A Stochastic Simulation of the Failure Process and Ultimate Strength of Blended Continuous Yarns

A previously developed micromechanical model is used to formulate the problem of a blended yarn, consisting of low elongation (LE) and high elongation (HE) fibers undergoing axial extension, with a fiber break in the central region of the hybrid fiber array. A hybrid parameter R, which is the ratio of the axial stiffness of the HE fibers to that of the LE fibers, is shown to have an important effect on the intact fiber stress concentration factor (SCF), and the broken fiber slip extent at the fiber break. While the SCF increases for HE fibers adjacent to broken LE fibers, it decreases for LE fibers adjacent to broken HE fibers as R takes on values away from unity (homogeneous yarn). Higher loading can therefore be sustained by the LE fibers, and a beneficial hybrid effect can be realized.Blended or hybrid yams, which consist of more than one kind of fiber, have been produced to develop improved strength and stiffness over what can be achieved in homogeneous yams. This so-called hybrid effect has been observed in hybrid composite sheets [2,14], indicating how higher loading and elongation can be sustained by high modulus (low elongation, LE) fibers than when they exist alone in a nonhybrid composite. The same effect appears to be possible for blended yams. This is corroborated by our current results, which show that the stress concentration factor (SCF) of an LE fiber next to a broken HE (high elongation) fiber decreases, while the SCF of an HE fiber next to a broken LE fiber increases with decreasing values of the hybrid parameter R, the ratio of the axial stiffness of the HE to that of the LE fibers. This has a positive effect for yams where the principal fibers are particular LE fibers, ,which are selected to be stronger than the dispersed HE fibers. It suggests that if a reduction in the SCF of the principal LE fiber has i dominant effect on yarn strength compared with the increased SCF of the HE fiber (since the HE fiber has a larger failure strain), a hybrid effect can be realized.Near a fiber break, the neighboring fibers will slip, and the slip extent plays a role similar to the yield zone in the matrix near a fiber break [14] in fiber composites. We will show here how the SCF decreases with larger slip extents, supporting the notion that a slip acts as a dissipative mechanism, similar to matrix yielding in fiber composites.In general, twisted fibrous structures, including yams, ropes, and cables, exhibit transverse compressive forces induced by the remote tension along the yam axis. Each fiber executes a quasi-helical path through the yam. so that a radially outwardly directed, distributed reaction force from underlying fiber layers balances the tension on the curved fiber. The compressive forces that occur permit load transfer between abutting fibers through friction and give the yarn cohesiveness. With increasing yarn tension, transverse compressive forces also increase, thereby increasing the magnitude of the frictional load transfer between -fibers. This mechanism, first noted by Galileo [31, is parti...

“…With the expression for q, given by Equation 13 and noting that the strain E -p/EA, the quantity Q in Equation 10 can be written as…”

Section: Nondimensional Fiber Loadsmentioning

confidence: 99%

mentioning

confidence: 99%

Hybrid Effect at Fiber Breaks in Twisted Blended Yarns

Rossettos

Godfrey

2002

“…In addition, the mechanics of the failure process and ultimate strength of a twisted yarn structure using a stochastic model were studied by Realff and colleagues. 9 The model acts to predict the strength and fracture behavior of a blended yarn with continuous components. The features of the blended yarn behavior were simulated and elucidated, including the strength-reinforcing mechanism of the twist yarn, the yarn break propagation pattern, and the effect of the twist on the yarn fracture behavior, as well as the shape effect of the component stress–strain curves.…”

Section: Resultsmentioning

confidence: 99%

CAD/CAE for stress–strain properties of a wide range of multifilament twisted man-made filament yarns

Sriprateep

2017

In a previous paper, the computer aided design (CAD)/computer aided engineering (CAE) approach was presented and compared via the stress–strain curves of high-tenacity rayon yarn and the energy method. The maximum stress–extension curves showed very good agreement with experimental results and were more accurate than the previous methods. In this paper, the CAD/CAE method is considered in relation to multifilament yarn, which is equally applicable to a wide range of man-made filament yarns from nine material types. The results of this prediction model were compared with the stress–strain curves of experimental results and the energy method. The maximum stress–extension curves showed very good agreement with the experimental results except for the high-tenacity Terylene and Fortisan. The reasons for the poor agreement between the experimental and predicted curves are discussed. The breaking points obtained with this method are also compared with experimental results and discussed.

“…The tension on the yarn equals the tension across any yarn section or the sum of the tension of all the filament segments in any yarn cross section. 30 In this case, calculating the yarn tension (F y ) based on all filament tensions is one of summing all filament axis tensions (F fj ) discounted by cos j , where j is the helix angle of the filament. Therefore, the equation can then be expressed as…”

Section: Filament-yarn Tension Relationshipmentioning

confidence: 99%

CAD/CAE for stress–strain properties of multifilament twisted yarns

Sriprateep

Bohez

2016

A method is presented for modeling the tensile behavior of multifilament twisted yarns. A filament assembly model and a computer-aided design/computer-aided engineering (CAD/CAE) approach are proposed for the tensile analysis. The geometry of the twisted yarn and the nonlinear filament properties were considered. The finite element method (FEM) and large deformation effects were applied for computation of the stress–extension curves. Ideal yarn structures of five layers with different twist angles were simulated to predict the tensile behavior of each filament and each layer. The stress acting on the filaments after yarn extension could be directly analyzed by the FEM. The stress distribution in the filaments showed that the highest stress regions were located at the filament in the center of the yarn and decreased slightly to the yarn surface. The stress–extensions of the filaments were converted to yarn tensile behavior that is shown in terms of the maximum and average stress–extension curves. The results of this prediction model were compared with the stress–strain curves of high-tenacity rayon yarn and the energy method. The maximum stress–extension curves showed very good agreement with experimental results and are more accurate than those obtained by previous methods.