Fiber Stress Research Articles

The maternal gut microbiome during pregnancy and offspring allergy and asthma

Environmental exposures during pregnancy that alter both the maternal gut microbiome and the infant's risk of allergic disease and asthma include a traditional farm environment and consumption of unpasteurized cow's milk, antibiotic use, dietary fiber, and psychosocial stress. Multiple mechanisms acting in concert may underpin these associations and prime the infant to acquire immune competence and homeostasis following exposure to the extrauterine environment. Cellular and metabolic products of the maternal gut microbiome can promote the expression of microbial pattern recognition receptors, as well as thymic and bone marrow hematopoiesis relevant to regulatory immunity. At birth, transmission of maternally derived bacteria likely leverages this in utero programming to accelerate postnatal transition from a TH2- to TH1- and TH17-dominant immune phenotype and maturation of regulatory immune mechanisms, which in turn reduce the child's risk of allergic disease and asthma. Although our understanding of these phenomena is rapidly evolving, the field is relatively nascent, and we are yet to translate existing knowledge into interventions that substantially reduce disease risk in humans. Here, we review evidence that the maternal gut microbiome impacts the offspring's risk of allergic disease and asthma, discuss challenges and future directions for the field, and propose the hypothesis that maternal carriage of Prevotella copri during pregnancy decreases the offspring's risk of allergic disease via production of succinate, which in turn promotes bone marrow myelopoiesis of dendritic cell precursors in the fetus.

Measurement of Residual Stress in Silicon Carbide Fibers of Tubular Composites Using Raman Spectroscopy

Silicon carbide (SiC) fiber-reinforced ceramic matrix (SiCf/SiCm) composites have been identified as potential materials for nuclear fuel cladding. These composites are fabricated by braiding the SiC fibers around a mandrel into a cylindrical tube and then densifying this preform with SiC matrix using chemical vapor infiltration (CVI). However, during this fabrication process residual stresses develop in the composite, either due to the mechanical braiding process or due to high temperature CVI deposition of the SiC matrix phase. Micro-Raman spectroscopy has been employed to measure the residual stress in the SiC fibers at various stages of the fabrication process. Samples of the composite were analyzed after mechanical braiding and at 33%, 66% and 100% CVI densification of the composites. Raman spectra obtained at the above stages revealed significant band shifts of the SiC peaks and these peak-shift corresponded to -716 MPa of residual stress following the braiding process and -1075 MPa after the densification process. Interestingly, the Raman spectra also revealed carbon bands whose origin was traced to the presence of nanoscale turbostratic graphite throughout the nanograined SiC microstructure.

Study on Mechanical Bearing Strength and Failure Modes of Composite Materials for Marine Structures

With the gradual application of composite materials to ships and offshore structures, the structural strength of composites that can replace steel should be explored. In this study, the mechanical bearing strength and failure modes of a composite-to-metal joining structure connected by mechanically fastened joints were experimentally analyzed. The effects of the fiber tensile strength and stress concentration on the static bearing strength and failure modes of the composite structures were investigated. For the experiment, quasi-isotropic [45°/0°/–45°/90°]2S carbon fiber-reinforced plastic (CFRP) and glass fiber-reinforced plastic (GFRP) specimens were prepared with hole diameters of 5, 6, 8, and 10 mm. The experimental results showed that the average static bearing strength of the CFRP specimen was 30% or higher than that of the GFRP specimen. In terms of the failure mode of the mechanically fastened joint, a cleavage failure mode was observed in the GFRP specimen for hole diameters of 5 mm and 6 mm, whereas a net-tension failure mode was observed for hole diameters of 8 mm and 10 mm. Bearing failure occurred in the CFRP specimens.

Determination of stresses and dynamic coefficients when testing railway overpasses

This paper presents some results of instrumental measurements of dynamic coefficients and fiber stresses of reinforced concrete girder spans of railway overpasses under mobile load. The results obtained can be used for further monitoring of similar structures on the main railway lines of the Republic of Kazakhstan, to identify damage in the structures of bridges.

Influence of structural and material property uncertainties on biomechanics of intervertebral discs - Implications for disc tissue engineering

This study investigated how variations of structural and material properties of human intervertebral discs (IVDs) affect the biomechanical responses of the IVDs under simulated physiological loading conditions using a stochastic finite element (SFE) model. An SFE method, which combined an anatomic FE model of human lumbar L3-4 segment and probabilistic analysis of its structural and material properties, was used to generate a dataset of 500 random disc samples with varying structural and material properties. The sensitivity of the biomechanical responses, including intervertebral displacements/rotations, intradiscal pressures (IDP), fiber stresses and matrix strains of annulus fibrosus (AF), were systematically quantified under various physiological loading conditions, including a 500N compression and 7.5Nm moments in the 3 primary rotations. Significant variations of the IDPs, IVD displacements/rotations, and stress/strain distributions were found using the dataset of 500 ramdom disc samples. Under all the loading conditions, the IDPs were positively correlated with the Poisson's ratio of the NP (r=0.46 to 0.75, p=0.004-0.001) and negatively with the Young's modulus of the annulus matrix (r=-0.48 to -0.65, p=0.003-0.001). The primary intervertebral rotations were significantly affected by the Young's modulus of the annulus matrix (r=-0.44 to -0.71, p=0.001-0.032) and the orientations of the annular fibers (r=-0.45 to -0.69, p=0.001-0.029). The heterogeneity of structures and material properties of the IVD had distinct effects on the biomechanical performances of the IVD. These data could help improve our understanding of the intrinsic biomechanics of the IVD and provide references for optimal design of tissue engineered discs by controlling structural and material properties of the disc components.

A microstructurally motivated constitutive description of collagenous soft biological tissue towards the description of their non-linear and time-dependent properties

A versatile constitutive model for load-carrying soft biological tissue should incorporate salient microstructural deformation mechanisms and be able to reliably predict complex non-linear viscoelastic behavior. The advancement of treatment and rehabilitation strategies for soft tissue injuries is inextricably linked to our understanding of the underlying tissue microstructure and how this defines its macroscopic material properties. Towards this long-term objective, we present a generalized multiscale constitutive framework based on a novel description of collagen, the most mechanically significant extracellular matrix protein. The description accounts for the gradual recruitment of undulated collagen fibrils and introduces proteoglycan mediated time-dependent fibrillar sliding. Crucially, the proteoglycan deformation allows for the reduction of overstressed fibrils towards a preferential homeostatic stress. An implicit Finite Element implementation of the model uses an interpolation strategy towards collagen fiber stress determination and results in a memory-efficient representation of the model. A number of test cases, including patient-specific geometries, establish the efficiency of the description and demonstrate its ability to explain qualitative properties reported from macroscopic experimental studies of tendon and vascular tissue.

Simulation and burst validation of 70 MPa type IV hydrogen storage vessel with dome reinforcement

The dome reinforcement (DR) technology was studied to reduce the amount of carbon fiber of the type IV hydrogen storage vessel in this paper. Firstly, the influence of the angle and thickness of the dome reinforcement part on the stress distribution of the dome section is studied by finite element analysis. Secondly, the weight reduction of carbon fiber composite layer is studied based on the dome reinforcement model. The strain-based Hashin progressive damage model is used to predict the burst pressure and burst mode with user-defined material subroutine (UMAT) of ABAQUS. Finally, the dome reinforcement technology is further verified in comparison with non-dome reinforcement by burst tests. The results show that the progressive damage model can effectively represent matrix cracking and fiber fracture, and the predicted burst pressure and mode is consistent with the test results. The fiber stress near the equator of the dome section affects the burst mode, and the smaller the angle of dome reinforcement parts, the better the reinforcing effect, and the dome reinforcement technology can help to improve the fiber damage state at the dome, transfer the maximum stress to the cylinder section of the vessel, and ensure the burst mode to be a safe mode. Also, it can help to reduce the consumption of carbon fiber by up to 5.5% in composite material.

β-Glucans as Dietary Supplement to Improve Locomotion and Mitochondrial Respiration in a Model of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a severe X-linked neuromuscular childhood disorder that causes progressive muscle weakness and degeneration. A lack of dystrophin in DMD leads to inflammatory response, autophagic dysregulation, and oxidative stress in skeletal muscle fibers that play a key role in the progression of the pathology. β-glucans can modulate immune function by modifying the phagocytic activity of immunocompetent cells, notably macrophages. Mitochondrial function is also involved in an important mechanism of the innate and adaptive immune responses, owing to high need for energy of immune cells. In the present study, the effects of 1,3-1,6 β-glucans on five-day-old non-dystrophic and dystrophic (sapje) zebrafish larvae were investigated. The effects of the sonication of β-glucans and the dechorionation of embryos were also evaluated. The results showed that the incidence of dystrophic phenotypes was reduced when dystrophic embryos were exposed to 2 and 4 mg L−1 of 1,3-1,6 β-glucans. Moreover, when the dystrophic larvae underwent 8 mg L−1 treatment, an improvement of the locomotor performances and mitochondrial respiration were observed. In conclusion, the observed results demonstrated that 1,3-1,6 β-glucans improve locomotor performances and mitochondrial function in dystrophic zebrafish. Therefore, for ameliorating their life quality, 1,3-1,6 β-glucans look like a promising diet supplement for DMD patients, even though further investigations are required.

Fiber break model for tension-tension fatigue of unidirectional composites

Damage progression in unidirectional (UD) composites in tension-tension fatigue is vital to understanding fatigue in more complex laminates and loading conditions. We therefore developed the UD fatigue model that considers fiber breaks, fiber-matrix debond growth, fiber fatigue as well as interactions of these damage modes. The contribution of each mode of damage in fatigue is assessed and those that dominate fatigue damage are identified. The model accounts for Weibull statistics of fiber strength and stress redistribution around fiber breaks. The predictions for fatigue loading indicate a significantly higher density of fiber breaks and clusters compared to quasi-static loading at the same stress level. The model predicts S–N curves in pure uniaxial tension-tension fatigue loading and does not consider stress concentrations caused near the grips; the predictions therefore tend to overpredict fatigue life compared to experimental S–N curves available in the literature. The model has potential to be developed for different loading conditions.

Residual force enhancement is reduced in permeabilized fiber bundles from mdm muscles

Residual Force enhancement (RFE) is defined as the increase in steady state force after active stretch compared with force after isometric contraction at the same final length. Recent studies have demonstrated a pivotal role for titin in RFE. In myofibrils stretched beyond overlap of thick and thin filaments, Ca2+ activated myofibrils had a higher titin-based force and a steeper increase with force with stretch than passively stretched myofibrils at the same average sarcomere length. These results suggest higher titin-based stiffness in active myofibrils, perhaps due to N2A titin-actin interactions in active wild type (WT) muscle. Mdm mice carry a small deletion in titin that includes 53 amino acids in Ig83 in the N2A region. It has been proposed that the mdm mutation prevents N2A titin-actin interactions so that active mdm muscles are more compliant than WT muscles. This decrease in active muscle stiffness should be associated with a reduction in RFE. Based on this rationale, we investigated RFE in permeabilized soleus (SOL) and extensor digitorum longus (EDL) fiber bundles from 20-30 day old mdm mice (n=5), harvested at a young age to diminish the effects of degeneration and regeneration, and 30-60 day old WT mice (n=5). Contractile stress and RFE of EDL (mdm n=19 and WT n=20) and SOL fibers (WT n=19 and mdm n=16) was analyzed using JMP and Graph pad (PRISM) software. Statistics included Shapiro-Wilk (normality), Levene's and Bartlett (homogeneity of variances), Welch's one-way ANOVA (unequal variances), Dunnett's T3 (multiple comparisons), and T-tests with Welch's correction (unpaired). To investigate differences in RFE between genotypes, we performed isometric contractions, as well as active and passive stretch from an average sarcomere length of 2.6 - 3.0 µm on each fiber. This stretch amplitude, within the physiological range, resulted in no observable breakage or slipping of fibers during experiments. We predicted that mdm fiber bundles would show reduced RFE compared to WT fibers. Contractile stress when activated at 2.6 µm was significantly greater in WT EDL (Welch's one-way ANOVA; P<0.05) bundle and SOL (Welch's one-way ANOVA; P<0.05) compared to fiber bundles. Our results showed that mdm muscles exhibit significantly lower RFE than WT for both SOL (Welch's one-way ANOVA; P<0.0001) and EDL (Welch's one-way ANOVA; P<0.0001). This result is consistent with previous observations in single myofibrils and intact muscles. The data support the hypothesis that titin contributes to RFE. We suggest that RFE is reduced in mdm muscles due to impaired Ca2+ dependent titin-actin interactions, resulting from the small deletion in titin that includes 53 amino acids in Ig83 in the N2A region.

Proteomic analysis of the ascending aorta in a hamster model of BAV disease

Bicuspid aortic valve (BAV) is the most prevalent human congenital cardiac malformation, which predisposes to ascending aortic dilatation (AD). Disease predisposition probably results from a congenital defect leading to anomalies in both, the morphology of the valve and the histology of the ascending aorta. Altered hemodynamics caused by the abnormal valve morphology would accelerate aortic media degeneration. AD in BAV patients results from medial smooth muscle cell (SMC) apoptosis probably caused by defective cell-matrix adhesion. Alterations of the TGFβ pathway seem to be central in disease initiation and progression, affecting extracellular matrix homeostasis. However, currently there are neither clear pathophysiological mechanisms nor effective biomarkers of disease predisposition or progression.The only spontaneous animal model of BAV disease consists of an inbred (T) strain of Syrian hamsters with a high (40%) incidence of BAV. Although AD has never been described in this model, animals of the T strain show significant SMC apoptosis and altered elastic lamina in the aortic media, irrespective of aortic valve morphology. We reasoned that analysing differentially expressed proteins in the aortic wall of animals with normal aortic valve (TAV) of the T strain compared to a control strain would inform about 1) the validity of the T strain as a model for BAV aortopathy predisposition; 2) the congenital origin of AD associated to BAV; 3) the proteins involved in AD etiology, independent of the effect of hemodynamics.To this aim, we compared the proteome of the ascending aorta of animals with TAV of the T strain (n=6) and a control outbred strain (n=6) by three independent experiments of quantitative proteomics (ESI-Quadrupole-Orbitrap LFQ). The analysis yielded expression data for over 1,954 proteins. Of these, 57 proteins (2.9%) showed concordant expression in at least two of the three experiments and were deregulated over 2.6-fold.Fourteen of these 57 proteins (24.6%) were previously proposed as AD biomarkers in patients. After database search, the 57 selected proteins were found to significantly interact (p<0.05 following FDR adjustment) within 16 molecular pathways and 27 biological processes on the STRING website. Most of these pathways and processes were relevant to AD pathophysiology, of note are the TGFβ non-canonical pathways (10/57; 17.5%; p=0.043), programmed cell death (14/57; 24.6%; p=3.5e-4), cell adhesion (15/57; 26.3%; p=2.4e-4), supramolecular fiber organization (9/57; 15.8%; p=3.8e-4) and stress fiber assembly (2/57; 3.5%; p=0.037).These results were obtained comparing the proteomes of aortas of individuals with TAV from an affected and a control strain. Thus, genetic rather than hemodynamic factors explain the structural abnormalities of the ascending aorta in this model. We propose that the T strain is an appropriate model for AD predisposition, as it replicates the ethiophysiological processes observed in patients. Deep study of our ascending aorta proteome analysis may uncover new molecular players and markers associated with aortopathy predisposition and progression.

The Constitutive Model of a Unidirectional SiC Fiber-Reinforced Titanium Matrix Composite During Spectrum Loading

An approach to simulate the constitutive model of a unidirectionally SiC fiber-reinforced titanium matrix composite during spectrum loading was developed in this paper. Based on the assumption that there is a microcrack in the matrix and the maximum shear stress criterion, the debonding length and the distribution of interfacial slip zone under spectrum loading were derived. The stress at a loading point was divided into four stages including crack opening section, positive slip zone, reverse slip zone, and bond zone. Based on the partial crack shear-lag model, the stress of fiber and matrix in the four stages was derived, and the constitutive model of the composite under spectrum loading was established. At last, the effects of different damages on the constitutive model and interfacial debonding zone of a unidirectionally SiC fiber-reinforced titanium matrix composite were investigated.

Effect of nickel electroplating followed by a further copper electroplating on the micro-structure and mechanical properties of high modulus carbon fibers

The nickel electroplating followed by a further copper electroplating process was conducted on high modulus carbon fibers (HMCFs), and the HMCFs were oxidized in nitric acid prior to the Ni-plating process. Effect of the electroplating process on the microstructure and mechanical properties of HMCFs was investigated. Uniform nickel particles were observed on the surfaces of Ni-plated HMCFs and fiber diameter increased from 5.0 μm to 6.1 μm. With a further Cu-electroplating process, the fiber diameter continued increasing to 7.5 μm. The Ni-plating process resulted in increased surface roughness, whereas the surface RMS and Ra values dropped significantly after the Cu-plating process. Owing to the Ni-plating treatment, the relative content of carbon element on fiber surfaces decreased from 96.54 % to 36.74 %. After a further Cu-plating process, the relative content of Cu element on HMCF surfaces was as high as 54.01 %. The electroplating process resulted in decreased tensile modulus from 415.71 GPa to 407.71 GPa. By contrast, the tensile strength of electroplated HMCFs increased by 1.1 % due to the reduction of fiber defects and stress concentration. Results also showed that both the Ni-plating and Cu-plating process could lead to significant decreases in the values of electrical resistance and resistivity.

Prediction of biomechanical responses of human lumbar discs - a stochastic finite element model analysis

Background Accurate biomechanical investigation of human intervertebral discs (IVDs) is difficult because of their complicated structural and material features. Aim To investigate probabilistic distributions of the biomechanical responses of the IVD by considering varying nonlinear structural and material properties using a stochastic finite element (FE) model. Methods A FE model of a L3-4 disc was reconstructed, including the nucleus pulposus (NP), annular matrix and fibers. A Monte Carlo method was used to randomly generate 500 sets of the nonlinear material properties and fiber orientations of the disc that were implemented into the FE model. The FE model was analyzed under seven loading conditions: a 500 N compressive force, a 7.5Nm moment simulating flexion, extension, left-right lateral bending, and left-right axial rotation, respectively. The distributions of the ranges of motion (ROMs), intradiscal pressures (IDP), fiber stresses and matrix strains of the disc were analyzed. Results Under the compressive load, the displacement varied between 0.29 mm and 0.76 mm. Under the 7.5Nm moment, the ROMs varied between 3.0° and 6.0° in primary rotations. The IDPs varied within 0.3 MPa under all the loading conditions. The maximal fiber stress (3.22 ± 0.64 MPa) and matrix strain (0.27 ± 0.12%) were observed under the flexion and extension moments, respectively. Conclusion The IVD biomechanics could be dramatically affected by the structural and material parameters used to construct the FE model. The stochastic FE model that includes the probabilistic distributions of the structural and material parameters provides a useful approach to analyze the statistical ranges of the biomechanical responses of the IVDs.

Visco-thermo-elastic Simulation Approach For Prediction of Cure-induced Residual Stresses in Fiber Reinforced Composites

Liquid composite molding (LCM) has established as a high quality manufacturing process for fiber reinforced composite structures. In order to reduce cycle times significantly, novel fast curing matrix resins are being introduced into series production. These put high requirements on process control and part reproducibility. Problems that may be encountered in this context involve process-induced distortion and surface waviness resulting from anisotropic and cure-dependent material properties. Numerical simulations represent a powerful approach to avoid the use of costly trial-and-error methods. For this reason, a simulation approach is being developed which aims at the prediction of residual stresses and accompanying effects on different length scales. Based on a resin characterization comprising reaction kinetics, cure-dependent relaxation modulus as well as thermal expansion and pressure-dependent chemical shrinkage, a generalized MAXWELL model is selected to describe the process-related mechanical behavior of the thermoset. Taking into account the influence of the process parameters on the resin properties enables a detailed analysis of process-property-relationships. By this, the developed simulation approach offers the possibility of a comprehensive analysis of both local and global process-induced phenomena and hence prevention of flaws.

A new model characterizing the fatigue delamination growth in DCB laminates with combined effects of fiber bridging and stress ratio

For composite multidirectional laminates widely used in engineering, there is still no effective model to characterize the fatigue delamination behavior with the combined effects of fiber bridging and stress ratio. A new fatigue delamination model was thus proposed in this study to deal with this problem. The model was established based on the fatigue driving force and fatigue delamination resistance, which characterized the effects of stress ratio and fiber bridging, respectively. A series of mode I fatigue delamination tests on composite multidirectional laminates were conducted under various stress ratios (0.1, 0.3 and 0.5) and different pre-crack lengths. Both the experimental results of this study and public fatigue data from laminates with other materials and various interfaces showed that a single master curve with a narrow band can be obtained by using the new model for all fatigue data under different stress ratios and fiber bridging effects. In addition, the determined model parameters obtained from fatigue data under specific stress ratios were used for predicting the fatigue delamination behavior under other stress ratios. Good agreements between the predictions and experimental results can be achieved, which further indicated the model’s applicability.

Fatigue Behavior of Aramid Fiber Reinforced Rubber Matrix Sealing Composites

This paper presents an experimental and theoretical study of aramid fiber reinforced rubber sealing composites (AFRC). The fatigue performance of AFRC with different stress amplitudes and fiber mass fractions was tested, and the residual strength of AFRC after different fatigue cycles was conducted. The fracture morphology of AFRC samples with different fiber mass fractions, stress amplitudes and fatigue cycles were observed by scanning electron microscope (SEM), and the fatigue damage modes of AFRC were discussed. The experimental results were analyzed and predicted by fatigue life model, residual stiffness model and residual strength model. It was found that the results predicted by theoretical model agreed well with that measured by experimental results, which indicated that the proposed model gave an advantage in evaluating the fatigue behavior of AFRC without further morphological experiments.

Relationship of Fiber Intake, Stress Level, Physical Activity with Blood Pressure of Pre Elderly and Elderly in Lubang Buaya and Kampung Tengah

High blood pressure is defined as systolic blood pressure that is equal to or above 140 mm Hg or diastolic blood pressure equal to or above 90 mm Hg (JNC VIII, 2013). In 2018, the prevalence of hypertension in Indonesia is based on the characteristics of the age 45-75 years and above with an average of 58.33% (Riskesdas, 2018). The aimed of this study was to determine of fiber intake, stress levels, and physical activity with blood pressure in pre elderly and elderly at RW 03 Lubang Buaya and RW 09 Kampung Tengah, East Jakarta. This research method is observational with cross sectional approach followed by 80 respondents with simple random sampling technique Data collection was taken, namely blood pressure measurement using a Sphygmomanometer, fiber intake using the Food Recall form 2 x 24 hours (Weekend and Weekday), stress levels with the DASS-14 questionnaire, and physical activity with the Baecke questionnaire. Data processing was analyzed by univariate and bivariate using Chi-Square test. The results of bivariate analysis with chi-square test showed a significant relationship between fiber intake (p value = 0.007), stress level (p value = 0,000), and physical activity (p value = 0.022) with blood pressure. There is a relationship between fiber intake, stress level, and physical activity with blood pressure in the elderly and elderly in Lubang Buaya and Kampung Tengah.

Thermal-mechanical-oxidation coupled first matrix cracking stress model for fiber reinforced ceramic-matrix composites

In this work, we research the combined influence of residual thermal stress, interface debonding and oxidation, and temperature on first matrix cracking stress of fiber reinforced ceramic-matrix composites (FRCMCs). Based on the shear-lag theory, the axial stress distribution of matrix and fiber considering interface oxidation and residual thermal stress is given, and we propose a criterion for interface debonding. Then, a thermal-mechanical-oxidation coupled first matrix cracking stress model is proposed for FRCMCs, according to energy balance approach. Reasonable agreement is obtained between the model predictions and available experimental results of SiCf/RBSN and SiCf/SiC composites. Moreover, the effects of some key material parameters and oxidation time on first matrix cracking stress are analyzed quantitatively by the model. This research offers a quantitative tool for evaluating and predicting the matrix cracking behavior of FRCMCs under thermal-mechanical-oxidation coupled environment.

Prediction of stress–strain response of unidirectional ceramic matrix composites under arbitrary loading and unloading

ABSTRACT The constitutive response of ceramics matrix composites (CMCs) under arbitrary loading and loading was studied. A method for determining the distribution of slip regions under arbitrary loading was proposed based on the shear lag model and slip law. Furthermore, a method for judging the closure of the matrix cracks was given based on the assumption that the fibre strain consists of the elastic strain and the pseudo-plastic strain of CMCsss. The stress–strain response of CMCs was obtained in form of matrices based on the distribution of the slip regions instead of the integration of fibre stress in each slip region. The simulated results show that the proposed method improves the computing efficiency greatly compared with previous approaches. Additionally, the simulated results agree well with experimental data, proving that the method proposed in this paper is credible.