Single Fiber Strength Research Articles

A computationally-efficient micromechanical model for the fatigue life of unidirectional composites under tension-tension loading

Failure of fibre-reinforced composites is affected by fatigue, which increases the challenge in designing safe and reliable composite structures. This paper presents an analytical model to predict the fatigue life of unidirectional composites under longitudinal tension-tension. The matrix and fibre-matrix interface are represented through a cohesive constitutive law, and a Paris law is used to model fatigue due to interfacial cracks propagating from fibre-breaks. The strength of single-fibres is modelled by a Weibull distribution, which is scaled hierarchically though a stochastic failure analysis of composite fibre-bundles, computing stochastic S-N curves of lab-scaled specimens in less than one minute. Model predictions are successfully validated against experiments from the literature. This model can be used to reduce the need for fatigue testing, and also to evaluate the impact of constituent properties on the fatigue life of composites.

Preparation of polyetherimide nanoparticles on carbon fiber surface via evaporation induced surface modification method and its effect on tensile strength and interfacial shear strength

In this work, polyetherimide (PEI) nanoparticles were prepared on carbon fiber (CF) surfaces via an evaporation-induced surface modification method. Scanning electron microscopy analysis revealed that the average diameter of the PEI nanoparticles linearly increased with increasing PEI concentration. This finding indicated that the nanoparticle size on the CF surface could be controlled by changing the PEI concentration used in the surface modification process. The possible formation mechanism of the PEI nanoparticles on the CF surfaces was also investigated by cross-section observation of CF using field-emission scanning electron microscopy (FE-SEM). In addition, the single fiber strength and interfacial shear strength between the CFs and epoxy resin were observed to increase after the surface modification. The interfacial shear strength (IFSS) results between treated CF before and after heating show that the presence of PEI nanoparticles had a great influence on IFSS. At a PEI concentration of 0.2%, the IFSS value reached its maximum value, 44.02% more than that of desized CF.

The use of chitosan/PLA nano-fibers by emulsion eletrospinning for periodontal tissue engineering

Objective: In this study, nanofibrous scaffolds base on pure polylactic acid (PLA) and chitosan/PLA blends were fabricated by emulsion eletrospinning. By modulating their mechanical and biological properties, cell-compatible and biodegradable scaffolds were developed for periodontal bone regeneration.Methods: Pure PLA and different weight ratios of chitosan nano-particle/PLA nano-fibers were fabricated by emulsion eletrospinning. Scanning electron microscope (SEM) was performed to observe the morphology of nano-fibers. Mechanical properties of nano-fibers were tested by single fiber strength tester. Hydrophilic/hydrophobic nature of the nano-fibers was observed by stereomicroscope. In vitro degradation was also tested. Cells were seeded on nano-fibers scaffolds. Changes in cell adhesion, proliferation and osteogenic differentiation were tested by MTT assay and Alizarin Red S staining. Reverse transcription-polymerase chain reaction (RT-PCR) assay was used to evaluate the expression of (Toll-like receptor 4) TLR4, IL-6, IL-8, IL-1β, OPG, RUNX2 mRNA.Results: It is shown that the mean diameter of nano-fibers is about 200 nm. The mean diameter of chitosan nano-particles is about 50 nm. The combination of chitosan nano-particles enhanced the mechanical properties of pure PLA nano-fibers. By adding a certain amount of chitosan nano-particles, it promoted cell adhesion. It also promoted the osteogenic differentiation of bone marrow stem cells (BMSCs) by elevating the expression of osteogenic marker genes such as BSP, Ocn, collagen I, and OPN and enhanced ECM mineralization. Nonetheless, it caused higher expression of inflammatory mediators and TLR4 of human periodontal ligament cells (hPDLCs).Conclusion: The combination of chitosan nano-particles enhanced the mechanical properties of pure PLA nano-fibers and increased its hydrophilicity. Pure PLA nano-fibers scaffold facilitated BMSCs proliferation. Adding an appropriate amount of chitosan nano-particles may promote its properties of cell proliferation and osteogenic differentiation. The higher expression of inflammatory mediators caused by nano-fibers may be regulated via TLR4 pathway.

Ecofriendly treatment of aloe vera fibers for PLA based green composites

Green Composites (Biocomposites) comprising of lignocellulosic fibers are low cost sustainable materials having huge potential to replace petroleum derived commodity and engineering plastics. In order to improve the interfacial interaction with the matrix, lignocellulosic fibers are subjected to fiber surface modification. The present research endeavor aims to explore the use of ecofriendly fiber surface treatment in order to limit the environmental hazards of conventionally used chemical treatments. Fiber surface modification of Aloe Vera fibers prior to their incorporation into PLA based biocomposites was done using an aqueous solution of sodium bicarbonate (10% (w: v)). FTIR spectroscopy, thermal analysis, lignocellulosic composition, single fiber strength and fiber morphology were examined to ascertain the effect of varying treatment time (24, 48, 72, 120 and 168 hours) on the fiber characteristics. The biocomposite test specimens were developed using Extrusion-Injection molding process. An optimum fiber treatment time of 72 hours exhibited highest improvement in tensile, flexural and compressive behavior of the developed biocomposites. The biocomposites incorporating treated (72 hours) Aloe Vera fibers exhibited 104.9% higher impact strength as compared to neat PLA. Hence, the use of sodium bicarbonate treatment for lignocellulosic-fiber surface modification ensures greener and safer processing of biocomposites without compromising their mechanical properties.

Statistical approach to tensile strength of abaca single fiber

Statistical approach to tensile strength of abaca single fiber

Modeling the temperature and test rate dependent fracture strength of zirconia and alumina single crystal fibers

Abstract In this paper, based on the Griffith fracture theory, the slow crack growth theory and the temperature-dependent fracture surface energy model, a temperature and test rate dependent fracture strength model for zirconia and alumina single crystal fibers was established. As a comparison, the other one based on the temperature-dependent free surface energy was also deduced and discussed. These models were verified by comparison with the experimental data of the two types of ceramic single crystal fibers. Good agreement between the model predictions and the experimental data was obtained. Moreover, based on the present model and the existing material parameters, the influencing factor analysis for these ceramic single crystal fibers were systematically conducted. Some new findings regarding their high temperature fracture strengths were provided for the first time.

Size scaling of failure strength with fat-tailed disorder in a fiber bundle model.

We investigate the size scaling of the macroscopic fracture strength of heterogeneous materials when microscopic disorder is controlled by fat-tailed distributions. We consider a fiber bundle model where the strength of single fibers is described by a power law distribution over a finite range. Tuning the amount of disorder by varying the power law exponent and the upper cutoff of fibers' strength, in the limit of equal load sharing an astonishing size effect is revealed: For small system sizes the bundle strength increases with the number of fibers, and the usual decreasing size effect of heterogeneous materials is restored only beyond a characteristic size. We show analytically that the extreme order statistics of fibers' strength is responsible for this peculiar behavior. Analyzing the results of computer simulations we deduce a scaling form which describes the dependence of the macroscopic strength of fiber bundles on the parameters of microscopic disorder over the entire range of system sizes.

Preliminary Study on the Exploitation of Chinese Fevervine Fibre

In this paper, the Rubiaceae Chinese Fevervine stem as raw material was used, with pool dipping, sodium hydroxide scouring and acid dipping as degumming methods, to produce Chinese Fevervine fibre (CF fibre). The components and structure of the fibre were tested and indicated with the relative component test method, infrared spectroscopy and a scanning electron microscope. The CF fibre produced possesses good spinnability: cellulose content 82.82%, specific gravity 1.323 g/cm3, length 41 mm, diameter 40.29 μm, linear density 2.93 tex, single fibre strength 55.4 cN, tenacity 18.9 cN/dtex, and break elongation 2.87%. The results show that CF fibre is natural cellulose fibre, whose components is similar to those of flax.

Curing behaviour of unsaturated polyester resin and interfacial shear stress of sugar palm fibre

Studies on the effect of cobalt of unsaturated polyester resin and the effect of treated sugar palm fibre with sodium hydroxide on single fibre strength and interfacial shear strength (IFSS) are presented in this paper. 1% of methyl ethyl ketone peroxide was used as the initiator, while cobalt of variable percentages (0.05%, 0.1%, 0.2%, 0.4 %,0.6%, 0.8% and 1%)was used as the hardener. The effects on glass transition and exothermic reaction of unsaturated polyester were studied for post curing temperature determination using differential scanning calorimetry by heating the samples at 10oC/min heating rate from 30oC to 120oC with flowing of purge nitrogen gas atmosphere . For the single fibre test and IFSS, the treatment was carried out using sodium hydroxide solution with 1% concentration for one hour soaking time. Based on the optimisation percentage of cobalt, it was found that the higher the percentage of cobalt, the faster the sample tested to gel and cured. Treated sugar palm fibre exhibited better single fibre strength and IFSS between the matrices compared to untreated fibre due to the effectiveness of the alkali treatment. This can be attributed to the rearrangement of fibrils along the direction of tensile force and the removal of the coating layer and impurities after the alkaline treatment.

Structure and properties of ethylene-tetrafluoroethylene fibers fabricated by melt spinning

Ethylene-tetrafluoroethylene (ETFE) fibers were fabricated by a single-screw melt spinning machine at different drawing roll speed ratios and different drawing roll temperatures. Thermogravimetric analyzer, differential scanning calorimetry, X-ray diffraction (XRD), digital fiber sound velocimeter and single fiber strength testers were used to discuss the impacts of spinning processes on the structure and performance of ETFE fibers. The results indicated that four different fibers showed a similar melting temperature at around 257℃. XRD results revealed that the largest crystallinity of four ETFE fibers was 41.1%. As the drawing temperature increased, the crystallinity of ETFE fibers decreased and the grain size increased. The breaking strength of four as-spun ETFE fibers reached up to 1.12 cN/dtex. The minimum shrinkage of ETFE fibers at 200℃ was 7%, and it was only 1% at most below 150℃. The maximum creep strain of ETFE fibers was 6% when the loading capacity was 20% of the breaking strength at room temperature and ETFE fibers had a high recovery ratio of >90% after the load was removed. Moreover, ETFE fibers showed exceptional corrosion resistance and good performance of irradiation resistance.

Palmyra Fiber as Additional Materials on Solid Concrete Brick of Aggregate

Abstract The use of waste as an additional material on the building work was increasingly actively developed, such as straw, styrofoam, bagasse, cow manure. The key drivers of the use of waste is the potential for waste is increasing, due to the depletion of nonrenewable resources. Papyrus rod diameter 60 cm, length 30 meters, has a volume of 5,652m3 as well as the edges of the Rods that can be used for construction with a thickness of 3 cm has a volume 0,942m3, Pith and fiber volume content of the stem 4,71m3/rod, then in one rod, there are 2 to 3 bunches each fruit bunches yield as much as 20 to 30 items for one harvest, by weight of fruit fiber 101.2 gram / fruit, Fiber characteristics are round and smooth is expected to reduce cracks in solid concrete brick and also can reduce the use of sand. This study aims to determine the compressive strength of the composition of the additional material of Rods fiber content and Fiber of palmyra fruit with a percentage 3%, 6% and 9%, mixing ratio; 1 cement and 5 sand in the manufacture of solid concrete brick. Rods fiber content used the average Ø1,031mm with a tensile strength of single fiber 39,305N / cm and fruit fiber to an average value Ø0,40mm with a tensile strength of single fiber 33,691N / cm. Making test specimen with a length of 20cm, width 10cm and thick 8cm. The test results of compressive strength after 14 days with the lowest value at 3% of additional material combination of fiber content of 6% fiber stem and fruit by 70,384Kg/cm² with a water content of 15,254% In weight position 2,935Kg as well as the highest value on the combination of additional material 0% rods fiber content and 3% fruit fiber by 98,821Kg/cm² with a water content of 15,031% In weight position 3,058Kg. While N (without additional material) with a compressive strength below the average id 63,704Kg/cm2 with water content of 10,167 in weight position 3,072Kg. Research result of solid concrete brick with additional material of rods fiber content and palmyra fruit fiber was included on the type B70, the average value of the compressive strength of 78.57 Kg / cm² (SNI-03-1348-1989) with a water content of <25%.

Effect of Cellulose Crystal Content on the Mechanical Property of Nano-Crystalline Cellulose/Lignin Composite Fibrous Film

Lignin is abundant in nature and it is good materials for carbon fiber, but the mechanical strength of the carbon fiber prepared by the lignin extracted from the paper mill waste is low. In this study, nanocellulose whisker (NCW) was used to reinforce lignin and the NCW/lignin composite fibrous film was prepared by electrospinning. By scanning electron microscopy (SEM), single fiber strength tester, the morphologies and mechanical properties of the composite films were researched; the influence of the mass fraction of NCWs on the mechanical property of lignin fibrous film was studied. In the range of this experiment, the results show that adding NCWs into lignin improved the spinnability of lignin, with the increase of the content of NCWs, the mechanical property of lignin fibrous film increased, but there is an optimum content of NCW and the NCWs must be dispersed evenly in the lignin. As the content of NCW increased from 0.3% to 5.0%, the tensile strength and modulus of NCW/lignin fibrous film increased, but the elongation at break decreased. The spinnability of lignin will be worsen if the contend of NCW was more than 5.0%.

Correlation between Pod Shape Traits and Its Fiber Quality of Wild Calotropis Gigantea

ABSTRACTSeed fiber in the Calotropis gigantea (C. gigantea) pods is the most valuable component and can be developed into textile material. Cultivating high-yield and high-quality seed fibers for C. gigantea is one of the critical preconditions for its textile industrialization. In this paper, pods picked from wild C. gigantea plants were used as the experimental materials. The fiber length distribution of the pods was studied. The pod characters (pod shape, single pod weight, fiber weight per pod and seed number per pod, etc.) and the crucial quality characteristics of seed fibers (length, diameter and strength) were tested. The correlations between them were analyzed. The results show that the fiber lengths at the tip, the petiole and the middle part of the pods are significantly different: the fibers from the two sides of the middle part are the longest and more uniform. The pod shape is closely correlated with the fiber length, fineness and strength: longer pods have longer fiber length, smaller length variation and larger fiber diameter, and the percentage of low strength fiber (single fiber strength <1.2 cN) is significantly lower compared to smaller pods. Cultivating C. gigantea with large size and heavy pods will improve the seed fiber yield and the fiber quality.

Compressive Strength Measurements of Single Fibers Using an Improved Automatic Control Method

In the present study, an improved method for single-fiber compression sample preparation and compressive strength experiments is developed. This method improves the experiment efficiency and accuracy of the obtained results. Two improvements over the previous studies were implemented. Firstly, a special device is provided to improve the efficiency of compression specimen preparation using a mini-motor control platform. Secondly, an improved device for measuring the compressive strength of a single fiber is developed and verified using the results of analysis of four carbon fibers. More than 75 high-quality specimens were obtained compared to only one specimen when using the previous method. Compression tests of four types of carbon fibers that were used in our previous study were performed again using the improved device. Our results show good agreement with previous results, which indicates the validity of the two devices used for measuring the compressive strength of single fibers.

The influence of drawing pressure on the properties of PET/PA6 bicomponent spunbonded fibers

The properties of fibers were significantly affected by drawing during the spunbond process. In this paper, the influence of drawing pressure on the properties of spunbonded PET/PA6 hollow pie wedge bicomponent filaments was studied, and their performance was characterized by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, Beion F6 fiber fineness tester, and single fiber strength tester. The hollow pie wedge bicomponent fiber had a distinct interface between the two polymers due to poor compatibility. With increasing of drawing pressure, diameter of the fibers reduced regularly. When the drawing pressure increased, both the degree of crystallinity and orientation of bicomponent fibers enhanced, and the melting point of polyester component increased as well. Furthermore, with increasing of drawing pressure, the breaking strength of the fibers increased, but the breaking elongation and linear density decreased.

Improved testing method for the compressive strength of single fiber

In this study, an improved method is developed to test the compressive strength of single fibers. Two improvements were carried out compared with the previous work, and they were composed of: (1) a skillful device for preparing the compression sample with the advantage of greatly saving time and highly efficiency; (2) an improved system for directly testing the single fiber’s compressive strength with high accuracy and repeatability. More than fifteen qualified samples were successfully prepared within two hour compared with even only one sample in a day for the poor manipulation accuracy of previous work. Compressive strength of single fiber was tested based on four kinds of PAN-based carbon fibers. Experimental results from the new method show great agreement with the data published, which prove the designed method and improved device is more applicable for testing the compressive strength of single fiber in the optimization of cost and efficiency.

Reinforcement of ozone pre-treated and enzyme hydrolyzed longer jute micro crystals in poly lactic acid composite films

Abstract In present study, jute fibers were pre-treated with ozone gas to remove the lignin. The effect of ozone treatment on change in single fiber strength, fiber surface morphology, whiteness, moisture absorbency, etc was studied. For comparison purpose, chemical pre-treatment of jute fibers was also carried out. In subsequent step, untreated, chemical and ozone pre-treated jute fibers were hydrolyzed by cellulase enzymes for separation of longer jute micro crystals. The influence of non-cellulosic contents on the enzyme hydrolysis and morphology of obtained micro crystals was presented. Later, 3 wt% of these jute micro crystals were incorporated into poly (lactic acid) matrix to prepare composite films by solvent casting. The reinforcement behavior was evaluated from tensile tests, dynamic mechanical analysis, and differential scanning calorimetry.

A model for longitudinal tensile strength prediction of low braiding angle three-dimensional and four-directional composites

Abstract Based on random crack core theory, a model for predicting the longitudinal tensile strength of three-dimensional (3D) four-directional composites with low braiding angle is established. The model carries out accurate theoretical predictions of the longitudinal tensile strength of 3D four-directional braided carbon fiber/resin composites. The average stiffness method is used to calculate elastic constants of an inner single cell of 3D four-directional braided composites. Meanwhile, the corresponding relationship between failure probability of a unidirectional composite fiber bundle and stress level is given based on the random crack core model of the longitudinal tensile strength of a unidirectional composite. Furthermore, strength algorithms of low braiding angle 3D four-directional composites under different damage modes are built on the basis of the Tsai-Hill criterion. In this paper, the dispersion of single fiber strength is also considered in the model, so the size effect of the composite strength can be reflected effectively. At last, the longitudinal tensile strength of 3D four-directional braided carbon fiber/resin composites is predicted and analyzed, and the result shows that this model has high prediction accuracy.

Tough biopolymer IPN hydrogel fibers by bienzymatic crosslinking approach

In this report, bienzymatic crosslinking approach was applied to prepare biopolymer hydrogel fibers composed of gelatin and chitosan with an interpenetrating polymer network (IPN) structure. The IPN biopolymer hydrogel fibers were prepared by wet spinning while microbial transglutaminase (mTG) catalyzed the formation of one network of gelatin and horseradish peroxidase (HRP) in the presence of H2O2 induced another network of chitosan grafted with phloretic acid (chitosan-PA) intertwining with the former. The mechanical performances of the hydrogel fibers were measured by an electronic single fiber strength tester. It was found that the mechanical properties of the gelatin/chitosan IPN hydrogel fibers had a significant improvement with the increase of the concentration of gelatin and chitosan, and the IPN fiber has the highest tension of 38.6 cN and elongation of 387.2%. Accelerated degradation in the presence of papin indicated that the gelatin/chitosan-PA IPN hydrogel fibers own controllable degradability. In addition, biological evaluation indicated the IPN hydrogel fibers can support cell adhesion and proliferation. Moreover, hand weaving trail showed the knittablity of the IPN hydrogel fibers. Therefore, the gelatin/chitosan IPN hydrogel fibers prepared by bienzymatic crosslinking approach possess excellent biocompatibility and mechanical strength, which may be desirable candidates for engineering tissue scaffolds.

Revealing the Hierarchical Mechanical Strength of Single Cellulose Acetate Electrospun Filaments through Ultrasonic Breakage.

The tensile strength of single cellulose acetate electrospun fibers is determined through sonication-induced fragmentation in water using a model previously developed by Terentjev and co-workers. The fragmentation of the electrospun fibers results in a gradual shortening of their length until a constant modal length is achieved. A single electrospun CA fiber tensile strength of ≈ 150 MPa (55-280 MPa) is determined based on fracture statistics. It is also observed that the fragmented fibers show bunches of nanofilaments at their ends with similar diameters to those of round structures observed in the cross-section of the initial electrospun fibers (≈ 38 nm). The sonication of these nanofilaments gives rise to spherical particles with similar diameter dimensions, which allows the estimation of a value of the tensile strength of the order of 2 MPa for these nanostructures. The aggregation and the alignment of the nano filaments inside the electrospun fiber should be the source of its higher strength value.