Transverse Yarns Research Articles

Textile reinforced concrete members subjected to tension, bending, and in-plane loads: Experimental study and numerical analyses

Textile reinforced concrete has raised increasing research interest during the last years, mainly due to its potential to be used for freeform shell structures involving complex load situations. Yet, most experimental work has focused on test setups with primarily uniaxial loading. In the current work, such setups are complemented with a novel test setup of deep beams, including in-plane bending and shear. Further, nonlinear finite element analyses were carried out, applying an earlier calibrated bond-slip relation and efficiency factors for strength and stiffness of the textile reinforcement. It was found that the structural behaviour in terms of the overall stiffness, ultimate load and deformation, number of cracks, and total (summed) crack width, could be described with reasonably good accuracy. The inclusion of a calibrated efficiency factor for the stiffness of the yarn was shown to be vital. Moreover, it was shown to be important to weaken and randomise the material properties of the concrete at the location of transverse yarns, to trigger localisation (cracking) in the numerical model.

Experimental study on the bond behavior of polymer impregnated basalt textile embedded in a fine‐grained concrete

AbstractThe bond properties between polymer impregnated basalt textile and fine‐grained concrete were studied by pull‐out test considering the effects of bond length, impregnation polymer type, surface condition, and transverse yarn. The experimental results showed the pull‐out load increased with the bond length increasing, and the slight decrease in bond strength was attributed to the nonlinear distribution of bond stress. Owing to the high viscosity and good permeability of epoxy resin, the bond strength of epoxy resin‐impregnated textile was 238% and 592% higher than that of textile impregnated with acrylic emulsion and polyvinyl chloride, respectively. Moreover, the bond properties were improved significantly for impregnated textile with sticking sand or fiber by increasing the interfacial friction between textile and concrete, and the highest bond strength was obtained for yarn sticking sand with particle sizes of 0.09 ~ 0.18 mm. The transverse yarn of epoxy resin‐impregnated textile can generate an interlocking effect to concrete due to the semi‐rigid node, which increased the bond strength by 48.6%, whereas this did not happen for textile impregnated with flexible material. Furthermore, the anchorage lengths of textile were calculated, and the proposed simple bond slip model can be used to describe the pull‐out response of polymer impregnated basalt textile embedded in concrete.

Tensile behavior and failure mechanism of 3D woven fabric reinforced aluminum composites

This paper aims to study the mechanical behavior and the complicated failure mechanism of a novel Al matrix composites reinforced with 3D orthogonal woven carbon fiber. The quasi-static tensile behavior, local stress response and progressive failure process are investigated via numerical and experimental approach. According to the microstructure at fiber and yarn scale, microscopic and mesoscopic finite element models were established to carry out multiscale simulation. The calculated tensile stress-strain curve is basically in accordance with the experimental curves, where the elastic moduli, tensile strength, and elongation are 118.6 GPa, 777.3 MPa and 0.84%, respectively. Local stress distribution of the matrix pocket and yarns exhibits apparent periodicity and heterogeneity, which is related to the specific fabric architecture. Interface debonding induces the local damage of matrix alloy and transverse cracking of binder and weft yarns successively, resulting in nonlinear response of the tensile curves. The catastrophic rupture of the composites is caused by the axial fracture of warp yarns that resulted from the combination of matrix failure and transverse yarns cracking. The fracture morphology of binder and weft yarns is flat and that of warp yarns exhibits limited fiber pull-out, which can be interpreted by the predicted failure mode. Based on the validated model, the influence of fabric structure parameters on the macroscopic properties was further evaluated. The results indicate that the increase of warp or weft density could improve the tensile strength and elastic modulus, but the tensile elongation decreases with the increase of weft density.

A novel mechanical behavior and failure mechanism analysis of 3D six-directional braided composites in liquid nitrogen subjected to compression

The influence of temperature, braiding angle, and braided structure on compressive mechanical properties and failure mechanisms of three-dimensional six-directional braided composites (3D6DBCs) were comprehensively analyzed. At low temperature, the out-of-plane and transverse strength increased by 16.2% and 50.1%, respectively. Interfacial damage caused a 25.3% decrease in longitudinal strength. The increase in braiding angle leads to a decrease in longitudinal and transverse strengths. At room temperature, the failure of the yarn-matrix interface and the deformation of the composites are the main reasons for the failure of 3D6DBCs. At low temperature, 3D6DBCs exhibits brittle fracture and shear failure modes. The braiding angle affects the deformation of 3D6DBCs. The composites with different braided structures have significant property differences. The addition of axial and transverse yarns significantly improves the longitudinal and transverse properties of 3D6DBCs.

Multi-instrumented analysis of fatigue behavior and damage mechanisms in jute fiber-reinforced polyester composites

The present work deals with the fatigue behavior of a jute fiber-reinforced polyester composites. Two stacking sequences were considered [0]8 (JP_0) and [+45/−45]2S (JP_45). The fatigue lifetimes diagrams were determined. They exhibit a fatigue limit lower than 20 MPa for JP_0 composites and lower than 15 MPa for JP_45, whereas the mean ultimate tensile stress σR is 42.9 MPa for JP_0 and 31.1 MPa for JP_45, and the lifetimes lower than 500000 cycles for JP_0 and 250000 cycles for JP_45. An exhaustive analysis of the fatigue damage is carried out by combining four approaches: measurement of the mechanical parameters, microscopic observations, X-ray tomography, acoustic emission (AE) monitoring. X-ray tomography revealed the presence of multiple fiber/matrix debondings within transverse yarns for the composites [0]8 and yarn/matrix debondings for the composites [+45/−45]2S. Density of matrix cracks is always more important (about 80%) for JP_45 than for JP_0 at the same relative stress level/σR, and decrease of a 3 times factor for JP_0 (5 for JP_45) when the relative stress increases from 50% to 80%. Two types of behaviors are observed: one for low stresses and another for high stresses. Damage evolution is followed by AE by using a supervised classification with 3 classes of events: matrix cracking, fiber/matrix debonding and fiber breakage. The global activities are at the most of 600000 signals, and decreases 10 times from 50% σR to 80% σR. The results of AE highlighted in addition the greater number of matrix cracks for low stresses in agreement with X-ray tomography in the same proportions. High stresses are characterized by a larger number of fiber breaks (4 times for both composites) and fibre/matrix debondings (2 times) for JP_0, unless for fiber/matrix debonding in JP_45 which decreases 3 times. The multi-instrumented damage approach allows to make a precise and quantitative analysis of the fatigue damage mechanisms. The results highlight that for the weak stress levels matrix cracking is predominating whereas for the high stress levels the fiber breakages are significant. A scenario of fatigue damage is proposed: for low stresses the behavior is controlled by the matrix and for high stresses the behavior is controlled by the fibers.

The anti‐oxidation mechanism of SiCf/SiC–B4C modified with Al2O3 in wet atmosphere based on machine learning

AbstractTo study the anti‐oxidation mechanism of SiCf/SiC–B4C modified with Al2O3 in wet atmosphere, the damage evolution of composites after oxidation was explored by unsupervised machine learning technology (k‐means). Results display that the mean feature values of cluster‐1 (some small cracks in oxidation layer and matrix as well as fiber debonding) in composites modified with Al2O3 are larger than that in virgin after oxidation. Meanwhile, as the oxidation time increases, the concentrated area of cluster‐2 (fiber breakage, cracks in axial and transverse yarns) in both composites gradually shifts toward the direction of high mean feature values. Because Al2O3 can protect the BN from oxidation, the increase of peak frequency and risetime of composites modified with Al2O3 is less than that of virgin. Moreover, the proportion of cluster‐3 (big transverse matrix cracks) in composites modified with Al2O3 is always more than that of virgin. Based on the research results, the corresponding relationship between each damage behavior and each cluster is thoroughly built.

An approach to estimate crack opening displacement in two-dimensional plain-woven silicon carbide fiber-reinforced silicon carbide composite considering different matrix cracking modes

Understanding of cracking opening behavior is important for the prediction of residual strength and lifetime of silicon carbide fiber-reinforced silicon carbide ceramic–matrix composites at elevated temperatures. Under tensile loading below the proportional limit stress, multiple matrix cracking modes in the longitudinal and transverse yarns of a two-dimensional plain-woven silicon carbide fiber-reinforced silicon carbide composite appear in the matrix with debonding at the fiber/matrix interface. Crack opening displacement is a key parameter to characterize the crack opening behavior in silicon carbide fiber-reinforced silicon carbide composites and is affected by the multiple matrix cracking modes. In this article, a damage-based micromechanical crack opening displacement model for two-dimensional plain-woven silicon carbide fiber-reinforced silicon carbide composites is developed considering different matrix cracking modes. Two typical matrix cracking modes in a two-dimensional plain-woven silicon carbide fiber-reinforced silicon carbide composite, that is, cracking mode III with cracking in the matrix of the longitudinal and transverse yarns and cracking mode V with cracking only in the matrix of the longitudinal yarns, are considered. Micro stress field in the fiber, matrix of the longitudinal yarns, and transverse yarns are obtained. The crack opening displacement and related damage parameters are determined. Relationships between composite's crack opening displacement, constitutive properties, woven parameters, and damage state are established. Experimental crack opening displacements of cracking modes III and V in a two-dimensional plain-woven melt-infiltration silicon carbide fiber-reinforced silicon carbide composite from the published literature are predicted. For cracking mode III with partial interface debonding, the crack opening displacement increased nonlinearly with applied stress; and for cracking mode V with complete interface debonding, the crack opening displacement increased linearly with applied stress.

Development and mechanical properties of three-dimensional flat-knitted fabrics with reinforcement yarns

Three-dimensional (3D) flat-knitted fabrics have become a topic of interest in the field of composites in recent years because of the growing need for rapid preparation of complicated shape preforms. In order to improve the mechanical properties of 3D flat-knitted fabrics, two types of 3D flat-knitted fabrics with reinforcement yarn (FKFR) were developed using ultra-high molecular weight polyethylene (UHMWPE) yarn. Their basic structures were composed of plain structure and interlock structure with tuck stitch, respectively, and the reinforcement yarn was integrated into the fabric as the weft inlay. The tensile, bending, drape, and bursting properties of the two fabrics were characterized. Results showed that the basic structure of the fabric has impacted on the mechanical properties of the fabric significantly. The tensile and bending properties of the fabric with interlock structure were better than that of the fabric with plain structure. During the transverse stretching process, the surface structure of the fabric with interlock structure was more stable. Moreover, transverse yarn strength utilization of the fabric with interlock structure was 1.05, which reached the level of ordinary woven fabric. In addition, the bursting force of the fabric with excellent tensile properties was lower than that of the fabric with a plain structure because the latter has better extensibility.

How does a glass fabric tear under cyclic force?

In many applications, glass fabrics are subject to cyclic forces. Here we show that a glass fabric can tear under a much lower cyclic force than monotonic force. For samples of a given width, a threshold force exists below which the fabric does not tear under cyclic load, and a critical force exists at which the fabric tears under monotonic load. For example, for 80 mm wide sample, the threshold force is 12.78 N, and the critical force is 344.73 N. Under cyclic force of amplitude between the threshold force and critical force, tear initiates after some number of cycles. Under either cyclic or monotonic force, the fabric tears in three modes: pullout of transverse yarns, pullout of transverse yarns and break of longitudinal yarns, and break of transverse and longitudinal yarns. We summarize the observed tear modes on the plane of two axes: the amplitude of force and the width of sample. It is hoped that this study will aid the development of fatigue-resistant fabrics and fabric reinforced composites.

Large deformation bending of single‐ply fabric reinforced polymer composite

AbstractThis study investigates the large deformation bending properties of a single‐ply fabric reinforced polymer composite (SpFRPC) by the innovative counterweight balanced column bending test (CWB‐CBT) and microscopic analysis. The influences of temperatures and asymmetric weave structure on SpFRPC's bending properties are emphasized. In glassy state at 15°C, SpFRPC failed in a brittle manner, with the ultimate moment and initial bending stiffness per width 19.16 Nmm and 448.61 Nmm2. The bending capacity decreased to negligible at 40°C in the rubbery state but vice versa for deformability, reaching the curvature of 0.135 mm−1 within maximum accommodation of this CWB‐CBT fixture. The asymmetric weave structure enabled larger deformability when bent outward than inward, resulting in more significant stiffness and ultimate moment inward than outward. The transverse yarns' gaps were the weak locations of bending fracture, especially at weave intersection edges. In general, the present work provides an exploratory study for understanding the folding mechanical properties of the SpFRPC.

Single edge crack effect on mechanical property of polyimide flexible composite envelope

The existence of cracks has a great influence on the life span of the envelope material of aerostats, especially for stratospheric airships that operate in harsh environments. Understanding the relationship between fracture mechanism and composite structure of envelope materials is of great significance to the design and development of envelope materials. To explore the fracture mechanism of envelope material, a novel polyimide (PI) envelope was developed by lamination method. Then, the fracture behavior and mechanism of PI envelope with single edge crack was studied and analyzed in detail by means of experimental method and theoretical model analysis. It was found that the crack orientation has no significant effect on the fracture strength of PI envelope, while the increase of crack length will increase the strength loss rate and decrease the crack sensitivity. These phenomena suggest that the fracture strength loss of envelope is mainly determined by the number of cut-off longitudinal yarns. And the stress transfer effect of coating and transverse yarns which causes stress concentration in the crack tip region is another important factor affecting the fracture strength of PI envelope. Besides, the interfacial properties between coating and fibers as well as the size effect of coating also play an important role in the fracture property of PI envelope. Finally, stress intensity factor theory and critical stress field theory were chosen to study the fracture behavior of PI envelope. The calculation results indicated that critical stress field theory can better predict the fracture strength of PI envelope.

The tensile damage behavior of SiCf/SiC–B4C after oxidation in wet atmosphere based on acoustic emission pattern recognition

AbstractIn this research, SiCf/SiC–B4C composites were prepared through slurry impregnation and reaction melting infiltration (RMI). To explore the damage evolution of this composites after oxidation in wet atmosphere, the changes of damage behavior of composites before and after oxidation were studied using acoustic emission (AE) pattern recognition (PR) technology. Results show that since the damage behavior of the composites changes after oxidation, the optimal number of clusters transforms from 3 to 5. In addition, as the oxidation time increases, the area of concentration of damage events is gradually broadened towards lower stress direction due to the decrease of damage threshold of composites. Meanwhile, because the BN interface is gradually oxidized, the density of C3‐cracks (axial yarns cracks) near the fracture and the proportion of Cluster‐4 (the signals of transverse yarns cracks) will increase, for which the rising of interfacial shear stress should be responsible. Through this research, not only can the damage evolution of SiCf/SiC–B4C composites after oxidation be understood, but also the method employed in this research can be as guide for studying other similar materials.

Meso-scale modeling and damage analysis of carbon/epoxy woven fabric composite under in-plane tension and compression loadings

The mechanical properties and damage behaviors of carbon/epoxy woven fabric composite under in-plane tension and compression are studied at the meso-scale level through experiment and simulation. An efficient representative volume element (RVE) modeling method with consistent mesh, high yarn volume fraction and realistic geometry is proposed. The material constitutive laws with plasticity, tension-compression asymmetry and damage evolution are established for the three components - yarn, matrix and interface, respectively. Significantly different mechanical properties and damage evolutions are observed depending on loading conditions and initial geometry characteristics. It shows a non-linear stress-strain curve with clear transition region and intensive damage in tension, while a quasi-linear behavior up to facture is observed in compression with little damage prior to final fracture. Moreover, compared to the constant Poisson's ratio with straining in compression, a dramatic increase in Poisson's ratio appears in tension. Simulation shows damage mechanisms including transverse damage, matrix damage and delamination, which all play critical roles in the property evolution. In particular, the rapid damage accumulation after elastic deformation destroys the strong bonds and causes the easy deformation of transverse yarns which results in the transition region and large Poisson's ratio in tension. All the mechanical behaviors and damage evolutions are well captured and explained with the current RVE model.

Mechanical properties and failure mechanisms of 3D six-directional braided composites at elevated and liquid nitrogen temperatures

3D six-directional braided carbon/epoxy composites are fabricated successfully, and their mechanical properties and failure mechanisms at room, elevated and liquid nitrogen temperatures are reported. The results show the temperature has an important influence on load-deflection curves and bending properties. All the curves are divided into three stages: initial linear elastic, nonlinear and final fracture stage. At room temperature, the linear characteristic is obvious and properties are excellent. The failure is a gradual process from external to internal due to good reinforcement of transverse yarns, and fibers are sheared and pulled out. At elevated temperatures, the curves decline successively and nonlinear features increase, with decrease of bending properties. The damage is matrix softening and plasticization, interface debonding. At liquid nitrogen temperature, zigzagged fluctuation feature increases and linear elastic characteristic strengthens. Bending properties have been improved significantly and failure is fibers shear fracture and formation of shear bands among fiber/matrix interface.

Tensile behavior of fabric-cement-based composites reinforced with non-continuous load bearing yarns

The main aim of this work was two-fold, to study the ability of the fabric within a TRC to carry loads when not all the yarns along the loading direction are continuous and to better understand the role of the transverse yarns when subjected to tensile loading. An excellent correlation was found between the behaviors of the composites and fabrics studied. The load values in stages one and two (while the matrix is still participating in load carrying) were much greater than expected, i.e., not proportionally correlated with the number of continuous yarns. This suggests that during the first two stages of loading, not only the continuous yarns are active and carry the loads, but also the discontinuous (cut) ones participate in load bearing via stress transfer from the transverse yarns and the matrix. Use of an effective ratio between the cross-sections of the yarns and the matrix enables ‘smooth’ tensile behavior, essential in structural elements. A greater matrix cross-section produces a composite with improved tensile stress (at the end of the multiple cracking) which is more ductile and having greater energy absorption but at the expense of a significant drop in load.

Mesoscale analysis of damage growth in woven composites

The characteristic damage mechanisms of a four-layer plain weave glass fiber/epoxy matrix composite are analyzed by means of optical microscope observations on the edge of a rectangular specimen under tensile loading. Digital image correlation is used to determine the size of transverse yarn cracks and yarn-yarn debonding around the crack tips. An algorithm based on Finite Fracture Mechanics is proposed to model crack and debond initiation and propagation in the composite, which takes into account possible couplings between the cracks. The predicted debond and crack densities are in good agreement with the experimental observations.

Failure and damage characterization of (±30°) biaxial braided composites under multiaxial stress states

This paper focuses on the mechanical characterization of (±30°)2×2 biaxial braided composites under multiaxial stress states. Off-axis experiments in tension and compression were used to introduce multiaxial stresses in the material. The characterization was focused on nonlinear deformation and failure behavior: loading/unloading of the specimen was used to identify the mechanisms for nonlinear deformation and a high-speed-camera is used to record the failure mode of the specimen. It has been found that the failure modes are mainly dominated by shear-induced transverse cracking. A dependency of the failure mode on the transverse yarn stress was observed. The deformation was strongly nonlinear, and dominated by the shear-behavior of the yarns. An equivalent laminate model was employed for failure prediction, showing that the failure of the biaxial braided composites can be predicted accurately, when the knockdown induced by yarn waviness is considered in the material input parameters.

Effect of projectile nose geometry on the critical velocity and failure of yarn subjected to transverse impact

Three different types of yarn have been subjected to transverse impact experiments in efforts to gain an understanding of local yarn failure and to provide input parameters for future transverse yarn impact simulations. Dupont™ Kevlar® KM2, DSM Dyneema® SK76, and AuTx® from JSC Kamenskvolokno were selected as representative materials, as the former two are commonly implemented into bullet resistant panels and the latter is a promising material for future impact resistant fabrics. In order to assess the effect of projectile nose shape on the critical rupture velocity range for each yarn type, three missile geometries have been implemented, namely a 0.30 caliber rounded head, a 0.30 caliber chisel nosed fragment simulation projectile (FSP), and a high-carbon steel razor blade. As opposed to one single velocity wherein yarn behavior transitions from transverse wave development to immediate local failure, a range is defined wherein progressive filament failure is detected with increasing impact velocities. Such ranges are determined for all yarn types using the three projectile geometries yielding critical velocity transition regions of increasing value when impacting via razor blade, FSP, and round projectile heads, accordingly. In addition, post-mortem fracture surfaces recovered from impact experiments have been imaged so as to elucidate the mechanism of failure throughout the range of velocities tested for each projectile type and yarn material and said fracture surfaces correlate well with impact velocity and projectile nose geometry.

Micromechanical Modeling for Tensile Behaviour of Carbon Fiber − Reinforced Ceramic − Matrix Composites

The stress–strain curves of fiber − reinforced ceramic − matrix composites (CMCs) exhibit obvious non-linear behaviour under tensile loading. The occurrence of multiple damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding and fibers fracture, is the mainly reason for the non-linear characteristic. The micromechanics approach has been developed to predict the tensile stress–strain curves of unidirectional, cross-ply and woven CMCs. The shear-lag model was used to describe the micro stress field of the damaged composite. The damage models were used to determine the evolution of micro damage parameters, i.e., matrix crack spacing, interface debonded length and broken fibers fraction. By combining the shear-lag model with damage models and considering the effect of transverse multicracking in the 90° plies or transverse yarns in cross-ply or woven CMCs, the tensile stress–strain curves of unidirectional, cross-ply, 2D and 2.5D woven CMCs have been predicted. The results agreed with experimental data.

Prediction of Yarn Strength Utilization in Cotton Woven Fabrics using Artificial Neural Network

The paper presents an endeavor to predict the percentage yarn strength utilization (% SU) in cotton woven fabrics using artificial neural network approach. Fabrics in plain, 2/2 twill, 3/1 twill and 4-end broken twill weaves having three pick densities and three weft counts in each weave have been considered. Different artificial neural network models, with different set of input parameters, have been explored. It has been found that % SU can be predicted fairly accurately by only five fabric parameters, namely the number of load bearing and transverse yarns per unit length, the yarn crimp % in the load bearing and transverse directions and the float length of the weave. Trend analysis of the artificial neural network model has also been carried out to see how the various parameters affect the % SU. The results indicate that while an increase in the number of load bearing or transverse yarns increases the % SU, an increase in the float length and the crimp % in the yarns have a detrimental effect.