional nonlinear elastic model that takes into account the combined effect of surface tension and nonlinear elasticity during the rippling initiation and its evolution in compliant polymer nanofibers. The polymer nanofiber is modeled as an incompressible, isotropically hyperelastic Mooney-Rivlin solid. The fiber geometry prior to rippling is considered as a long circular cylinder. The governing equation of surface rippling is established through linear perturbation of the static equilibrium state of the nanofiber subjected to finite axial prestretching. The critical stretch and ripple wavelength are determined in terms of surface tension, elastic property, and fiber radius. Numerical examples are demonstrated to examine these dependencies. In addition, a critical fiber radius is determined, below which the polymer nanofibers are intrinsically unstable. The present model, therefore, is capable of predicting the rippling condition in compliant nanofibers, and can be further used as a continuum mechanics approach for the study of surface instability and nonlinear wave propagation in compliant fibers and wires at the nanoscale.

Long Carbon Nanotubes Grown on the Surface of Fibers for Hybrid Composites

Hybrid composite architectures employing traditional advanced composites and carbon nanotubes offer significant potential mechanical and multifunctional performance benefits. The architecture investigated here is composed of aligned fibers with carbon nanotubes grown radially on their surface. A novel process for rapidly growing dense, long, high-quality, aligned carbon-nanotube forests is employed. Two fundamental issues related to realizing hybrid composite architectures are investigated experimentally: wetting of the carbon nanotubes by thermoset polymers and retention of mechanical (stiffness and strength) properties of the fibers after the carbon-nanotube growth process. Wetting of carbon-nanotube forests by two commercial polymers (including a highly viscous epoxy) is demonstrated at rates conducive to creating a fully dispersed carbon-nanotube/matrix region around the fibers in a typical composite. Single-fiber tension tests indicate no mechanical degradation for alumina fibers undergoing the carbon-nanotube growth process. Results indicate that hybrid carbon-nanotube/composite architectures are feasible, and future work focuses on mechanical and multifunctional property characterization of other hybrid architectures and scaling to a continuous carbon-nanotube growth process.

Strength distribution of elementary flax fibres

Flax fibres, along with a number of other natural fibres, are being considered as an environmentally friendly alternative of synthetic fibres in fibre-reinforced polymer composites. A common feature of natural fibres is a much higher variability of mechanical properties. This necessitates study of the flax fibre strength distribution and efficient experimental methods for its determination. Elementary flax fibres of different gauge lengths are tested by single fibre tension in order to obtain the stress–strain response and strength and failure strain distributions. The applicability of single fibre fragmentation test for flax fibre failure strain and strength characterization is considered. It is shown that fibre fragmentation test can be used to determine the fibre length effect on mean fibre strength and limit strain.

Non-contacting strain measurements of ceramic and carbon single fibres by using the laser-speckle method

A non-contacting laser correlation sensor is used to determine the strain of different ceramic (alumina, silicon carbide) and carbon fibres in a single fibre tension test. The diameter of these fibres varies from 15 to only 5 mm, which makes the application of conventional strain sensors impossible. The advantage of the non-contacting method is that the strain is directly measured and end-effects from the gripping system need not to be considered. Results for different ceramic and carbon fibres with linear and non-linear stress ‐strain curves are presented as an example. q 2003 Elsevier Ltd. All rights reserved.

Effect of interfacial adhesion and statistical fiber strength on tensile strength of unidirectional glass fiber/epoxy composites. Part. II: comparison with prediction

Abstract An analytic model by Curtin and Takeda (Curtin WA, Takeda N. Tensile strength of fiber-reinforced composites: I. Model and effects of local fiber geometry. Journal of Composite Materials 1998;32(22):2042–59; Curtin WA, Takeda N. Tensile strength of fiber-reinforced composites: II. Application to polymer matrix composites. Journal of Composite Materials 1998;32(22):2060–81) is used to predict the ultimate tensile strength (UTS) of unidirectional (UD) glass fiber/epoxy composites with different interfacial adhesion and statistical fiber strength. Data for the fiber strength σc at the critical fiber length δc for five kinds of treated fibers are used for predicting UTS, which is obtained from both single fiber composite (SFC) and single fiber tension (SFT) tests. σc from SFC is attained using the Curtin theory on the fragmentation of SFC, while that from SFT is determined using a linear extrapolation of SFT data. Under good interface adhesion, the predicted UTS values based on the SFC data show the best agreement with measured ones at various fiber volume fractions, but a higher predicted value is obtained if the interface failure is matrix-controlled. For poor interfacial adhesion, the predicted UTS values are rather high compared to experimental ones due to the ineffective stress transfer. The predicted values based on the SFT data are much higher than the measured value for good interfacial adhesion.

The estimation of statistical fiber strength by fragmentation tests of single-fiber composites

Both evaluation of interfacial properties and statistical strength theories for the failure of unidirectional composites require information about fiber strength distributions and, in particular, the Weibull scale and shape parameters, σ L and m, at some characteristic gauge length, L, such as the critical fiber length. In this paper, the in situ strengths of E-glass fibers with five different kinds of surface treatments in epoxy matrix have been estimated by fragmentation tests on single-fiber composites (SFC). The number of fiber breaks as a function of applied stress is simulated according to the Curtin theory for SFC with various fiber strengths and interfacial properties. The Weibull scale parameter, σ o, and shape parameter, m, at short gauge lengths are determined for each type of fiber through best-fit of the calculated and measured numbers of fiber breaks versus applied fiber stress. Lower values of σ o and higher values of m are obtained when compared with those obtained from single-fiber tension (SFT) tests for all kinds of fibers. However, the effects of surface treatments and gauge length on the fiber strength showed similar trends for both methods. It is found that the relatively low values of interfacial shear strengths calculated from SFC data are considered to be reasonable than those from SFT tests.

A new theory to obtain Weibull fibre strength parameters from a single-fibre composite test

A theory is developed to obtain the Weibull scale and shape parameters for in situ fibre strength utilizing the data obtained from a single-fibre-composite (SFC) test. It is well known that during the SFC test, the fibre fractures several times along its length at successive weak points that are randomly located. The SFC technique, although most commonly used for measuring the fibre/matrix interfacial shear strength, is an excellent way to determine the fibre flaw spacings and the in situ fibre failure stress at every fracture location. In the present technique, the SFC specimen is partitioned into a relatively large number of small sections of equal length such that each section will have either one or no fibre fracture point. Because all the sections may not include the fibre fracture points because of their random nature, the test data are regarded as “censored data”. In other words, the theory is constructed for the estimation of Weibull parameters that takes into account the censored nature of the data. The Weibull parameters predicted using the present theory are in the same range as those obtained from the single fibre tension tests. For several reasons the values obtained from the SFC test tend to be slightly higher than those obtained from the simple tension tests. However, the in situ fibre strength values obtained using SFC technique may be more realistic and thus may be more useful in modelling composite strength.