Single Fiber Strength Research Articles

Predicting the tensile strength of single wool fibers using artificial neural network and multiple linear regression models based on acoustic emission

The acoustic emission (AE) technique is widely used at the present time for almost any kind of material characterization. The main aim of the present study was to predict the tensile strength of wool by using artificial neural networks and multiple linear regression analysis based on AE detection. With this aim, a number of single wool fibers were stretched to fracture and the signals at break were recorded by the AE technique. The energy, amplitude, duration, number of hits, average rectified value and root mean square value were used as input parameters to predict the strength of the wool. A feed-forward neural network with a backpropagation (BP) algorithm was successfully trained and tested using the measured data. The same input parameters were used by multiple stepwise regression models for the estimation of wool strength. The coefficients of determination of the BP neural network and stepwise regression indicate that there is a strong correlation between the measured and predicted strength of wool with an acceptable error value. The comparative analysis of the two modeling techniques shows that the neural network performs better than the stepwise regression models. Meanwhile, the relative importance of the input parameters was determined by using rank analysis. The prediction models established in the present work can be applied to AE studies of fiber bundles or fiber-reinforced composite materials.

Effects of different ultrahigh molecular weight polyethylene contents on the formation and evolution of hierarchical crystal structure of high‐density polyethylene/ultrahigh molecular weight polyethylene blend fibers

AbstractIn this paper, the blend fibers of ultrahigh molecular weight polyethylene (UHMWPE) and high‐density polyethylene (HDPE) were prepared by solution blending and gel spinning process. The uniformity of the blend fibers has been confirmed by rheological data and thermodynamic unimodal curve. They were further characterized by single fiber strength test, scanning electron microscopy, wide‐angle X‐ray diffraction, small‐angle X‐ray scattering, and so forth, to explore the structural evolution mechanism with the change of UHMWPE content. The results showed that when the molar content of UHMWPE was only 2.9 mol%, entanglement appeared in the structure of shish‐kebab, and when the proportion reached 20 mol%, an interlocking structure could be observed. With the increase of UHMWPE content, kebab began to be networked, and when the content reached 33 mol%, kebab's orientation reached its peak. After that, the interlocking network structure gradually improved. When the content reached 50 mol%, the shish's orientation reached saturation, and the shish‐kebab network became perfect. In addition, with the increase of UHMWPE content, stress‐induced recrystallization occurred on the wafer, some kebab would be converted into shish crystals, and when the content exceeded 50 mol%, the microfibers began to merge, and the wafer became denser, but still had entanglements. Our work has proposed a quantitative explanation for the evolution of hierarchical crystal structure of HDPE/UHMWPE blend fibers.

Fiber recognition with machine learning methods by fiber tensile fracture via acoustic emission method

Energy release usually accompanies the single-fiber tensile fracture, and can be monitored using acoustic emission technology. Generated during the process of molecular structure fracture of various fibers, the acoustic emission signals can be extracted to identify different fracture types of fiber, which is especially important to the yarn formation process. In this study, a low-noise fiber-stretching device was employed to process the weak-intensity signal generated during fiber tensile fracture; in addition, the Hilbert–Huang transform (HHT), principal component analysis (PCA) and least squares support vector machine (LSSVM) algorithms were combined to identify the collected acoustic emission signals of polyester and cotton fibers. At the same time, it was verified that compared with the single-fiber breaking acoustic emission signal obtained by the electronic single-fiber strength tester, the signal acquisition device based on pneumatic components proposed in this paper can significantly improve the signal-to-noise ratio of the signal. According to the algorithm recognition results, the recognition rate of the two fibers increased from 74% to 95%.The experimental results indicate successful measurements of different fractures of two types of fiber.

Mechanical Properties of Benzoylation Treated Sugar Palm Fiber and Its Composite

Studies on the effect of treated sugar palm fiber with alkaline treatment and benzoylation treatment on single fiber tensile strength and interfacial shear strength (IFSS) are shown in this paper. Also shown is the tensile strength of treated sugar palm fiber composite with variable fiber loading (10%, 20% and 30%). For alkaline treatment sodium hydroxide (NaOH) was used, while benzoyl chloride (C7H5ClO) was used in benzoylation treatment. Polymer matrix that was used in the process of making sugar palm fiber composite is epoxy resin with hardener. For the single fiber test and IFSS, the alkaline treatment was carried out using 1% concentration of sodium hydroxide for one hour soaking time while 5ml of benzoyl chloride was used to agitate with sodium hydroxide for benzoylation treatment with variable soaking time (10, 20 and 30 minutes). Treated sugar palm fiber showed higher single fiber strength and IFSS compared to untreated fiber due to the efficiency of both treatments which help rearrangement of fibrils along the tensile force direction. Tensile properties of sugar palm fiber composite show improvement in tensile stress and tensile modulus for treated sugar palm fiber composite while tensile strain show the opposite result. This is because the bonding strength between fiber and matrix increased by removing the outer layer together with impurities from the fiber during chemical treatment. Thus, with this treatment method, sugar palm fiber can be use as reinforcement material for composite and use them for commercial use such as for furniture and component inside vehicle.

Comparative Analysis of Alkaline and Enzymatic Degumming Process of Hemp Fibers

In this study, a comparison between alkaline and enzymatic degumming process of hemp fibers has been carried out. Degumming of hemp fibers is essential to remove the lignin content and to segregate the individual fibers for textile grade applications. In this research, optimization of degumming process parameters was carried out to reduce the strength loss in fibers. The percentage weight loss of hemp fibers after the degumming process was studied. Two approaches comprising alkaline and enzymatic methods were used. Hemp fiber diameter was determined along with the single fiber strength before and after the degumming process. Stiffness is directly linked to fiber diameter. Therefore, the fiber diameter was also taken into consideration for optimization of the degumming process. The chemicals used in alkali degumming were sodium hydroxide, magnesium sulfate, hydrogen peroxide, and magnesium chloride. Alkali degumming was the best-suited degumming method for segregating the individual hemp fibers. The optimized parameters obtained for alkali degumming method were heating time 50 min and heating temperature 75 °C. Enzymatic degumming is an eco-friendly method, but the result obtained does not provide a better separation of fibers and fine fiber diameter.

Promoting natural fiber from bark of Hibiscus tiliaceus as rope to reduce marine pollution from microplastic fiber yield from synthetic rope

Synthetic ropes are popular for application in marine boat as docking, anchor, tow, and sailing. The advantages of synthetic ropes are waterproof, strong and durable, can be designed for sinks or floats and able to stretches. Synthetic ropes are stronger, more resistant to rotting than ropes created from natural fibers. Synthetic ropes also possess certain disadvantages of slipperiness, and can be damaged more easily by UV light. Synthetic ropes is recognizes as a source of microplastic fiber pollutant in marine area. In this work a bark of Hibiscus tiliaceus three is introduced as candidate source of natural fiber for rope to reduce number of microplastic fiber pollutant from synthetic rope. The bark was taken from a trunk with diameter around 20 cm. The bark was immersed in water for 7 days and subsequently was soaked in 5% NaOH solution for 2 hours. Fiber obtained then was dried. It was prepared 7 valid single fiber samples. The average of tensile strength of single fiber obtained by using this method is found around 44.604 MPa. The average of Modulus elasticity E is found 365.864 MPa. The failure strain is found 11.6 %.

System-size-dependent avalanche statistics in the limit of high disorder.

We investigate the effect of the amount of disorder on the statistics of breaking bursts during the quasistatic fracture of heterogeneous materials. We consider a fiber bundle model where the strength of single fibers is sampled from a power-law distribution over a finite range, so that the amount of materials' disorder can be controlled by varying the power-law exponent and the upper cutoff of fibers' strength. Analytical calculations and computer simulations, performed in the limit of equal load sharing, revealed that depending on the disorder parameters the mechanical response of the bundle is either perfectly brittle where the first fiber breaking triggers a catastrophic avalanche, or it is quasibrittle where macroscopic failure is preceded by a sequence of bursts. In the quasibrittle phase, the statistics of avalanche sizes is found to show a high degree of complexity. In particular, we demonstrate that the functional form of the size distribution of bursts depends on the system size: for large upper cutoffs of fibers' strength, in small systems the sequence of bursts has a high degree of stationarity characterized by a power-law size distribution with a universal exponent. However, for sufficiently large bundles the breaking process accelerates towards the critical point of failure, which gives rise to a crossover between two power laws. The transition between the two regimes occurs at a characteristic system size which depends on the disorder parameters.

Novel ceramic matrix composites with tungsten and molybdenum fiber reinforcement

Ceramic matrix composites usually utilize carbon or ceramic fibers as reinforcements. However, such fibers often expose a low ductility during failure. In this work, we follow the idea of a reinforcement concept of a ceramic matrix reinforced by refractory metal fibers to reach pseudo ductile behavior during failure. Tungsten and molybdenum fibers were chosen as reinforcement in SiCN ceramic matrix composites manufactured by polymer infiltration and pyrolysis process. The composites were investigated with respect to microstructure, flexural- and tensile strength. The single fiber strengths for both tungsten and molybdenum were investigated and compared to the strength of the composites. Tensile strengths of 206 and 156 MPa as well as bending strengths of 427 and 312 MPa were achieved for W/SiCN and Mo/SiCN composites, respectively. The W fiber became brittle across the entire cross section, while the Mo fiber showed a superficial, brittle reaction zone but kept ductile on the inside.

Surface Modification of PET Fiber with Hybrid Coating and Its Effect on the Properties of PP Composites.

Surface modification fundamentally influences the morphology of polyethylene terephthalate (PET) fibers produced from abandoned polyester textiles and improve the compatibility between the fiber and the matrix. In this study, PET fiber was modified through solution dip-coating using a novel synthesized tetraethyl orthosilicate (TEOS)/KH550/ polypropylene (PP)-g-MAH (MPP) hybrid (TMPP). The PET fiber with TMPP modifier was exposed to the air. SiO2 particles would be hydrolyzed from TEOS and become the crystalline cores of MPP. Then, the membrane formed by MPP, SiO2 and KH550 covered the surface of the PET fiber. TMPP powder was investigated and characterized by fourier transform infrared spectroscopy, scanning electron microscope (SEM) and thermogravimetric analysis (TGA). TMPP-modified PET fiber was researched by X-ray diffraction and SEM. Furthermore, tensile strength of single fiber was also tested. PET fiber/PP composites were studied through dynamic mechanical analysis and SEM. Flexural properties of composites were also measured. The interfacial properties of PET fiber and PP matrix were indirectly represented by contact angle analysis. Results showed that the addition of TEOS is helpful in homogenizing the distribution of PP-g-MAH. Furthermore, TMPP generates an organic-inorganic ‘armor’ structure on PET fiber, which can make up for the damage areas on the surface of PET fiber and strengthen each single-fiber by 14.4%. Besides, bending strength and modulus of TMPP-modified PET fiber-reinforced PP composite respectively, increase by 10 and 800 MPa. The compatibility between PET fiber and PP was also confirmed to be increased by TMPP. Predictably, this work supplied a new way for PET fiber modification and exploited its potential applications in composites.

Tensile strength and failure behavior of bare single mode fibers

Abstract We have investigated systematically the tensile strength and failure behavior of bare single mode fibers (SMFs) prepared by mechanical stripping technique. The tensile strength of bare SMFs under different temperatures is analyzed based on Weibull statistics. At room temperature, the bare SMFs show lower tensile strength than the SMFs with coating. The Weibull modulus referring to the width of the tensile strength distribution decreases when the gauge length of bare SMFs increases. The fractographic examination indicates that the fracture initiates from the outer cladding surface. As testing temperature increases from room temperature to 900 °C, we find that the tensile strength of bare SMFs decreases for the reason of the structural surface relaxation of SMF. The Weibull modulus decreases firstly then increases. Such change of bare SMFs is due to the partial restoration of flaws on fiber surfaces as testing temperature increases. The obtained results could provide guidance for the application of bare SMF prepared by mechanical stripping technique in harsh environment.

The effect of hemicellulose content on mechanical strength, thermal stability, and water resistance of cellulose-rich fiber material from poplar

The hemicellulose content of cellulosic material from poplar chemi-thermomechanical pulp (CTMP) was controlled by a microwave-assisted formic acid (MFA) extraction process. The environmentally friendly, self-bonded, and cellulose-rich fiber sheets (around 0.3 mm thick and 280 g/m2 grammage) were fabricated via a molding and compression process. The results showed that the MFA treatment effectively controlled the hemicellulose content in the range from 6.8% to 20.4%. Mechanical testing results showed a good linear relationship between the tensile strength and the hemicellulose content, where a higher hemicellulose content obtained a stronger tensile strength. Meanwhile, as hemicellulose content decreased, the onset temperature, representing the thermal stability, increased from 318.1 °C to 335.7 °C and the elastic modulus, representing the mechanical stiffness, increased from 0.047 MPa to 0.068 MPa. Additionally, as the hemicellulose content decreased, the water-resistance of the cellulose-rich fiber sheets improved. During the hemicellulose removal process, the strength of single fibers was found to have a dominant role in the mechanical strength of the cellulose-rich fiber sheets, rather than the inter-fiber bonding strength. This was contrary to research on the delignification process, where the inter-fiber bonding strength was found to be more important than the strength of single fibers in deciding the material strength.

Investigation of Atmospheric Moisture during Heat Treatment of Glass Fibres

The tensile strength of single water-sized E-glass fibres that were thermally conditioned, either in air or under vacuum, was investigated. The vacuum removed water from the conditioning atmosphere, as well as the fibre surfaces, at room temperature but retained tensile strength of fibres treated in the absence of water were not significantly different from those thermally conditioned in a standard air furnace. The results suggest that water, either in the treatment atmosphere or on the surface of the fibres, is not a significant factor in fundamental glass fibre strength loss at an elevated temperature. It may, therefore, be necessary to consider alternative theories to explain this strength loss.

Novel application of chitosan: ameliorative effect of homogeneous and floccular chitosan on the interfacial property of carbon fiber/epoxy resin composites

A novel homogeneous floccular chitosan was directly grafted onto carbon fiber surface by a simple and controllable method. Scanning electron microscopy (SEM), single fiber strengths and interlaminar shear strength (ILSS) have been applied to characterize the fiber and the interface bonding. Compared with raw carbon fibers, the chitosan-treated ones demonstrate significant increases in the surface roughness and wettability. Particularly, about 21.21% increase in the mechanical properties of composites was obtained, which is attributed to good adhesion between functional carbon fiber and resin matrix in the interlaminar regions, as revealed by fracture surfaces.

Investigation on improving banana fiber fineness for textile application

The banana is one of the most commonly consumed fruits in Sri Lanka; after the fruit is harvested, the pseudostem is thrown down as waste. The banana pseudostem is a good source of natural fiber. The purpose of this project is to investigate the effects of banana fiber extraction, examine treatment parameters on fiber fineness and establish suitable methods to reduce the fineness that enable banana fibers to be used as textile materials. Ten popular Sri Lankan varieties of banana pseudostem were selected for this study. From the mechanically extracted banana fiber of these 10 varieties, Ambun (genome AAA) was selected for further analysis because it had the lowest fiber fineness. Four layers from the pseudostem of Ambun were extracted and put through a fineness and single fiber strength test. Scanning electron microscopy and fiber linear density were used to observe and determine the fineness of the enzyme and chemical treated banana fiber. The mechanical strength of the treated banana fibers was obtained by using a universal tensile tester machine. The test result showed the second and the third layers of the pseudostem to be the finest. The mechanically extracted fiber of the second and third layers of the pseudostem were put through an enzyme and chemical treatment. Results showed enzyme and chemical combined treated fibers to be the finest, with a reduced diameter from 168.4 µm to 48.8 µm, which is about 71% reduction compared to mechanical extraction.

A Practical Approach for Validation of Aptitude of Sized Carbon Fibers for the In-Mould -Impregnation Process

As a new and innovative processing method for carbon fiber reinforced thermoplastic composites, the In-Mould-Impregnation process (IMI) adopts carbon fibers as a heating element by electrical conduction. During heating of the dry carbon fibers in the production process, temperatures up to over 500°C can occur. However, the surface properties of carbon fibers and sizing may change under such conditions and thus affect the resulting composite. The present study is a practical approach to validate the suitability of sized carbon fibers for the IMI. The influence of a thermal treatment according to the parameters of the IMI-Process on carbon fiber-thermoplastic matrix interfacial adhesion was investigated by means of micromechanical and optical test methods. The experimental results demonstrate that the thermal treatment of carbon fibers causes a reduction of tensile strength of single fibers. It does not show an influence on the micromechanical breaking behavior in a PA 6 composite but the surface tension of carbon fibers changes. The change in surface tension can affect the wettability of the carbon fiber with a thermoplastic matrix.

Feasibility of using seawater to produce ultra‐high ductile cementitious composite for construction without steel reinforcement

Using seawater as mixing water to produce concrete may lead to excessive chloride content inside cementitious paste. This dramatically increases the risk of steel corrosion in the service life of RC structures. To address this issue, the authors tried to develop cementitious composites with sufficient ductility and strength, making it a structural material free from steel reinforcement, so that seawater can be used freely in mixture. In this article, ultra‐high ductile cementitious composites (UHDCC) were fabricated using 100% natural seawater, sea‐fresh water (50 + 50%) and 100% freshwater, in which the water‐soluble chloride contents reached 0.288, 0.181, and 0.073%, respectively. Mechanical test results indicated that the presence of chloride ions has negligible influence on the strength of single polyethylene fiber and fracture toughness of UHDCC matrix. Also, no significant difference was found existing in tensile strength, tensile strain capacity, and composite bridging capacity of the UHDCCs mixed with seawater or freshwater. Four‐point bending test demonstrated that plain UHDCC beams mixed with seawater, sea‐fresh water or freshwater have the similar load bearing capacity to a reference RC beam having steel reinforcement of 0.57%. Generally, the present experimental study demonstrates that chloride content has negligible influence on the mechanical properties of UHDCC, thus providing a solution for concrete constructions located in coastal areas and isolated islands.

Evaluation of Mechanical Properties of Dimpled PET Fiber Fabricated by Electrospinning Method

Insufficient endothelialization of stent grafts tends to cause a problem of thrombosis formation. Because the structure of nanofibers, generally defined as fibers with a diameter below 1 μm, resembles the structure of an extracellular matrix, nanofibers are applied to scaffolds for regenerative medicine. Using nanofibers as the covering material of the stent graft can be expected to solve the problem of the stent graft. Previous studies have shown that a porous scaffold offers better surfaces to anchor and culture endothelial cells than a nonporous scaffold. Therefore, fibers with nanoorder dimples are expected to promote endothelialization. As a method of forming the dimple shape on the surface of the PET fiber, there is a method utilizing a difference in the volatilization rate of the solvent in the high humidity environment in the electrospinning method. For practical application of the stent graft to artificial blood vessels, the mechanical properties of the dimpled PET fiber should be clarified. In this study, the mechanical properties of single nanofibers and nonwoven fabrics of PET fibers with dimples on their surface were evaluated by tensile test. By forming the dimple shape on the fiber surface, the tensile strength of single PET fibers with dimples was 90 % lower than that of single PET fibers with a smooth surface. In the fabrication process of nonwoven fabric, the addition of EG delayed the volatilization of the PET solution, and the fibers adhered to each other. The bonding between the fibers contributed to the tensile strength of the nonwoven fabric.

Enhancing interfacial properties of carbon fibers reinforced epoxy composites via Layer-by-Layer self assembly GO/SiO2 multilayers films on carbon fibers surface

To enhance the interfacial properties of carbon fibers (CFs) reinforced epoxy composites without sacrificing fiber strength. A facile and effective Layer-by-Layer (LbL) self assembly method was proposed to deposit graphene oxide/silica (GO/SiO2) multilayers films onto CFs surface. The negatively charged GO and positively charged SiO2 can be assembled on the surface of fiber based on electrostatic interactions. Surface microstructures of CFs were characterized systematically. Scanning electron microscopy (SEM) revealed the GO/SiO2 multilayers films compact and homogeneous coverage onto CFs surface. This coverage significantly increases the roughness and surface energy of the fibers, improving the wettability and mechanical interlocking between fibers and resin. The optimal interfacial shear strength (IFSS) of composites with 5 layers (CF-L5) was 84.40 MPa, which increased by 86.1% compared to that of Untreated-CF composites (45.36 MPa), and the interlaminar shear strength (ILSS) of CF-L5 composites (76.34 MPa) increased by 89.3% compared to that of Untreated-CF composites (40.33 MPa). In addition, the flexural strength of CF-L5 composites (765.57 MPa) was 30.4% higher than that of Untreated-CF composites (587.19 MPa). The fractured surface, energy dispersive spectroscopy (EDS) mapping and dynamic mechanical properties of CFs composites also show a great improvement in interfacial adhesion. Moreover, the tensile strength (TS) of single fiber increased from 3.52 GPa to 3.68 GPa after LbL assembly of GO/SiO2. Our work suggested that such LbL self assembly is a green and promising approach toward preparing high interfacial properties in CFs composites.

Tensile strength prediction of irregular fibres using diameter-dependent Weibull analysis

A modified Weibull model incorporating the within-fibre diameter variation is applied to examine the fibre diameter effect on the strength of single fibres. Australian Superfine Merino Wool (ASFW) and Inner Mongolia Cashmere (IMC) were used in the present work, since these animal fibres tend to have relatively large diameter variations. To determine single fibre strength, tensile measurements were carried out for fibres with diameters varying between 9 and 21 μm at a constant gauge length. It was found that an increase in the diameter disparity along the fibre reduces the strength of fibres. To validate this, the accuracy of predicting weak-link scaling was evaluated; the results showed that the application of modified Weibull distribution gives a better relationship with the empirical data than the standard Weibull model. The results suggest that the modified Weibull model is more accurate in predicting the size dependence and strength of single fibres with diameter variations.

Performance and drug release studies of poly (ɛ-caprolactone)/γ-poly (glutamic acid) fibrous membranes

Fibrous membranes of poly(ɛ-caprolactone)/γ-poly(glutamicacid) (PCL/γ-PGA) composites were successfully produced via an electrospinning process. In doing so, the water solubility of florfenicol (FF) could be enhanced and the drug release properties of FF could be controlled. The mechanical, morphologic, and thermal properties of the fibrous membranes of PCL/γ-PGA were studied by using an electronic single fiber strength machine, scanning electron microscopy, and differential scanning calorimetry. The wettability of the fibrous membranes of PCL/γ-PGA was also measured as discussed in the subsequent section. Fourier transform infrared spectroscopy was applied in the structural analysis of the PCL/γ-PGA-FF fibrous membranes. The results indicated that FF was well blended in the composite membranes of PCL/γ-PGA. In vitro dissolution tests showed that PCL/γ-PGA (85/15; 8%) as both a biodegradable and biocompatible blend may improve the solubility of FF. Therefore, fibrous membranes of PCL/γ-PGA may represent ideal materials for the controlled drug release in various clinical applications.