Fiber Stress Research Articles

Effect of curing age on pullout behavior of aligned and inclined steel fibers embedded in UHPFRC

Ultra High-Performance Fiber Reinforced Concrete (UHPFRC) is a promising material for applications in precast industry characterized by fast construction. However, there is a gap in investigations on the pullout behavior of inclined fibers at different ages. Therefore, pullout tests were performed in UHPFRC at 1d, 3d, 7d, and 28d, with fibers having embedment angles of 0°, 30°, and 45° for each age. An exponential function described well the growth of bond strength. It was found an increase in average bond strength of 2.98, 4.50, and 3.89 for fiber inclinations of 0°, 30°, and 45°, from 1d to 28d. For equivalent bond strength, the increase was 3.68, 4.37, and 2.82, respectively, from 1d to 28d. The smaller growth for 45° than 30° is attributed to greater matrix spalling for higher inclinations. In contrast, the more significant increase for fiber inclined 30° is mainly attributed to the increased friction at the interface due to the snubbing effect. Furthermore, maximum fiber stresses reached ratios to the tensile strength of 0.54, 0.65, and 0.59 for fiber inclinations of 0°, 30°, and 45°.

Hyperbolic Cosine Rayleigh Distribution and Its Application to Breaking Stress of Carbon Fibers

In this paper, we introduce generalization of Rayleigh distribution using hyperbolic cosine family distribution and it is named as hyperbolic cosine Rayleigh distribution. Further we present various mathematical properties of the proposed distribution including explicit expressions for moments, quantiles, asymptotic behaviour, order statistics, stochastic orderings and reliability function. Maximum likelihood estimation method is used to obtain estimators for the parameters of the distribution. Finally we have shown that the proposed model has application in studying breaking stress of carbon fibers.

Three-dimensional stress formula in fiber direction and its application under internal and external pressure

A three-dimensional (3D) fiber stress formula was developed to reduce the deviation of the two-dimensional (2D) fiber stress formula in calculating the 3D stress. The on-axis and off-axis stress–strain relationship was first presented. The 3D fiber stress formula was then derived analytically. Finite element method (FEM) of filament-wound (FW) thick-walled cylinders with symmetrical/balanced-layers was built, and numeric results were calculated and analyzed. Good agreement of the fiber stresses in the fiber direction and the strength ratios were achieved. It was found that the 3D fiber stress formula yields more accurate stress and lower strength ratio than the 2D formula in the triaxial stress state.

Pullout Behavior of Recycled Waste Fishing Net Fibers Embedded in Cement Mortar.

In this study, recycled waste fishing net (WFN) short fibers were proposed to be used as short fiber reinforcements. The pullout resistance of WFN short fibers embedded in cement mortar was investigated by conducting fiber pullout tests. Three types of WFN short fibers and two types of commercial polypropylene (CP) fibers were investigated. To quantitatively compare the pullout resistance of WFN short fibers and CP fibers, pullout parameters, including peak pullout load (peak bond strength), peak fiber stress, slip at peak load, and pullout energy (equivalent bond strength) of the pullout specimens, were analyzed. In addition, the analysis of fiber images, captured by using a stereoscopic digital microscope, before and after pullout tests, elucidated the different mechanisms of fiber pullout corresponding to the type of fibers. The bundled structures of the WFN fibers generated mechanical interaction between fiber and matrix during fiber pullout; consequently, they produced higher bond resistance and more damage on the surface of fibers after the pullout. Therefore, the bundled WFN fibers showed comparable pullout resistance with CP fibers.

BN/SiBCN light-leakage-proof coatings of silica optical fiber for long term sensors at high temperatures

SiBCN and BN/SiBCN light-leakage-proof coatings were prepared on silica optical fibers for sensing applications at high temperatures. Scanning electron microscopy was used to characterize the surface morphology and microstructure of the coated fiber. Mechanical and optical properties of the coated fiber were characterized by Raman, optical and tensile tests. Compared with the original fiber, the tensile strength of SiBCN and BN/SiBCN coated fiber show an increase of about 60% and 90% at room temperature, respectively. In addition, the tensile strength of BN/SiBCN coated silica optical fiber was increased by about 42% at 700 °C. It has been found that the improvement of the strength of BN/SiBCN coated silica optical fiber is related to the healing of defects and residual compressive stress in fibers. From the light transmittance performance of the coated fiber, it was found that BN/SiBCN double coating could be an ideal total reflection solution to protect silica optical fiber from light leakage during high temperature sensing operation.

Mechanical stimuli for left ventricular growth during pressure overload.

The mechanical stimulus (i.e. stress or stretch) for growth occurring in the pressure-overloaded left ventricle (LV) is not exactly known. To address this issue, we investigate the correlation between local ventricular growth (indexed by local wall thickness) and the local acute changes in mechanical stimuli after aortic banding. LV geometric data were extracted from 3D echo measurements at baseline and 2 weeks in the aortic banding swine model (n = 4). We developed and calibrated animal-specific finite element (FE) model of LV mechanics against pressure and volume waveforms measured at baseline. After the simulation of the acute effects of pressure-overload, the local changes of maximum, mean and minimum myocardial stretches and stresses in three orthogonal material directions (i.e., fiber, sheet and sheet-normal) over a cardiac cycle were quantified. Correlation between mechanical quantities and the corresponding measured local changes in wall thickness was quantified using the Pearson correlation number (PCN) and Spearman rank correlation number (SCN). At 2 weeks after banding, the average septum thickness decreased from 10.6 ± 2.92mm to 9.49 ± 2.02mm, whereas the LV free-wall thickness increased from 8.69 ± 1.64mm to 9.4 ± 1.22mm. The FE results show strong correlation of growth with the changes in maximum fiber stress (PCN = 0.5471, SCN = 0.5111) and changes in the mean sheet-normal stress (PCN= 0.5266, SCN = 0.5256). Myocardial stretches, however, do not have good correlation with growth. These results suggest that fiber stress is the mechanical stimuli for LV growth in pressure-overload.

Numerical and Experimental Investigation of the Through-Thickness Strength Properties of Woven Glass Fiber Reinforced Polymer Composite Laminates under Combined Tensile and Shear Loading

The purpose of this paper is to investigate the through-thickness stresses of woven glass fiber reinforced polymer (GFRP) composite laminates under combined tensile and shear loading. Tensile tests were carried out with cross specimens at room temperature under various stacking angles, and the through-thickness strength properties of the woven GFRP laminates were evaluated. The failure characteristics of the woven GFRP laminates were also studied by optical microscopy observations. A three-dimensional finite element analysis (FEA) was carried out to calculate the stress distributions in the cross specimens, and the failure conditions of the specimens were examined. The numerically determined interlaminar tensile and shear stresses at failure location were consistent with Hoffman and Mohr-Coulomb failure criteria when the stacking angle was relatively small. This work is the first attempt to quantify the relation between interlaminar tensile and shear strengths of GFRP composite laminates under tensile and shear loading simultaneously using a combined numerical and experimental approach. A method based on finite element stress analysis was developed for estimating the through-thickness strength of the composite laminates using the experimentally determined fracture load and location. The results suggest that the through-thickness strength under combined tensile and shear loading can be determined effectively by this approach for relatively small stacking angles.

Surrogate Model Based Analysis of Inter-Ply Shear Stress in Fiber Reinforced Thermoplastic Composite Sheet Press Forming

The anisotropic nature of fiber reinforced composite materials causes great challenges in predicting the inter-ply shear stress during forming. The complexity of understanding the functional dependency of inter-ply shear stress on multiple forming parameters such as blank temperature, pressure load, inter-ply slippage, and the relative fiber orientation angle of adjacent plies further limits the effort to produce a defect-free composite structure. Performing real experiments for various combinations of the mentioned parameters is both time consuming and economically costly. To overcome these difficulties, a surrogate-based analysis of inter-ply shear stress is proposed in this study. Based on the ranges of the forming parameters, computer experiments were performed. Using these experimental data, a radial basis function (RBF) based surrogate model that mimics inter-ply shear stress during composite press forming was developed. The fidelity of this model was checked with test data and found to be over 98% efficient.

Change of deformation mechanism through nano-structuring of pearlite: An in-situ study

The deformation mechanisms and fracture of nano-structured pearlitic steels with inter-lamellar spacing between 60 and 160 nm have been studied in-situ using a tensile stage inside a scanning electron microscope. Fragmentation of cementite lamellae for finer pearlite was observed post ultimate tensile strength (UTS) in regions where the lamellae were aligned along the tensile axis. For coarse pearlite, cementite fragmentation initiated prior to UTS which became more severe post UTS. For coarse pearlite, the fragmented regions were distributed randomly and fragmentation was also observed for lamellae inclined to the tensile axis, thus suggesting a shear cracking dominated fracture. With refinement of lamellae spacing, fragmentation of cementite lamellae occurred simultaneously traversing the entire width of a pearlitic colony because of the strain energy release suggesting a dominating fiber stress transfer failure mechanism. For coarser pearlite, cracks in multiple colonies got connected after reaching the UTS.

Electrospinning core-sheath piezoelectric microfibers for self-powered stitchable sensor

Abstract Owing to the limitations of two-dimensional devices such as easily damaged and airtight characteristics in practical applications, flexible fiber electronics which can narrow the gap between devices and wearable applications due to their unique stitchable function have been attracting tremendous attention nowadays. Here, this paper introduced a simple strategy for fabricating the piezoelectric microfiber with a novel core-sheath structure by directly electrospinning the poly(vinydene fluoride-trifluoroethylene) (P(VDF-TrFE)) onto the flexible conductive wire. Precise control of the fiber diameter and thickness of P(VDF-TrFE) functional layer can be achieved. Specifically, this stitchable fiber exhibits high sensitivity of 60.82 mV/N and excellent durability of 15000 cycles under positive compression, and finite element method (FEM) was carried out cooperating with practical experiment to analyze the stress and electric field distribution of piezoelectric fibers under both positive compression and bending modes through COMSOL software. The flexible stitchable fiber can bear various complex, even severe deformations such as bending and knotting, enabling itself to be woven into textile and further generate power and response when subjected to external deformation, which is of significance for the portable and wearable electronics that are expected to be breathable and comfortable. This work also offers a general and effective solution for the flexible and wearable electronic devices.

Reducing the energy capacity of the cutting of stem fodder

In the paper provided efficiency analysis different types of feed processing with purpose decreasing energy use in cutting stalk crops and creating appropriate cutting units, also study results in assescment energy use in cutting with a rectangular knife and received formulation cutting strength change, the results of a change of knife for case in cutting of prebend stalk of various sizes. Results of theoretical research of catting work, the tensile stress of the upper fiber, stresses on the blade of the knife which is necessary for the destruction of the fiber. The use of pre-bending during the cutting of cutter material reduces the cutting work in comparison with the cutting work is 201.12 N cm this is compared to the chopping 290 N cm reduces cutting performance by 35.05 percent.

Structure Tensors for Dispersed Fibers in Soft Materials

Soft tissues, such as skin, myocardium, and chordae tendineae, typically display anisotropic mechanical behavior due to their fibrous nature. In constitutive modeling, fiber families frequently are assumed to be unidirectional. Recent numerical results, however, display the need to incorporate dispersion of fiber orientation. This evidence gets supplemented by new experimental results based on high-resolution second-harmonic imaging microscopy. Generalized structure-tensor (GST) models are frequently utilized to model fiber dispersion, as they are mathematically easy to treat and demand only a little effort to implement. They can be regarded as Taylor-series expansions of the numerically more challenging angular-integration (AI) method, which encompasses a distribution of fiber orientations together with the associated fiber stress. In this work, we show how low-order GST models give rise to numerical instabilities as they show strong sensitivity with regards to the mean fiber orientation. To overcome these instabilities, we propose a different class of GST models, termed squared GST (SGST), which computes faster, is easier to implement, and converges to the AI faster than previous GST models of similar order. The SGST models promise to be adaptable to generalized problems, such as functional decomposition of fiber density as well as coupling between different fiber families. Advanced simulations with the proposed models will shed light on the complex behavior of fiber reinforced soft materials.

A quasi-incompressible and quasi-inextensible finite element analysis of fibrous soft biological tissues.

The contribution presents an extension and application of a recently proposed finite element formulation for quasi-inextensible and quasi-incompressible finite hyperelasticity to fibrous soft biological tissues and touches in particular upon computational aspects thereof. In line with theoretical framework presented by Dal (Int J Numer Methods Eng 117:118-140, 2019), the mixed variational formulation is extended to two families of fibers as often encountered while dealing with fibrous tissues. Apart from that, the purely Eulerian setting features the additive decomposition of the free energy function into volumetric, isotropic and anisotropic parts. The multiplicative split of the deformation gradient and all the outcomes thereof, e.g., unimodular invariants, are simply dispensed with in the three element formulations investigated, namely Q1, Q1P0 and the proposed Q1P0F0. For the quasi-incompressible response, the Q1P0 element formulation is briefly outlined where the pressure-type Lagrange multiplier and its conjugate enter the variational formulation as an extended set of variables. Using the similar argumentation, an extended Hu-Washizu-type mixed variational potential is introduced where the volume averaged squares of fiber stretches and associated fiber stresses are additional field variables. The resulting finite element formulation called Q1P0F0 is very attractive as it is based on mean values of the additional field variables at element level through integration over the element domain in a preprocessing step, earning the model vast utilization areas. The proposed approach is examined through representative boundary value problems pertaining to fibrous biological tissues. For all the cases studied, the proposed Q1P0F0 formulation elicits the most compliant mechanical response, thereby outperforming the standard Q1 and Q1P0 element formulations through mesh-refinement analyses. Results prompt further experimental investigations as to true deformation fields under biologically relevant loading conditions which would make the assessment of Q1P0 and Q1P0F0 more based on physical grounds.

Cholic acid and deoxycholic acid induce skeletal muscle atrophy through a mechanism dependent on TGR5 receptor.

Skeletal muscle atrophy is characterized by the degradation of myofibrillar proteins, such as myosin heavy chain or troponin. An increase in the expression of two muscle-specific E3 ligases, atrogin-1 and MuRF-1, and oxidative stress are involved in muscle atrophy. Patients with chronic liver diseases (CLD) develop muscle wasting. Several bile acids increase in plasma during cholestatic CLD, among them, cholic acid (CA) and deoxycholic acid (DCA). The receptor for bile acids, TGR5, is expressed in healthy skeletal muscles. TGR5 is involved in the regulation of muscle differentiation and metabolic changes. In this paper, we evaluated the participation of DCA and CA in the generation of an atrophic condition in myotubes and isolated fibers from the muscle extracted from wild-type (WT) and TGR5-deficient (TGR5-/- ) male mice. The results show that DCA and CA induce a decrease in diameter, and myosin heavy chain (MHC) protein levels, two typical atrophic features in C2 C12 myotubes. We also observed similar results when INT-777 agonists activated the TGR5 receptor. To evaluate the participation of TGR5 in muscle atrophy induced by DCA and CA, we used a culture of muscle fiber isolated from WT and TGR5-/- mice. Our results show that DCA and CA decrease the fiber diameter and MHC protein levels, and there is an increase in atrogin-1, MuRF-1, and oxidative stress in WT fibers. The absence of TGR5 in fibers abolished all these effects induced by DCA and CA. Thus, we demonstrated that CS and deoxycholic acid induce skeletal muscle atrophy through TGR5 receptor.

Differing Associations Between the Most Abundant Genera of the Fecal Microbiome and Sex, Fiber Intake Score, Stress, Stool Consistency and BMI in Healthy Young Adults

Abstract Objectives The objective of this secondary analysis was to characterize the relationships between the most abundant genera of the fecal microbiome and sex, fiber intake scores, stress, stool consistency and body mass index (BMI) in healthy young adults using data from the 1-week baseline period of a clinical study. Methods Data from a total of 182 participants (n = 120 female) with a mean age of 19.7 ± 0.1 y (mean ± SEM) and a healthy body mass index (BMI; 23.4 ± 0.3 kg/m2) were used. Participants self-reported stool consistency (Bristol stool score) as an estimate of gastrointestinal transit time and stress (0 = no stress to 10 = extremely stressed) daily for 1 week. The Rapid Eating Assessment-short questionnaire was completed at the end of baseline to assess intake frequency of fruits, vegetables and whole grains. The food frequency scores from the 3 food categories were summed for the fiber intake score. Microbial composition was determined by 16s rRNA sequencing of 1 stool sample provided during the baseline period. The top 15 genera, identified by % abundance of OTU reads, were selected for further analysis. Relationships between each of the genera and sex, fiber intake score, stress, stool consistency and BMI were assessed using a multiple linear regression model. Results The top 15 genera in descending % abundance were Bacteroides, Faecalibacterium, Dialister, Prevotella, Parabacteroides, Ruminococcus, Oscillospira, Sutterella, Phascolarctobacterium, Blautia, Bifidobacterium, Lachnospira, Roseburia, Eubacterium and Collinsella. The % abundance of Faecalibacterium was higher in men (P = 0.018) and was inversely related to intake of fiber containing foods (P = 0.034). Ruminococcus % abundance was inversely related to BMI (P = 0.020). Oscillospira % abundance was higher in women (P = 0.012) and decreased with increasing BMI (P = 0.024), stress (P = 0.032) and stool consistency score (i.e., looser stools; P = 0.027). Lachnospira % abundance increased with a increasing stool consistency score (P = 0.029) and with decreasing intake of fiber containing foods (P = 0.025). Conclusions These findings show differing associations between the most abundant genera of the fecal microbiome and sex, fiber intake score, stress, stool consistency and BMI in healthy young adults. Funding Sources Supported by Wakunaga of America Co., Ltd.

Numerical simulation of the fiber spinning with the viscoelastic Giesekus constitutive model

The numerical simulation of the first stage of fiber-spinning process was performed. The single-mode Giesekus model was used for polymer fiber stress calculations. Fiber profiles, longitudinal velocity, tensile stress and apparent elongational viscosity were analyzed depending on the stretch speed and the degree of anisotropy of the polymer.

Effect of moisture movement on the tensile stress–strain behavior of SHCC with alkali treated curauá fiber

This work presents the influence of the wetting and drying cycles on the tensile behavior of the strain-hardening cement-based composites reinforced with natural curaua fiber. The 3 sets of 10 dog bone shape specimens were prepared and submitted to the cycles. After 15, 30 and 45 cycles the composites were tested under tensile load in wet (5 specimens) and dry conditions (5 specimens) and compared to the reference specimens. After the cycles, composites presented strain-softening behavior. The residual fiber stress and strain at rupture were verified on fibers extracted from the composites submitted to the tensile test. This procedure was applied to the determination of the matrix environment influence on fiber properties after accelerated aging cycles. The strain-softening behavior of the composites submitted to the wetting and drying cycles was correlated with the fiber-matrix interfacial observations under a microscope and highlighted by fiber pull-out work indicators. The strain-softening behavior is strongly related to the natural fiber volume change and defibrillation induced by the moisture movement during aging.

Determination of the influence of thermo-mechanical factors on the residual stresses of cylindrical composite tubes: Experimental and computational analyses

The well-established benefits of compressive residual stresses over the fatigue lifetime constantly motivate engineers to scrutinize these trapped stresses in mechanical/civil structures. This research deals with characterization of thermal residual stresses in fiber reinforced polymer (FRP) tubes. Three important thermo-mechanical parameters, namely “cooling temperature”, “CNT reinforcement” and “tube size” are taken into account with the aim of achieving optimum design in manufacturing of FRP tubes. The work includes experimental evaluation of residual stresses coupled with developing a MATLAB programming code and performing a thorough finite element (FE) analysis. After fabricating several hybrid FRP tubes with respect to the mentioned parameters, we measured residual stresses conducting “slitting” semi-destructive method. The impact of either of parameters is then examined and some key points are suggested regarding controlling residual stress in FRP structures. The outcomes of this work suggest that slitting method can practically provide access to the in-depth distribution and through thickness of trapped stresses in the FRP laminates with a good accuracy. It is also underscored that studied parameters could play a crucial role in creation of thermal residual stresses.

Development of beneficial residual stresses in glass fiber epoxy composites through fiber prestressing

The undesired residual stresses in fiber reinforced polymer composites are developed during their manufacturing processes due to the thermal and chemical shrinkage of the polymer matrix, which negatively affect the performance of the composites. Applying tensile stress to the reinforcement fibers during the curing of the matrix can reduce or eliminate the undesired residual stresses. Furthermore, the undesired tensile residual stress within the matrix can be replaced with beneficial compressive residual stress which can improve the mechanical properties of the composites. In this study, theoretical stress analysis was performed in order to determine the value of the optimum compressive residual stress that is associated with the highest tensile strength. This value was determined based on the tensile testing result of prestressed composites with a 40% fiber volume fraction. For the composites with different fiber volume fractions, a new approach was introduced to estimate the optimum fiber prestressing level which generates the optimum compressive residual stress within the matrix and consequently, the highest tensile strength can be achieved. In order to validate this approach experimentally, prestressed composites with 25 and 30% fiber volume fraction were prepared by applying the estimated optimum fiber prestressing levels during curing of matrix and tensile testing was performed. The result of the stress analysis showed that the value of the optimum compressive residual stress corresponding to the highest tensile strength is 2.5 MPa approximately. The tensile testing results confirmed the validity of the new approach in estimating the optimum fiber prestressing level for the composites with different fiber volume fractions. For both prestressed composites with 25 and 30% fiber volume fraction, the highest tensile strength was achieved when the theoretically estimated optimum fiber prestressing level was applied to the fibers during the curing of the matrix.

Microstructure and Mechanical Properties of Platinum Fiber Fabricated by Unidirectional Solidification

The microstructure and mechanical properties of platinum (Pt) fibers fabricated by unidirectional solidification using the alloy-micro-pulling-down (A-μ-PD) method were investigated using a Universal Testing Machine and Electron Backscattered Diffraction (EBSD). The Pt fiber fabricated at a growth rate of 10 mm/min was composed of relatively large grains with <100> crystal orientation along the growth direction. The crystal orientation was consistent with the easy axis of the crystal growth on the face-centered-cubic (f.c.c.) structure. On the other hand, the adjacent grains of the Pt fiber fabricated at 50 mm/min were randomly oriented owing to a faster growth rate. In tensile tests, the Pt fibers fabricated by the A-μ-PD method indicated extremely different stress–strain curves compared to the commercial Pt wire. The maximum tensile stress of the Pt fiber reached ~100 MPa, and the Pt fiber ruptured after 58% nominal strain.