Yarn Failure Research Articles

Composite structures under ballistic impact

In the present study, investigations on the ballistic impact behaviour of two-dimensional woven fabric composites has been presented. Ballistic impact behaviour of plain weave E-glass/epoxy and twill weave T300 carbon/epoxy composites has been compared. The analytical method presented is based on our earlier work. Different damage and energy absorbing mechanisms during ballistic impact have been identified. These are: cone formation on the back face of the target, tensile failure of primary yarns, deformation of secondary yarns, delamination, matrix cracking, shear plugging and friction during penetration. Analytical formulation has been presented for each energy absorbing mechanism. Energy absorbed during each time interval and the corresponding reduction in velocity of the projectile has been determined. The solution is based on the target material properties at high strain rate and the geometry and the projectile parameters. Using the analytical formulation, ballistic limit, contact duration at ballistic limit, surface radius of the cone formed and the radius of the damaged zone have been predicted for typical woven fabric composites.

THE MECHANISM OF END BREAKAGE IN RING SPINNING: A STATISTICAL MODEL TO PREDICT THE END BREAK IN RING SPINNING

Abstract The mechanism of end breakage in ring spinning is a complex phenomenon, and is entirely different from the yarn failure mechanism during a tensile test. In this paper a possible mechanism of end breakage is reported. A statistical model is developed for predicting the likely end breakage rate in ring spinning. The important factors in governing end breaks are the mean yarn strength, yarn strength variation, mean value of the peak spinning tensions and the variation of yarn mass irregularity. Some practical aspects have also been discussed to tackle the problem of when the breakage rate suddenly increases.

Slow Penetration of Ballistic Fabrics

A quasistatic penetration test is designed and implemented to provide insight into the evolution and phenomenology of fabric deformation and failure during penetration. The results are needed to guide development of a physics-based computational model of fabric response to projectile impact. The test involves slowly pushing a rigidly held fragment simulator into and through a single ply fabric specimen. The stroke and load on the penetrator are recorded during the test, and a videocamera and microphone enable the fabric failure phenomena to be time-correlated with the load-stroke history. The three distinct modes of fabric failure observed in these tests—local yarn rupture, remote yarn failure, and yarn pullout—are the same modes observed in impact tests, although the extent to which each mode occurs is different in static and dynamic tests. The conditions under which the different failure modes occur and the effects on the load-stroke curve and the energy absorbed are determined.

Influence of Fiber Length Distribution on Strength Efficiency of Fibers in Yarn

The tensile and tear strengths and hence the durability of a cotton fabric are greatly influenced by the length and strength of cotton fibers in addition to the fabric structure. This is so because fiber length to a large extent determines yam strength, which ultimately contributes to fabric strength. Also, fiber length and its distribution affect fiber processing and hence yarn performance during subsequent mechanical processing, including knitting and weaving. Therefore, fiber length distribution and its ultimate effect on the yarn strength are important. To better understand the length-strength relationship in cotton fibers, we have tried to model the strength of fibers assemblies in a yarn, based on some simple assumptions. In this model, we address an important issue of friction among adjacent fibers in a yarn structure and also introduce and derive a new parameter called the "strength efficiency" of fibers in a yarn, which may contribute to an understanding of the yarn failure mechanism. The paper should be helpful to the scientific community involved in improving the properties of cotton fibers, yarns, and fabrics.

A damage model for knitted fabric composites

Abstract A progressive damage model is presented for the prediction of the overall non-linear tensile behaviour of knitted fabric composites. The model is an extension of a recently developed inclusion method for textile composites, taking into account the major damage modes of knitted fabric composites simultaneously. Matrix non-linearities, playing an important role in the behaviour of knitted fabric composites, are implemented using the secant stiffness method. Whereas, non-linearities can be attributed to different sources, depending upon the resin toughness, only some limited yielding was currently investigated. Yarn/matrix debonding, predominantly responsible for the knee behaviour of knitted fabric composites, is investigated using a simple interfacial failure criterion. A selective degradation scheme based upon a finite set of interfacial damage state variables is employed in the reduction of the inclusion stiffness. Finally, a Hoffman criterion is used for yarn failure. The model was used to simulate the tensile behaviour of knitted fabric E-glass/epoxy composites, showing the ability to predict the material response with reasonable accuracy in the region before ultimate failure.

Tension Variations During Cone Winding on an Open-End Spinning System

The two main criteria for successful high speed yam winding with no yarn failure are maintaining yarn tension variations at a level sufficiently high to achieve package stability while at the same time keeping tension fluctuations to a minimum. Their importance arises from the fact that uneven tension causes uneven package density. which in turn results in unevenness in subsequent technological processes such as dyeing, knitting, weaving, etc. Therefore, to manufacture a package with acceptable quality features such as stability, constant density, constant package stiffness, etc., the yarn winding tension must be controlled during winding operations.

Mechanism of failure of complex fibres. Determination of the critical filament length

The critical filament length in failure of a complex fibre was quantitatively estimated. The effect of the clamped length of the sample on the critical length was demonstrated. A correlation was established between the critical length and the frictional interaction of the filaments in a complex fibre, which increases with an increase in twisting. A quantitative estimation of the average shear stresses between the filaments in failure of yarns was presented.

Tension Measurements in Weaving of Singles Worsted Wool Yarns

The variation of tension in weaving 25 tex singles worsted wool yarns is investigated using a commercial on-line tension measuring device. The maximum rate of tension change in warp yarns is 35 to 45 N/s (at beat-up) and in weft yarns 60 to 1000 N/s (depending on the system of weft insertion). Weft yarn failure rates are predicted from measured weft tensions and Uster Tensojet results. Clinging of warp yarns is shown to increase the average tension by up to 20% for a plain weave.

Strengths of Twisted Blend Fibrous Structures: Theoretical Prediction of the Hybrid Effects

Hybrid structures have been applied in many areas such as textiles and composites. However, the mechanisms giving rise to the advantages associated with fiber blending, presumably due to the interactions between constituents of different types, are still poorly understood. This work is an attempt to look into the internal interactions through theoretical analysis. A twisted structure (yarn) of two distinct fiber types with statistically distributed strengths is studied. It has been established in yarns of the single fiber type that the interaction via friction between fibers will lead to a substantial increase of fiber effectiveness, and consequently the yarn strength. Incorporating this concept into the present hybrid case makes it possible to more accurately predict the strength and its distribution for the blended yarn. Moreover, it is revealed in this study that the interaction between fibers prior to the initiation of yarn failure may be the most important factor which causes the so-called hybrid eff...

Effective Thermomechanical Behavior of Plain-Weave Fabric-Reinforced Composites Using Homogenization Theory

A micromechanical analysis is presented to obtain the effective macroscale orthotropic thermomechanical behavior of plain-weave fabric reinforced laminated composites based on a two-scale asymptotic homogenization theory. The model is based on the properties of the constituents and an accurate, three-dimensional simulation of the weave microarchitecture, and is used for predicting the thermomechanical behavior of glass-epoxy (FR-4) woven-fabric laminates typically used by the electronics industry in Multilayered Printed Wiring Boards (MLBs). Parametric studies are conducted to examine the effect of varying fiber volume fractions on constitutive properties. Nonlinear constitutive behavior due to matrix nonlinearity and post-damage behavior due to transverse yarn failure under in-plane uniaxial loads is then investigated. Numerical results obtained from the model show good agreement with experimental values and with data from the literature. This model may be utilized by material designers to design and manufacture fabric reinforced composites with tailored effective properties such as elastic moduli, shear moduli, Poisson’s ratio, and coefficients of thermal expansion.

Tensile Fatigue Behavior of Staple Yarns

The failure of warp yarns on a loom is often caused by repeated cyclical elongation at small stresses well below the breaking point applied under static load. The phenom enon, commonly known as fatigue, is caused by the gradually diminishing resistance of the material, attributable to cumulative damage. Generally, there is no prior indi cation of impending failure due to fatigue. In this work, we have studied the fatigue behavior of warp yarn under cyclical elongation accompanied by abrasion action as measured on a Sulzer-Ruti Webtester on the basis of three criteria—failure, damage rate, and visual appearance. Fatigue behavior expressed in terms of cycles at failure exhibits a wide scatter, displaying a pattern that deviates from normal distribution. A three-parameter Weibull distribution fitted to experimental results consistently displays a unimodal pattern. The rate of fatigue damage expressed in terms of loss in tensile property indicators has proven useful in assessing the fatigue-sustaining capacity of yarn and thereby predicting impending failure. SEM photographs display the abrasion fatigue damage inflicted on the fine structure of yarns and fibers. We have systematically studied, the effect of fatigue parameters that characterize the intensity of fatigue action, such as base tension, speed of fatiguing, abrasion pin position, and strain amplitude. Increasing intensity of fatigue action results in rapid yarn deterioration. Base tension and abrasion pin deflection have profound effects on fatigue. Fatiguing speed and strain amplitude tend to accelerate yarn deterioration, though the experimental results show a slower rate but greater variability. Representing fatigue data based on failure criterion in terms only of characteristic lifetime, which is one of the three parameters of the Weibull distribution, is not enough. A representation in terms of complete distribution yields more useful information about the extent of dispersion and the extreme value in the experimental results.

Mechanical Properties of Fabric Woven from Yarns Produced by Different Spinning Technologies: Yarn Failure in Woven Fabric

A study has been conducted on the mechanisms of in-situ tensile failure of staple yams during uniaxial tensioning, as in a conventional ravel strip test. The yarns were PET/cotton blends processed on ring, rotor, and airjet spinning systems, and then woven into plain or twill weave fabrics. Load-extension behaviors of the yarns were recorded for the in-fabric state as well as for the free state (out-of-fabric), and SEM comparisons were made of the fractured yam ends obtained in the two states. When the tensioned yarns became jammed between cross yarns before straightening, the fracture ends were abrupt, similar to those observed in near zero gauge length tests of free-state yarns. However, when fabric structure was such that tensioned yams could straighten without cross yam jamming, the resulting failure zones were considerably longer, with a mixture of fiber fracture and slippage similar to that observed in long gauge length tests of free-state yams. The interaction between yarn properties and weave geometry had a strong influence on the local disturbance of cloth structure resulting from isolated yam failure during fabric tensioning. The extent of such dis turbance permitted estimates of the stress recovery length of the failed yam and showed its dependence on cloth tightness and yarn type.

Friction and wear behaviour of Kevlar fabrics

Experimental results of a number of tribological tests carried out on aramid woven fabrics are presented in this paper. Kevlar Ht, Kevlar 29 and Kevlar 49 aramid plain fabrics were employed in this work. The friction and wear phenomena of the fabrics were investigated, considering both fabric-fabric and metal-fabric interaction. From the experimental data, the evolution of parameters such as static and dynamic friction coefficients, dissipated energy, volume loss of the material, wear rate, specific wear and wear strength were studied. Moreover, values of the static force needed to pull out a single fibre from the woven fabric were measured. All these data are important for the numerical modelling of impact on such materials. In fact, experimental findings on yarn failure mechanisms show that apart from tensile rupture, failure modes such as cutting, shearing and fibre degradation take place in fabrics subjected to the ballistic impact of low-and medium-calibre ammunition.

Mechanism of Yarn Failure

The importance of interfiber friction in determining yarn strength has been acknowledged by several authors. Studies of the effect of friction on yarn strength were often based on determining the influence of twist level, a structural factor, to change the level of friction. To our knowledge, no study is available in which varying fiber frictional characteristics are introduced into a constant yarn structure ( i.e., the same twist, fiber type, fiber length, etc.). This effect has been accomplished through a surface treatment that changes the level of interfiber friction, and subsequent yarn testing provides useful and interesting information about how fiber interaction contributes to yarn strength. The results presented here show that interfiber friction can (under certain circumstances) be the dominant factor in determining the tensile properties of a ring spun staple yarn. Friction and yarn strength results show that moderate changes in the interfiber friction can produce large changes in yarn strength. We suggest that interfiber friction should receive more attention as a determinant of yarn properties, particularly strength.

Mechanical Properties of Fabrics Woven from Yarns Produced by Different Spinning Technologies: Yarn Failure as a Function of Gauge Length

In a study of yam strength translation into woven fabric behavior, experiments were conducted to establish the effect of test gauge length on yarn properties. Yams produced on each of the three major spinning systems were tensile tested at varying gauge lengths. Yam strength data were fit to two-parameter Weibull distributions and corresponding shape and scale parameters were determined. Strength increased as gauge lengths decreased, a trend indicated by the weakest-link theory. At very short gauge lengths, however, the data deviated from prediction based on the weakest-link theory, thus suggesting a change in the yam failure mechanism, as one would expect when the gauge length approximates the staple length. More direct evidence of such a change is provided in SEM photomicrographs of tensile failures of long versus short gauge test specimens. Combined fiber slippage/pullout and breakage prevailed at longer gauges, whereas a greater extent of fiber breakage with less slippage occurred at shorter gauge lengths. The balance between fiber slippage and fiber breakage varied with yarn structure as produced on different spinning systems. Finally, tensile tests were con ducted on plain and twill weave fabrics woven from yams produced on the different spinning systems. The resultant fabric tenacities approximated corresponding yarn tenacities only for the shortest gauge lengths.

Studies on the Abrasion-resistance of Weaving Yarns

An investigation is reported in which use was made of a simple test instrument designed to study the behaviour of yarns when they fail under abrasive forces. Yarn abrasion-resistance was found to depend primarily upon ply twist in two-fold yarns, with singles twist having only a small degree of influence. The abrasively weak places in two-fold yarns were found to be those of lower-than average twist, which are the thick places. The mechanism of yarn failure was observed to be a slow, incremental drafting of the yarn in the abraded zone, the rate of drafting increasing as the ply twist was reduced. Some estimate of weavability can be made by a method of interpreting the abrasion-test results that predicts the probability of occurrence of abrasively weak places in the yarn.

Structural causation of the yarn failure process

Structural causation of the yarn failure process

Effect of length of a complex yarn on its mechanism of failure in extension

A quantitative characterization of nonsimultaneity in failure of the elementary filaments in a complex yarn on the right-hand part of the stretching diagram has been given. Some features of the failure of elementary filaments in a complex yarn at various sample clamped lengths have been examined. A method has been proposed for evaluating nonuniformity in breaking characteristics of elementary filaments in a complex yarn from the right-hand part of the stretching diagram at a low clamped length, and also from the ratio of the works of deformation to maximum loading and to complete yarn failure.

Applied Statistics: A Handbook of BMDP Analyses

BMDP programs used (or suggested) for the examples.- Some points on the BMDP instructions.- Examples.- A Admissions to intensive care unit.- B Intervals between adjacent births.- C Statistical aspects of literary style.- D Temperature distribution in a chemical reactor.- E A 'before and after' study of blood pressure.- F Comparison of industrial processes in the presence of trend.- G Cost of construction of nuclear power plants.- H Effect of process and purity index on fault occurrence.- I Growth of bones from chick embryos.- J Factorial experiment on cycles to failure of worsted yarn.- K Factorial experiment on diets for chickens.- L Binary preference data for detergent use.- M Fertilizer experiment on growth of cauliflowers.- N Subjective preference data on soap pads.- O Atomic weight of iodine.- P Multifactor experiment on a nutritive medium.- Q Strength of cotton yarn.- R Biochemical experiment on the blood of mice.- S Voltage regulator performance.- T Intervals between the failure of air-conditioning equipment in aircraft.- U Survival times of leukemia patients.- V A retrospective study with binary data.- W Housing and associated factors.- X Educational plans of Wisconsin schoolboys.- Further Sets of Data.- Set 3 Survival times of rats.- Set 14 Grouping of perfumes.- References.

Penetration of Nylon Ballistic Panels by Fragment-Simulating Projectiles

The purpose of this report is to present evidence supporting the thesis that the major mode of penetration of nylon ballistic panels by fragment-simulating projectiles is a cutting, shearing mechanism: Shear forces required for yarn failure are usually less than tensile forces. Penetration is always at a slight angle, with the 90° edge of the FSP leading. Many yarn ends terminated in a smooth surface (in a tensile break the filaments break at random places along the yarn). Penetration of the cloth in certain experimental situations occur in a manner precluding tensile failure. The force required for nylon or Kevlar yarn failure is less for a rectangular leading surface than it is for a chisel-shaped leading surface.